Interrelationships of precipitation, soil moisture and spring wheat production in northern Montana
by Torlief S Aasheim
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Agronomy at Montana State College
Montana State University
© Copyright by Torlief S Aasheim (1954)
Abstract:
The amount and percent of precipitation conserved in the soil during the fallow period was determined
for two areas in Northern Montana. The efficiency of water use in a system of continuous cropping was
compared with the efficiency of use in an alternate crop-fallow system.
Correlations were calculated between crop yield and several moisture factors some of which were, soil
moisture at time of crop emergence, precipitation during the growing season, and combinations of soil
moisture and precipitation.
Conservation of moisture, in the soil, during the fallow period varied with the time of year and the
amount of precipitation received. Evaporation losses were extremely high during the summer months
and the correlation between the amount of precipitation and the percentage conserved was high during
that time of year.
Spring wheat grown on fallow used an average of 2 inches more water from the soil than the same crop
in a continuous cropping system. Fallow outyielded continuous cropping by 8.9 bushels.
The average amount of water used to produce a pound of dry matter on fallow was less than the
average used in a system of continuous cropping but the water requirement of spring wheat on fallow
in low producing years was as high as the average water requirement on spring plowing.
An inch of precipitation during the growing season was calculated to be only 70 per cent as effective as
an inch of moisture stored in fallow soil.
Yields predicted by the use of multiple regression deviated an average of four bushels from actual
yields.
The correlation between yield and precipitation was higher than the correlation between yield and soil
moisture at time of crop emergence. INTERRELATIONSHIPS OF PRECIPITATION, SOIL MOISTURE
■AND SPRING WHEAT PRODUCTION IN NORTHERN MONTANA
by
TORLIEF s . AASHEM
A THESIS
S ubm itted to th e G raduate F a c u lty
in
p a r t i a l f u l f i l l m e n t o f th e re q u ire m e n ts
f o r th e d e g re e o f
M aste r o f S c ie n c e i n Agronomy
at
M ontana S ta te C o lle g e
A pproved:
H ead, M ajor D epartm ent
C hairm an, Exam ining Committee
Bozeman, M ontana
Ju n e , 1954
' 11-rUClU
t: Ni M
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ACKNOWLEDGEMENT
Data u sed from th e N orth Montana B ranch S ta tio n was o b ta in e d from un­
p u b lis h e d re c o rd s on f i l e a t t h a t lo c a t io n .
T his d a ta was c o lle c te d by-
p e rs o n n e l c o o p e r a tiv e ly employed by th e Montana A g r ic u ltu r a l Experim ent
S ta tio n and th e Bureau o f P la n t I n d u s tr y .
I n d iv id u a ls who have been r e ­
s p o n s ib le f o r th e c o l l e c t i o n o f t h i s d a ta in c lu d e George W. Morgan, M. A.
B e ll and John J . Sturm .
The d a ta p re s e n te d from th e work n e a r F r o id , M ontana, was o b tain ed
from a n n u al r e p o r ts p re p a re d by S u p e rv is o rs o f t h i s p r o j e c t .
Ralph C lin e
was p r o j e c t s u p e r v is o r d u rin g th e p e rio d I 943 th ro u g h 1945 in c lu s iv e .
The
w r i t e r s u p e rv is e d t h i s p r o j e c t d u rin g th e r e s t o f th e tim e i t has been in
o p e r a tio n .
T his i s a c o o p e ra tiv e p r o je c t in c lu d in g the Montana A g r ic u ltu r ­
a l E xperim ent S t a t i o n , th e S o il C o n se rv a tio n S e r v ic e , th e Montam E xten­
s io n S e r v ic e , S o il C o n se rv a tio n D i s t r i c t s o f Work Group X, and th e Moen
B ro th e rs o f C u lb e rts o n , Montana.
The w r i t e r i s f u r t h e r in d e b te d t o M. A. B e ll who su g g este d th e
problem and o f f e r e d a s s is ta n c e and a d v ic e in o b ta in in g and sum m arizing th e
d a ta .
R. F. E s lic k , D r. E. R. Hehn, and D r. J . C. Hide a s s i s t e d in a n a ly z ­
in g th e d a ta and o ff e re d many h e lp f u l s u g g e s tio n s re g a rd in g th e method o f
p r e s e n tin g the m a te r ia l.
110366
. 3
TABLE OF CONTENTS
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LIST QF- TABLES
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EXPERIMMTAL RESULTS
SIMfcARY
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LITERATURE OITED
APPENDIX
o o o e e o o e o e o e o o o o e o e o O o o e o o e e e p o o o o o o o o e o e o o e o o o o o
o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o a o o o o o o o o o o o o o o o o o o o o o o
7U
72
4.
LIST OF TABLES
Page
Table I 0
Table I I .
Table I I I .
Table IT..
Table V.
T able T I.
T able T H .
Table T i l l .
Table IZ . .
Table X.
Irich es o f w a te r in the" s o i l to" a d ep th , o f 4 f e e t a t
d i f f e r e n t tim e s o f sa m p lin g ' 0 "a n d ' D"p l o t s ' i n M. G.
S o rieS a t H av reg KIbntana Ooeeeeooooeoeee»eooeeooo*oeee
27
In c h e s o f w a te r g a in e d o r l o s t betw een sam pling
d a te s , arid’th e t o t a l g a in ed "during the. fa llo w
p e rio d o f a p p ro x im a te ly 21 m o n th s ,"G"arid"D"p lo ts"
i n M. G. S e r ie s a t H av re, M ontana6. . . . . . . . . .
28
In c h e s o f p r e c i p i t a t i o n betw een s o i l m o istu re
sam p lin g s during" the. fa llo w p e rio d .o f" a p p ro x ­
im a te ly 21 months a t H av re, M o n ta n a .... . . . . . . . . . . . . . .
23
P e rc e rit o f p r e c i p i t a t i o n coriserv ed in th e s o i l b e ­
tw een s o i l m o is tu re sam pling d a te s d u rin g th e f a l ­
low p e rio d o f a p p ro x im a te ly " 21 months a t H avre,
M ontana.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
In c h e s o f w a ter a v a ila b le to th e s p rin g w heat cro p
grown on fa llo w in O and"D"p l o t s ' a t H av re, M ontana,
d u rin g p e rio d 1 ^21—1^43.
32
S p rin g w heat p ro d u c tio n , g ra in and s tr a w , on fa llo w ­
ed l a n d :i n 0" arid D"p l o t s , M. 0 . S e r i e s , a t" H a v re ,
M ontana, 1321—1 3 4 5 . . . . . . . . ..o * @ .. . . . . . . . . . . . . . . . . . . . .
33
A c tu a l and p r e d ic te d y i e l d s 'o f s p rin g w heat on f a l - "
low a t H avre, M o n tan a.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
38
C o r r e la tio n c o e f f i c i e n t s betw een y i e l d , s o i l m ois­
tu r e and p r e c i p i t a t i o n f o r cro p s grown on f a llo w ,
G a n d .D p l o t s , H av re, M ontana, d u rin g th e p e rio d
1 321—1345 . . . . . . . . . . . . . . 0 0 . 0 0 0 0 . . . . . a . . . . . ►
060000066'»
33
S o il m o is tu re , p r e c i p i t a t i o n .a n d y ie ld d a ta from
th e A p l o t i n . M. 0 . S e r ie s o f d ry lan d crop rota*=*'
t i o n s a t H avre, M ontana.. . . . . . . . O . . . . . . . . e . . . . . . . . . . .
42
Pounds, o f grain" and straw" p ro duced p e r a c r e in a
c o n tin u o u s c ro p p in g "sy ste m , p l o t A of-M, 0 . " S e rie s
a t H avre, Mont ana
43
5
Page
T able X I.
Table X II.
T able X I I I .
T able XIV.
Table XV.
T able XVI.
T able XVII.
Pounds o f g ra in and stra w produced on fa llo w d u r­
in g te n y e a rs o f low p ro d u c tio n , and th e amount
o f s o i l m o istu re a t se e d in g tim e , a n d .th e growing
seaso n p r e c i p i t a t i o n G and D p l o t s , H av re, M o n ta n a ...
46
In c h e s o f w a ter in th e s o i l to a d e p th o f 4 f e e t
a t h a r v e s t and th e fo llo w in g s p r in g , p r e c i p i t a t i o n
f o r th e p e rio d a n d "p e rc e n tag e o f p r e c i p i t a t i o n "con­
serv ed i n th e s o i l . A p l o t , H avre, M ontana^. . . . . . . . .
4?
In c h e s o f w a te r in s o i l in s tu b b le c o n tin u o u s ly
cropped and in s tu b b le in a n a l t e r n a t e cro p fa llo w
system d u rin g t h e ' f a l l ' a n d ' s p r i n g ' o f ' th e y e ar a t"
H avre, Mont a n a . . 6. . . . . . . . o
. . . . o
.
48
In c h e s o f water" in th e s o i l a t v a rio u s d e p th s a t
tim e o f crop emergence" .'and a t h a rv e s t in a . con­
tin u o u s cro p p in g system and a system o f a l t e r n a t e
crop and fa llo w , H a v re , . M ontana3 f o r th e p e rio d
1921-1945# O O O O 6 O 0 0 . . . . . . . . . . . . . . . . . . - 6 . O ' . . * . 0 . O 1. - . - .
0 6
C o r r e la tio n c o e f f i c i e n t s betw een y i e l d , s o i l m ois­
t u r e and p r e c i p i t a t i o n - for. crops" grown .on, s p rin g
plow ing ,Ca p l o t ) H av re, 1Mont a n a . . . . . . . . . . o . . . . . . . . . . .
51
In c h e s o f s o i l m o istu re p r e s e n t , in fa llo w la n d " i n " '
th e f a l l , by f o o t d e p th s , C u lb e rts o n , M o n tan a.. . . . . . .
52
I n c h e s .o f s o i l m o istu re p r e s e n t in fa llo w la n d in ,
t h e .s p r i n g " a t se e d in g tim e , by f o o t d e p th s , C u lb e rtso n ,
Mont a n a . . . . . . . o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
Table X V III. - in c h e s o f w a te r p r e s e n t to a d e p th o f f iv e f e e t in
fa llo w la n d a t C u lb e rts o n , M ontana, in th e f a l l and
sueceeding"‘s p rin g a n d "th e in c h e s o f g a in o r l o s s d u r­
in g th e same p e r i o d . . . . o . . . . . . . . . . . . . . 55
Table XIX.
T able XE.
In c h e s o f s o i l m o is tu re p r e s e n t in s tu b b le la n d in
th e f a l l " o f th e y e ar b y f o o t d e p th s , C u lb e rts o n ,
M o n ta n a . . . . . . . . . . . . . . . . . . 666. . . . . . . . . . . . . . . . . e . . * . . *
54-
In ch es o f s o i l m o istu re p r e s e n t . in s tu b b le la n d in
th e s p rin g .of th e y e a r a t se e d in g tim e by fo o t '
d e p th s , C u lb e rts o n , M ontana. . . . . . . . o . . . . . . . . . . . . . . . . .
5^*
6
Page
Table XXI.
In c h e s o f w a te r p r e s e n t to a d e p th o f " f iv e f e e t in '
s tu b b le " la n d a t C u lb e rtso n ,- M ontana, in th e f a l l
and su cceed in g s p rin g a n d 't h e ' in c h e s g a in o r l o s s
-d u rin g th e same p e rio d o 0o0000000@o@000@00**00 00 0000@0
T able XXII0
In c h e s o f s o i l w a te r g ain ed o r l o s t in fa llo w b e ­
tw een sam pling d a te s and th e t o t a l g a in ed d u rin g
th e f a llo w ' p e rio d o f'a p p ro x im a te ly " 21-months:,
C u lb e rts o n , Slontana0 *0000* 00o00000 . . . . . . . . . . . . . . . . . . . -
55
In c h e s o f p r e c i p i t a t i o n betw een s o i l m o istu re sam­
p li n g s ' d u rin g th e fa llo w p e r i o d 'o f a p p ro x im a te ly 21
m onths, C u lb e rts o n , M o n t a n a . . . . . . . . . . . . . * . . . . . . . . . . . *
56
P e rc e n t o f p r e c i p i t a t i o n co n serv ed i n th e s o i l be­
tw een "sam pling d a te s d u rin g th e fa llo w p e r i o d 'o f
a p p ro x im a te ly 21 m onths, C u lb e rts o n , M o n t a n a .......* ,.
56.
Table X X III.
T able XXEV0
I
LIST OF APPENDIX TABLES
Page
T able 1«
Table I I .
T able I I I .
Table 17.
T able 7 .
T able T I.
T able 711.
T able 7 I I I .
S o il" m o is tu re s a m p lin g 'd a te s ' a t ' th e N orth"M ontana
■B ranch Station*eo************************************
/73
In ch es o f -water in v a rio u s f o o t d e p th s o f s o i l a t
tim e o f crop emergence in a" system o f c o n tin u o u s. .
c ro p p in g a t th e N o rth Montana Branch S t a t i o n , H avre,
Mont a na #.
.
.
.
*
#
.
*
*74
In c h e s o f w a te r in " v a rio u s fo o t" d e p th s o f s o i l a t
h a r v e s t time" in a system o f c o n tin u o u s cro p p in g a t
th e N o rth M ontana B ranch S t a t i o n , H avre, M o n ta n a # ....
75
In c h e s o f w a te r in v a rio u s f o o t d e p th s o f s o i l " i n
s tu b b le to be "fallow ed , a t h a rv e st, tim e . N o rth
M ontana Branch S t a t i o n , H av re, M o n tan a.. . . . . . . . . . . . . .
?6
In c h e s o f w ater, in v a rio u s f o o t d e p th s o f s o i l in"
s tu b b le t o be fallow ed", a t tim e o f crop em ergence.
N o rth Montana Branch S t a t i o n , H av re, M ontana.. . . . . . . .
77
In c h e s o f w a te r in v a rio u s f o o t d ep th s o f s o i l i n
fa llo w a t" 'h a rv e s t tim e . N o rth Montana B ranch S ta tio n ,
H a v re , M ontanao . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7^
In c h e s o f w a te r in v a rio u s f o o t d e p th s' o f s o i l in
fa llo w a t tim e o f crop em ergence, "North M ontana
Branch S t a t i o n , H a v re , M
o
n
t
a
n
a
Summary o f p e r tin e n t in fo rm a tio n developed"from
N orth Montana Branch S ta tio n d a t a . . . . . . . . . . . . . . . . . . . .
■ 75
8©
8
ABSTRACT
The amount and" p e rc e n t o f p r e c i p i t a t i o n co n serv ed in ' th e s o i l d u rin g
th e fa llo w p e rio d was determ ined f o r two a re a s i n N o rth e rn M ontana. The
e f f ic ie n c y o f w a te r u se in a system "o f c o n tin u o u s c ro p p in g w as compared
w ith th e e f f ic ie n c y o f use in an a l t e r n a t e cro p —fa llo w system .
C o r r e la tio n s were c a lc u la te d betw een crop y ie ld and s e v e ra l m o istu re
f a c to r s some o f which w e re , s o i l m o is tu re a t tim e o f crop em ergence, p r e ­
c i p i t a t i o n d u rin g th e grow ing s e a so n , and co m b in atio n s o f s o i l m o istu re and
p re c ip ita tio n .
•
•
C o n se rv a tio n o f m o is tu re , in th e s o i l ," d u r i n g th e fa llo w p e rio d v a rie d
w ith th e tim e o f y e a r and th e amount o f p r e c i p i t a t i o n re c e iv e d . E v a p o ra t­
io n lo s s e s were e x tre m e ly "h ig h d u rin g th e summer months and th e c o r r e la tio n
betw een th e amount o f p r e c i p i t a t i o n and th e p e rc e n ta g e co n serv ed was high
d u rin g t h a t tim e o f y e a r .
.S p rin g w heat grown on fa llo w used an av erag e o f 2 in c h es more w a te r
from th e s o i l th a n th e same crop i n a co n tin u o u s cro p p in g sy stem . Fallow
o u ty ie ld e d c o n tin u o u s c ro p p in g by 8 .9 b u s h e ls .
The a v e r a g e am ount o f 'w a te r u s e d t o p r o d u c e a p o u n d o f d r y m a t t e r on
f a l l o w w a s l e s s t h a n t h e a v e r a g e u s e d i n a s y s te m o f c o n ti n u o u s c r o p p in g
b u t t h e w a t e r r e q u i r e m e n t o f s p r i n g w h e a t o n f a l l o w i n low p ro d u c in g , y e a r s
w as a s h i g h a s "the a v e r a g e w a t e r r e q u ir e m e n t on s p r i n g p lo w in g .
An in c h o f p r e c i p i t a t i o n d u rin g th e grow ing season was c a lc u la te d to
be o n ly 7Q p e r c e n t a s e f f e c t i v e a s a n in c h of- m o istu re s to r e d in fa llo w
s o il.
Y ie ld s p r e d i c te d by th e u s e o f m u ltip le r e g r e s s io n d e v ia te d an a v e ra g e
o f f o u r b u s h e l s fro m a c t u a l y i e l d s .
The c o r r e l a t i o n " b e t w e e n y i e l d a n d p r e c i p i t a t i o n w as h i g h e r t h a n t h e
c o r r e l a t i o n b e tw e e n y i e l d and s o i l m o is t u r e a t tim e o f c ro p e m e rg e n c e .
?
. INTRODUCTION
The c o u n tie s in N o rth e rn M ontana, w hich b o rd e r on Canada and which l i e
betw een th e Rocky M ountain's and th e N o rth Dakota boundary, com prise an a re a
g e n e r a lly r e f e r r e d t o in Montana a s th e "High L in e " ,
R o o se v e lt County though
i t does n o t b o rd e r on Canada i s c o n sid e re d ag b e in g in c lu d e d i n t h i s a r e a .
The d ry la n d a g r i c u l t u r e o f t h i s s e c t i o h 'o f Montana c o n s is ts alm ost e n t i r e ­
l y o f li v e s t o c k , h ay and cash g r a in p ro d u c tio n .
s p r in g w h eat.
The epsh g r a in i s l a r g e ly
M o istu re i s g e n e ra lly , th e lim i t i n g f a c t o r o f crop p ro d u c t­
io n w hich account's f o r th e p o p u la r ity o f summer fa llo w as a p r a c t i c e .
A pproxim ately' tw o - th ir d s o f the wheat grown i s p la n te d on summer fa llo w .
The N o rth Montana Branch S t a t i o n which h as been c a r r y in g on d ry la n d
a g r i c u l t u r a l i n v e s t ig a ti o n s s i n c e '1916 i s lo c a te d n e a r Havre and i s about
. i n th e c e n te r o f th e w e ste rn h a l f o f .th e ."H igh,L ine" a r e a .
The d ry la n d
i n v e s t ig a ti o n s conducted have in c lu d e d d e te rm in a tio n s o f s o i l m o istu re and
crop y ie ld r e s u l t i n g from v a r io u s t i l l a g e p r a c t i c e s , crop r o t a t i o n s and th e
n a t u r a l v a r i a t i o n s o f w e a th e r .. A d a i l y re c o rd of. te m p e ra tu re s , wind
v e l o c i t i e s , and p r e c i p i t a t i o n th ro u g h o u t th e y e a r h as b een k e p t a lo n g w ith
a d a i l y re c o rd o f th e e v a p o ra tio n from a f r e e w a te r s u rfa c e d u rin g th e s ix
month p e rio d A p ril th ro u g h S eptem ber.
U npublished d a ta from th e S ta tio n
w e ath e r re c o rd s show t h a t the av erag e an n u al p r e c i p i t a t i o n f o r th e t h i r t y fo u r y e a r p e rio d 1917 th ro u g h 1950 i s 1 1 .5 1 in c h e s .
. The S o il C o n se rv a tio n S e r v ic e , in co o p eratio n , w ith th e Montana A g ri­
c u l t u r a l E xperim ent S ta tio n and o th e r s , h a s been co n d u ctin g a stu d y o f
v a rio u s , t i l l a g e p r a c t i c e s n e a r E c o id , M ontana, s in c e 1940.
T h is stu d y iq
b e in g conducted to determ ine what t i l l a g e p r a c t i c e s a re th e m ost r e s i s t a n t
10
t o w ind and w a te r e ro s io n and what th e e f f e c t o f v a rio u s t i l l a g e p r a c t i c e s
i s on m o is tu re c o n s e rv a tio n and cro p p ro d u c tio n .
D a ily p r e c i p i t a t i o n re*=
c o rd s have been k e p t a t o r n e a r t h i s p r o j e c t s in c e i t was s t a r t e d and s o i l
m o is tu re d e te rm in a tio n s have been made d u rin g th e f a l l , and s p rin g o f th e
y ear,
The 1941 Y ear Book, "C lim ate and Man" 9 shows an a v e ra g e an n u al p r e ­
c i p i t a t i o n f o r a t h i r t y - e i g h t y e a r p e r Iqd o f 1 2 ,6 7 in c h e s f o r P o p la r,
M ontana, w hich i s lo c a te d ab o u t 30'm il.es w est o f F ro id ,
The d ry :l a n d ‘work a t th e N o rth Montana B ran ch ' S ta tio n was l a s t -sum­
m arized in 1937 i n Montana A g r i c u l t h r a l E xperim ent S t a t i o n B u l l e t i n 336 by
M, A, B e l l,
Montana A g r ic u ltu r a l E xperim ent S ta tio n B u l le tin 468 p u b lis h e d
i n 1949 by T0 S0 Aasheim summarized th e t i l l a g e work n e a r F ro id th ro u g h
1947,
S o i l an d c l i m a t i c c o n d i t i o n s a t H a v re a n d F r o i d a r e r e p r e s e n t a t i v e o f
c o n d i t i o n s w h ic h o c c u r a lo n g m o s t .o f t h e "H ig h L i n e " ,
The w ork a t H a v re
a p p l i e s i n g e n e r a l t o t h e w e s t e r n tw o t h i r d s o f t h e a r e a a n d t h e w o rk a t
F r o i d m ore n e a r l y a p p l i e s t o t h e e a s t e r n p o r t i o n .
The m a te r ia l p re s e n te d in t h i s p a p e r was d e riv e d from work done a t th e
two lo c a t io n s m entioned.
W hile some o f t h i s work has been p re v io u s ly sum­
m a riz e d , i t i s th e p u rp o se o f t h i s p a p e r to b r in g th e sum m aries more n e a r ly
u p - to - d a te and t o p r e s e n t some o f th e r e l a t i o n s h i p s o f p r e c i p i t a t i o n , s o i l
m o is tu re and crop p ro d u c tio n which have n o t been p re v io u s ly d eterm in ed .
The r e l a t i o n s h i p s d e te r m in e d fro m t h e d a t a a t tb e N o r th M ontana B ra n c h
S ta tio n in c lu d e ,
I,
The am o u n t and p e r c e n t a g e o f p r e c i p i t a t i o n w h ic h i s c o n s e r v e d i n
th e s o i l d u rin g th e e n t i r e fa llo w p e r io d and d u rin g v a rio u s p a r t s o f i t .
11
2,
The y ie ld o f g r a in and stra w produced on fa llo w and co n tin u o u s
cro p p in g w ith s tr a w - g r a in r a t i o s fo r b o th sy stem s.
3e
The amount o f w a ter r e q u ir e d to produce a pound o f d ry m a tte r on
fa llo w and c o n tin u o u s cro p p in g und er f i e l d c o n d itio n s .
4.
The im portance o f s o i l m o is tu re a t se e d in g tim e as compared w ith
p r e c i p i t a t i o n d u rin g th e grow ing seaso n .
5«
C o r r e l a t i o n s an d r e g r e s s i o n s sh o w in g r e l a t i o n s h i p s b e tw e e n s o i l
m o i s t u r e , p r e c i p i t a t i o n , and c ro p p r o d u c t i o n .
The d a ta a v a ila b le from th e work a t F ro id i s much more lim ite d th a n
d a ta from th e N o rth Montana Branch S t a t i o n and f o r t h i s re a so n th e a n a ly s is
o f r e s u l t s o b ta in e d th e r e i s n o t a s e x te n s iv e .
The r e l a t i o n s h i p s d e term in ­
ed from th e F ro id d a ta a re lim it e d t o th e amount and p e rc e n ta g e o f p re ­
c i p i t a t i o n which, i s conserved d u rin g v a rio u s p a r t s o f th e fa llo w p e rio d .
The d a ta p re s e n te d a p p lie s more g e n e r a lly to th e "High L in e'' a re a th a n
to any o th e r la r g e a re a in Montana b u t m ost o f th e r e s u l t s . w i l l p ro b a b ly
f i t q u ite c lo s e ly w ith th o s e which m ight have been o b ta in e d i n o th e r d ry
la n d s e c tio n s o f th e s t a t e where s p rin g wheat i s g ro w n .' The s o i l m o istu re
p r e c i p i t a t i o n r e l a t i o n s h i p s no doubt a p p ly q u ite g e n e r a lly t q a l l d ry la n d
a re a s on th e p l a i n s o f Montana r e g a r d le s s o f th e crop grown.
12
LITERATURE REVIEWED
Summer fa llo w h as become a g e n e r a lly a c c e p te d p r a c t i c e on d ry la n d i n
m ost p a r t s o f Montana=
T here a re s t i l l in d iv id u a ls who do n o t fo llo w t h i s
p r a c t i c e and th e r e a re a re a s and o p e ra to rs t h a t p r o f i t more by th e system
th a n o th ers=
Summer fa llo w i s “used n o t o n ly i n Montana b u t i s g e n e r a lly
p r a c tic e d th ro u g h o u t th e G re at P l a i n s .
Mathews ( l 6) r e p o r ts t h a t a t D a l-
h a r t 9 T e z a s, w hich h as an a n n u al p r e c i p i t a t i o n o f 17=5 in c h e s and a seaso n ­
a l p r e c i p i t a t i o n o f 13=7 in c h e s m o is tu re i s s t i l l a li m i t i n g f a c t o r o f p ro ­
d u c tio n on fa llo w e d la n d .
F allow ed la n d a p p e a rs to have th e f e r t i l i t y n e ­
c e s s a ry t o produce h ig h y ie ld s and in c r e a s e s in y ie ld th ro u g h th e a d d itio n
o f o rg a n ic m a tte r have n o t o c c u rre d .
D iff e re n c e s o f .o p in io n have b een e x p re sse d c o n c e rn in g ■th e p r a c tic e o f
summer fa llo w by fa rm e rs and in v e s t i g a t o r s f o r some tim e .
G h i l l c o t t (4 ) in
1931 had t h i s t o say about summer fa llo w - "Many a d v o ca te s o f summer fa llo w ­
in g l a y g r e a t s t r e s s upon th e in s u ra n c e f e a tu r e s o f t h i s p r a c t i c e .
I t is
tr u e t h a t d anger o f com plete f a i l u r e when summer fa llo w in g i s p r a c tic e d i s
l e s s th a n w ith c o n tin u o u s cro p p in g b u t i t i s f a r from w hat can be c a lle d i n ­
su ra n c e .
I t i s a t b e s t b u t a s l i g h t re d u c tio n o f th e h a z a r d .r — —I t i s
o b v io u s t h a t th e summer fa llo w in g system a s a n in s u ra n c e a g a in s t t o t a l l o s s
o f c ro p s i s a m yth, w h ile crop r o t a t i o n and liv e s to c k a re r e a l i t i e s . - - - - P o s s ib ly s e n tim e n t may have som ething to do w ith the.; r a i s i n g o f w heat on
summer fa llo w e d la n d .
Any. farm er l i k e s to r a i s e b ig c ro p s .
He g e ts much
more s a t i s f a c t i o n o u t o f w atch in g a 30. b u s h e l cro p o f w heat grow th a n t o
w atch a 20 b u s h e l c ro p " .
B e ll (2) in summarizing th e work a t th e .N o rth Montana B ranch S ta tio n
!
from 1917 th ro u g h 1935 w r i t e s , " I t becomes e v id e n t t h a t n o t o n ly were th e
a n n u al av erag e y ie ld 's o f sm all g r a in s on d isk e d s tu b b le ab o u t h a l f th o se
from f a llo w , b u t th e p r o b a b i l i t y o f abandoning p a r t o f o r th e e n t i r e d isk e d
s tu b b le a c rea g e was. a t l e a s t th r e e o r f o u r tim e s a s g r e a t a s t h a t in d ic a te d
f o r w e ll p re p a re d fa llo w "0
Economic a s p e c ts o f th e fa llo w sy stem , in a d d itio n to y i e l d , were
b ro u g h t o u t by S ta rc h (21) in 1933«
He concluded t h a t th e r e was n e a r ly
enough'" b e n e f it d e riv e d from la b o r d i s t r i b u t i o n and tim e ly o p e ra tio n to w ar­
r a n t th e a p p lic a tio n o f the system i f th e r e were no o th e r elem en ts in i t s 1
fa v o r such as. m o is tu re c o n s e rv a tio n and s o i l n i t r i f i c a t i o n , ,
Ih e f a c t t h a t summer fa llo w i s n o t e f f i c i e n t in c o n se rv in g th e p re ­
c i p i t a t i o n t h a t f a l l s d u rin g th e fa llo w p e rio d h as been p r e v io u s ly d e term in ­
ed,,
B e ll (2) found t h a t the a c tu a l amount o f w a ter s to r e d i n th e s o i l to
a d ep th o f 4 f e e t d u rin g 16 fa llo w p e rio d s av erag ed 4.0 6 in ch es*
T h is amount
o f m o is tu re re p re s e n te d a p p ro x im a te ly 20 p e r c e n t o f th e av erag e p r e c i p i t a ­
t i o n re c e iv e d in a fa llo w p e rio d o f 21 t o 22 months d u ra tio n *
The amount,
o f w a te r s to re d d u rin g in d iv id u a l y e a rs d u rin g t h i s p e rio d ranged from 15
to 32 p e r c e n t o f th e t o t a l p r e c ip ita tio n *
Doughty ( l l ) fo u n d , a f t e r a n a ly s ­
in g s o i l m o is tu re and r a i n f a l l d a ta o b ta in e d a t S w ift C u r r e n t, t h a t much o f
th e summer p r e c i p i t a t i o n i s l o s t in a f u t i l e w e ttin g and d ry in g o f th e s u r ­
fa c e s o i l w ith l i t t l e perm anent s to r a g e * • Under c o n d itio n s t h e r e , about 25
p e r c e n t o f th e p r e c i p i t a t i o n t h a t f a l l s d u rin g th e fa llo w p e rio d i s s to re d
i n th e s o il*
Doughty ( l l ) a ls o found t h a t a s m a lle r p e rc e n ta g e o f th e p r e c i p i t a t i o n
w hich f a l l s d u rin g th e summer months i s conserved th a n from p r e c i p i t a t i o n
.
14
w hich o c c u rrs d u rin g th e c o o le r months o f th e y e a r .
Over a p e rio d o f fo u r
y e a rs 38. 6/0 o f th e p r e c i p i t a t i o n which f e l l betw een h a r v e s t and the n e x t
s p rin g was c o n se rv e d , 12.9% o f th e p r e c i p i t a t i o n betw een l a y and November
was saved and d u rin g th e second fa llo w w in te r from November th ro u g h A p r i l ,
17.3% was sav ed .
B e ll ( 2) a ls o found t h a t s o i l m o istu re in c re a s e d c o n sid ­
e ra b ly d u rin g the months o f low e v a p o ra tio n b u t made no a n a ly s is a s to th e
p e r c e n t o f p r e c i p i t a t i o n o r th e amount o f w a te r saved d u rin g v a rio u s p e r ­
io d s o f th e y e a r.
At Handan9 N o rth D ak o ta, T h y s e ll (24) found t h a t d u rin g th e p e rio d
from f a l l u n t i l s p rin g , some t i l l a g e tre a tm e n t's co nserved up to 36 p e r c e n t
o f t h e p r e c i p i t a t i o n which f e l l in c e r t a i n y e a r s .
There w ere however some
y e a rs when some tre a tm e n ts showed a lo s s i n s o i l m o istu re d u rin g th e d o r­
mant- p e r io d .
On th e a v e ra g e , fa llo w la n d saved o n ly ab o u t 10 p e r p e n t o f
th e p r e c i p i t a t i o n re c e iv e d from tim e o f h a r v e s t u n t i l s p rin g a t seed in g
tim ei
Over a p e rio d o f seven y e a rs a t F r o id , M ontana, Aasheim ( l ) found t h a t
i d l e o r s tu b b le land g a in e d a c o n s id e ra b le amount o f m o is tu re in th e s o i l
w hereas mowed s tu b b le o r c o m ground w ith a s h o r t s tu b b le g a in ed very
little .
T h is s tr o n g ly in d ic a te d t h a t snow which d r i f t e d in to th e s tu b b le
p la y e d an im p o rta n t p a r t in adding m o is tu re t o th e s o i l .
F l o r e l l (12) rec o g n ize d th e im p o rtan ce o f s tu b b le i n holding, snow f o r
m o is tu re c o n s e rv a tio n .
He su g g e ste d c u t t i n g s tu b b ie h ig h and to avoid g ra z
in g i n o rd e r to h o ld a s much snow a s p o s s ib le . ■A t H uron, S o u th D ak o ta, in
th e s p r in g o f 1937 he found t h a t th e s o i l in a t h i s t l e f i e l d was wet down
25 in c h e s more th a n i t was in th e f a l l , w hereas s o i l in b a re fa llo w was wet
15
o n ly an a d d itio n a l 8 inches*
He a ls o su g g e s ts t h a t snow c o v er n o t o n ly adds
w a te r to th e s o i l b u t a lso re d u c es e v a p o ra tio n o f m o istu re from th e s o il*
T h y s e ll (24) a ls o found t h a t b are g ro u n d . (w hether f a l l plow ed, fa llo w
o r c o m s tu b b le ) gained l e s s " s o il m o istu re d u rin g th e w in te r months th a n
ground covered w ith a g ra in stu b b le *
H is i n t e r p r e t a t i o n was t h a t s tu b b le
reduced r u n o f f , reduced s u rfa c e e v a p o ra tio n and h e ld snow to such an e x te n t
t h a t th e M o istu re Saving which s ta n d in g s tu b b le e f f e c te d overshadowed th e
lo s s o f w a te r w hich m ight r e s u l t from weed grow th a f t e r h a r v e s t.
Morgan and B e ll .(.17) re p o rte d t h a t snow r e ta in e d by s tu b b le and th e
low er r a t e o f e v a p o ra tio n d u rin g th e w in te r months g e n e r a lly r e s u lte d i n a
h ig h e r m o is tu re c o n te n t in th e s u rfa c e f o o t a t seed in g tim e on la n d p r e ­
p a re d by s p r in g plow ing th a n on t h a t which was f a l l plowed*
-
The snow which s tu b b le h o ld s i s p erh ap s th e c h ie f re a so n fo r more
m o istu re i n th e s o i l u n d er s ta n d in g s tu b b le b u t e v a p o ra tio n o f m o istu re
from u n p ro te c te d s o i l can be q u ite a fa c to r*
L eb ed eff (15) h a s s tu d ie d
s o i l m o istu re movements very e x te n s iv e ly and he e x p la in s how th e s e s o i l
m o is tu re movements ta k e p la c e p a r t i c u l a r l y a s th e y a p p ly t o e v a p o ra tio n
lo s s e s d u rin g p e rio d s o f co ld w eather as f o llo w s :
" I f d u rin g th e summer a
c o ld s p e l l comes on and th e s u rfa c e o f th e s o i l i s co o led o f f , a movement
o f w a te r in th e form o f vapor in to th e u p p er la y e r s may be o b se rv e d , th e
low er la y e r s o f th e s o i l lo s e th e r e f o r e p a r t o f t h e i r w ater*
With th e o n -
come o f a h o t s p e l l th e w a te r drawn up to th e s u rfa c e w i l l b e l o s t by th e
s o i l and th u s a c o ld s p e l l d u rin g th e summer n o t accompanied b y r a i n may be
in d u c iv e to a more e n e r g e tic d ry in g up o f th e lo w er la y e r s o f th e s o i l " ,
"The phenomenon o f th e movement o f w a te r from th e low er in to th e u p p er
16
l a y e r s d u r in g a c o ld s p e l l i n t h e summer tim e i s m ore d i s t i n c t l y n o t i c e a b l e
d u r in g t h e w i n t e r #
I n t h e w i n t e r tim e t h e u p p e r h o r i z o n s o f t h e s o i l a r e
g r e a t l y c o o le d o f f ; on .t h e o t h e r h a n d t h e d e e p e r l a y e r s p o s s e s s a com­
p a r a t i v e l y h i g h te m p e r a tu r e #
The v a p o r p r e s s u r e a d j u s t s i t s e l f i n a c c o r d ­
a n c e w i t h t h e t e m p e r a t u r e o f t h e s o i l a n d t h e d e e p e r down i t w i l l be
g re a te r”»
D uring th e w in te r o f 1914-1915 a t O dessa, R u s s ia , he found t h a t rough­
l y one q u a r te r o f an in c h o f w a te r moved from lo w er d e p th s and was l o s t in
th e form o f e v ap o ratio n # .
H ilg e m a n (1 4 ) r e p o r t e d t h a t a p p r o x i m a t e ly 1#3 i n c h e s o r 10 p e r c e n t o f
t h e w a t e r a v a i l a b l e i n t h e s o i l 5 d a y s a f t e r i r r i g a t i o n w as n o t p r e s e n t 55
days la te r#
I n t h e same a r e a h e fo u n d t h a t a f t e r 22 m o n th s h e h a d l o s t 47
p e r c e n t o f t h e w a t e r a v a i l a b l e a t th e b e g in n i n g o r 9#8 i n c h e s .
The im p o r ta n c e o f ' t h e am ount o f w a t e r s t o r e d i n t h e s o i l a t s e e d in g
t im e was e x p r e s s e d b y Q o le a n d M athew s (8 ) i n 1 9 4 0 .
T hey q u e s ti o n e d w h e th ­
e r a s o i l w e t t o l e s s t h a n I f o o t a t s e e d i n g tim e h h o u ld b e s e e d e d .
In
some l o c a l i t i e s t h e y q u e s ti o n e d w h e th e r 2 f e e t p r o v id e d a s a t i s f a c t o r y m a r­
g in o f s a fe ty #
P e n g fa (l8 ) s t a t e s t h a t th e r e a p p e a rs to be l i t t l e
w i t h i n t h i s subhum id a r e a i n p u t t i n g s e e d i n t o e x tr e m e l y d r y s o i l #
o b je c t
He
s u g g e s t s t h a t b y a v o id i n g t h e c o s t s o f s e e d i n g , h a r v e s t i n g , a n d s o f o r t h
d u r i n g y e a r s w i t h lo w s o i l m o i s t u r e r e s e r v e s , f a r m in g i n t h e G r e a t P l a i n s '
w o u ld b e r e l i e v e d o f much o f t h e u n c e r t a i n t y i n v o lv e d i n p r e s e n t p r a c t i c e s #
He f u r t h e r recom m ends t h a t m ore a t t e n t i o n b e g i v e n t o a d a p t i n g fa rm o p e r ­
a t i o n s t o com ply w i t h w e a t h e r and s o i l c o n d i t i o n s t h a t o c c u r fro m y e a r t o
y e a r.
,
'
L
-
f
17
H a lls te d and Mathews (1 3 ) in summing up. r e s u l t s w ith w in te r w heat in
K ansas found t h a t when see d in g was done in a d ry s o i l th e r e was o n ly one
chance in f o u r o f a y ie ld o f as much a s 10 b u s h e ls p e r a c re and no chance
o f a h ig h y i e l d 0
Ih e n o n ly th e f i r s t fo o t was w e t, th e chances were ab o u t
th r e e in fiv e ' t h a t th e y ie ld would be l e s s th a n 10 b u s h e ls p e r a c re and o n ly
one i n seven t h a t the y ie ld would be 20 b u s h e ls o r more p e r a c r e .
W ith '
w a te r in th e f i r s t 3 f e e t o r d e ep e r th e chance o f th e y ie ld f a l l i n g below
10 b u s h e ls was o n ly one i n t h i r t y - o n e and th e chances were n e a r ly seven in
e ig h t t h a t a y ie ld o f 20 b u s h e ls o r more would be produced*
They concluded
t h a t an adequate su p p ly o f w a te r a t see d in g tim e i s one o f th e g r e a te s t
a ss u ra n c e s o f a. crop and t h a t hopes o f o b ta in in g a good Crop i n s p i t e o f
p o o r c o n d itio n s a t se e d in g tim e a re n o t l i k e l y to be f u l f i l l e d *
P en g ra (18) h a s concluded t h a t w ith in th e subhumid a re a s o f .th e G re at
P la in s s e a s o n a l p r e c i p i t a t i o n i s r a r e l y g r e a t ' enough t o overcome a marked
s o i l m o istu re d e f ic ie n c y a t see d in g tim e .
^
He a ls o s t h t e s t h a t on G reat
P la in s s o i l s t h a t w i l l absorb and r e t a i n m o is tu r e , p rb s e a s o n a l p r e c i p i t a t i o n
ap p ears to be a t l e a s t as s i g n i f i c a h t ,in ' th e p ro d u c tio n o f sm all g r a in as
i s t h a t re c e iv e d d u rin g th e grow ing season*
He shows a h ig h e r c o r r e la tio n
f o r s e a s o n a l p r e c i p i t a t i o n and y ie ld th a n f o r p r e s e a s o n a l p r e c i p i t a t i o n and
y ie ld *
Under th e c o n d itio n s he s tu d ie d th e s e a so n a l p r e c i p i t a t i o n was h ig h .
The r e g r e s s io n c o e f f i c i e n t s o f y ie ld o f w heat in b u s h e ls on p re s e a s o n a l
and s e a s o n a l p r e c i p i t a t i o n were g e n e r a lly h ig h e r f o r p re s e a s o n a l p r e c i p i t a ­
tio n .
• D o u g h ty ,( I l )
c o n c lu d e d t h a t t h e i n c r e a s e i n y i e l d p e r. i n c h o f p r e c i p i -
t a t i o n w as o v e r o n e a n d o n e h a l f t im e s a s l a r g e a s t h e i n c r e a s e p e r i n c h o f
Zz
18
s to re d w a te r used*
C ole and Mathews ( 6 ) , how ever, had in d ic a tio n s t h a t
s o i l m o istu re and p r e c i p i t a t i o n w ere about e q u a lly e f f e c tiv e *
They fo u n d ,
how ever, t h a t y ie ld was more dependent on p r e c i p i t a t i o n th a n on s o i l
m o is tu re ; t h i s was due t o th e f a c t t h a t i n m ost y e a rs p r e c i p i t a t i o n g r e a t ­
l y exceeded th e s to r e d w a te r used from th e s o i l .
Some d if f e r e n c e o f o p in io n e x i s t s a s to th e w a te r re q u ire m e n ts o f
p l a n t s u n d er d i f f e r e n t l e v e l s o f f e r t i l i t y and s o i l m o istu re s t r e s s .
Thom.
i
and H o ltz ( 23) found t h a t any c o n d itio n which d i s t u r b s the, norm al lif e ,
p ro c e s s e s be i t s o i l , atm o sp h eric o r p a th o lo g ic a l th e w a te r re q u ire m e n ts
a re in c re a s e d to j u s t such a d eg ree a s th e norm al fu n c tio n in g s o f th e
p la n t a re d e p re s s e d .
They a ls o acc e p ted th e f in d in g s o f some o th e r i n ­
v e s t i g a t o r s t h a t c o n c e n tra tio n o f s o lu tio n i s a f a c t o r c a u s in g a v a r ia ­
t i o n in w a te r re q u ire m e n t, ,and t h a t w ith in th e l i m i t s o f c o n c e n tra tio n
in w hich p la n ts w i l l grow th e p la n ts i n th e more c o n c e n tra te d s o lu tio n
w i l l use th e s o i l m o istu re more e c o n o m ic a lly .
They concluded t h a t summer
f a llo w , by in c r e a s in g th e a v a i l a b i l i t y o f p la n t fo o d , in c r e a s e s th e
s tr e n g th o f th e s o i l s o l u t i o n and p e rm its a more econom ical use o f s o i l
w a te r by th e p l a n t s .
They found t h a t w heat grown in ta n k s , which were in
fa llo w th e p re v io u s y e a r , u sed 34% l e s s to produce a pound of d ry m a tte r
th a n d id th e same v a r i e t y o f w heat when' grown i n s o i l t h a t had produced
w heat th e p re v io u s y e a r .
S te p h e n s, Oveson and M itc h e ll -(22) found t h a t th e w a te r re q u irem en t
o f w heat grown i n uncovered p o ts a t Moro, Oregon, v a r ie d from 1075 pounds
o f w a te r p e r pound of d ry m a tte r on la n d which was cropped t t e p re v io u s
y e a r and re c e iv e d no f e r t i l i z e r to 725 pounds o f w a te r p e r pound o f d ry
19
m a tte r on la n d which was cropped th e p re v io u s y e a r b u t re c e iv e d 200 pounds
■of ammonium s u lp h a te p e r acre*
Wheat grown on fa llo w la n d had a w a te r r e ­
q uirem ent o f 848 poundso
D oughty, and o th e r s ( l l ) determ in ed th e w a te r re q u ire m e n t o f wheat on
fa llo w to be c o n s id e ra b ly l e s s th a n t h a t o f w heat on c o n tin u o u s c ro p p in g .
T h e ir w ork, w hich was done in open ta n k s , in c lu d e d e v a p o ra tio n and t r a n s ­
p ira tio n lo s s e s .
O n-fallow th e w a te r -requirem ent was 605 pounds p e r pound
o f d ry m a tte r and on c o n tin u o u s c ro p p in g i t was 806 pounds,
W adleigh and H ic h ard s (25) i n a p p r a is in g th e work done by a number o f
in v e s t i g a t o r s up to a r e c e n t d a te made th e fo llo w in g s ta te m e n t, " p re s e n t
d a ta seem to in d ic a te t h a t l a r g e d e c re a se s in.,grow th and y ie ld r e s u l t i n g
from d e f i c i e n c i e s o f n u t r i e n t s and m o istu re may cause o n ly nom inal i n ­
c re a s e s i n w a te r re q u ire m e n t.
Adequate d a ta a re n o t a v a ila b le fo r a
q u a n tita tiv e e v a lu a tio n b u t th e fo re g o in g evidence in d ic a te s t h a t th e
e f f e c t o f n u t r i e n t d e f ic ie n c ie s and s o i l m o is tu re s t r e s s on th e w a te r r e ­
q uirem ent i s s m a ll" .
I t h as been e s ta b lis h e d beyond a do u b t t h a t th e w a te r req u ire m e n t o f
p la n ts v a r ie s w ith s e a so n a l c o n d itio n s ,
D illm an (lO ) found a ran g e in
w a te r re q u ire m e n ts o f w heat from 533 pounds p e r pound o f d ry m a tte r to 531
p ounds.
D uring th e same 11 y e a r p e r io d , a l f a l f a v a rie d in i t s * w a te r r e ­
quirem ent from 602 to 1056 pounds,
Gole and Mathews ( 6 ) found t h a t so u th e rn s t a t i o n s r e q u ir e d more w a te r
to produce a pound o f d ry m a tte r th a n n o r th e r n s t a t i o n s ,
At Havre th e y r e ­
p o r t t h a t y ie ld s o f g r a in have r e s u l t e d from th e use o f l e s s th a n 4 ,5
in c h e s o f w a te r,
A t S c o tts b lu f f , N e b rask a , s i m i l a r y ie ld s re q u ire d 7 to 8
20,
in c h e s o f w a te r, w h ile a t D a lh a r t, T ex as, t o t a l f a i l u r e s . o f b o th g r a in and
s tra w have r e s u lte d from th e u se o f w a te r v a ry in g from 4 .1 2 to 9*46 in c h e s .
Doughty and o th e r s ( l l ) found t h a t th e w a te r re q u ire m e n t o f w h eat, in
a c o n tin u o u s cropping system under f i e l d c o n d itio n s , v a rie d from 391 to :£v.
2100 pounds.
The amount o f w a te r r e q u ir e d to p ro d u ce a pound o f g r a in v a r ie s mbre
th a n t h a t r e q u ir e d to produce a pound o f t o t a l d r y ‘m a tte r.b e c a u s e straw i s
o f te n produced w ith o u t p ro d u cin g g r a in ,
d o le and M athews' ( W r e p o r t t h a t
th e q u a n tity 'O f w a te r used b e f o r e 'a y ie ld o f g r a in i s o b ta in e d v a r ie s from
4 to 10 in c h e s i n th e G re at P la in s a r e a .
Each u n i t in c r e a s e o f w a te r con­
sumed above t h i s minimum a p p e a rs 1t o - r e s u l t i n a u n i t in crem en t o f y i e ld .
At S w ift C u rre n t Doughty and o th e rs ( l l ) fin d t h a t th e y ie ld o f g r a in
i s n i l . u n t i l th e w a te r used--exceeds ab o u t 4 .9 in c h e s , th e n i t in c re a s e s
a lm o s t- lin e a r ly a t th e r a t e of- 4 .7 b u s h e ls f o r each in c h -o f a d d itio n a l
w a te r.
F t1Om a n a ly s is o f work done a t D ick en so n , N o rth D ak o ta, b y D avis and
P a lle s e n (9) i t a p p e a rs t h a t f o r s p rin g w heat th e e f f e c t o f a d d itio n a l
r a i n f a l l . r a p i d l y d im in is h e s a f t e r h e ad in g tim e .
The g r e a t e s t b e n e f ic ia l
e f f e c t i s from r a i n t h a t comes d u rin g th e p e rio d when th e .,p la n t i s growing
m ost r a p id ly re a c h in g a maximum a b o u t 3 weeks b e fo re h ead in g o r 70 to 90
days a f t e r se e d in g .
E v a p o ra tio n ta k e s a trem endous t o l l o f s o i l m o is tu r e ,n o t o n ly d u rin g
th e fa llo w p e rio d b u t d u rin g th e tim e when p l a n t s a re growing on th e s o i l
a s w e ll.
T h y s e ll (24) r e p o r t s t h a t a t Mandan, N orth D ak o ta, th e w a te r r e ­
q uirem ent o f w heat grown on fa llo w was tw ic e a s h ig h a s f o r w heat grown in
21
covered p o t s ,
WSlton and W ilson (26) w orking w ith e v a p o ra tio n lo s s e s from
law ns and b a re s o i l in .O h io found t h a t a grow ing g ra s s co v er o f one inch in
h e ig h t d e c re a se d e v a p o ra tio n from th e s o i l by sh ad in g n e a r ly a s much a s i t
in c re a s e d th e t o t a l w a te r l o s s by t r a n s p i r a t i o n .
Most a u t h o r i t i e s on d ry la n d a g r ic u ltu r e ag ree t h a t w a te r i s g e n e r a lly
th e m ost li m i t i n g f a c t o r of p ro d u c tio n u n d er d ry lan d c o n d itio n s .
S in ce i t
i s so im p o rta n t i t seems v ery l o g i c a l t o assume th g t m uch,of th e f u tu r e d ry
la n d r e s e a r c h •w i l l be d i r e c t e d tow ard f e t t e r c o n se rv a tio n o f p r e c i p i t a t i o n
f o r p la n t u s e ,
Shaw - (2 0 ) s t a t e s t h a t , " I t i s e v id e n t t h a t th e re s e a rc h
f r o n t i e r o f growing w heat in th e G re at P la in s has n o t been, advanced sin ce
1915» .U n le s s .th e re s e a rc h f r o n t i e r i s advanced by borne in n o v a tio n ra d ­
i c a l l y a f f e c t i n g m o is tu re , average w heat y ie ld s i n th e G reat P la in s w i l l
n o t go much h ig h e r 61.
22
MATERIALS AHD METHODS
H o rth Montana Branch S t a t i o n , H a v re , Montana
The d ry la n d i n v e s t ig a ti o n s a t th e N o rth Montana B raneh S ta tio n i n "elude a group o f p lo ts r e f e r r e d to a s th e m o is tu re c o n s e rv a tio n o r "Me G0"
s e r ie s *
There a re s e v e r a l system s o r tre a tm e n ts i n t h i s s e r i e s and s e v e ra l
c ro p s a re grown*
I n t h i s stu d y o n ly th e s p rin g w heat p lo ts ..A , C9 and D
were u se d * ' The A p l o t i s c o n tin u o u s ly cropped to s p rin g w heat grown on
s p rin g plow ing, t h e O and D p l o t s a r e a l t e r n a t e l y cropped and fallo w ed w ith
th e G p l o t i n s p rin g w heat d u rin g th e even numbered years, and th e D p l o t in
eyop d u rin g th e odd numbered y e a r s .
The p e rio d in c lu d e d ' i n t h i s s tu d y c o v e rs th e crop y e a rs 1921 through
1945*.
D uring t h i s tim e s o i l m o is tu re sam ples were ta k e n on th e s e p l o t s by
f o o t d e p th s t o a d e p th o f fo u r f e e t a t s e v e ra l tim e s d u rin g th e y e a r .
The
p a r t i c u l a r s o i l m o istu re sa m p lin g s-u se d in t h i s p a p er were th o s e ta k e n a t
th e tim e o f crop emergence and th o s e ta k e n a t h a r v e s t tim e .
In th e e a se o f
fa llo w th e s o i l m o is tu re sam ples w ere ta k e n a t th e . same tim e a s th e sam ples
were ta k e n in th e A p lo t*
S o il m o is tu re sam ples were ta k e n w ith a King
s o i l tube and th e p e rc e n ta g e m o istu re p r e s e n t was d eterm in ed by d ry in g a t
IOO0 0, f o r 24 h o u rs .
B e ll and o th e r s have d eterm in ed t h a t th e w eig h t o f a .c u b ic fo o t o f
s o i l i n th e v i c i n i t y o f th e s e p l o t s w eighs &U9 pounds p e r c u b ic fo o t in
th e to p f o o t , 8 5 ,5 pounds in th e second f o o t , 9 3 ,4 pounds i n th e t h i r d f o o t
and 94,8 p o u n d s-in th e f o u r th f o o t .
By u s in g th e s e f ig u r e s to g e th e r w ith
th e p e rc e n ta g e o f m o is tu re p re s e n t th e amount o f w a ter p re s e n t in in c h e s was
d eterm in ed f o r each f o o t d e p th by c a lc u la tin g th e pounds o f w a te r p re s e n t
23
and c o n v e rtin g to inches*
P r e c i p i t a t i o n d a ta was ta k e n from th e a n n u al r e p o r t s o f th e N o rth
Montana B ranch S ta tio n w hich g iv e s p r e c i p i t a t i o n by days a s re c o rd ed in
r a i n gauges a t t h a t lo c a tio n *
G rain and s tra w y ie ld s were d eterm in ed on th e s e p l o t s by w eighing
b u n d le s h a rv e s te d w ith a g r a in b in d e r and w eighing th e th re s h e d 'g ra in *
S in c e th e g r a i n s tu b b le was n o t in c lu d e d in th e bundle w e ig h ts an a d j u s t ^ ment was made .in th e s tra w y ie ld s to com pensate f o r th is* . .$he average
h e ig h t o f g r a in i n a system o f c o n tin u o u s cro p p in g was 24 in c h e s and o f
g r a in grown on fa llo w was 29 in c h e s .
I t was e stim a te d t h a t a s tu b b le
h e ig h t o f 4 in c h e s was an a v erag e fo r t h e p e rio d and on I h i s b a s i s 14% was
added t o th e stra w y ie ld on fa llo w and 17% was added to t h e , straw y ie ld on
c o n tin u o u s cropping*
Ih e fo llo w in g t a b l e s lo c a te d i n th e ap p en d ix g iv e d e t a i l s p e r ta in in g
to th e d a ta used*
-
Table I*
S o i l m o is tu re sam pling d a tes*
T able I I .
In c h e s o f w a te r in v a rio u s f o o t d ep th s o f .s o i l a t .tim e .o f
crop emergence un d er a system o f c o n tin u o u s cropping*
Table I I I ,
In ch es o f .w ater i n .v a rio u s f o o t d e p th s o f s o i l a t h a rv e s t
. tim e under a system o f c o n tin u o u s c ro p p in g .
T able IT .
In c h e s .o f w a te r in v a rio u s f o o t d e p th s o f s o i l in s tu b b le
to be fa llo w e d Cat h a r v e s t time.)©
Table T,
/..inches o f w a te r in v a rio u s f o o t d e p th s o f s o i l i n s tu b b le
to be fa llo w e d ( a t tim e o f c ro p em ergence).
T able TI*
In c h e s o f w a te r in. v a rio u s f o o t d e p th s o f s o i l in fa llo w
( a t . h a r v e s t tim e )*
"
"
T able T H ,
I n c h e s .o f w a t e r .in v a rio u s f o o t d e p th s of s o i l in fa llo w
( a t t ime o f crop ,em ergence) i
24
T illa g e D em onstration F aun, CtLLbertson, M oatana0
At C u lb e rts o n th e r e w ere n in e d i f f e r e n t methods o f t i l l a g e , s tu d ie d in
a cro p fa llo w ro ta tio n ®
In a d d itio n to t h i s , th e r e w ere th r e e d i f f e r e n t
t i l l a g e methods employed in a two y e a r crop ™ one y e ar fa llo w system®
Y ie ld s o f g r a in and s tra w were o b ta in e d on a l l p l o t s by th e q u a d ra t
method®
Twelve Cmeter sq u are) q u a d ra ts were h a rv e s te d from e a c h plot®
The
stra w was c u t c lo s e to th e ground w ith hand s i c k l e s so n e a r ly a l l o f th e
stra w was harvested®
The b u n d le s were d r i e d , w eighed and th re s h e d and th e
y ie ld o f straw was determ ined by s u b tr a c ti n g th e w eig h t o f th e g r a in from
th e t o t a l w eight o f th e bundle®
S o i l m o istu re sam ples w ere ta k e n a t f o o t d e p th s w ith a King s o i l tu b e
to a d e p th o f f iv e f e e t on a l l fa llo w p l o t s in th e f a l l o f th e y e a r and
■s h o r t l y a f t e r see d in g i n th e spring®
S o i l m o istu re sam ples were a ls o ta k e n
i n th e f a l l and su cceed in g s p r in g , a f t e r th e f i r s t y e a r crop i n th e two
y e a r .c ro p - one y e a r fa llo w ro ta tio n ®
These s tu b b le sam ples were ta k e n in
th e same manner a s th o s e on fallow® . A ll p l o t s were sampled a t fo u r Ip c a * '
t i o n s and th e sam ples were d rie d f o r 24 h o u rs a t 100 d e g re e s centigrade®
The p e rc e n ta g e o f m o istu re i n th e s o i l sam ples was, d e te m irie d ' by u s in g th e
d ry w eight o f th e s o i l a s th e b a s i s o f determ ination®
The w eig h t o f an a c re fo o t o f s o i l was c a lc u la te d from one hundred
sam ples ■(ta k e n w ith , th e K ing s o i l tu b e) from each fo o t l e v e l to a d ep th o f
f i v e feet® . The K ing s o i l tu b e has a d ia m e te r o f 20 mm® o r c o v e rs an a re a
o f 5 o l4 l6 's q u a r e c e n tim e te rs which means t h a t th e re , a re 1 2 , 878,319 c o re
sam ples p e r acre® . The a v e ra g e w eight o f th e one hundred c o re sam ples p e r
f o o t o f s o i l and th e c a lc u la te d w eight o f each c u b ic f o o t o f s o i l , by
25
d e p th , i s g iv e n in th e t a b l e which f o llo w s s
A verage' .Weig h t
Core Samples
(Grams)
Depth
F i r s t ' fo o t
Second f o o t
T hird fo o t
F p h rth fo o t
F if th fo o t
Average W eight
P e r Cubic Foot
(Pounds?
116126
145
75
82
94
105
115
158
.174
The p e rc e n ta g e o f w a te r in th e s o i l was c o n v erted to in c h e s by f $ r s t
g e t t i n g th e w eight o f th e w a te r p r e s e n t and th e n c a lc u la tin g th e d e p th i n
in c h e s .
The c a lc u la tio n s from pounds of w a te r t o in c h e s was on th e b a s is
t h a t one a c r e in c h o f w a te r w eighs 226,512 pounds.
The f i g u r e s used f o r th e amount o f m o is tu re p r e s e n t i n fa llo w were
a r r iv e d a t b y ta k in g a n av erag e o f th e lB p l o t s in Ih e crop - fa llo w rotaA
tio n s ,
Only f o u r s tu b b le p l o t s were sampled f o r m o is tu re each y e a r and th e
s o i l m o is tu re f ig u r e s f o r .s tu b b le la n d were ta k e n from th e s e sam p lin g s.
An a u to m a tic re c o rd in g r a i n g au g e, i n s t a l l e d a t ' th e D em o n stratio n
Farm, was used to m easure p r e c i p i t a t i o n d u rin g th e months o f A p ril th ro u g h
O ctober in c l u s i v e .
P r e c i p i t a t i o n f i g u r e s . f o r th e r e s t o f th e y e a r a re from
th e re c o rd s o f Mr,, Whitcomb; W eather O b serv er a t G u lb e rtsoil,
C u lb e rtso n i s
ro u g h ly te n m ile s s o u th w est o f th e D em o n stratio n Farm,
• For a d d i t i o n a l in fo rm a tio n o h 'a c tu a l t i l l a g e methods u sed in the. work
a t C u lb e rts o n , r e f e r t o Montana E xperim ent S ta tio n B u l le tin 468,
26
EZPEHiHEKfTAL RESULTS
N orth Montana Branch S t a t i o n , H avre, Moatana
E allow
A v e ry com plete re c o rd o f s o i l m o istu re sam pling a t Havre made p o s s i^
b le a s tu d y o f s o i l m o is tu re c o n d itio n s which e x is te d d u rin g 25 c o n se c u tiv e
years*
The t a b l e s which fo llo w g i v e , th e amount o f m o is tu re p r e s e n t a t
v a rio u s d a te s o f sam pling d u rin g t h e 'f a l l o w s e a s o n . T able 1 5 th e amount o f
w a te r g a in e d o r l o s t betw een sam pling d a te s .8 T able I I ; th e in c h es o f p r e ­
c i p i t a t i o n betw een sam pling d a t e s , T ab le I I I ; and th e p e r c e n t o f p r e c ip ­
i t a t i o n conserved in th e s o i l betw een sam pling d a te s , T able IV*
T ables I 8?I I , I I I , and IV a re q u i t e s e lf - e x p la n a to r y b u t some th in g s
in c lu d e d in them sh ould be em phasized.
Table I I I . g iv e s th e d i s t r i b u t i o n o f p r e c i p i t a t i o n d u rin g th e fa lld w
p e rio d and T ab les I ,- I I , and IV show how much and what p e rc e n ta g e o f the
p r e c i p i t a t i o n was co n serv ed d u rin g ;th e th r e e i n t e r v a l s in to which th e f a l ­
low p e rio d i s d iv id ed *
The fa llo w p e rio d i s d iv id e d in to th e fo llo w in g
th r e e c o n se c u tiv e , in te r v a ls *
( l ) th e f i r s t i n te r - c r o p i n t e r v a l o r th e in ­
t e r v a l betw een h a r v e s t and th e tim e o f cro p emergence on la n d seeded to
s p rin g g r a i n , ( 2.) th e i n t e r v a l betw een th e crop emergence d a te and h a r v e s t
and (3) th e second i n t e r - crop i n t e r v a l o r th e i n t e r v a l betw een h a r v e s t and
th e emergence o f s p r in g g rain *
These th r e e i n t e r v a l s , f o r la n d .n o t in c ro p ,
a re s e t up in t h i s way so a s to c o in c id e w ith d a te s ^ h ie h w ere used in t a k ­
in g s o i l m o is tu re sam ples from p l o t s t h a t a re cropped*
■ The p r e c i p i t a t i o n d u rin g th e summer p e rio d i s s l i g h t l y l e s s th an d u r­
in g th e w in te r p e rio d b u t. th e amount o f m o istu re co n serv ed i s much l e s s d u r-
27
Table I .
In c h e s o f w a te r in the. s o il..to a d ep th o f 4 f e e t a t d i f f e r e n t
tim e s o f sam pling C and D p l o t s in M. C. S e r i e s , a t H av re,
Montana*
Y ears
1919- 20-21
1920- 21-22
1921-22-23
1922-23-24
1923-24-25
1924-25-26
1925-26-27
1926- 27-28
1927-28-29
1928-29-30
1929-30-31
1930-31-32
1931-32-33
1932-33-34
1933-34-35
1934-35-36
1935-36-37
1936-37-38
1937-38-39
1938-39^40
1939-4.0-41
1940—41—42
1941-42-43
1942—43—44
1 943-44-45
Average
P lo t
,
.
D
0
D
0
D
C
D
C
D
G
B
G
D
G
D
G
D
■. 'G
B
.0
B
d
B
G
B
...Stubble .
F aH
S p rin g
5.031
5.62
5 .7 1
4.8 7
5 .6 1
6.21
5>32
5.49
6.69
5 .9 ?
. 4 .5 1
6.02
W
5.88
5 .6 4
5 .7 1
5 .9 4
4.89
5 .2 9
5 ,3 8
4 .6 3
5 .1 8
6.40
6.00
4 .7 6
5 .6
.
Sr. 09
6.98
7 .9 7
6.58
6.00
6.78
7 .6 1
1 0.54
6,98
8 .7 8
7 .6 2 .
6.8 4
6.25
8 .5 3
8 .1 0
9 .0 3
5 .2 6
5 .8 8
5 .9 5
5 .3 2
9.15
6 .0 7
8.43
6 .8$
5 .7 9
7 .3
... .Fallow
F a ll
S p rin g
8 .4 4
7 .9 1
'7 .6 0
9.6 1
7 .0 1
8.2 0
6 .5 0
1 0.77
9.09
9 .0 3
7 .7 1
6.85
8 .3 7
7.30
9 .3 4
8 .0 5
4 .8 6
8 .0 6
- 7 .8 5
6 .12
7 .5 9
7 «,42
9 .5 8
7 .8 0
6 .2 4
9 .1 2
9.19
8.0 6
8.9 6
8.45
9.7 9
11.73
9 .6 6
9 .9 1
10.20
8.05
8.22
10.42
9.7 9
9.9 0
8.38
6.25
8.52
8.37
7.9 7
9 .2 1
10.43
9 .9 2
,8 .4 7
7.14
7 .9
9 .1
28
T able II*
Y ears
1919-20-21
1920-21-22
1921-22-23
1922-23-24 ,
1923-24-23
1924-25-26
1925-26-27
1926-27-28
1927-28-29
I 928- 29- 3O
1929-30-51
1930-31-32
1931- 32-33
1932-33-34
1933-34-35
1934-35-36
1935-36-37
1936-37-38
1937-38-39
1938-39-40
1939-40-41
1940-41-42
1941-42-43
1942-43-44
1943^44-45
Average.
In c h e s o f w a te r gained o r l o s t betw een ' sam pling d a te s and th e
t o t a l g a in ed d u rin g th e fa llo w p e rio d o f a p p ro x im a te ly 21
m onthsj 0 and D p l o t s in Mo C, S e r ie s a t H av re, Montana*
P lo t
D
C
D
G
D
C
b
G
D
0
D
0
D
G
D
C
D
0
D
C
D
G
D
G
D
S tu b b le
T h ll to S p rin g
0 .4
0 .9
—0 .4
3^0
1 .0
1 .4
■pl.l
0 .2
2 .1
0 .3
0 .1
. 0 .0
2 .1
—1 .2
0 .2
- 1 .0
- 0 .4
2.2
1 .9
0 .8
- 1 .6
1 .4
1 .2
0.90 .5
3 .1
1 .4
2 .3
1 .7
0 .4
0*6
2 .3
5 .1
0 .3
2 .9
3 .1
0*8
- 0 .2
2 .7
2 .5
3 .3
- 0 .7
1 .0
. 0 .7
- 0 .1
• 4 .5
0 .9
2 .0
0 .9
1 .0
1 .7
Fallow
S p rin g to F a l l
'
0 .6
F allow
F a l l to S p rin g
067'
1 .3
Qi5
-047
1.4- .
1 .6
5 .2
—lie11 '
o ;8
1 ,2
0 .3
1 .4
2 .0
2,5.
U 6 .
0*3
1 .4
. oa5
0 .5
1 .9
1 .6
3 .0
0 .3
0 .7
0 .9
1 .2
T o ta l
4.23»6
2 .4
4 .0
2.83 .6
6 .4
4 .2
3 .2
4 .4
3 .5
2 .2
3 .9
4 .0
4 .3
2 .6
0.3'
3 .7
3 .1
2 .6
4 .5
5 .3
3 .5
2 .5
2 .4 .
3 .5
29
T able I I I .
In ch es o f p r e c i p i t a t i o n betw een s o i l m o istu re sam p lin g s.. d u r­
in g th e " fa llo w p e rio d o f a p p ro x im a te ly 21 months a t H avre,
M ontana.
T ear
P lo t
1919-20-21
1920-21-22
1921-22-23
1922-23-24
1923-24-25
1924-25-26
1925-26-27
1926-27-28
1927-28-29
1928-29-50
1929-50-31
1930-31-32
1931-32-33
1932-33^34
1933-34-35
1934-35-36
1935-36-37
1936-37-38
1937-38-39
1938-39-40
1939-40-41
1940-41-42
1941-42-43
1942-43-44
1943-44-45
D
C
D
G
D
G
D ' x
C
D
G
D
G
D
0
' D
G
D
C .
' B
G
D
0
B
G
B
Average
F a ll
to
S p rin g
S p rin g
to
F a ll
5o>
7 .6
7 .1 4 .9
6 .5
6 .4
7 .8
.12.6
4 .5
7 .2
7 .3
5 .2
6. 6
. 7 .3
9 .7
7 ,9
3 .3
. 4 .9
. 4 .3
5 ,0 .
7 .8
6 .1
7 ,4 6.3 .
2 .8
4 .2 •
5 .7
3 .7
9 .9
6 .8
7 .5
2 .6
8 .0
7 .4
3 .9
2 .7
3 .4
7 .5
3 .8
3.8,
2 ,7
2.Q
6 .9
7 .7
6 ,7
3 ,5
5 .5
8 .7
7.6,
7 ,8
6 .6
5 .6
F a ll
to
S p rin g
7 .6
7 .1
4 .9
6 .5
6 .4
7 .8
12,6.
4 .5
7 .2
7 ,3
5 .2
6 .6
7 .3
9 .7
7 .9
3 .3
4 .9
6 ,3
5 ,0
7 .8
6 .1
7 ,4
6 .3
2 .8
3 .8
6. 5:
T o ta l
.
1 7 .7
2 0 .4
1 5 .7
21 .3
1 9 .7
21 .7
23 .0
2 5 .1
1 9 .1
l8 04,
1 5 .2
1 5 .2
2 1 .4
20.8
2 1 .4
1 3 .9
1 0 .2
1 8 .1
1 9 .0
1 9 .5
1 7 .4
1 9 .0
2 2 .4
1 6 .7
1 4 .4
1 8 .7
30
T able IV.
P e rc e n t o f p r e c i p i t a t i o n co nserved in th e s o i l between s o i l
m o is tu re s a m p lin g 'd a te s d u r in g .th e fa llo w p e r io d o f approx­
im a te ly 21 m onths, Havre., M ontana,
P lo t
S tu b b le
F a ll.to
S p rin g
1919-20-21
D
1920-21-22
.0
1921-22-2?
D
1922-23-24
C
D
1923-24-25
0
1924-25-26
D
1925-26-27
1926-27-28
G
D
1927-28-29
0
1928-29-30
B
1929-30-31
0
1930-31-32
D
1931-32-33
G
1932-33-34
D
1933-34-33
G
1934^35-36
D
1935-36-37
1936-37-38
.0
1937-3.8-39 ■ D
G
1938-39^40
1939-40-41 '
D
1940-41-42.
G
D
1941-4.2-43
G
1942-43-44
D
1943-44-45
5 2 ,5
.11,8
32,3
34.7
. 6 ,1 .
.9.4
2 9 .4
.40.4
.6.7
4 0 .2
4 2 .5
1 5 .4
- 3 .0
3 6 .9
25.7
4 1 .7
-2 1 .2
2 0 .0
1 1 .1
- 2 .0
5 7 .7
1 4 .8
27.0
1 4 .3
35.7
Y ear
Average •
■
2 5 .7
Fallow
S p rin g
to F a ll
Fallow
F a l l ’ to
S p rin g ■
^Average
fo r
Fallow
P e rio d
9 .5
1 5 .8
-1 0 .8
30 .3
1 4 .7
1 8 .7
-4 2 .3
2 .5
2 8 .4
7 .7
3 .7
0 .0
2 8 .0
-3 1 .6
'5.3
- 3 7 .0
-2 0 .0
3 1 .9
2 4 .7
1 2 .0
-4 3 .7
2 5 .5
13 .8
1 1 .8
6 .4
9 .2
1 8 .3
1 0 .2 . ,,
-1 0 .8
21 .9
2 0 .5
4 1 .3
-2 4 .4
1 1 .1
l6 .4
5 .8
21.2
2 7 .4
25.8
2 0 .3
94
2 8 .6
7 .9
1 0 .0
2 4 .4
2 6 .2
4 0 .5
4 .8
2 5.0
2 3.7
23.717 .6
15 .2
1 8 .7
..!4*2
16. 5 '
21.8
16. 7 ,
1 6 .7
23 .9
2 3 .0
1 4 .4
18 .2
19 .2
20 .0
1 8 .7
2.9
2 8 .4
1 6 .3
13.3
25.8
27.8
15 .6
14 .9
1 6 .6
•
io .7
‘ 1 8 .5
= IU 'j
^ A v e ra g e s c a l c u l a t e d fro m t a b l e s I I a n d I I I ,
1 8 .7
31
in g th e ' summer.
Table I I shows 1 ,7 in c h e s o f m o istu re co n serv ed in s tu b b le
from h a r v e s t u n t i l th e fo llo w in g s p rin g and o n ly 0 ,6 o f an in c h conserved
i n fa llo w d u rin g th e summer m onths.
In b a re fa llo w 1 ,2 in c h e s o f m o is tu re
was co n serv ed betw een h a r v e s t tim e i n th e f a i l and th e fo llo w in g s p r in g .
Table. IV f u r t h e r em phasizes t h a t a g r e a t e r p e rc e n ta g e o f m o is tu re i s con­
se rv e d d u rin g th e w in te r months th a n d u rin g th e summer months and t h a t t h i s
i s e s p e c ia ll y t r u e when s tu b b le i s s ta n d in g in th e field ,* i
T ab les I I and I I I a ls o f u r n is h a b a s is f o r d eterm in in g th e p e rc e n ta g e
o f p r e c i p i t a t i o n conserved betw een th e s o i l m o istu re sam pling d a t e s .
Dur­
in g th e f a l l to s p rin g p e r io d , im m ed iately fo llo w in g h a r v e s t, t h e r e was an
a v e ra g e o f 6 ,6 in c h e s o f p r e c i p i t a t i o n , o f which 1 ,7 in c h e s o r 25,87»'was
c o n se rv e d , in th e s o i l .
D uring th e summer months th e r e was 5»6 in c h e s o f
p r e c i p i t a t i o n o f which 0 ,6 o f an in ch was co nserved o r 10.7%*
The fo llo w ­
ing, w in te r when th e lan d , was b a re 1 ,2 in c h e s were co n serv ed o f th e 6 .5
in c h e s o f p r e c i p i t a t i o n re c e iv e d o r 18.4%.
D uring th e e n t i r e fa llo w p e rio d
th e r e was an av erag e of 18*7 in c h e s o f p r e c i p i t a t i o n of which 3 ,5 in c h es
were c o n se rv e d o r 18. 7%.
T ab les I , I I , and IV in d ic a te t h a t s o i l m o istu re was a c t u a l l y l o s t
d u rin g some p e r io d s .
T his i s p ro b a b ly due t o a c e r t a i n : e x t e n t to' e r r o r s
in sam pling b u t may a ls o be due i n p a r t to weed grow th o r se v e re evapora­
tio n lo s s e s .
Low m o istu re c o n s e rv a tio n i s a s s o c ia te d w ith low p r e c i p i ­
t a t i o n , and i t i s p o s s ib le t h a t d u rin g some p e rio d s th e r e was a c t u a l l y more
m o is tu re l o s t from e v a p o ra tio n th a n was re c e iv e d in p r e c i p i t a t i o n .
The h ig h te m p e ra tu re s d u rin g th e summer m onths, which in c r e a s e ev ap o ra­
t i o n r a t e s , a re no doubt l a r g e l y r e s p o n s ib le fo r th e low m o istu re c o n se rv e -
32
T a b le V.
I n c h e s o f w a t e r a v a i l a b l e t o t h e s p r i n g w h e a t c r o p grow n on
f a l l o w i n C a n d B p l o t s a t H a v r e , M o n ta n a , d u r i n g p e r i o d 1 9 2 1 -
1945.
T ear
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
A verage
W ater i n s o i l
when crop
■ emerged
In ch es
W ater i n s o i l
a f te r h a rv e st
In ch es
-Water used
from ' th e
s o il
. In ch es
8 .5
. 7 .1 '
5 .7
4 .5
5 .6
6 .2
5 .3
5 .5
6 .7
5 .9
4 .5
6 .0
6 .5
5 .9
5 .6
h a il
5 .9
4 .9
5 .3
5 .4
4* 6
5 .2
6 .4
6 .0
4 .8
5.Q
5 .0
3 .4
4 .5
2 .5
2 .8
3 .2
-4.5
5 .0
3 .8
' 5 .4
4 .2
1 .6 .
2^3
" 4."8
h a il
4 .0
3 .5
- 1 .0
3 .1
3 .8
2 .8
2 .8
4 .4
5 .1
3 .5
2 .1
9*0
5 .5
9 .1
9 .2
8 .1
9 .0
8 .5
9 .8
ii.7
9 .7
9 .9
. .1 0 .2
8 .1
8 .2
. 1 0 .4
h a il
9.9
8 .4
6 .3
8 .5
8 .4
8 .0
9 .2
1 0 .4
.
.
3.-5
P r e c ip 0
S p rin g to
h a rv e st
Inches
.
5 .7
3 .7
9 .9
6 .8
7 .5
2.6
8 .0
7 .4
3 .9
2 .7
3 .4
7 .5
);8
h a il
2 .7
2 .0
6 .9
.7 .7 6 .7
3 .5
5 .5
8 .7
7 .6
7 .8 ,
4 .0 ■
5 .7
T o ta l w a te r
used in
e v a p o ra tio n
an d . tr a n s p .
In ch es
'
9 .1
8 .0
1 2 .4
9 .6
1 0 .7
6. 9
13 .0
1 1 .2
9»3
6.9
5 .0
9.8
8 .6
h a il
6 .7
5 .2
7 .9
10 .0
1 0 .5
6 .3
8 .3
13 .1
1 2 .7
11.-3
6*1
9 .2
,
33
T able T I .
T ear
1921
1922
1925
1924
1925
1926
1927
1928
1929
1930 . ■■
1931
1932
1932
1934
1932
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945..
A verage,
S p rin g w h e a t"p r o d u c tio n ,.. g ra in " and,:s tra w , on fallo w ed la n d in
0 and D p l o t s , Me . C. S e r i e s , a t H av re, M ontana, 1921-1945»
Y ield g r a i n p e r a c re
Bue
19.Q
12» 2
20o0.
19o0 .
18»5
1 3 .5
37.7
41» 2
12» 7
He 3
2 .0
27» 2
. 1 2 .8
h a il
1 3 .2
0 .3
2 .2
2 2 .7
9 .8
1 0 .8
1 9 .3
24.2
3i»3
3 1 .2
9 .0
1 7 .9 . . .
Y ie ld g r a in
p e r T acre
L b s.
Y ie ld straw
p e r a c re
L bs9
1140"
732
1200
1140
, 1110
.810
2262
2478
942
678
180
1622
768
■ h a il
792
18
33Q
1262
288
648
1128
1452
18781872
540
2000
1010
3100 '
2460
2610
1880 2190 1
'4070
2180
''!Ll 60 ^ "
310
2990
1340
h a il
700
410
.420
•2320
2240
970
1870
2960
4470
3060
.810
2028
.. 1071
T
Y ie ld "g r a in
and stra w
p e r .a c re
L bs.
3140
1742
4300
3600
3720
26?Q
4452
6548
3122
1828
490
4622
2108
h a il
1492
428
720
4712
2928
1618
3028
4412
6248
4952
1220
3099
34
t i o n d u rin g t h a t p e r io d .
The p e rc e n ta g e o f p r e c i p i t a t i o n saved in fa llo w d u rin g th e summer
months was much more h ig h ly c o r r e la te d w ith th e t o t a l p r e c i p i t a t i o n r e ­
c e iv e d th a n was th e p e rc e n ta g e sav e d d u rin g th e w in te r m onths.
The c o r­
r e l a t i o n betw een p r e c i p i t a t i o n in in c h e s and th e p e rc e n ta g e o f w a te r saved
d u rin g th e . summer months was ,726 and f o r th e two w in te r p e rio d s i t was
,420 and .4 1 2 .
T his was no doubt b ecau se a much s m a lle r p ro p o r tio n o f
m o is tu re was l o s t by e v a p o ra tio n d u rin g th e summers when p r e c i p i t a t i o n was
r e l a t i v e l y h ig h th a n d u rin g summers when p r e c i p i t a t i o n was r e l a t i v e l y low .
E v a p o ra tio n i s l e s s o f a f a c t o r and i s more v a r ia b le d u rin g w in te r months
and t h e r e f o r e th e p e rc e n ta g e o f w a te r saved i s n o t in flu e n c e d a s much by
th e amount re c e iv e d .
The amount of w a te r a v a il a b le to th e w heat crop grown on f a llo w , in
th e 0 and D p l o t s , i s g iv e n in T a b le .V ,
T h is f ig u r e is . d e riv e d by ad d in g
th e p r e c i p i t a t i o n from emergence u n t i l h a r v e s t to th e amount o f m o istu re
u sed from th e s a i l .
T his m o is tu re , o f c o u rs e , i s n o t a l l ,used by th e w heat
p la n t because some o f i t i s l o s t th ro u g h e v a p o ra tio n .
T his t a b l e shows t h a t a n average, o f 9 .2 in c h e s o f m o is tu re was a v a i l ­
a b le p e r y e a r to th e s p r in g w heat crop o f'w h ic h 2 .5 in c h e s came from th e
s o i l and 3«1 in c h es was in th e form o f r a i n f a l l , . C e r ta in ly some of th e
.
!
r a i n f a l l was l o s t by e v a p o ra tio n , and p e rh a p s a l i t t l e o f t h e s o i l m o is••
,
,
.....
.
■
-
.
-
-
t u r e , S3 n o t a l l o f t h e 9*2 in c h e s was tr a n s p ir e d th ro u g h th e c ro p .
The p ro d u c tio n o f g r a in and s tra w , i b r th e same p e r io d , i s g iv e n in
T ab le TL0
No g r a in o r straw y ie ld s a re g iv e n f o r th e y e a r 1924 because o f
h a i l damage to th e c r o p .
F o r th e same re a s o n no d a ta i s given in T a b le V
35
fo r th a t y e a ro
D uring t h e 24 y e a r s , f o r which y ie ld s a re g iv e n , th e a v e ra g e y ie ld o f
w heat was 1 7 .9 b u sh e ls p e r a c r e o f 1 0 7 1 'l b s . ,v The stra w y ie ld f o r th e same
p e rio d av erag ed 2028 pounds which i s a r a t i o o f 1 .9 pounds o f stra w to I
pound o f g r a in .
The a v e ra g e y ie ld o f 17.9 b u s h e ls p e r a c re was produced w ith an aver=
age o f 9*2. in c h e s o f w a te r w hich means t h a t a lm o st 2 b u s h e ls o f g r a in were
produced p e r in ch o f w a te r a v a i l a b l e .
As p r e v io u s ly m en tio n ed , some o f th e
9 .2 in c h e s o f w a te r was l o s t th ro u g h e v a p o ra tio n d u rin g th e grow ing seaso n
and some p o r ti o n o f t h i s a ls o would be l o s t th ro u g h weed gro w th .
The t o t a l g r a in and s tra w y ie ld f o r th e p e rio d av erag ed 3099 pounds ,
p e r a c r e w hich means t h a t one a c r e in c h o f w a te r produced 341 pounds of
g r a in and s tra w o r t h a t 664 pounds o f w a te r were r e q u ir e d to produce one
pound.
T his v a lu e i s on an a i r d ry b a s i s , th e g r a in had p e rh a p s 12% m ois­
tu r e and th e straw would no doubt be a l i t t l e d r i e r .
.Since th e straw com- .
p r i s e s ro u g h ly tw o - th ir d s o f t h e t o t a l y ie ld th e m o is tu re i n the. g r a in and
s tra w combined would p ro b a b ly have approached 10%.
I f th e 10% i s s u b t r a c t ­
ed from th e t o t a l w eig h t p ro d u c e d , th e n 307 pounds o f d r y m a tte r was p ro ­
duced by one a c re in c h o f w a te r and ap p ro x im a te ly 737 pounds o f w a te r were
r e q u ire d to produce one pound o f d ry m a t e r i a l .
"All o f t h i s w a te r was n o t
tr a n s p ir e d by th e crop B ecause some i s l o s t th ro u g h e v a p o ra tio n .
W ater r e ­
q u irem en ts w ith a llo w an ces f o r e v a p o ra tio n a re g iv en l a t e r .
The s o i l m o is tu re a t t h e tim e th e crop emerged h as av erag ed 9 .0 in ch es
and th e crop h as u sed 3*5 in c h es o f t h i s a s an av erag e d u rin g th e y e a rs
s tu d ie d w hich means t h a t 5 .5 in c h e s o f w a te r have rem ained in - th e s o i l , see
36
TSible Y0
The a v erag e p r e c i p i t a t i o n d u rin g th e p e rio d from cro p emergence
u n t i l h a r v e s t was 5»7 in c h e s which would su g g e st t h a t th e crop y ie ld was
more dependent on r a i n f a l l th a n i t was on s o i l m o istu re a t se e d in g tim e .
A n a ly s is o f $he d a ta b e a rs t h i s o u t.
The c o r r e l a t i o n betw een p r e c i p i t a ­
t i o n d u rin g th e grow ing seaso n and cro p y ie ld was ,680 w h ile th e c o r r e la ­
t i o n betw een in c h e s o f s o i l ,m o istu re a t th e tim e th e crop emerged and y ie ld
was o n ly 'o 4 7 2 0
The c o r r e l a t i o n betw een June p r e c i p i t a t i o n and y ie ld was
«521 and between- l[ay p r e c i p i t a t i o n and y ie ld i t was «419*
T h is m ig h t le a d one to assume t h a t s o i l m o istu re s to r e d was n o t
im p o rta n t; t h i s , o f c o u rs e , i s n o t th e c a s e .
The re a so n f o r th e h ig h e r
c o r r e l a t i o n betw een p r e c i p i t a t i o n and y ie ld i s t h a t s e a s o n a l p r e c i p i t a t i o n
c o n t r i b u t e s .more t o t a l in c h e s , i s more v a r i a b l e , and i s e s s e n t i a l fo r crop
p ro d u c tio n *
The c o r r e la tio n betw een growing seaso n p r e c i p i t a t i o n , p lu s s o i l m ois­
tu r e when th e crop em erged, wa& *834 in d ic a tin g t h a t m o i s t u r e .i s th e p r i n ■ •
.
..
C ip a l f a c t o r i n f l u e n c i n g c r o p y i e l d s on f a l l o w a t H avre*.
I t was p r e v io u s ly m entioned t h a t o n ly 3*5 in c h e s o f .th e 9 in c h e s o f
s o i l m o istu re was used by th e crop which le a v e s 5*5 in c h e s o f m o istu re in
th e s o i l which was n o t a v a il a b le to th e crop*
By u sin g m u ltip le r e g r e s s io n
to compute th e r e g r e s s io n o f y ie ld on s o i l m o istu re above 5*5 in c h e s , and
s e a s o n a l p r e c i p i t a t i o n i t was d e term in e d t h a t an in c h o f s o i l m o istu re
a c t u a l l y h a s more in flu e n c e on c ro p y ie ld th a n h a s an in c h o f p r e c i p i t a t i o n .
A f te r th e crop has used enough m o istu re f o r g r a in p ro d u c tio n to b e g in , th e n
each in c h o f s o i l m o is tu re above 5*3 in c h es in th e s o i l w i l l t h e o r e t i c a l l y
produce 4*39 b u s h e ls and each in c h o f p r e c i p i t a t i o n w i l l produce 3*15
31
b u s h e ls .
T h is co u ld in d ic a te th e n t h a t an in c h o f p r e c i p i t a t i o n i s only
727» a s e f f e c t i v e a s a n in c h o f s o i l m o is tu re .
These r e l a t i o n s h i p s do n o t
alw ays h o ld a s i s shown in ta b le -"V II, w hich g iv e s th e p r e d ic te d crop y ie ld
u s in g th e above f ig u r e s a s a b a s is f o r p r e d ic tio n .
By l i n e a r r e g r e s s io n i t was d eterm in ed t h a t th e y ie ld o f g r a in in
b u s h e ls p e r a c r e , on fa llo w , was e q u a l t o 4,1 7 tim e s th e in c h e s o f s o i l
m o istu re above
in ch es I a t th e tim e th e c ro p emerged) p l u s 3 « 2 .
I t was
a ls o determ ined t h a t y ie ld was e q u al to 3*07 tim e s th e p r e c i p i t a t i o n from
crop em ergence u n t i l h a r v e s t p lu s 0 ,4 o r Y = 0 ,4 ^ 3,07%,
S e v e ra l com b in atio n s o f s o i l m o is tu re and p r e c i p i t a t i o n were used in a
m u ltip le r e g r e s s io n w ith y ie ld in o rd e r to d eterm in e which com bination
would r e s u l t in a p r e d ic te d y ie ld c l o s e s t to th e a c tu a l y i e l d .
One o f th e
co m b in atio n s t r i e d was p r e c i p i t a t i o n from emergence to h a r v e s t and s o i l
m o istu re used w ith y i e l d ,
A nother was p r e c ip ita tio n " f r o m emergence up to
2 weeks p r i o r to h a r v e s t and s o i l m o istu re used w ith y i e l d .
The c lo s e s t
p r e d ic te d y ie ld was d e riv e d by u s in g s o i l m o istu re above 5 * 3 .in c h e s a t
emergence and p r e c i p i t a t i o n from crop emergence u n t i l h a r v e s t tim e .
The
c o r r e l a t i o n betw een s o i l m o istu re a t emergence and y ie ld was ,472 w h ile th e
c o r r e l a t i o n betw een s o i l m o istu re used each y e a r and y ie ld was o n ly ,353*
These a n a ly s is th e n in d ic a te t h a t th e amount o f m o istu re p re s e n t in th e
s o i l in th e s p rin g o f th e y e a r has had more b e a rin g on crop y ie ld th an h as
th e a c t u a l amount used by th e c ro p .
I t was p re v io u s ly m entioned t h a t a c e r t a i n amount o f w a te r was used
.*
by th e crop b e fo re any g r a in was produced..
'•
-
S o lv in g .th e r e g r e s s io n e q u a tio n
Y - ^ / b (% " X) when Y e q u a ls y ie ld in b u s h e ls p e r a c r e . an& f e q u a ls th e
38
T able 711»
A c tu a l and p r e d ic te d y ie ld s o f s p rin g w h eat.o n fa llo w a t" H a v re $
Montana**
■ 'i ■,
Year
1921
1922
1923
1924
1925
1926
1927
1928 .
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1943
S o il .
m oist*
above
3*3 in in c h e s
3 .6
3 .7
P re c i p .
S p rin g
to ‘
H a rv e st
In ch es
3 .4
3 .0
4*3
6*2
4 .2
4 .4
4*7
2*6
2 ,7
4 .9
h a il
4 .4
2 ,9
0 .8
3.Q
2,9
2 .5
3 .7
4 .?
4 .4
24.
I-6
. 5 .7
3 .7
9 .9
6 .8
7 .5
2 .6
8 .0
7 .4
3 .9
2*7
3 .4
7»5
3 .8
h a il
2 .7
2*0
.^ 9
7.7.
6 .7
3*5
5 .5
8 .7
7 .6
7 ,8
4 .0 ,
Average . 3.52
5 .6 7
Y ield
from
s o il
m oist*
Bu/A
Y ie ld
from .'
P r e c ip .
2I
Bu/A
P r e d ic te d
, Y ie ld
(X ^Z I »15*46)
'' Bu/A
1-5*80
1 6 .2 4
11.41
15,37
13.17
1 8 .88
27.21
1 8 ,44
19.32
20.63
H .4 1
1 1 .8 5
'21*51
h a il.
1 9.32
12*73
3 .5 1
13.71
12*73 .
10,9.8
1 6 .2 4
21,51
19.32
1 3 .17
7.02 ,
1 7 ,9 6
11*66
31*1.9
21.42
23.63
8.19
25.20
23,31
1 2 .2 9
8 .5 0
1 0 .7 1
23.63
11*97
H a il.
8.51
6*30
21.74
24.26
21.10
1 1 .0 2
17*33
27.40
2 3 .9 4
24.5,7
1 2 .6 0
18,30
1 2 .4 4
27.14
21.33
2 1 .3 4 ■1 1 .6 1
36.95
26*29.
16*1-5
1 3 .6 7
6» 66
20.02
1 8 .0 2
h a il V
1 2 .3 7
3 .5 7
9-79
21*97
18*37
6.5 4
18.11
33.45 27.80
22.28
4 .1 6
15*46
1 7.85
17.85
A c tu al
Y ie ld
Bu/A
19*0
1 2 .2
. 2 0 .0
19*0
1 8 .5
1 3 .5
3 7 .7
4 1 .3
1 5 .7
1 1 .3
,3 .0
27 .2
1 2 .8
h a il
1 3 .2
0 .3
5 .5
2 2.7
9 .8
1 0 .8
1 9 .3
2 4 .2
31*3
31 .2
9 .0
17.85
D if f e r ­
ence
/ 0 .7
- 0 .2
- 7 .1
“ 2 .3
— 2.8
/ 1 .9
/ 0 .7
/1 5 .0
“ 0 .5
- 2 .3
“ 3*6
/ 7*2
“ 5 .2
h a il,.
/ 0 .8
- 3.5
“ 4 .3
/ 0 .7
- 8 .6
/ 4 .3
/ 1 .2
- 9 .5
/ 3 .5
/ 8 .9
/ 4 .8
.
4.1 4 * »
-=H-—
"
* Y ie ld s p re d ic te d " from m u ltip le ' re g re ss io n , o f ,y ie ld on s o i l m o is tu re above
5e5 in c h e s and p r e c i p i t a t i o n fro m ,cro p emergence' u n t i l h a r v e s t , '
Y “ 3 o13% / 4»39%2 “ 15.o46 » %]_ “ ’p r e c ip ita tio n ' and Zg ? In ch es o f s o i l .
m o is tu re above 3*3 in c h e s a t tim e o f crop emergence*
^ ^ D iffe re n c e s t o t a l z e ro b u t av erag e d if f e r e n c e i s 4*14 b u sh els*
39
T a b le H I I „
C o r r e l a t i o n c o e f f i c i e n t s b e tw e e n y i e l d , s o i l m o is t u r e a n d
p r e c i p i t a t i o n f o r c r o p s grow n on f a l l o w , (C a n d D p l o t s ) ,
H a v r e , M o n ta n a , d u r in g t h e p e r i o d 1 9 2 1 -1 9 4 5 »
I te m s C o r r e l a t e d
r
G rain y ie ld and in c h e s o f w a ter i n th e s o i l a t seed in g tim e
„472*
G r a in y i e l d a n d i n c h e s o f w a t e r .u s e d b y t h e c ro p fro m t h e s o i l
„353
G rain y i e l d and in c h e s o f w a te r i n s o i l above 5»5 in c h e s a t
emergence p lu s p r e c i p i t a t i o n from Smergenee to h a r v e s t
»834**
G rain y ie ld and in c h es o f w a te r used from th e s o i l p lu s p r e ­
c i p i t a t i o n emergence to h a r v e s t
»802**
G rain y i e l d and s p rin g t o
, 680**
h a rv e st p r e c ip ita tio n
G rain y ie ld and p r e c i p i t a t i o n from s p rin g t o 2 weeks p r i o r to
h a rv e st
»641**
G r a in y i e l d and J u n e p r e c i p i t a t i o n
»521**
G r a in y i e l d a n d May p r e c i p i t a t i o n
»419*
G r a in y i e l d and J u l y p r e c i p i t a t i o n
»153
G rain y ie ld and in c h e s w a te r g a in ed o v er f i r s t w in te r
«129
P r e c i p i t a t i o n a n d .p e r c e n t o f p r e c i p i t a t i o n saved f i r s t w in te r
o f fa llo w p e rio d
«420*
P r e c i p i t a t i o n and p e r c e n t o f p r e c i p i t a t i o n saved d u rin g
summer o f fa llo w p e rio d
«726**
P r e c i p i t a t i o n and p e r c e n t o f p r e c i p i t a t i o n saved d rr in g
se c o n d w i n t e r o f f a l l o w p e r i o d '
'
»413*
Y ie ld o f d ry m a tte r and in c h e s o f w a te r i n s o i l above 5«5
i n c h e s a t e m e rg e n c e p l u s p r e c i p i t a t i o n fro m e m e rg en c e t o
h a rv e st
* S i g n i f i c a n t a t 5% l e v e l
* * S ig n ific a n t a t 1 / e l e v e l
‘
«844*!jt
40
mean o f s e a s o n a l p r e c i p i t a t i o n and s o i l m o is tu re above 5 ,5 in c h es com bined,
tae a r r i v e a t. a s o lu tio n o f T ~ 5,4% ■= 15o4»
T h is s u g g e s ts t h a t th e crop
w i l l use a p p ro x im a te ly 4 u n i t s o f % o r 4 in c h e s o f s o i l m o is tu re and seaso n ­
a l p r e c i p i t a t i o n in com bination b e fo re any g r a in i s produced*
I t h a s been su g g este d by some in d iv id u a ls t h a t th e e f f e c tiv e n e s s o f
s o i l m o istu re i s to a c e r t a i n e x te n t dependent upon how long th e s o i l m ois­
t u r e has been in th e s o il*
The c o n te n tio n b ein g t h a t th e .lo n g e r th e s o i l
i s wet th e more e f f e c t i v e th e s o i l m o is tu re w ill be*
T h is c o n te n tio n i s
n o t su p p o rte d by th e c o r r e l a t i o n betw een y ie ld and th e amount o f w a te r sav —
ed d u rin g th e f i r s t w in te r o f th e fa llo w p e r io d .
The c o r r e l a t i o n c o e f f i^
e i e n t betw een th e s e two ite m s was o n ly *129 which f a l l s f a r s h o rt o f b e in g
s i g n i f i c a n t a t th e 3% le v e l*
C o r r e la tio n c o e f f i c i e n t s betw een y ie ld and s e v e r a l co m b in atio n s o f
p r e c i p i t a t i o n and s o i l m o is tu re a re g iv e n i n T able . T i l l f o r cro p s grown on
fallow *
T able XT shows c o r r e l a t i o n c o e f f i c i e n t s c a lc u la te d f o r th e c o n tin ­
uous cro p p in g system*
C ontinuous C ropping
E x p e rim en ta l r e s u l t s , p re s e n te d from Havre up t o now have d e a lt w ith
th e c o n s e rv a tio n o f m o istu re on fa llo w and th e r e l a t i o n s h i p s e x i s t i n g b e­
tw een p r e c i p i t a t i o n , m o is tu re s to r e d in th e s o i l , and th e y ie ld o f s p rin g
w heat grown on fallow *
R e s u lts w i l l now be d is c u s s e d w h ic h .p e r ta in t o th e
c o n tin u o u s c ro p p in g o f s p r in g w heat and some com parisons o f th e two system s*
Table IX summarizes much o f th e d a ta o b ta in e d u n d er th e c o n tin u o u s
cropping system*
T h is t a b l e shows t h a t t h e r e was an av erag e o f 6*4 in c h es
o f w a te r in th e s o i l in s p rin g plowed s tu b b le , in a c o n tin u o u s cro p p in g
41
s y s te m , a t t h e tim e t h e c ro p em erged and t h a t t h e r e w as 4«9 i n c h e s p r e ­
se n t a f te r h a rv e s t.
T h is m eans t h a t t h r o u g h t h e 24 y e a r p e r i o d t h e c ro p
o n c o n ti n u o u s c r o p p i n g u s e d o n l y a n a v e r a g e o f 1 ,5 i n c h e s o f m o is t u r e fro m
t h e s u r f a c e f o u r " f e e t o f s o i l a s c o m p ared w i t h an a v e r a g e u s e o f J05 i n c h e s
fro m t h e s o i l on f a l l o w .
The p r e c i p i t a t i o n b e in g t h e s a m e , r e g a r d l e s s o f
t h e c r o p p i n g s y s te m , m eans t h a t w h e a t on c o n ti n u o u s c r o p p in g u s e d 7 ,2
i n c h e s d u r i n g t h e g ro w in g s e a s o n a s co m p ared w i t h 9 ,2 i n c h e s f o r w h e a t on
fa llo w .
The d i f f e r e n c e t h e n b e tw e e n a y i e l d of. 9 ,0 b u s h e l s p e r a c r e on
c o n ti n u o u s c ro p p in g and 1 7 *8$ b u s h e l s p e r a c r e on f a l l o w w as a s s o c i a t e d
w i t h t h e 2 ,0 i n c h e s o f a d d i t i o n a l s o i l m o i s t u r e i n f a l l o w a t th e b e g in n i n g
o f t h e g ro w in g s e a s o n .
Two i n c h e s o f s o i l m o i s t u r e 'w a s r e s p o n s i b l e f o r a
d i f f e r e n c e i n y i e l d o f 8 ,8 b u s h e l s o r 4 , 4 b u s h e l s p e r i n c h .
T h is f i g u r e o f
4 , 4 b u s h e l s p e r i n c h o f s o i l m o is t u r e a g r e e s w i t h t h e r e s u l t s o b t a i n e d b y
m u l t i p l e r e g r e s s i o n a s m e n tio n e d e a r l i e r .
T a b le X show s t h a t c o n tin u o u s c r o p p i n g p r o d u c e d an a v e r a g e o f ^ 42
p o u n d s o f g r a i n p e r a c r e a n d a n a v e r a g e o f 927 p o u n d s o f s t r a w .
T h is i s a
r a t i o o f 1*7 t o I a s com pared w i t h 1 , 9 t o I on f a l l o w , ' The 1071 p o u n d s o f
g r a i n p r o d u c e d p e r a c r e on f a l l o w i s l e s s t h a n tw ic e a s much a s t h e 542
p o u n d s p r o d u c e d b y c o n tin u o u s c r o p p in g b u t t h e r e w as m ore t h a n tw ic e a s
m uch s t r a w p r o d u c e d on fa llo w *
The t o t a l w e ig h e d c r o p o h c o n tin u o u s c r o p p i n g w as 1469 p o u n d s w h ich
i f r e d u c e d b y 10%* t o c o n v e r t t o d r y m a t t e r a s was done w ith f a l l o w , g i v e s
a t o t a l o f r o u g h ly 1522 p o u n d s o f d r y m a t t e r .
T h is m ean s one a e r e in c h o f
w a t e r (g ro w in g s e a s o n p r e c i p i t a t i o n p l u s s o i l m o i s t u r e a b o v e 4 ,9 i n c h e s )
p r o d u c e d I 85 p o u n d s o f d r y m a t t e r o r t h a t 1258 p o u n d s o f w a t e r w e re r e ?
42
T able IX ,
Year
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945..
Average
S o i l m o is tu re , ,p r e c ip ita tio n " a n d " y ie ld "d a ta from th e A p l o t in •
H. 0„ S e r ie s o f d ry la n d crop r o t a t i o n s a t H atrre, M o n tan a..
W ater i n
s o il a t ,
emergence
In c h e s
6 ;4
7 .2
6 .3
6 .2
5 .9
7 .2
IO bl
6 .9
7 .1
7 .0
5 .5
5 .5
5 .6 .
h a il
. 7 .1
5 .6
4 .9
6*6
' 5 .1
7 .5
5 .7
7 .7 .
6*1
5 .1
5 .8
6 ,4 ■ "
W ater in
s o il a t
W ater"used
h a rv e st
from, .s o i l
In ch es '
I n c h e s 1'
. P r e c ip ,
emergence
to h a rv e st
In ch es
4 .7
4 .3 .
6 ,3
4 .7
■4.7
4 .0
7 .6 .
5 .7
5 .1
5 .2
5 .0
5 .0
4*3
h a il
4 .7
3 .8
4 .5
5 .1
4 .0
4 .4
4 .9
6*0
4*1
5 .9
4*8
1 ,7
2 ,9
0 .0
1 ,5
1 ,2
3 .2
2*5
1*2
2 ,0
1*8
0 .5
0*5
1 ,3 .
h a il
2 .4
1 .8
0 .4
1 .5
1 ,1
3 .1
0 .8
1 .7
2*0
9*1
1 ,0
5 .7
3 .7
'
7 .9
6 .8
7 .5
2*6
8*0
7*4
3 .9
2 .7
3 .4
7*5
3 .8
.h a il ■ ■
2 ,7
2 .0
6.9
7 .7
6 ,7
3 .5
5 .5
8 .7
7 .6
7*8
4 .0
.
4 .9
1 .5
5 .7
W ate r.u sed
In c h e s
, Y ield o f
w heat
Bu0/a c r e
7.46 ,6
9 ,9
8 .3
8 ,7
5 .8
10*5
8 ,6
5 .9
4 ,5
3 .9
8*0
5 .1
h a il
5*1
3*8
7 .3
9*2
7*8
6*6
60.3
10*4
9 .6
7 .9
. 5*0
9 .7
7*2
16*7
11*8
16*3
4 .3
26*2
1 6 ,0
8 .3
2 .2
0 .8
2 1 .7
0 ,8
h a il
4*2
0*0
1 .2
13*2
1 .7
6.2
4 .0
19*2
16*0
6 .3
2 .8
7 .2
9*0
43
T able Xe
Straw p e r
a cret,
. Pounds
Year
1921
1922
1923
1924
1923
1926
1927
1928
1929
193Q
1931
1932
1933
1934
1935
1936
193.7
1938
1939
1940
1941
1942
1943
1944
1945
Pounds o f g ra in and s tra w produced p e r a c re i n a . c o n tin u o u s '
c ro p p in g system , p l o t A o f th e M. 0 . S e r i e s , H a v r e M ontanae
•
Average
840
.360
1760
1280
1250
670
1760
1100
990
430
230.
1930
"230.
h a il
530
60
210
l630
470
740
660
1990
1800
84©
270
927
G rain p e r
acre"
Pounds
.
G rain and s tra w
p e r a c re
Pounds
380
.4 3 0
1000
710
980
. 260
1570
960
300
130
..5 0
1300
' 30
h a il
250
,0
.70
790
100
370
240
1150
96O
380
170
1420
990
2760
1990.
2230
930
3330
•2060
1490
560
280
3230
280
h a il
780
60
280
2440
.370
1110
900
3140
2760
1220
440
342
1469
’ -
44
q u i r e d t o p r o d u c e one po u n d o f d r y m a tte r®
On t h e same b a s i s o n ly 737
p o u n d s o f w a t e r w e re r e q u i r e d t o p r o d u c e o n e p o u n d o f d r y m a t e r i a l on f a l ­
low®
T h e se f i g u r e s w ould l e a d one t o b e l i e v e t h a t th e w a t e r r e q u ir e m e n t
w as much h i g h e r on c o n ti n u o u s c r o p p in g b u t i n t h e a n a l y s i s w h ic h f o ll o w s
some c o n s i d e r a t i o n i s g i v e n t o w a t e r l o s t t h r o u g h e v a p o r a t i o n and t h e w a t e r
r e q u i r e m e n t t h e n i s n o t so d i f f e r e n t *
The c r o p , w h e re c o n t i n u o u s l y c r o p p e d , u s e d 1*5 i n c h e s o f s o i l m o is ­
t u r e p l u s 5*7 i n c h e s o f p r e c i p i t a t i o n w h i l e on f a l l o w i t u s e d 5*5 i n c h e s o f
m o i s t u r e fro m t h e s o i l w i t h t h e sam e am ount o f p r e c i p i t a t i o n *
I t w as p r e ­
v i o u s l y s u g g e s te d ,{page 3 7 ) t h a t p r e c i p i t a t i o n w as o n l y a b o u t 70% a s e f f e c ­
t i v e a s s o i l m o i s t u r e , t h e r e f o r e l e t s a ssu m e t h a t o n ly 70% o f t h e p r e c i p i ­
t a t i o n was o f u s e t o t h e c r o p , o r 4*0 inches®
T h is m akes a t o t a l o f 5 * 5
i n c h e s f o r c o n tin u o u s c r o p p in g a n d 7*5 i n c h e s f o r fa llo w * .
U s in g t h e s e f i g ­
u r e s 609 p o u n d s o f w a t e r w e re r e q u i r e d t o p r o d u c e one pound o f d r y m a t t e r
on f a l l o w a n d 942 p o u n d s o f w a t e r w e re r e q u i r e d t o p r o d u c e one pound o f d r y
m a t t e r on c o n ti n u o u s c r o p p i n g .
• W heat on f a l l o w b e g a n p r o d u c in g g r a i n a f t e r 4 i n c h e s o f m o i s t u r e h a d
b e e n u s e d and b y s im p le r e g r e s s i o n i t w as d e te r m in e d t h a t u n d e r c o n tin u o u s
c r o p p in g 3*7 i n c h e s w e re u s e d b e f o r e g r a i n p r o d u c t i o n b egan*
By s u b t r a c t ­
i n g 3*7 i n c h e s fro m t h e 5*5 i n c h e s c a l c u l a t e d f o r c o n tin u o u s c r o p p in g t h e r e
i s 1*8 i n c h e s l e f t w h ic h w as u s e d a f t e r t h e c ro p s t a r t e d p r o d u c in g g r a i n :
i n o t h e r w o r d s , t h e 5 4 2 .p o u n d s o f g r a i n w e re p r o d u c e d o n 1*8 i n c h e s o f
w a t e r w h ic h i s 311 p o u n d s o f g r a i n p e r a c r e inch® . F o u r i n c h e s o f w a t e r
w e re u s e d on f a l l o w b e f o r e g r a i n p r o d u c t i o n b e g a n . . By s u b t r a c t i n g 4 .0
i n c h e s fro m t h e 7*5 i n c h e s o f m o is t u r e c a l c u l a t e d i n t h e p r e v i o u s p a r a g r a p h
45
tJje re i s 5«5 in c h e s l e f t which was u sed by th e crop a f t e r g r a in p ro d u c tio n
b egan.
T his 3«5 in c h e s th e n was re s p o n s ib le f o r th e p ro d u c tio n o f 1065
pounds o f g r a in o r each in c h accounted f o r 304 pounds o f g r a in which i s a l ­
m ost th e same a s th e 307 pounds c a lc u la te d fo r c o n tin u o u s cropping*
I f th e w a te r re q u ire m e n t fo r g ra in p ro d u c tio n under th e two cro p p in g
system s i s th e same, i t seems t h a t th e w a te r req u irem en t m ight a ls o be th e
same f o r straw *
No r e g r e s s io n s were ru n t o d eterm in e r e la t i o n s h i p s be­
tw een m o is tu re and stra w y i e l d b u t the d a ta in T ab les 7 a n d ,T I b rin g s o u t
t h a t fa llo w was more e f f i c i e n t i n th e u se o f w a te r d u rin g t h e h ig h .y ie ld in g
y e a rs th a n i n th e y e a rs when low y ie ld s w ere o b tain ed * • T able :XI g iv e s th e
y ie ld s o b ta in e d and th e amount o f m o is tu re used d u rin g te n o f th e low y i e l d ­
in g y e a rs on fa llo w *
T his ta b le shows t h a t d u rin g th e s e t e n y e a rs y ie ld s
on fa llo w , av erag ed ab o u t t h e same a s th e 24 y e a r p e rio d on c o n tin u o u s cro p ­
ping*
Under th e s e c o n d itio n s fa llo w p ro duced 1440 pounds o f d ry m a tte r
( y ie ld minus 10%) w ith 3«I in c h e s o f s o i l m o is tu re and 4*0 in c h e s o f p r e ­
c ip ita tio n *
I f th e s o i l m o is tu re u s e d , d u rin g th e s e 10 low p ro d u c in g y e a r s , i s
added to 70% o f th e p r e c i p i t a t i o n , we a r r i v e a t a t o t a l of. 5*9 in c h e s o f
w a te r a v a ila b le to th e c ro p .
T h is 5*9 in c h e s b e in g 'r e s p o n s ib le f o r .1440 -/
pounds means t h a t each in c h was r e s p o n s ib le f o r 244 pounds o f d ry m a tte r o r
t h a t th e w a te r re q u ire m e n t was 928 pounds o f w a te r f o r one pound o f d ry
m a tte r*
Under th e c o n tin u o u s c ro p p in g sy stem , where 70% o f th e p r e c i p i ­
t a t i o n was added t o th e s o i l m o is tu re , th e r e was 5*5 in c h e s o f m o istu re
r e s p o n s ib le f o r 1322 pounds, o f d ry m a tte r.w h ic h i s 243 pounds p e r a c re
in c h o f w ater*
T h is would make th e w a te r re q u ire m e n t under c o n tin u o u s c ro p -
46
Table XIe
.Pounds "of"grain and stra w produced on fa llo w d u rin g te n y e a rs
o f low pro d u ctio n ," and th e amount o f s o i l m o is tu re a t seed in g
tim e and th e grow ing season p r e c i p i t a t i o n 0 and D p l o t s ,
H av re, M ontana.
S o il m o is- :
t u r e above
5 .5 in . a t
tim e o f "crop
emergence
Inches
. P r e c ip . p lu s
s o i l m o istu re
above 5 .5 i n ,
a t crop
emergence
Inches
T ear
Straw
per
a c re
Pounds
d ra in
per
acre "
Pounds
G rain and
stra w p e r
. a c re
Pounds
P recT pi crop
,emergence"
ib h a rv e st
' Ip c h e s
*
I
1929
1930
1931
1933
1935
1936
1937
1939
1940
1945
21-80
l l 60
310
1340
700
410
420
2340
970
810
940
680
180
770
790
20
530
4-50
650
540
3120
1840
490
2110
1490
430
750
2790
1620
1350
3*9
2*7
3 .4
3 .8
2 .7
2 .0
6 .9
6.7
3 .5
4 .0
4 .4
4 .7
2 .6
4 .9
4 .4
2.9
0 .8
-2 .9
2 .i
1 .6
8 .3
7 .4
6.0
8 .7
7 .1
4 .9
7 .7
9 .6
6 .0
5 .6
Avg0
1064
535
1599
4 ,0
3 .1
7 .1
47
T able HI<,
In c h e s o f w a te r .in th e s o i l .to a d e p th o f 4 f e e t a t h a rv e s t
and th e fo llo w in g s p r in g , p r e c i p i t a t i o n f o r th e p e rio d .a n d
p e r c e n ta g e .o f p r e c i p i t a t i o n co n serv ed in th e s o i l . A p l o t
H av re, M ontana.
W ater in
s o il a t
h a rv e st
tim e
In c h e s
W ater in
s o i l 1"the
next
s p rin g
In ch es
W ater.
saved!.
In ch es
P r e e ip 0
h a rv e st
to
s p rin g
In ch es
1919-20
1920-21
1921-22 .
1922-23
1923-24
1924-23
1923-26
1926-27
1927-28
1928-29
1929-30
1930-31
1931-32
1932-33
1933-34
1934-35
1935-36
1936-37
1937-38
1938-39
1939-40
1940-41
1941-42
1942-43
1943-44
4.7:
4 .6
4 .7
4 .3
6 .3
4 ,7
4 .7
4 .0
7 ,6
5 ,7
5 ,1
5 .2
5 .0
5 ,0
4 .3
4 .4 •
4 .7
3 .8
4 .5
5 .1
4 ;o
4 .4
4 .9
6 .0
4 .1
6 .6
6 .4
7 .2
4 .3
6.2
5 .9
7 .2
10;. I
6 .9
7 .1
7 .0
5 .5
5b5
5 .6
7 .5
7 .1
5»6
4 .9
6 .6
5 .1
7 .5
5 .7
7 .7
6 .1
5 .1
1 .9
1 .8
2 .3
2 .0
■,0 .1
1 .2
2 .5
6 .1
- 0 .7
1 .4
1 .9
0 .3
0 .5
0 .6
3 ,2
2 .7
0 .9
1 .1
2 .1
0 .0
3 .5
1 .3
2 .8
0 .1
1 .0
5 .9
7 .6
7 .1
4 .9
6 .5
6 .4
. 7 .8
1 2 .6
4 .5
7 .2
7 .3
5 .2
6 .6
7 .3
9 .7
7 .9
3 .3
4 .9
6 .3
5 .0
7 .8
6 .1
7^4
6 .3
2 .8
32.2
23.7
35.2
4 0 .8
^ 1 .5
19 .0
32.1
4 8 .4
- 1 5 .6
1 9 .4
26 .0
5 .8
7 .6
8 .2
3 3 .0
34 .2
27.3
2 2 .4
3 3 .3
0 .0
44« 9
2 1 .3
37 .8
1*6
35 .7
Average
4 .9
6 .5
1 .6
6 .6
24.2
Y ear
% P r e e ip .
saved
48
T a b le X I I I .
Tear
W a te r I n
s o i l in
A p lo t a t
h a rv e st
tim e
In ch es
1921
4 .7
1922
4-02
1922
6 .2
1924
4 .7
1922
4 .7
1926 .
4 .0
7 .6
1927
1928
5 .7
1929
5 .1
5 .2
1920
1921
5 .0
5 .0
1952
1925
4 .5
1924
■ 4o4
1925
4 .7
5 .8
1926
1927
4 ,5
1928
5 .1
4 .0
1929
1940
4 .4
1941
4 .9
6 .0
1942
1942.
4 .1
5 .0
1944
4 .8
1945
A v e ra g e
I n c h e s o f w a t e r . i n s o i l ' i n s t u b b l e c o n t i n u o u s l y c ro p p e d and
i n s t u b b l e i n ah a l t e r n a t e c r o p f a llo w , s y s te m .d u r i n g t h e f a l l
a n d s p r i n g o f t h e y e a r a t H a v r e , M o n ta n a .
4 .9
W a te r "in
s o il in .
C & D' p l o t s
a t" h a rv e s t
tim e
In ch es
■
5 .7
4 ,9
5 .6
6 .2
5 .5
5 .5
6 .7
5 .9
4 .5
6-.0
6.5
5 ,i
5 .6
5 .7
5 .9
4 .9
5 .5
5 .4
4 .6 '
5:. 2
6 .4
6 ,0
4 .8
5 .0
5 .0 -
5o5
D itf 0 in
fav o r", of"
a lte rn a te
c ro p & d
fa llo w
In ch es
1.00 .6
-OorJ
1 .5
0 .6
1 .5
-0 .9
0 .2
” 0 .6
0 .8
1 .5
0 .9
1 .5
1 .5
1 .2
I il
0 .8
Q.5
0 .6
0 .8
1 .5
0 .0
0 .7
0 .0
0 .2
0«6
W a te r. in
A p lo t in
s p rin g o f
y e a r . ..
In ch es
6 .4
7 .2
"6 .2
6 .2
5 .9
7 .2
1 0 .1
6 .9
7 .1 .
7 .0
5 .5
5 .5
5 .6
7 .5
7 .1
5 .6
4 .9
6 .6
5 .1
' 7 .5
'
. 5 .7 .
7 .7
6 .1
5 .1
5 .8
6.5
W a te r i n
s t u b b l e on
0 .& D p l o t s
i n , s p rin g
o f. y e a r
In ch e s
7 .0
8 .0
6 .6
6 .0
6.8,
7 .6
10 .5
7 .0
8 .8
7 .6
6 .8
6 .5
8 .5
■ 8 .1
9 .0
5 .5
5 .9
- 6 .0 '
5 .5
9 .2
6..I1
8.4'
H
5 .8 .
6 .5
7 .2
B if f, in
fa v o r o f
a lte rn a te
c ro p a n d
fa llo w .
In ch es
0 .6
0 .8
0 .5
- 0 .2 .
0 .9 .
0 .4
0 ,4
0 .1
1 .7
0 .6
.
1 .5
0 .8
2.9
0 .6
1 .9
0 .2
1 .0
—0« 6
0 .2
1 .7
0 .4
0 .7
0 .8
Ool
■Ool
0 .7
49
p i n g 932 p o u n d s o f w a t e r p e r pound o f d r y m a t t e r w h ic h i s a lm o s t i d e n t i c a l
t o t h e low p r o d u c in g y e a r s i n th e f a l l o w sy stem *
The i n c h e s o f w a t e r i n t h e s o i l , and t h e p e r c e n ta g e o f. p r e c i p i t a t i o n
s a v e d b e tw e e n h a r v e s t a n d t h e n e x t • s p r i n g , i n s t u b b l e w h ic h was p r o d u c e d b y
a c o n ti n u o u s c ro p p in g s y s te m , a r e g i v e n i n T a b le H I 6
T h is t a b l e shows
t h a t o f t h e 6 ,6 i n c h e s o f p r e c i p i t a t i o n w h ic h f e l l b e tw e e n h a r v e s t a n d t h e
f o l l o w i n g s p r i n g 1 ,6 i n c h e s w e re ' c o n s e r v e d o r 2 4 ,2 f = - = th is i s a lm o s t e x a c t l y
t h e same p e r c e n t a g e a s w as d e te r m in e d f o r f a l l o w
s t u b b l e w h ic h w as 25, 8%.
C o n tin u o u s c ro p p e d s t u b b l e h a d l e s s m o i s t u r e a t h a r v e s t tim e a n d
c o n s e q u e n t ly l e s s m o i s t u r e th e f o ll o w i n g
i s shown i n T a b le X I I I ,
s p rin g th a n f a llo w s tu b b le .
T h is
The c o n ti n u o u s c r o p p in g sy ste m " a p p a r e n t l y d ra w s
t h e s o i l m o is t u r e t o a lo w e r l e v e l t h a n t h e f a l l o w s y s te m d o e s .
T h y s e ll
(2 4 ) a l s o fo u n d t h a t t h i s w as t r u e a t H a n d a n ,. N o r th D a k o ta ,
I n t h i s c o n n e c t io n i t i s
i n t e r e s t i n g t o n o t e a t w h a t d e p t h s t h e c ro p
g e t s m o st o f i t s m o i s t u r e i n t h e tw o c ro p p in g , s y s te m s .
T a b le H I I shows
t h e i n c h e s o f m o is t u r e i n t h e s o i l a t tim e o f c r o p e m e rg en c e on f a l l o w a n d
c o n ti n u o u s c r o p p in g a n d a l s o show s t h e s o i l m o i s t u r e d i s t r i b u t i o n a t h a r -
'
v e s t.
T a b le XIY show s w h e re t h e c r o p on f a l l o w - p i c k s up t h e a d d i t i o n a l two
i n c h e s w h ic h i s a v a i l a b l e t o i t ,
.T he f a l l o w c ro p g e t s 0 ,2 5 o f a n i n c h m ore
fro m t h e f i r s t f o o t , O.6 7 o f an i n c h m ore from t h e s e c o n d f o o t , 0 ,7 4 m ore
fro m t h e t h i r d f o o t and 0 ,1 1 m ore fro m t h e f o u r t h f o o t .
B o th c ro p s u t i ­
l i z e d m ore m o i s t u r e fro m t h e f i r s t an d s e c o n d f o o t'e t h a n fro m th e t h i r d a n d
fo u rth .
The c ro p on c o n ti n u o u s c r o p p i n g u s e d v e r y l i t t l e
a n d f o u r t h f o o t and f a l l o w u s e d v e r y l i t t l e
from t h e t h i r d
fro m t h e f o u r f o o t a r e a .
50
Table Z%V.
Inoh.es o f w a te r in th e s o i l a t "various d e p th s a t tim e of
crop emergence and a t h a r v e s t in a c o n tin u o u s c ro p p in g ./
system and a system o f a l t e r n a t e .crop and. f a llo w , H avre,
M ontana, f o r th e p e rio d 1921s»1945<.
Go n tin u o u s“'Crdpping
" . Foot Depth
1 s t f t 2nd f t 3rd f t 4 th f t
Crop emergence
H a rv e st
Used
. F a llo w .
F oot Depth
1 s t f t 2nd f t 3rd f t 4 th f t
1 ,6 3
0 .9 1
0 ,7 2
1 .8 5
1 ,2 0
0 ,6 5
1,47
1 .3 5
0 .1 2
1 .47
1 .4 5
0.02
1.89
0 .9 2
-0.97
2,73
1 .2 1
1 .5 2
2.38
1.52
0.86
2.01
. 1.88
0 .1 3
44
35
8
I
51
56
36
6
48
43
8
I
28
43
25
4
P e rc e n t u s e d . P e rc e n t o f t o t a l
u sed
The c o r r e l a t i o n between th e d if f e r e n c e in in c h e s o f w a te r u sed from
th e s o i l and th e d if f e r e n c e in y ie ld o f g r a in o b ta in e d w ith th e two crop­
p in g system s was »497 which i s s i g n i f i c a n t a t th e 5% le v e l and alm o st th e
same c o r r e l a t i o n which e x i s t s betw een y ie ld and s o i l m o is tu re a t th e tim e
o f crop emergence*
S e v e ra l c o r r e l a t i o n s betw een y ie ld and m o istu re in th e fa llo w system
have been g iv e n .
I n th e c o n tin u o u s c ro p p in g system th e r e was a c lo s e r
c o r r e l a t i o n betw een s o i l m o is tu re , and cro p y i e l d , and growing season p r e ­
c i p i t a t i o n and cro p y ie ld th a n th e r e was in th e fa llo w sy ste m .
T h is seems
re a so n a b le becau se m o is tu re was more o f a l im it in g f a c t o r w ith th e crop
grown on s p rin g plo w in g .
On s p rin g plow ing th e c o r r e l a t i o n betw een s o i l
m o is tu re and y ie ld was , 510; between p r e c i p i t a t i o n from s p r in g to h a r v e s t
and y i e l d , i t was .7 3 4 ; and betw een y ie ld and s o i l m o is tu re , p lu s s e a s o n a l
p r e c i p i t a t i o n , i t was , 883,
The same c o r r e l a t i o n s r e l a t e d to fa llo w were
,4 7 2 , 068O and ,834 r e s p e c tiv e ly .
51
C o r r e la tio n c o e f f i c i e n t s c a lc u la te d f o r th e c o n tin u o u s cro p p in g system
a re g iv e n i n Table, XV.
T able XV.
'
C o r r e la tio n c o e f f i c i e n t s betw een y i e l d , s o i l m o is tu re and p r e c i p i t a t i o n f o r cro p s grown on s p rin g plow ing {A - p l o t ) H avre,
M ontana.
^ ■
Item s C o rre la te d
r
G rain y ie ld and in c h e s o f s p rin g t o h a r v e s t p r e c i p i t a t i o n
„754**
G rain y ie ld and in c h e s o f w a te r in s o i l ushen crop emerged
. 510**
G rain y ie ld a n d ,in c h e s o f w a te r in s o i l a t emergence p lu s
p r e c i p i t a t i o n s p rin g t o h a r v e s t
. 883^*
, Y ie ld o f d ry m a tte r and in c h e s o f w a te r in s o i l a t emergence
p lu s p r e c i p i t a t i o n s p rin g t o h a r v e s t
. 882**
D iffe re n c e in y ie ld betw een fa llo w and c o n tin u o u s cro p p in g
and d if f e r e n c e in s o i l m o is tu re a t emergence
. 497*
* S i g n i f ic a n t a t 5% l e v e l
^ ^ S ig n if ic a n t a t if . le v e l
T illa g e D em onstration. Farm, C u lb e rts o n , M ontana.
The amount o f s o i l m o is tu re p r e s e n t i n fa llo w e d la n d , a t v a rio u s
d e p th s in th e f a l l o f th e y e a r a t C u lb e rts o n , i s g iv e n in. T a b le .XVE.
The
y e a rs a r e n o t c o n s e c u tiv e b ecause changes which o c cu rred i n th e program
caused s o i l m o is tu re sam plings to be non™C ontinuous.
.The same in fo rm a tio n i s g iv e n i n T ab le XVII as in T able XH ex cep t
t h a t i t i s f o r s o i l m o is tu re p r e s e n t i n fa llo w th e fo llo w in g s p r in g .
The t o t a l in c h e s o f w a te r p re s e n t t o th e sam pled d ep th o f f i v e f e e t
i n fa lld w i s g iv e n i n Table. X V ltl.
T his t a b l e p r e s e n ts in condensed form
th e amount o f w a te r g ain ed o r l o s t in fa llo w from the- f a l l o f t h e y e a r
52
u n t i l se e d in g tim e th e f o llo td .ng s p rin g .
T able XVI,
Inches o f s o i l m o is tu re p r e s e n t i n fa llo w la n d i n th e f a l l , by
f o o t d e p th s , G u lb e rts o n , E o n tan a e
' ' . ' Depth ■
2nd f t ,
3 rd f t .
Y ear
1st f t .
1941
1942
1944
1945
1946
1949
l,8 l
1 .9 9
l,6 l
1 , 60
2,07
1 .4 0
2,02
2,13
2,12
2,20
2 ,3 4
1.79
2.30
2.48
2.5 5
2.6 4
2.7 5
2.15
Average1
1 .7
2 .1
2 .5
T able XVII,
5th ft<i
2.20
2.75
2.75
2.87
2.83
2,40
2.1-5
2.60
3.02
3 .1 2
3.12
2.95
. 2 .6
2 .8
In c h e s o f s o i l m o is tu re p r e s e n t 'i n fa llo w la n d in th e ' s p rin g
a t se e d in g tim e , b y f o o t,d e p th s , C u lb e rts o n , Montana,
1s t f t .
Y ear
1942
1943
1945
1946
1947
1950
4 th f t .
1 .6 1
1 .9 4
1 .7 3
1 ,5 7
1 .7 0
2.00
' '
Average
. 1 .8
' D epth "
2nd f t ,
3rd f t .
2. o i
2.35
2 .2 8
2.26
2.18
2.46
2 .2
2»30
2.8 2
2.77
2.5 7
2.66
2.72
.
2 .6
4 th f t .
*■■■
,
2.3 4
3ai
2 .5 3
2 .9 1
2 .7 9
2 .8 5 2 .7
5th f t .
2.32
3 .3 2
5.06
3.0&
3.06
.. ,2 .9 3
3 .0
These t a b l e s in d ic a te t h a t f r e q u e n tly ' o n ly a sm all amount o f w a te r i s
conserved d u rin g th e w in te r months on b a re fa llo w .
cause v e ry l i t t l e
T h is i s p ro b a b ly b e­
snow accum ulates on la n d devoid o f v e g e ta tio n .
Snow gen­
e r a l l y accum ulates in s tu b b le f i e l d s o r o th e r p la c e s which t r a p d r i f t i n g
snow-.
D uring th e w in te rs o f 1949-1950 and 1947-1945 th e r e was a v ery h ig h
g a in on b a re fa llo w .
These g a in s were no doubt due t o th e f a c t t h a t 1942
5?
and 1949 were h ig h in p r e c i p i t a t i o n d u rin g th e e a r l y f a l l and a ls o d u rin g
th e fo llo w in g s p rin g .
The p r e c i p i t a t i o n a t t h i s tim e o f th e y e a r mould be
i n th e form o f r a i n o r w e t•snow and would i n m ost c ase s s ta y where i t f e l l
and n o t be d r i f t e d from th e f ie ld *
T able XVIII*
In c h e s ' o f. w a te r p r e s e n t ..to. .a dep th o f f i v e f e e t in fa llo w
la n d a t G u lb e rtso n , M o n ta n a . in th e f a l l and su cc e ed in g
s p rin g and th e in c h es g a in o r l o s s d u rin g th e same p erio d *
In c h e s . o f w a te r
F a ll
Y ear
In c h e s o f w a te r '
S p rin g
'
1941-1942
1942=1945
1944=19451945-1946
1946=1947
1949-1950
10*5
12*0
12*0
12*4
15*1.
1 0 .7
10*6
13*5
12*8
1 2 .5
1 2 .5
12*6
Average
11*8
1 2 ,4
In ch es
g ain ed o r l o s t
.
6 .1
i* 5
0*8
=0 .1
—0 .6
1 .9
0*6
The amount o f m o istu re p r e s e n t in s tu b b le la n d - in th e f a l l and a t seed ­
in g tim e th e fo llo w in g s p r in g i s shown in th e t a b l e s which follow *
Table
XIX g iv e s th e in c h e s o f w ater p r e s e n t by f o o t d e p th s in th e f a l l o f th e
y e a r and T able XX g iv e s th e in c h e s o f w a te r p r e s e n t th e fo llo w in g sp rin g *
T able XXE g iv e s th e t o t a l amount o f w a te r p r e s e n t to a d e p th o f fiv e f e e t
a t each sam pling d a te and th e g a in o r l o s s betw een th e two sam pling d a te s *
By com paring T able X F III w ith T able XXI i t i s e a s i l y s e e n t h a t much '
more m o is tu re was accum ulated o v e r w in te r i n th e s o i l on s tu b b le la n d th a n
on fa llo w land*
D uring th e w in te r o f 1941-1942 th e r e was no g a in i n s o i l
m o is tu re on fa llo w w h ile s tu b b le la n d g a in ed a p p ro x im a te ly 2*9 in c h e s o f
w a te r 9 i n th e sam pled depth*
D uring th e w in te r o f 1945=1946 fa llo w g a in e d
54
n o th in g and s tu b b le g ain ed 3®0 in c h es o f w a te r between f a l l and s p rin g .
In
th e s p rin g o f 1946 s tu b b le la n d c o n ta in e d a s much s o i l m o is tu re a s fa llo w *
T able XIZe-
In ch es o f s o i l m o is tu re p r e s e n t in s tu b b le la n d in th e f a l l o f
th e y e a r by f o o t d e p th s , C u lb e rts o n , M ontana,
' Bepth:;;
Y ear
1st f t ,
1941
1942
1944
1945
1946
1949
0,50
2 ,0 1
0 ,9 8
1 ,3 7
O09.8
0 ,8 2
0 ,8 2
1*77
1 ,0 9
1 .1 1
1 .0 6
I i 23
IeO l
1 ,4 7
1*38
1.-38
1 .6 5
1 .5 7
l i 39
2 .0 6
I* 7P ,
2 .4 4
2.3 6
2 .1 4
1 ,8 7
2 .6 0
2 .2 3
2.99
2,9 1
2.80
Average
1 ,1 .
1 ,2
1 .4
2 .0
2 ,6
Table XX,
2nd f t , .
3 rd f t ,
Depth
3rd f t .
1st f t .
2nd f t .
1942
1943
19451946
1947
1950
1 .7 0
2.0?
1 ,9 0
1.8-3
1.6-3
1 .6 l
1 .5 0
2.23
1 .8 0
2,18
1*75
I .6 0
1 .3 8
2 .3 3
1*39
2.3 0
2.2 6
1 .7 7
1 .8
1 .8
1 .9
Average
5 th f t .
In c h e s of" s o i l m o istu re p r e s e n t in s tu b b le " la n d in th e s p rin g
o f the" y e a r a t se e d in g tim e b y fo o t d e p th s , O u lb ertso q .,
M ontana,
Y ear
1
4 th f t ,
"
"
4 th f t .
5 th f t .
1 .7 2
2 il8
1 .9 0
2 .85
2 ,48
2 .2 4
2.15
2.50
2.4 ?
3.12
3,02
2.67
2 .2 .
The d e c re a s e in s o i l m o istu re in d ic a te d d u rin g th e w in te r o f 19461947 in fa llo w co u ld be p a r t l y due t o th e v a r i a t i o n o r e r r o r which occurs
in s o i l m o istu re sam p lin g s.
W ith f o u r sam ples from each o f Eighteen p l o t s
ta k e n a t b o th sam pling d a te 's , i t seems t h a t th e sam pling e r r o r should be
55
s m a llo
I t seems more p ro b a b le t h a t weed grow th and e v a p o ra tio n a re re®
s p o n s ib le f o r t h i s lo s s ' o f s o i l m o istu re *
T h y s e ll (24) found t h a t th e r e
was a l o s s o f m o is tu re i n fa llo w e d la n d betw een sam pling d a te s in o c c a sio n ­
a l y e arso
The in c h e s o f w a te r g a in ed o r l o s t betw een th e sam pling d a te s th ro u g h .
•
••
J
o u t th e fallo w p e rio d o f ro u g h ly tw en ty -o n e months i s g iv e n in T able X H Ie
Table XXI,
In ch es o f w a te r .p r e s e n t to a d e p th .o f f i v e f e e t " i n stu b b le
lan d a t G u lb e rts o h 9 M ontana, i n t h e - f a l l a n d ,su c c ee d in g
s p rin g and th e in c h es g a in o r l o s s d u rin g th e same p e rio d .
In c h e s o f w a te r
F a ll
T ear
1941-1942
1942-1943
1944-1945
1945-1946
1946-1947
1949-1950
Average
T able XXII.
T ear
1940-41-42
1941-42-43
1943-44-45
1 944°34\5“"46
1945- 46-47
1948- 49-50
Average
.
In c h e s o f" w a te r
S p rin g £’
5 .6
9 .9
7 .4
9 .5
9 .0
8 .6
8 .5
1 1 .3
9 .5
1 2 .3
1 1 .1
9 .9
8 .3
10*4
Inches'
Gained o r l o s t
t
*
2 .9
1*4
2*1
3*0
2*1
1 .3
■ 2 .1
'
In c h e s o f s o i l w a te r g a in ed o r l o s t in fa llo w b e tw ee n .sam®
p lin g d a te s and th e t o t a l g a in ed d u rin g th e fa llo w p e rio d
o f a p p ro x im a te ly . 21 m o n th s, C u lb e rts o n , Montana*
F a ll.
to .
S p rin g
2 .9
1*4
2 .1
3 .0
2 .1
1 .3 '
■ 2 .1
S p rin g
to .
F a ll
F a ll
to
S p rin g
T o ta l
2*0
0*7
2*5
0*1
2*0
0*8
0*1
1 .5
0*8
—0*1
—0* 6
1 .9
5 .0
3 .6
5 .4
3 .0
3 .5
4 .0
.
0 .4
.
■■•.*■4*1
56
■ The p r e c i p i t a t i o n w hich o c cu rred betw een th e s o i l m o is tu re sam pling
d a te s i s g iv e n i n T able Z H I l e
Table Z H I I e
In c h e s o f 'p r e c i p i t a t i o n 'b e t w e e h .'s o i l m o is tu re , sam plings d u r­
in g th e " fa llo w p e rio d o f a p p ro x im a te ly 21 m onths, C u lb e rts o n ,
Montana*
F a ll
to
S p rin g
T ear
S p r in g ■
to
F a ll
F a ll
to
S p rin g
T o ta l
1940-41-42.
1941-42-4?
1943 -44=-45
1944=45—46
1945- 46=47
1948- 49-50
1*7
5 .7
2 .9
5 .8
2*7
9.41 0 ,6
1 0 ,2
7 .5
11*0
4 .9
1*7
5 .8
2 .9
5 .8
2*8
5 .0
15 .0
1 6 .1
16*8
1 4 .0
1 7.6
12*6
Average
5*1
■ 8 .9
5 .5
15*5
The p e rc e n ta g e o f th e p r e c i p i t a t i o n co n serv ed betw een th e v a rio u s
sam pling d a te s i s g iv en i n T able Z H i10
T able ZHVe
P e rc e n t o f p r e c i p i t a t i o n conserved, i n t h e i s o l l betw een
sam pling d a te s, d u r in g ' th e fa llo w p e rio d 0$ a p p ro x im a te ly
21 m onths, C u lb e rts o n , Montana*
s
T ear
F a ll
to
S p rin g ..
1940-41=42
1941-42-45
1945-44-45
1944-45-46
1945-46-47
1948-49-50
'% ,482*4
56*8.
1Q5.4
' 55.0 5
48*1
21*5
6*6
2 4 .5
. 1 .4
18 .2
16*5
5.4.
59*5
2 7.6
- 2*6
-2 1 ,4
5 8 .0 .
5 5.5
22*5
52*1
21,4
19 .9
. 51.7 .
67*7
15*7
1 8 .2
26.'8
^Average
.
S p rin g
- to
F a ll
F a ll
• to
S p rin g
P e rc e n t 1
to ta l
saved
,^ C alcu lated from a v erag e f ig u r e s in T ab les Z Z II and Z H I lo
I t i s q u ite e v id e n t from t h i s l a s t ta b l e t h a t a much g r e a te r propor-
57
t i o n o f th e p r e c i p i t a t i o n i s co n serv ed d u rin g th e f i r s t w in te r o f th e f a l 4
low p e rio d when- s tu b b le i s on th e ground th a n d u rin g th e second w in te r when
th e fa llo w i s b a r e .
The h ig h p e rc e n ta g e o f m o istu re saved in s tu b b le d u r­
in g th e w in te r o f 1944-1945 i s p e rh a p s due in p a rt, to sam pling e r r o r bu t i s
a ls o no doubt p a r t l y due t o th e f a c t t h a t mow was d r i f t e d from th e a d ja c e n t
fa llo w s t r i p in to th e S tu b b le e
T h e .p e r c e n t o f m o is tu re sav ed o v er w in te r
in s tu b b le la n d was h ig h e v ery y e a r b u t to g e t c o n s e rv a tio n a p p ro a ch in g
100% i s . h ig h e r th a n would be "expected*
The y ie ld o f g r a in and s tra w produced i s n o t p re s e n te d b ecau se th e
s o i l m o istu re sam pling d a te in th e f a l l d id n o t c o in c id e w ith th e tim e o f
h a r v e s te
F a l l m o istu re sam ples were ta k e n around O c to b e r. I and h a rv e s t had
u s u a lly been com pleted s i x weeks t o two months p r i o r to t h a t tim e*
S in ce
th e r e was no s o i l m o istu re d e te rm in a tio n made a t h a r v e s t , i t i s n o t p o s s i­
b le to c a lc u la te w a te r re q u ire m e n t f o r th e crop growno
58
DISCUSSION
Our p r e s e n t methods o f summer fa llo w a re v e ry I n e f f i c i e n t in co n - •
s e rv in g th e p r e c i p i t a t i o n re c eiv e d *
At Havre l e s s th a n 1?% o f th e p r e ­
c i p i t a t i o n re c e iv e d d u rin g -th e fa llo w p e rio d was co n serv ed in th e s o i l d u r in th e 25 fa llo w sea so n s s tu d ie d , ; A pproxim ately 26% o f th e p r e c i p i t a t i o n
re c e iv e d d u rin g th e f i r s t w inter, o f th e fa llo w p e rio d was r e ta in e d in the
s o il*
D uring th e second w in te r when th e s o i l was b a re I 8% was conserved
and d u rin g th e summer months o n ly 11% o f th e m o is tu re re c e iv e d was sav ed ,
AtivC u lb e rtso n $ d u rin g th e s ix fa llo w p e rio d s s tu d ie d , an a v erag e o f
2?% o f th e p r e c i p i t a t i o n , which came l u r i n g th e fa llo w p e r io d , was con­
se rv e d ,.
Ih e p e rc e n ta g e o f m o istu re saved from e a r ly O c to b er, fo llo w in g
h a r v e s t , u n t i l th e n e x t s p rin g was 68% b u t only I 6% was saved d u rin g th e
summer months and 18% was saved d u rin g t h e .second w in te r o f th e fa llo w p e r i ­
od*
.
.
The d if f e r e n c e s i n th e p e rc e n ta g e o f p r e c i p i t a t i o n con serv ed a t th e s e
two lo c a t i o n s a re q u ite s t r i k i n g a s a re th e d if f e r e n c e s in m o is tu re con(
.
s e r r a t i o n a t v a rio u s tim e's o f th e y e a r .
The low c o n s e rv a tio n d u rin g th e
summer months a t Havre i s due a lm o st e n t i r e l y to e v a p o ra tio n because weeds
I
w ere k e p t u n d er c o n tr o l and v e ry l i t t l e w a te r was l o s t by r u n o f f .
Weeds
were a ls o k e p t u n d er c o n tr o l a t C u lb e rts o n , b u t c o n s id e ra b le ru n o f f oc­
c u rre d d u rin g s e v e r a l t o r r e n t i a l r a i n s so a t t h a t lo c a tio n r u n o f f was a
f a c t o r a s w e ll a s e v a p o ra tio n .
The sandy s u rfa c e s o i l a t C u lb e rtso n i s
more r e c e p tiv e to w a te r th a n .th e Havre s o i l and a llo w s f o r q u ic k e r and
d e ep e r p e n e tr a ti o n .
The n e t r e s u l t i s t h a t l e s s m o istu re i s l o s t th ro u g h
e v a p o ra tio n and a g r e a t e r p e rc e n ta g e o f m o is tu re i s saved in s p i t e o f r u n ­
59
o f f lo s s e s *
The c h ie f re a s o n s f o r th e r e l a t i v e l y h ig h p e rc e n ta g e o f m o is tu re con­
s e r v a tio n d u rin g th e f i r s t w in te r a r e t h a t snow blown from a d ja c e n t s t r i p s
i s tra p p e d in th e s ta n d in g s tu b b le , and a low e v a p o ra tio n r a t e a t t h i s tim e
a ls o a id s m o is tu re conservation®
a re q u ite fre q u e n t a t Havre®
Chinooks seldom o c c u r a t C u lb e rts o n , b u t
T h is d if f e r e n c e i n th e c lim a tic c o n d itio n s a t
th e two l o c a t i o n s , coupled w ith th e sandy s u rfa c e s o i l a t C u lb e rts o n , no
do u b t l a r g e l y e x p la in s th e d if f e r e n c e i n th e p e rc e n ta g e o f p r e c i p i t a t i o n
saved, a t th e two l o c a t io n s d u r in g ‘th e w in te r months®
a re h ig h when Chinook w inds a r e blowing®
E v a p o ra tio n lo s s e s
The f a l l to s p rin g p e rio d a t
■Culbertson began l a t e r in th e f a l l and ended somewhat e a r l i e r in th e s p rin g
th a n th e same i n t e r v a l a t Havre because o f d if f e r e n c e s in sam pling dates®
T h is would a ls o te n d to show a h ig h e r p e rc e n ta g e o f m o is tu re saved in s tu b ­
b le a t C u lb e rts o n d u rin g t h i s p e rio d b e ca u se th e e v a p o ra tio n l o s s would be
low and m ost o f th e p r e c i p i t a t i o n would be in th e form o f snow®
S in c e snow
c o n tr ib u te s v e ry l i t t l e t o s o i l m o is tu re on b a re fa llo w i t i s n o t to be
expected, t h a t th e same r e l a t i o n s h i p o f m o is tu re saved would e x i s t betw een
th e two la n d c o n d itio n s a t th e two lo c atio n s®
The low p e rc e n ta g e o f m o is tu re conserved d u rin g th e second w in te r a s
compared w ith th e f i r s t w in te r , o f th e fa llo w p e r io d , i s a t t r i b u t e d to th e
f a c t t h a t snow i s u s u a ll y blown from th e b a re fa llo w and lo d g ed in th e ad­
jo in in g s tu b b le strip s®
D uring th e w in te r o f 1946-1947 a c o n s id e ra b le l o s s
o f s o i l m o is tu re was re c o rd ed a t C u lb e rtso n i n b a re fallow®
ed lo s s e s co u ld be d u e . t o . sam pling ; e r r o r o r evaporation®
These re c o rd ­
- I t seems sam pling
e r r o r sh o u ld be low s in c e 360 in d iv id u a l s o i l sam p les, ta k e n by fo o t d ep th s
60
t o a depth, o f 5 f e e t a t 72 l o c a t i o n s , were used to make up th e s e a v e ra g e s e
A l o s s was a ls o re c o rd e d a t Havre d u rin g two w in te rs on b a re fallow *
D oughty, J 0 L0 e t a i ( I l ) found t h a t th e r e were s e v e r a l w in te rs in which
b a re fa llo w g a in e d no m o is tu re a t S w ift G u rfa n t, Saskatchew an an# T h y s e ll
(24) r e p o r t s a lo s s o f s o i l m o istu re d u rin g some w in te rs a i Mandan, H o rth
Dakota*
...
The p e rc e n t o f p r e c i p i t a t i o n which i s c o n se rv e d in th e s o i l i s an i n ­
t e r e s t i n g f ig u r e b u t i s n o t a s im p o rtan t a s th e amount o f m o is tu re which i s
a c t u a l l y sto re d *
At. Havre 1*6 in c h e s o f m o istu re were co nserved in th e
s o i l u n d er sta n d in g s tu b b le from h a r v e s t u n t i l th e tim e t h e c ro p emerged
th e fo llo w in g sp rin g *
D uring th e su cc e ed in g summer months 0*6 o f an inch
was s to r e d and d u rin g t h e second w in te r p e rio d 1*2- in c h e s were conserved*
At C u lb e rts o n 2*1 in c h e s o f w a te r were s to r e d d u rin g t h e f i r s t w in te r from
h a r v e s t u n t i l seed in g tim e and 1*4 in c h e s were co n serv ed d u rin g th e summer
months *
Only O06 o f an in c h was s to r e d d u rin g th e second w in te r o f th e f a l
low p e rio d *
The d if f e r e n c e s in d ic a te d in th e way i n which m o istu re i s conserved
'
a t th e se two lo c a tio n s i s p a r t l y b e ca u se sam pling d a te s were d i f f e r e n t and
i s a ls o p a r t l y due to d if f e r e n c e s in s o i l ty p e and w eather*
The f a l l sam­
p lin g o f th e s o i l a t Havre was a t h a r v e s t tim e w h ile a t C u lb e rtso n i t was
s i x weeks t o two months l a t e r *
The l a t e r sam pling d a te a t C u lb e rtso n made
a lo n g e r summer p e rio d and n a t u r a l l y more in c h e s o f m o is tu re would b e con­
se rv e d in a lo n g e r p erio d *
The p e rc e n ta g e saved would n o t b e high d u rin g
th e e a r l y f a l l b e ca u se o f h o t w e a th e r arid f a l l weed growth*
The w in te r
p e rio d on th e o th e r hand was s h o rte n e d b y th e l a t e f a l l sam pling and con­
61
s e q u e n t l y t h e r e w as a t e n d e n c y f o r l e s s w a t e r to b e c o n s e r v e d b u t t h e p e r ­
c e n ta g e w as h ig h b e c a u s e low t e m p e r a t u r e s p r e v a i l e d d u r in g t h e e n t i r e p e r i ­
od.
T o r r e n t i a l r a i n s w e re m o r e 1f r e q u e n t a t C u l b e r t s o n t h a n a t H a v re r e ­
s u l t i n g i n a g r e a t e r l o s s fro m r u n o f f .
The C u l b e r t s o n s o i l s ' a r e s a n d y on
t h e s u r f a c e a n d f o r t h i s r e a s o n e v a p o r a t i o n l o s s e s a r e lo w e r t h a n a t H av re
w h ere t h e s o i l i s h e a v i e r ,
S a n d y s o i l s p e r m i t d e e p e r p e n e t r a t i o n o f sim ­
i l a r am o u n ts o f w a t e r t h a n do t h e s o i l s o f f i n e r t e x t u r e .
The d if f e r e n c e s m entioned in th e s o i l and w e a th e r, a t th e s e two lo c a ­
tio n s a re im p o rta n t ite m s to c o n s id e r i n p la n n in g th e c ro p p in g system s and
la n d management,
A t C u lb e rts o n , where th e r e i s c o n s id e ra b le r u n o f f d u rin g
th e summer, p r a c t i c e s such a s c o n to u r s t r i p cro p p in g a r e more im p o rtan t
th a n th e y a r e a t Havre where t o r r e n t i a l r a i n s a r e l e s s f r e q u e n t.
The sandy
s o i l a t C u lb e rtso n w ith a s m a lle r w a te r h o ld in g c a p a c ity makes t h a t s o i l
b e t t e r ad ap ted to a system o f c o n tin u o u s c ro p p in g .
S in ce such e f f e c t i v e
m o is tu re c o n s e rv a tio n i s ach iev ed i n s tu b b le f i e l d s , i t seems t h a t more
c o n s id e ra tio n sh o u ld be g iv en to th e tr a p p in g o f snow p a r t i c u l a r l y in th e
C u lb e rtso n a r e a .
The h ig h e r e v a p o ra tio n lo s s e s w hich ta k e p la c e d u rin g t h e summer
months a re r e f l e c t e d in c o r r e l a t i o n c o e f f i c i e n t s betw een p r e c i p i t a t i o n and
th e p e rc e n ta g e o f m o is tu re saved d u rin g d i f f e r e n t p a r t s o f t h e y e a r,
At
Havre th e c o r r e l a t i o n betw een s e a s o n a l p r e c i p i t a t i o n and th e p e rc e n ta g e
o f m o is tu re saved d u rin g t h e summer months was ,7 2 6 and d u rin g t h e w in te r
months th e c o r r e l a t i o n betw een th e same two f a c t o r s was ,4 2 0 ,
D uring sum­
mer when e v a p o ra tio n i s h ig h a la r g e amount o f p r e c i p i t a t i o n g e n e r a lly
means t h a t a l a r g e r p e rc e n ta g e o f i t i s saved because a m a i l e r p e rc e n ta g e
i s l o s t th ro u g h e v ap o ratio n *
I n th e w in te r tim e when e v a p o ra tio n i s low
th e e v a p o ra tio n o f m o istu re i s not a s much o f a fa c to r*
The av erag e amount o f w a te r a v a ila b le to th e cro p on fa llo w a t H avre,
d u rin g th e 24 y e a r p e rio d was 9*2 inches*
T his 9*2 in c h e s c o n s is te d of
m o is tu re used from, th e s o i l p lu s p r e c i p i t a t i o n from th e tim e th e crop
emerged u n t i l h a r v e s t time*
The y ie ld o f s p rin g w heat d u rin g t h i s same
p e rio d averaged 17*9 b u s h e ls p e r acre' w hich means t h a t th ro u g h th e y e ars
ab o u t one in c h of w a te r was r e q u ir e d to produce two b u s h e ls o f s p rin g w heat
D uring th e tim e t h a t . s p r in g w heat av erag ed 17*9 b u sh e ls o r 1071 pounds
o f g r a in p e r a c re th e s tra w y ie ld s av erag ed 2028 pounds p e r a c r e w hich i s
a r a t i o o f 1*9 to I*
S p rin g w heat grown on s p rin g plow ing in a system o f
c o n tin u o u s cropping produced an a v e ra g e o f 542 pounds o f g r a in p e r a c re
and 927 pounds o f stra w which i s a r a t i o o f 1*7 to I*
s h ip a ls o e x i s t s a t C u lb e rts o n , Aasheim ( l) *
T his same r e l a t i o n ­
The p r o p o r tio n a te ly h e a v ie r
y ie ld o f s tra w on summer fa llo w s u g g e s ts t h a t a n a ll g r a in s grown f o r hay
should be grown on fa llo w r a t h e r th a n fo llo w in g a n o th e r crop*
The g e n e r a l
p r a c t i c e among d ry la n d fa rm e rs in Montena is t o grow sm all g r a in s f o r hay
on la n d viiich was cropped th e p re v io u s year*
On fa llo w t h e s p rin g wheat cro p used a p p ro x im a te ly 4 in c h e s o f m ois­
t u r e ( s o i l m o is tu re and s e a so n a l p r e c i p i t a t i o n grouped to g e th e r) b e fo re any
g r a in was p roduced.
I n ' th e c o n tin u o u s cro p p in g system 5*7 in c h es were used
b e fo re g r a in p ro d u c tio n began.
T his d if f e r e n c e i s no t la rg e b u t i t i s
l o g i c a l t h a t s in c e fa llo w u s u a lly has a lu s h e r grow th th a n co n tin u o u s c ro p ­
p in g more m o is tu re w i l l be used by such a crop b e fo re g r a in i s produced
th a n by a crop grown i n a system o f c o n tin u o u s c ro p p in g .
63
S p rin g w heat on fa llo w a t Havre u sed an av erag e o f 3 ,5 in c h e s o f w a te r
from th e s o i l b u t i t used o n ly I 05 in c h e s from th e s o i l on la n d c o n tin u ­
o u s ly c ro p p ed .
e ls p e r a c re 0
The average y ie ld o f w heat on s p rin g plowing was 9„0 bush­
The two a d d itio n a l in c h es t h a t th e crop used from th e s o i l
on fa llo w was r e s p o n s ib le f o r an 6 .9 b u s h e ls d if f e r e n c e in y ie ld o r in
o th e r words each in c h o f m o istu re was re s p o n s ib le fo r a' 404 b u sh els in ­
c re a s e in y ie ld *
T h is i s in agreem ent w ith r e s u l t s d eterm ined by th e use
o f m u ltip le r e g r e s s io n to compute th e r e g r e s s io n o f y ie ld on s o i l m o istu re
above 5 ,5 in c h e s and s e a s o n a l p r e c i p i t a t i o n .
T h is ty p e o f a n a ly s is in d i­
c a te d t h a t a f t e r th e crop has used enough m o is tu re f o r g r a in p ro d u c tio n t o
b e g in , th e n each in ch o f s o i l m o istu re u sed by th e cro p w i l l on the aver--"
age produce 4 ,4 b u s h e ls o f g r a in p e r a c re and e ac h in ch o f p r e c i p i t a t i o n
w i l l produce 3»15 bud h els p e r a c r e .
The r e l a t i o n s h i p s t h a t s o i l m o is tu re and p r e c i p i t a t i o n h o ld to y ie ld
were a ls o d eterm in ed by l i n e a r r e g r e s s io n and found to b e aboub th e same
by t h i s method as by m u ltip le r e g r e s s io n .
The e f f e c tiv e n e s s o f p r e c i p i t a ­
t i o n , a c c o rd in g t o th e r e l a t i o n s h i p s d e te rm in e d , i s o n ly ab o u t 70% o f t h a t
o f m o is tu re s to r e d in th e s o i l .
I t seems re a so n a b le t h a t s o i l m o istu re
would be more e f f e c t i v e because a c o n s id e ra b le amount o f p r e c i p i t a t i o n i s
l o s t th ro u g h e v a p o ra tio n .
P r e c i p i t a t i o n , how ever, i s a s s o c ia te d w ith c o o l­
e r w eath er and low t r a n s p i r a t i o n and e v a p o ra tio n which te n d s to g iv e p r e ­
c i p i t a t i o n some ad v an tag es s o i l m o is tu re does n o t have.
The f a c to r s such
a s cool w eath er which accompany r a i n f a l l .have n o t been s e p a ra te d ou t in
th e a n a ly s is o f th e d a t a ,
.
■
I n c a l c u l a t i n g w a t e r r e q u ir e m e n t, t h e r e a r e s e v e r a l m e th o d s o f a p ­
64
p ro a c h ,
u sed .
I n t h i s s tu d y two methods o f d e te rm in in g w a te r re q u ire m e n t were
In th e one method a l l o f th e p r e c i p i t a t i o n betw een th e tim e the
crop emerged u n t i l h a rv e s t tim e was added t o th e m o istu re used from th e
s o i l and t h i s amount o f m o istu re was c o n sid e re d a s th e amount o f w a te r used
by th e c ro p .
I n th e o th e r method o n ly
o f th e p r e c i p i t a t i o n du rin g th e
above m entioned p e rio d was added to th e s o i l m o is tu re u sed .
The 70% f ig u r e
was used b ecau se p r e c i p i t a t i o n was found t o be ro u g h ly 70% a s e f f e c t iv e as
s o i l m o is tu re .
Ho d o u b t t h i s l a s t method o f f ig u r in g w a te r re q u ire m e n t i s
s t i l l h ig h becau se some s o i l m o is tu re i s l o s t th ro u g h e v a p o ra tio n and weed
grow th.
When a l l o f th e p r e c i p i t a t i o n betw een crop emergence and h a r v e s t was
c o n sid e re d a s th e amount o f w a te r used by th e c ro p th e n s p rin g w heat on
fa llo w r e q u ir e d 737 pounds of w a te r to produce one pound o f d ry m a tte r and
s p rin g w heat on s p rin g plow ing in a system o f c o n tin u o u s cro p p in g re q u ire d
1238 pounds o f w a te r t o produce one pound o f d ry m a tte r .
When 70% o f t h e p r e c i p i t a t i o n betw een crop emergence and h a rv e s t was
s u b s t i t u t e d in p la c e o f a l l o f th e p r e c i p i t a t i o n re c e iv e d d u rin g t h a t p e r i ­
od th e n s p r in g w heat on fa llo w r e q u ir e d 609 pounds o f w a te r t o produce one
pound o f d ry m a tte r and 942 pounds w ere r e q u ir e d to produce one pound o f
d ry m a tte r on s p rin g plow ing. .
Both o f th e s e methods o f c a lc u la tin g w a te r req u irem en t show a n advan­
ta g e f o r th e c ro p s grown on fa llo w b u t t h i s may be b ecau se m o istu re was
more e f f i c i e n t ip producing m a te r ia l a f t e r a c e r t a i n amount o f w a te r was
used.
C e r ta in ly th e r e i s c o n s id e ra b le m o istu re u sed b e fo re any m easu rab le
amount o f d ry m a tte r i s p ro d u ced .
D uring a p e rio d o f 10 y e a r s , when g ra in
65
y ie ld s on fa llo w averaged th e same a s th e .24 y e a r p e rio d f o r co n tin u o u s
c ro p p in g , th e r e was v e ry l i t t l e d if f e r e n c e in th e w a ter re q u ire m e n t.
Under
th e s e c o n d itio n s ro u g h ly 885 pounds o f w a te r ( 70yt o f s e a s o n a l p r e c i p i t a t i o n
p lu s s o i l m o is tu re u sed ).w as r e q u ir e d t o produce one pound o f d ry m a tte r on
f a llo w .
I n re g a rd to th e p ro d u c tio n o f g r a in , i t was d eterm in ed t h a t a f t e r th e
minimum re q u ire m e n ts o f m o is tu re n eed ed . f o r g r a in p ro d u c tio n to b e g in have
been m et, th e n c o n tin u o u s cro p p in g i s e q u a lly e f f i c i e n t in p ro d u c in g a pound o f w heat as fa llo w .
I t i s q u ite e v id e n t t h a t w ater, re q u ire m e n t w i l l v a ry from y e a r to y e a r
f o r th e same cro p w ith in th e same cro p p in g system .
Y ie ld s p r e d ic te d on t h e .b a s i s o f m u ltip le r e g r e s s io n .o f y ie ld on p r e ­
c i p i t a t i o n and s o i l m o istu re show, c o n s id e ra b le d e v ia tio n from th e a c tu a l
y ie ld .
In 1928 th e p r e d ic te d y ie ld was 26*5 b u s h e ls and th e c ro p ' a c t u a l l y
y ie ld e d 4 1 .5 b u s h e ls .
I t i s e v id e n t t h a t d u rin g t h a t p a r t i c u l a r y e ar th e r e
were f a c t o r s w hich w ere n o t c lo s e to no rm al.
There were 5 .1 1 in c h e s o f
r a i n f a l l i n June w hich, o f c o u r s e , was much above norm al and may have come
a t a p a r t i c u l a r l y opportune tim e s in c e May was r e l a t i v e l y d r y .
Gool tem­
p e r a tu r e s and low er th a n norm al wind v e l o c i t i e s may a ls o have p re v a ile d as
w e ll a s o th e r c o n d itio n s fa v o ra b le fo r p l a n t grow th.
The mean d e v ia tio n o f
th e p r e d ic te d y ie ld from th e a c tu a l y ie ld was s l i g h t l y o v er 4 b u s h e ls .
The c o r r e la tio n betw een y ie ld o f s p rin g w heat on fallo w , and in c h e s o f
p r e c i p i t a t i o n i n June was .521 and th e c o r r e l a t i o n betw een y ie ld and in c h es
o f p r e c i p i t a t i o n i n May-was .4 1 9 .
These s i g n i f i c a n t c o r r e l a t i o n c o e f f i ­
c i e n t s betw een y i e l d and p r e c i p i t a t i o n d u rin g th e s e two months in d ic a te th e
66
im portance o f r a i n f a l l d u rin g t h a t tim e o f year®
The c o r r e l a t i o n betw een ■
y ie ld and J u ly p r e c i p i t a t i o n was o n ly .153*
N e a rly a l l o f th e m o istu re used from th e s o i l by th e crop in th e A
p l o t came from th e f i r s t and second f o o t d e p th s o f so il* .
The crop on f a l ­
low however used a good d e a l o f m o istu re from th e t h i r d f o o t .
At h a r v e s t tim e th e fa llo w e d s o i l was more m o ist a t d e p th s o f 3 and
4 f e e t th a n was th e c o n tin u o u s ly cropped s o i l .
T h is in d ic a te s t h a t wheat
d e p le te s th e s o i l m o istu re to a g r e a t e r d eg ree u n d er a system o f c o n tin u o u s
cropping th a n un d er an a l t e r n a t e c ro p -fa llo w sy stem .
The c o r r e l a t i o n betw een y i e l d and p r e c i p i t a t i o n and y ie ld and s o i l
m o is tu re was c l o s e r on th e A p l o t th a n i t was on th e G a n d .D p l o t s .
T his
no doubt i s due to th e f a c t t h a t m o istu re was more o f a lim itin g f a c to r in
th e p l o t s c o n tin u o u s ly cropped*
'
67
■ SIMABY
A t .H avre, M ontana, d u rin g a p e rio d o f tw e n ty -fiv e y e a r s , (-1921-1945)
o n ly 5 e5 in c h e s o f w a te r, o r 18. 7% o f th e p r e c i p i t a t i o n re c e iv e d d u rin g
th e fa llo w p e r io d , was conserved in th e s o ilo
A pproxim ately o n e -h a lf o f
th e m o is tu re conserved was conserv ed d u rin g th e p e rio d from h a r v e s t u n t i l
th e fo llo w in g s p r in g .
At C u lb e rts o n , M ontana, 27/. o f th e p r e c i p i t a t i o n re c e iv e d d u rin g th e
fa llo w p e rio d was co n serv ed in th e s o i l ,
A l i g h t e r s o i l and a h ig h e r p e r ­
centage o f m o is tu re saved d u rin g th e f i r s t w in te r o f th e fa llo w p e rio d
acco u n ted f o r most o f the d if f e r e n c e i n e f f ic ie n c y o f m o is tu re s to ra g e a t
th e two lo c a t io n s .
The p e rc e n ta g e o f p r e c i p i t a t i o n saved i n th e fa llo w e d s o i l d u rin g th e
summer months was low a t b o th p la c e s , and i t was h ig h ly c o r r e la te d w ith th e
amount o f p r e c i p i t a t i o n re c e iv e d ,
At Havre an av erag e o f 3 ,5 in c h e s o f w a te r was used from th e s o i l by
s p rin g w heat grown on f a llo w .
One and o n e - h a lf in c h e s w ere used from th e
s o i l when s p rin g w heat was grown on s p r in g plow ing.
The y ie ld o f s p r in g w heat on fa llo w av erag ed 17 .9 b u s h e ls p e r a c re and on' c o n tin u o u s c ro p p in g i t averag ed 9 .0 b u sh e ls' p e r 'a c r e .
The d i f f e r ­
ence in y i e l d o f 8 .9 b u s h e ls p e r a c re was produced on th e two in c h e s o f
a d d itio n a l s o i l m o is tu re a v a ila b le t o th e crop grown on fa llo w .
About, fo u r in c h e s o f w a te r were used by th e cro p grow ing on fa llo w
b e fo re any g r a in was p ro d u ced .
A f te r th e 4 in c h e s w ere used each a d d itio n ­
a l in c h o f s o i l m o istu re a v a ila b le t o th e crop produced about 4 .4 b u s h e ls
o f g r a in and each a d d itio n a l in c h o f p r e c i p i t a t i o n produced about 3 ,1
68
b u s h e ls o f g ra in ..
T his in d ic a te s t h a t p r e c i p i t a t i o n re c e iv e d d u rin g th e
growing season i s o n ly ab o u t 70f. a s e f f e c t i v e a s au e q u a l amount o f m ois­
tu r e s to re d in th e s o i l .
S in ce p r e c i p i t a t i o n was c a lc u la te d to be o n ly 70% a s e f f e c t i v e as s o i l
m o is tu re , o n ly 70% o f th e p r e c i p i t a t i o n was in clu d e d when d e te rm in in g th e
w a te r re q u ire m e n ts o f the s p rin g w heat c ro p .
On t h i s b a s is th e w a te r r e ­
q uirem ent o f s p rin g w heat on fa llo w av erag ed 609 pounds o f w a te r p e r pound
o f dry m a tte r f o r the 24 y e a r p e r io d .
Gn c o n tin u o u s cro p p in g th e w a ter r e ­
q uirem en t av eraged 942 pounds o f w a te r p e r pound o f d ry m a tte r .
Ten cro p s
grown on fa llo w , w hich produced an a v e ra g e y ie ld o f 9 b u s h e ls o f g ra in p e r
a c re , had a w a te r re q u ire m e n t a lm o s t' as h ig h a s cro p s produced, d u rin g th e
24 y e a rs i n th e c o n tin u o u s croppin g sy stem .
T h is in d ic a te s t h a t th e w a te r
re q u ire m e n ts f o r th e same crop w i l l v a ry c o n s id e ra b ly from y e a r to y e a r and
t h a t th e n u t r i e n t le v e l may n o t be to o im p o rta n t a s f a r as e f f ic ie n c y o f
w a te r use i s c o n c e rn e d .
Y ie ld s p r e d ic te d on th e b a s i s o f m u ltip le r e g r e s s io n o f y ie ld on s e a ­
s o n a l p r e c i p i t a t i o n and s o i l m o is tu re show an av erag e d e v ia tio n o f 4 '.bush­
e l s from th e a c tu a l y i e l d .
Four y e a rs o u t o f th e 24 w ere re s p o n s ib le f o r
a lm o st o n e -h a lf o f t h i s d e v ia tio n .
The c o r r e l a t i o n betw een y ie ld and s p rin g to h a r v e s t p r e c i p i t a t i o n was
h ig h e r •th a n betw een y ie ld and s o i l m o is tu re a t tim e o f crop emergence#
P re­
c i p i t a t i o n i n l a y and June was v e ry h ig h ly c o r r e la te d w ith y ie ld o f g r a in .
There was c l o s e r c o r r e l a t i o n betw een y ie ld and s o i l m o istu re and y ie ld and •
p r e c i p i t a t i o n in th e c o n tin u o u s c ro p p in g system th a n t h e r e was in th e f a l ­
low system .
'
69
M o istu re u t i l i z a t i o n from th e s o i l was more com plete in th e f i r s t and
second fo o t th a n i t was a t lo w er d ep th s i n d ic a tin g t h a t th e crop was n o t
a s e f f e c t i v e i n u t i l i z i n g m o is tu re a t th e lo w er levels®
/
70
LITERATURE CITED
I#
AASHEIM, T o S 0 - The e f f e c t o f t i l l a g e method, on s o i l a n d .m o istu re
c o n s e rv a tio n i n the. P la in s Area o f N o rth e rn M ontana. Mont0 A gr. Exp6
S ta o B u i. 468. 194?0
2.
BELL, Mo A. - The effect" o f t i l l a g e m ethod, crop seq u en ce, and d a te o f
se e d in g upon th e y ie ld a n d " q u a lity o f "cereals"an d o t h e r . cro p s grown"
under d ry la n d c o n d itio n s i n N o rth C e n tra l M ontana. M ont. A gr. Exp0
S t a . B u i. 536. 1927.
3o
, L. J . and SHANTZ, E. L. - T he' w a te r req u irem en t o f p l a n t s .
U.S.DoA. B ur. P la n t Ind,. B ul6 No. 284. 1913.
B R IG G S
4»
CHILLCOTT, E. "G. - The r e l a t i o n s betw een c ro p ' y ie ld s and p r e c i p i t a ­
t i o n in th e G re at P la in s a r e a . U . S . D o A . M isc0 C ir c u la r No. 8l
Supplem ent I . 1921»
5o
COLE, JOHN S . " - C o r r e la tio n s betw een an n u al p r e c i p i t a t i o n and th e
y ie ld o f s p rin g w heat in th e G reat P l a i n s . U.S.D .A . Tech. B u i. 636.
1938.
^0
COLE, JOHN 8 . and MATHEWS, 0. "Ri —Use o f w a te r by s p r in g w heat on
th e G reat P l a i n s . U.S.D .A . B ul6 1004» 1923.
7o
■
______ _______"
"S u b s o il m o is tu re u n d er se m ia rid co n d i­
t i o n s , U .S.D .A . Tech. B u i. No. 637. 1929.
8»
"______
"
R e la tio n o f t h e d e p th to which th e s o i l
i s wet a t seed in g tim e " to th e ; y i e l d .o f . s p r in g w heat on th e G reat
P l a i n s . "U.S.D.A. C ir c . Nd. 363. 1940.
9.
.DAVIS, .P. E . and PALLESEN, J . "E. - E f f e c t o f th e am ount"and d i s t r i b u ­
t i o n o f r a i n f a l l a n d "e v a p o ra tio n d u rin g th e ;g ro w in g seaso n on y ie ld s
o f corn and s p r in g w h eat. Jour*- A gr0 R es. 6 0 5 ls l-2 4 . 1940.
10.
DILLMAN; ARTHUR""C". -"The w ater" re q u irem en t o f .c e r t a i n cro p p la n ts and
weeds in th e N o rth e rn G re at P l a i n s . J o u r . A gr. R es. 4 2 ;I 87- 238.
1931.
11.
DOUGHTY, J . L . , e t . a l . - S o i l " m o i s t u r e , wind e r o s io n , and f e r t i l i t y
o f some C anadian p r a i r i e " s o i l s . Dominion o f Canada - D ep t, o f A gr.
Tech. B u i. No. 71. 1949.
12.
FLORELL, V. H. - High crop s tu b b le and snow c o n s e rv a tio n .
s e r v a tio n 31223- 226. 1940.
S o il Con­
71 .
IJ0
HALLSTED, A. L. and MATHEWS, 0. He
S o il m o is tu re and w in te r wheat
w ith s u g g e s tio n s on abandonm ent. Kansas A gre Expe S ta e B u le Koe 27J*
1956o
14»
HILGEEAH, B. He .-"C hanges in s o i l m o is tu re in th e to p e ig h t f e e t o f
a b a re s o i l d u rin g tw enty-tw o months a f t e r w i l t i n g , J o u r e Ame Soce
Agrone 40:10:919-925» 1948»
150
LEBEDEFF, A. F0 - The movement o f ground and s o i l w a te r s . P ro ceed —"
in g s and p a p e rs o f th e F i r s t I n t e r n a t i o n a l C ongress o f S o i l Science*
459-494. 1928c
16.
MATHEWS, Oe He arid BASHES, Be Fe — D ryland cro p s a t th e D a lh a rt
(T exas) f i e l d s t a t i o n . H0S eDeAe C ir c e 564. 1940.
17» . MOHGAH, GEOHCE W» and. .BELL, He Ae "- Wheat ex p erim en ts a t "th e .'N orth­
e rn Montana Branch S ta t i o n . H onte A gre Expe S ta e B u le Koe 197. 1926.
l8 .
PEKGHA, R0 ".Fe". - E stim a tin g , crop y ie ld s ..at see d in g tim e in G reat
P l a i n s , A g rp n ,-j o u r . 4 4 :5 :2 7 1 -4 . 1952.
190 SHANTZ, He Le arid PIEMEISEL, LTDIA-Ne "- The water, re q u ire m e n t o f
p l a n t s a t A kron, C o lo ra d o . J o u r. A gre R es, 54:1093-1190. 1927.
20.
2 1.
22.
SHAW, ."Be Te -.T h e r o l e o f r e s e a r c h iri m eetin g f u tu r e a g r i c u l t u r a l r e ­
q u ire m e n ts. Agrone J o u r . 4 5 :3 :8 5 -9 2 . 1953.
STARCH," Ee A V - Farm o rg a n iz a tio n a s a f f e c t e d by m e c h a n iz a tio n .
. A gr. Exp. S t a e B u i. No. 2?8. 1933*
H o n t.
STEPHENS-, DAVID" Ee , OVESON, MERRILL""M0 and- MITCHELL," GEORGE A0 - "
W a te r're q u ire m e n t of" wheat a t th e Sherman Branch E xperim ent S ta t i o n .
Oregon A gre Exp. S t a 0 Tech. B u i. No. I . 1943.
23» THOM,. C0 Ce arid HOLTZ,. He.."F, - F a c to rs in flu e ric in g th e w a te r r e q u ir e ­
m ents o f p l a n t s . Wash. A gre E xp. S t a e B u le No. 146. 1917.
24.
THYSELL, . J . C0 - C o n se rv a tio n arid u se o f "soil".m oisture a t "Mandan,
N o rth D akota. U0S 0D0A0 T e c h n ic a l B u l l e t i n No. 617. 1938.
25»
WADLEIGH, L0 A. arid RICHARDS, Ce ".H0 - . S o i l w ater and " p la n t grow th.
S o il P h y s ic a l" C o n d itio n s .a rid P la n t Growth. E d ite d by Bryon Te Shaw.
Academic P r e s s I n c . 73-253. 1952.
26.
WELTON, Fe A0 . and WILSON, J e D. - C om parative r a t e s o f w a te r lo s s from
s o i l t u r f and w a te r s u r f a c e s .
Ohio A gr. Exp. S ta e B im onthly B u i. 23:
1 3 -1 6 .. 1939.
72
APPENDIX
Tke t a b l e s w hich fo llo w c o n ta in d e ta i le d in fo rm a tio n on s o i l m ois­
tu r e sam p lin g d a te s and in c h es o f w a te r p e r f o o t d e p th o f s o i l f o r th e
d i f f e r e n t sam pling d a te s , by y e a r s , f o r b o th la n d in fa llo w and land, con­
tin u o u s ly cropped a t H a v re , M o n tan a.' T able V III summarizes p e r t i n e n t i n ­
fo rm atio n developed from N orth Montana B ranch S ta tio n d a ta .
T h is in fo rm a tio n i s p re s e n te d h e re in o rd e r to p r e s e r v e . some o f th e
d e ta i le d in fo rm a tio n on which a good sh a re o f t h i s p a p e r i s b a se d .
I n th e
e v e n t f u r t h e r a n a ly s is o f th e d a ta sh o u ld be a tte m p te d t h i s b a s ic d a ta w i l l
be e a s i l y a v a il a b le .
T able 1».
Sp,il m o is tu re sam pling d a te s a t t h e . N ortli-M ontana „B ranch S t a t i o n ,
H a v re , M ontana.
Year
S p rin g
1919
1920
1921
1922
1925.
1924
192-51926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
5-18
5-17
5-22
5-21 '
5-20
5-18
5-18
5-27
5-14
. 5-20 .
5-16
5-13
5 -1 ?
5-16
5 -8
5-21
5-14
5-11
5-?lQ
5 -3
5-15
5 -8
4-29
5 -7
5-15
5-15
5-23
F a ll
-
-
8-16
8-2
8-1
7^31
7-30
8-4
8-3
8-4
8-4
8-8
7-31
7-31
7-22
7-31
8-2
7-31
8-5
7-22
8-4
8-2
8-5
7-30
7-3Q
7-30
10-1©
10-5
9-10
74
T able I I *
T ear
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930'
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
In ch es o f w a te r in " v a rio u s f o o t d e p th s o f s o i l a t tim e .of cro p
emergence „in a system o f c o n tin u o u s .c ro p p in g -a t" th e Hforth
Montana B ranch S t a t i o n , H av re, Montana*
1st f t.
1*76
I 0B9
1*67
. 1 .5 8
1 .5 0
1 .3 8
2. 181 .5 f
1 .7 6
1 .8 2
1 .3 3
1 .5 7
1 .8 3
1 .6 2
1 .9 2
1 .3 0
1 .1 4
1..74
1 .3 0
1 .7 9
1 .5 9
1 .8 6
1 .8 0
. 1 .2 3
1 .5 3
2nd f t .
.
2.00
2.3 9
1 .7 7
1 .9 5
1 .6 6
2 .4 4
2.98
1 .7 5
2 .0 3
1 .8 4
1 .4 3
1 .2 5
1*26
2.39
2.1 5
1 .6 9
1 .3 2
2.0 6
1 ,3 1
2 .60
lo.44
2 .6 6
1 .5 3
1 .2 3
1 .6 2
3rd f t . ,
1,30
1.57
1 .4 6 1 .3 3 ■
1 .4 6
1 .8 4
2.9 3
1.58
1 . 60
1 .5 5
'
I .28
1 .2 4
1.30
. 1.-87
1 .5 5
1.2 2
1 .2 1
1 .4 8
1.2 2
1 .3 3
1 .3 0
1.75.
1.4 0
- 1 .1 1
1 .2 5
4 th f t .
1.29
1 .3 8
.1.40
1 .3 5
1 .2 7
1 .5 1 .
2.02
1 .9 7
1 .7 3
1 .8 2
1 .4 7
1 .4 2
1 .2 4
1 .5 9
1 . 46
1*35
1 .2 4
1 .3 1
lo,24
1.7 5
1.38
■'1 .4 0
1.3 8
1 .51
1*37
75
T able I I I 0
T ear
In c h e s o f w a te r In v a rio u s fo o t" d e p th s o f s o i l a t h a r v e s t tim e
in ,,a system o f co n tin u o u s, d ro p p in g a t th e N o rth Montana
B ranch S t a t i o n , H avre, E b n ta a a 0
1 s t f to
2nd f t .
5rd f t .
4 th f t .
-------- ------------------------- i-T -----------------------1921
1922
192?
1924
1925
19.26
1927
1928
1929
1950 1951
1952
1955
1954
1955
1956
1957
1958
1959
1940
1941
1942
1945
1944 .
1945
0 .8 5
0 .6 9
I e 46
1 .0 4
9 .7 7
0 .6 1
1 .5 5
1 .2 2
1 .0 6
1 .1 0
1 .2 4
1 .1 1
0 .5 2
0 .5 6
0 .7 5
0 .4 5 .
0 .7 5
1 .0 9
9 .5 7
0 .7 4
1 .0 2
1 .5 2
0 .5 8
0 .8 5
0 .7 1
1 .1 6
1 .1 9
1.7 5
1 .0 8
1 .2 0
0 .9 5
1 .9 5
1 .2 0
1 .0 5
1 .0 2
1.2 0
1 .0 8
1 .0 8
1.05
1.1 2
0 .8 ?
1 .1 6
1 .5 0
1 .0 0
1 .0 8
l.l6
1 .7 5
1 .1 0
1 .5 0
1 .0 8
--------------- 'Ij 11 1
.
1 .4 0
1 .5 1
1 .5 7
l « r 51
'
1 .5 9
1.1 5
2 .0 5 v
1.49
1 .5 7
1 .5 1
1 .2 2
1 .2 8
1 .5 0
.
1657:
1 .5 5
1 .2 6
. 1 .2 8
1.5.0
Iill
1 .2 1
1.5 7
1 .5 7
1 .1 7
1 .4 4
1 .2 1
--- ------------------
1—
—
—------------------------------
1 .5 5
1.0 9
1.5 1
1 .2 9
1 .5 5
1 .5 5
2.29
1.7 8
1 .6 6
1 .7 5
1 .5 5
1 .49
1 .4 2
1 .40
1 .4 4
1.-2?
1.5 5
1 .5 7
. 1 .2 7
1 .5 7
1 .5 5
1 .5 1
1 .2 4
1644
1.8 8
76
Table IT 0
T ear
In b h e s o f m ate? in v a rio u s f o o t d e p th s o f s o i l i n .s tu b b le to be
fa llo w e d a t h a r v e s t tim e,, N o rth Montana B raneh S ta t i o n ,
H avre, M ontana6
1 st fte
2nd f
3 rd f t .
4 th f t .
T o ta l
;
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930.
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1.943
1944
1945
.
O6S l
1 6Q5
1»05
0 .7 3
1 .3 0
1 ,3 4
' 1 ,0 0
O6 79
lo09
0 .9 4
0 .5 0
0 ,6 1
1 .0 5
0 .7 0
0 .7 3
0 .6 5 .
0 ,8 3
0 .6 0
• 1.02
0 .9 3
0 ,7 0
1 .4 5
1 .2 0
1.46
0 .5 8
0 .8 2
0 .7 1
1 .1 5
1 .3 1
1 .3 1
1 .1 0
1.21
1 .3 8
1 .1 8
1 .3 3
1.49
1 .2 1
0 ,9 2
1 .1 3
1 .5 7
1*18
1 .2 6
1 .1 3
1 .1 3
1*05
1 .2 3
1 .2 5
W 3
1 .0 8
1*43
1 .2 6
1 .1 3
1 .1 1
1 .0 8
1 .3 0
1 .4 9
1 .4 9
1.4-9
1 .4 6
1 .6 2
1.3 9
1.4 8
1*?6
1.49.
1 .2 2
1 .6 6
1 .7 5
1 .5 7
1.5 8
1 ,5 8
1.6 5
1 .4 4
1 .4 2
1*71
1 .4 8
1.2 8
1 .7 5
1 .6 2
1 .3 3
1 .3 9
1 .4 6
1 .7 7
1 .7 7
1 .8 6
1.5 5
1 .6 4
1 .8 ?
1:75
1.89
2.35
2.2 8
1 .8 7
2.6 2
2.0 9
2.4 3
2.07
2 .3 5
2 .3 3
1 .8 0
,, 1 .6 2
. 1»49
. 1 .4 2 ■
1 .3 7
2.02
1. 6.6
1.7 2
1.6 6
1 .7 8
5 .0 3
5.6 2
5 .7 1
4 .8 7
5 .6 1
6.21
5 .3 2
5 .4 9
6.69
5 .9 2
4 .5 1
6.02
6 .46
5 .8 8
5 .6 4
5 .7 1
5 .9 4
4 ,8 9
5 .2 9
5 .3 8
4 .6 3
5 .1 8
6,40
6.00
-4.76
4,9.8
5 ,0 3
77
T able Ve
Inchds o f w a te r in v a rio u s f o o t d e p th s, p f . s o il, in s tu b b le to be
fa llo w e d a t tim e of.: cro p em ergence, F o r th Montana Branch
S t a t i o n , H avre, .Mont a n a ,*
T ear
1st f t .
2nd f t .
3 rd f t .
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1952
1933
1934
1935 .
1936
1937
1938
1939
1940
1941
1942
1943
19441945
1946
I a57
1 ,9 6
1 ,9 8
1 ,5 1
I 051
I , 24
l a 65
2 ,2 4
1 ,4 4
I , 96
1 .8 8
1 .5 5
1 .7 1
2 ,0 1
1 .3 7
2,08
0,98
1 .3 0
l,.6 l
I .2 3
1 .9 5
1 .6 3
■1.98
1,88
1 .2 6
1,62
1,46
2 ,8 5
2,11
2.77
1 .8 7
1 .8 5
2,08
2,56
3.00
2,03
2.87
2,10
1 .8 7
1 ,6 2
2,38
2 ,6 6
2.79
1 .3 8
1 .8 7
1,62
1 .3 8
3.15
1 .6 2
2 ,6 ?
1 .8 5
1 .3 4
1 ,8 4
1.85
2,16
1 .4 0
1 .7 3
1.5 T
1 ,2 6
1 .6 6
1 .7 1
3.2 8
1 .6 2
2.09
1 .6 4
1 .5 5
1 .3 9
2 ,03
2 .3 6
1 .9 0
1.3 9
1 .3 3 .
1 .2 8
1 ,3 1
2.50
1.35
2.1 4
1 .5 3
1 .3 9
1 ,40 .
1 .3 1
.
"
.
4 th f t .
1 .5 1
1 .5 1
1 .4 9
1.6 9
1 .3 8
■ - 1 .8 0
1 .6 9
2b-02
1.89
1 .8 6
1.9 8
1 .8 7
1 .5 3
2,11
1 .7 1
- 2.26
1.51
1.38
1 .4 4
1,40
1 .5 5
1 .4 7
1 .6 4
1 .6 2
1 .8 0
1 ,6 7
1.58
-
T o ta l
8.09
6.98
7 .9 7
6.58
6.0 0
6.78
7 ,6 1
1 0,54
6 .58
8 ,7 8
7.;62
6 ,8 4
6,25 '
8 .5 3
8 ,1 0
9 .0 3
5 .2 6
5 .8 8
5 .9 5
5 .3 2
9.15
6 .0 ?
8 .4 3
6.88
5 .7 9
6 .5 3
6,20
^These s o i l m o is tu re .s a m p le s were ta k e n in s tu b b le which was t o be f a llo w .e a t h a t summer. The sam pling d a te .,co in cid ed w ith th e tim e o f crop '
emergence on fa llo w seeded to s p rin g V heat0
78
,T a b le , H a
Tear
Ijacbes o f w a ter, in ..v a rio u s f o o t d e p th s o f s o i l in fa llo w a t
h a r v e s t tim e 0 N orth M ontana B ra n ch .S t a t i o n , H av re, Montana* .*
1st f t O
2nd ft,.
3rd f t .
4th f t .
Total
2. Tl'
2 .6 6
2 .5 4
3.08
2 .4 4
2.66
1 .9 8
2.89
2. 62
2.56
2 .3 4
I . 82
2.46
2d 41
2.56
2.28
Io 34
2. 61
2.71
Io 77
2.48
2.48
2 .7 1
2 .5 3
I . 67
1.48
2.15
2.38
Io 78
1 .9 4
2 .5 0
1 .8 2
2 .3 6
1 .7 6
3 .1 9
2 .5 4
2.5 4
1 .7 3
lo,66
2 .3 6
Io 58
2 .4 3
2.25
1 .4 6
2 .1 0
1 .8 2
I . 40
2.12
Io 62
2.6 8
2 .3 4
1 .4 4
1 .3 3
1 .6 9
1.7 5
1 .6 4
1&55
I j 69
1.2 7
Io 66
lo 5 3
2d 88
2.09
2.3 1
2 .5 4
2.00.
1 .8 7
1 .7 7
1 .8 6
1,9 8
I . 42
1 .4 9
1.3 8
I . 55
Io 60
1 .62
1.95
1 .5 7
1 .7 1
I . 35
1^62
8 ,4 4
7 .9 1
Vo 60
9 .6 1
7»01
80 20
6,50
1 0 .7 7
9 .0 9
9 .0 3
7 .7 1
6 .8 5
8 .3 7
7.3 0
8 .3 4
8 .0 5
4 .8 6
80O6
7 .85
6.12
7.59
7 .4 2
9 .5 8
7 .8 0
6 .2 4
5 .1 2
7.0 9
-- 1---------1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1 9 3 9 ........
1940
1941
1942
1943
1944
1945
1946
1 .6 0
1 .8 3
1*57
2» 34
1.48
. Io 52
1*23
I 081
Io 84
Io 62
IolO
1 .3 7
I . 68
lo;541.49
1 .5 4
O0 64
1 .8 6
1 .9 4
1 .4 0
1.39
Io 70
2 .2 4
1 .3 6
1 .4 2
0 .? 6
1 .6 3
'
.
*These s o i l m o is tu re ,sa m p le s were ta k e n i n fa llo w lan d t o be seeded to
' s p rin g w heat th e fo llo w in g sp rin g o The sam pling d a te c o in c id e d w ith th e
d a te o f h a r v e s t on p l o t s in crop®
79
.Table V II6
. Iriehes o f welter i n v a rio u s f o o t d ep th s o f s o i l .in fa llo w a t
tim e o f crop em ergence, H o fth Montana B ranch S t a t i o n , H avre,
M ontana.*
'V
'
7
Y ear
1st f t 0
2nd f t .
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1932
1934
1925
1926
1927
1938
1939
1940 .........
1941
1942
1943
1944
1945
1946
1947
2.06
2„06
1 .8 2
Io 81
1 . 71
1 ,7 6
2.40
1,79
1 ,9 6
2 .2 0
Io 52
1 .8 2
2.10
1 .7 6
2 014
1*56
1*48
1*98
1*77
Io 94
2*05
1*98
2*05
1»57
1 .8 9
1*58
I* 69
2.08
2*02
2*62
2*97
2*77
2.82
3 .2 6
2 .6 1
2*94
3.11
2.15
2.57
3*06
2*66
2*84
2*44
1 . 62
2 .7 6
2*76
2 .7 7
2.87
2,89
2.80
2.67
2.15
2.59
2 .3 6
..
3 rd f t .
2 .2 7
2*48
- 1*96
2 .4 5 .
2*39
2.72
3.29
2 .7 5
2*59
2 .6 3
2*02
1 .9 6
2*75
2.81
2*59
2*2©
1*51 •
2*14
2*27
1 .9 1
2 .5 4
2 .9 0
2 .7 4
2*39
1*57
1 .8 0
I* 64
4 th f t .
.
1 .7 1
1*62
I* 66
1*7.3
1.58
. 2.49
2.78
2%53
2.42
2*26
2.35
1 .8 7
2.51
2.56
2.3 3
2*18
1 .6 4
1*64
lo 5 7
1.3 5
1*75
2.66
2 .3 3
1*84
1*53
1 .7 5
:* 7 5
T o ta l
9.12
9*19
8.06
8*96
8*45
\ 9.7 9
11.73
9*66
9 .9 1
10.20
8*05
8.2 2
1 0.42
9.7 9
9.9 0
8.38
6.25
8*52
8*37
7.97
9*21
10.43
9.92
8 .4 7
7 .1 4
7 .7 2
7 .4 4
*These m o istu re sam ples were ta k e n a f t e r th e fa llo w was seed ed and th e crop
was em erging.
Sg
T able H I I .
Summary o f p e r tin e n t" in fo rm a tio n developed from N o rth Montana
B ranch S t a t i o n , D a ta.
Fallow
P r e c ip . ~ F a l l to .s p rin g - f i r s t w in te r o f fa llo w p e rio d
O ont8
Crop
6 .6
P r e c ip 8 - Emergence to h a r v e s t
P r e c ip . - F a l l to s p rin g - second w in te r o f fa llo w p e rio d
P r e c ip . - E n tir e fa llo w p e rio d
g
5<,7
6 .5
6 .5
1 8 .7
Amount o f w a te r used from s o i l by cro p
3 05
1»5
P r e c i p i t a t i o n p lu s s o i l m o istu re u sed
9P2
7»2
M o istu re co n serv ed f i r s t w in te r o f fa llo w p e rio d (in c h e s )
1 .7
1*5
M o istu re conserved f i r s t w in te r o f fa llo w p e rio d (p e rc e n t) 2 5 .7
25 .1
M o istu re conserved from cro p emergence to h a r v e s t (in c h e s)
M o istu re conserved from crop emergence t o h a r v e s t (p e r­
c e n t)
10*7
M o istu re conserved second w in te r o f fa llo w p e rio d (in c h e s)
M o istu re conserved second w in te r o f fa llo w p e rio d (p e r­
c e n t)
0 .6
1 .2
1 8 .5
In ch es
o f w a te r in s o i l in s tu b b le i n f a l l
5 .6
4 .9
In c h e s
o f w a te r i n s o i l in s tu b b le i n s p rin g
7 .3
<U .
In ch es
o f w a te r i n s o i l i n fa llo w in f a l l
7*9
In c h e s
o f w a te r i n s o i l i n fa llo w in s p r in g
9*1
M o istu re co n serv ed d u rin g e n t i r e
fa llo w p e r io d
(in c h e s ) 3*5
1 .5 '
M o istu re co n serv ed d u rin g e n t i r e fa llo w p e r io d (p e rc e n t)
1 8 .7
23ol
B u sh e ls o f w heat p e r a c re
1 7 .9
9 .0
Pounds o f w heat p e r a c r e
1071
542
81
T able V I I I .
(c o n tin u e d )
F allow
Gonte
. Grop
Pounds o f s tra w p e r a c re
2028
927
Pounds o f w h eat and s tra w p e r a c re
3099
1469
Pounds o f d ry m a tte r p e r a c re (w heat and s tra w l e s s 10?»)
2790
1322
Pounds o f w a te r ( p r e c ip , / s o i l m o is tu re ) to produce I
pound o f g r a in
1946
3009
Pounds o f w a te r ( p r e c ip . / s o i l m o is tu re ) to produce I
pound o f d ry m a tte r
737
1238
Pounds o f w a te r (70?. p r e c ip . ^ s o i l m o is tu re to produce
I pound o f d ry m a tte r
609
Pounds o f w a te r (70?. p r e c ip . / s o i l m o is tu re )" to produce
I pound o f g r a in a f t e r g r a in p ro d u c tio n b eg in s
745
728
Pounds o f w a te r (20% p r e c ip . / s o i l m o is tu re ) to produce
I pound o f d ry m a tte r
373
445
Pounds o f w a ter (10% p r e c ip . ^ s o i l m o istu re ) to produce
I pound o f d ry m a tte r
330
354
'
942
IllUt' I/1 Ji/ M i ( H ) ) ;
110366
MONTANA STATE UNIVERSITY LIBRARIES
CN
CO
1311I7 III IIIIIII 81Il 5III5
001
W578
A a77i
c o p .2
110366
A a sh e im , T o r l i e f S
I n t e r r e l a t i o n s h i p s o f p r e c ip i- J
n a t i o n , s o i l , m o i s t u r e ,& s p r i n g w heal
W
AMt AMBiB
7o
AWG I f '3-
c Op Z
UUN 1 %
i t
110366