Soil characterization by diffusion measurements
by Truman Winfield Massee
A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of
DOCTOR OF PHILOSOPHY in Crop and Soil Science
Montana State University
© Copyright by Truman Winfield Massee (1973)
Abstract:
A mathematical derivation from diffusion theory was applied to soil diffusive flow to an exchange
resin sink. The measured flux was used to estimate some factors influencing soil fertility. These
included initial (before diffusive flow) solution phosphorus and potassium concentration, adsorbed
concentration, buffer capacity, soil impedance values, soil solution concentration changes with time of
diffusion, and quantity of fertilizer needed to bring about predetermined flux rates. At least two
diffusion measurements were needed for each soil. One was needed from an unspiked portion (no
fertilizer or chloride added) and one from a spiked portion.
Reasonable precision was obtained in measuring impedance factors from determining the quantity of
added chloride that diffused, and resulting values were similar to ones previously published. The
calculated solution and adsorbed quantities of potassium (from diffusion) were usually nearly the same
as were measured from routine chemical methods determining solution and labile amounts. There was
variation in the quantity of calculated solution and adsorbed phosphorus from diffusion methods
depending on the quantity of spiking done. This variation was believed to be associated with non-linear
adsorption isotherms as were depicted from the chemical extractions done.
Plant uptake of phosphorus on various soils fairly well Correlated with diffusive flux from these soils,
while potassium-plant correlations were much better. A potential was evident for estimating fertilizer
needs from diffusion flux measurements, expe-cially for potassium. S O IL C H A R A C T E R IZ A T IO N B Y D IF F U S IO N M E A S U R E M E N T S
by
T R U M A N W IN F IE L D M A S S E D
A t h e s i s s u b m i t t e d to th e G r a d u a t e F a c u l t y in p a r t i a l
f u l f i l l m e n t o f th e r e q u i r e m e n t s f o r th e d e g r e e
of
D O C T O R O F P H IL O S O P H Y
in
C r o p a n d S o il S c ie n c e
.
A p p ro v e d :
f t ,
H e a d , M a jo r D e p a rtm e n t
M O N T A N A S T A T E U N IV E R S IT Y
B o z e m a n ^ M o n ta n a
A u g u s t, 1 9 7 3
ABSTRACT
A m a t h e m a t i c a l d e r i v a t i o n f r o m d if f u s io n t h e o r y w a s a p p l ie d
to s o i l d if f u s iv e flo w to a n e x c h a n g e r e s i n s in k .
The m e a s u re d
f lu x w a s u s e d to e s t i m a t e s o m e f a c t o r s i n f l u e n c in g s o i l f e r t i l i t y .
T h e s e in c lu d e d i n i t i a l ( b e f o r e d if f u s iv e flo w ) s o lu ti o n p h o s p h o r u s
an d p o ta s s iu m c o n c e n tra tio n , a d s o rb e d c o n c e n tra tio n , b u ffe r c a p a ­
c i t y , s o i l im p e d a n c e v a l u e s , s o i l s o lu ti o n c o n c e n t r a t i o n c h a n g e s
w ith t i m e o f d i f f u s io n , a n d q u a n t ity o f f e r t i l i z e r n e e d e d to b r i n g
a b o u t p r e d e t e r m i n e d f lu x r a t e s .
A t l e a s t tw o d if f u s io n m e a s u r e ­
m e n ts w e re n e e d e d fo r e a c h s o il.
O ne w a s n e e d e d f r o m a n un­
s p ik e d p o r t i o n (no f e r t i l i z e r o r c h l o r i d e a d d e d ) a n d o n e f r o m a
s p ik e d p o r t i o n .
R e a s o n a b l e p r e c i s i o n w a s o b ta in e d in m e a s u r i n g im p e d a n c e
f a c t o r s f r o m d e t e r m i n i n g th e q u a n t i t y o f a d d e d c h l o r i d e t h a t d if ­
f u s e d , a n d r e s u l t i n g v a l u e s w e r e s i m i l a r to o n e s p r e v i o u s l y
p u b lis h e d .
T h e c a l c u l a t e d s o lu ti o n a n d a d s o r b e d q u a n t i t i e s o f
p o t a s s i u m ( f r o m d if f u s io n ) w e r e u s u a l l y n e a r l y th e s a m e a s w e r e
m e a s u r e d f r o m r o u t i n e c h e m i c a l m e th o d s d e t e r m i n i n g s o lu ti o n a n d
la b ile a m o u n ts .
T h e r e w a s v a r i a t i o n in th e q u a n tity o f c a l c u l a t e d
s o l u t i o n a n d a d s o r b e d p h o s p h o r u s f r o m d if f u s io n m e th o d s d e p e n d in g
o n th e q u a n t ity o f s p ik in g d o n e .
T h is v a r i a t i o n w a s b e l ie v e d to b e
a s s o c i a t e d w ith n o n - l i n e a r a d s o r p t i o n i s o t h e r m s a s w e r e d e p ic te d
f r o m th e c h e m i c a l e x t r a c t i o n s d o n e .
P l a n t u p ta k e o f p h o s p h o r u s o n v a r i o u s s o i l s f a i r l y w e ll C o r ­
r e l a t e d w ith d if f u s iv e f lu x f r o m t h e s e s o i l s , w h ile p o t a s s l u m - p l a n t
c o rre la tio n s w e re m uch b e tte r.
A p o te n tia l w a s e v id e n t f o r e s t i ­
m a t i n g f e r t i l i z e r n e e d s f r o m d if f u s io n f lu x m e a s u r e m e n t s , e s p e ­
c ia lly fo r p o ta s s iu m .
ii
ACKNOW LEDGEM ENTS
T h e l i s t i n g o f p e r s o n s w h o c o n t r i b u t e d to t h i s s tu d y i s le n g th y ,
a n d s p a c e d o e s n o t a llo w a d e t a i l e d d e s c r i p t i o n o f e a c h i n d i v i d u a l r s
c o n trib u tio n .
E v e n s o , th e a u t h o r g r e a t f u l l y a c k n l w l e d g e s t h e i r
a s s i s t a n c e a n d e x p r e s s e s h i s a p p r e c i a t i o n a n d g r a t i t u d e w ith th e a l p h a ­
b e t i c a l l i s t i n g s o f th e f o llo w in g p e r s o n s , p l a c e d u n d e r s e v e r a l g e n e r a l ■
<*
s u b je c t m a tte r c a te g o r ie s .
.
M y G r a d u a te C o m m itte e :
■
D r s . C . S c o tt C o o p e r , A . H a y d e n
F e r g u s o n , R a l p h A . O ls e n , J a m e s R . S im s , a n d E a r l O.
S k o g le y ( C h a i r m a n ) , a l l o f M o n ta n a S t a t e U n i v e r s i t y .
A d v ic e o n d if f u s io n t h e o r y a n d a p p l ic a t io n :
D rs. W. D o ra l
K e m p e r, C o lo ra d o S ta te U n iv e r s ity ; P h illip L o w , P u r d u e
'
U n i v e r s i t y ; R o b e r t L . N i c k e l s o n , M o n ta n a S t a t e U n i v e r s i t y ;
S t e r l i n g R . O ls e n , ■A R S - USD A , F o r t C o l l i n s , C o lo r a d o ;
P h i l l i p H . N y e , O x f o r d U n i v e r s i t y ; a n d R o n a ld E . P h i l l i p s ,
U n i v e r s i t y o f K e n tu c k y .
L a b o ra to ry an d Shop A s s is ta n c e :
A s a e l D ilw o r th , A R S - USD A ,
K i m b e r l y , I d a h o ; J e a n n e E a r l , M u r ta u g h , I d a h o ; C l a r e n c e
I
- H a y d e n , A R S -U S D A , K i m b e r l y , I d a h o ; m y f a m i l y - - B e v ­
e r l y , R a c h e l, R e b e c c a , a n d D a n i e l M a s s e e , T w in F a l l s ,
I d a h o ; a n d H a r o l d W a g g o n e r , A R S - USD A , K i m b e r l y , Id a h o .
1
S o ils c o l l e c t i o n a n d i d e n t i f i c a t i o n :
S te v e n B o o th , C a l i f o r n i a
r e s i d e n t ; A . L . B la c k , A R S - USD A , S id n e y , M o n ta n a ,
C h a r l e s C a s e , S C S - U SD A , G o o d in g , I d a h o ; D r . W i l l i a m
iv
R.
G ill, A R S - U SD A , A u b u r n , A l a b a m a ; R o n a ld G i t h e n s ,
J u n c t io n C ity ,
O re g o n ,
F a r m e r ; R o b e rt H agenow ,
f a r m e r ; D r e D o r d o n H u n tin g to n ,
I n d ia n a
U n iv e rs ity of C a lifo rn ia ;
A lv in Kfohl, I l l i n o i s f a r m e r ; H e r b e r t K o h l, I l l i n o i s f a r m e r ;
I
a n d G e o r g e E e O t t e , S C S - U SD A , H i l l s b o r o , O r e g o n .
R e s i n T e c h n o lo g y ;
W o rk s,
S t,
M a th e m a tic s :
D r e W a lte r D e a n ,
M a llin c k ro d t C h e m ic a l
L o u i s ,. M i s s o u r i .
C h a r le s B ro c k w a y , • U n iv e rs ity o f Id a h o ; D r,
R o b e rt B ur m an .
A R S - U SD A ,
U n i v e r s i t y o f W y o m in g ; H ,
K im b e rly ,
Id ah o ; D r.
W. R.
v e r s it y o f W isc o n s in ; P e d ro H e rn a n d e z ,
B en J ,
P ra tt,
A R S - U SD A ,
K im b e rly ,
D a le F i s h e r ,
G a rd n e r,
U n i­
U n i v e r s i t y o f Idah o ;
Id a h o ; a n d J o s de
S o n n e v il le , ■ U n i v e r s i t y o f I d a h o .
M a n u s c rip t re v ie w : W a r r e n W .
R a s m u s s e n , A R S - U SD A ,
K im b e rly ,
Id a h o .
M a n u s c r i p t ty p i n g :
/
D o ris A d a m s ,
Jero m e,
T w in F a l l s , I d a h o ; a n d D a la W a lto n ,
Id a h o ; B e v e r l y M a s s e e ,
B u rle y ,
U se o f la b o r a to r y a n d l i b r a r y f a c i l i t i e s : D r s .
an d H e n ry F .
To th e s e n a m e d ,
a g in g ,
c ritic a l,
M ay l a n d , A R S - U SD A ,
a n d to o t h e r s ,
and c o n c e rn e d ,
I
.. v
Id ah o .
M a r v in E .
K im b e rly ,
Jensen
Id ah o „
w h o h a v e be,e n p a t i e n t ,
e n c o u r­
th e a u t h o r w i l l a l w a y s b e in d e b te d .
TA B LE O F CONTENTS
Page
I
IN T R O D U C T IO N .
L i t e r a t u r e R e v ie w .
H y p o th e s is
. . ...............................
. . . .
. . .
. . . . .
I
. . .
E X P E R I M E N T A L M E T H O D S A N D M A T E R IA L S
T h e o r e t i c a l D e v e lo p m e n t
.
23
. . . . .
25
.... . . . . . . . . . . .
25
S o ils U s e d a n d G e n e r a l C h e m i c a l a n d
P h y s ic a l A n a ly s is
.....................
29
C h e m i c a l D e t e r m i n a t i o n o f S o lu ti o n a n d S o r b e d
C o n c e n tr a tio n and C a p a c ity F a c t o r s f o r P h o s ­
p h o r u s a n d P o t a s s i u m ...........................................
33
D e t e r m i n a t i o n o f S o lu tio n a n d S o r b e d C o n c e n ­
t r a t i o n , B u f f e r C a p a c i t y a n d I m p e d a n c e V a lu e s ,
b y D i f f u s i o n ..........................
34
D e t e r m i n a t i o n o f P l a n t U p ta k e f r o m S o ils
38
,R E S U L T S A N D I N T E R P R E T A T IO N S
......
. . . . . . . . . . .
39
I m p e d a n c e V a lu e s f r o m C h l o r i d e D if f u s io n . . . .
39
D if f u s io n a n d C h e m i c a l l y D e t e r m i n e d S o il
P o t a s s i u m . „ . •...............................
-
• 41
P l a n t P o t a s s i u m U p ta k e C o m p a r e d to C h e m i c a l
a n d D if f u s io n T e s t s . . . . . . . . . . . . . . . .
.4 5
. D if f u s io n a n d C h e m i c a l l y D e t e r m i n e d S o il
P h o sp h o ru s . . . . . . . . . . . . . . . . . . . .
50
P l a n t P h o s p h o r u s U p ta k e C o m p a r e d to C h e m ­
i c a l a n d D if f u s io n T e s t s . . . . . . . . . . . . . . .
55
SUM M ARY
i/
. . . . .
. . * . . . @. , . .
/ •
vi .
59
Page
R E F E R E N C E S C IT E D
A P P E N D IX E S
. . .
62
..........................
69
A p p e n d ix A - R e s u l t s o f c h e m i c a l d e t e r m i n ­
a t io n s o f s o i l p o t a s s i u m - ( s o i l b u lk d e n s i t y
i s in c lu d e d f o r c o n v e r t i n g v o lu m e d a t a to a
w e ig h t b a s i s i f d e s i r e d )
..........................
6.9
A p p e n d ix B - R e s u l t s o f c h e m i c a l d e t e r m i n a ­
tio n s o f s o i l p h o s p h o r u s - ( s o i l b u lk d e n s i t y
i s in c lu d e d f o r c o n v e r t i n g v o lu m e d a t a to a
w e ig h t b a s i s i f d e s i r e d ) . . . . . . . . . . . . .
70
A p p e n d ix C - C a l c u l a t e d im p e d a n c e v a l u e s
(I) a n d q u a n tity o f p o t a s s i u m d i f f u s i n g to r e s i n
s i n k s u r f a c e (7 . 92 c m 8 ) p e r 2 4 - h o u r p e r i o d
(JS4^_) . . . . . . . . . . .
o e
. . . * . . . . . . .
71
Appendix D - Calculated impedance values
(I) a n d q u a n t ity o f p h o s p h o r u s d if f u s in g to
r e s i n s i n k s u r f a c e (7 . 92 c m 8 ) p e r 2 4 - h o u r
p e r i o d (M j.) . . . . . . . . . . . . . . . . . . . .
v ii
• / '
■
! '
;'
72
LIST O F T A B L E S
Page
R e s u lts o f s o il p h y s ic a l an d c h e m ic a l
d e te r m in a tio n s on s o ils u s e d in e x p e r i-
I.
I Yl B n t S
2.
3o
4.
/
'
5.
I
6.
7.
o e e o o e e o e ' e e e e e e e e o
30
C o m p a ris o n s b e tw e e n c h e m ic a l d e te r m in ­
a t i o n s a n d d if f u s io n d e t e r m i n a t i o n s o f
l a b i l e K , (C + C ), a n d s o l u t i o n K , (C ) .
42
C o m p u te d q u a n t i t i e s o f K s p ik in g n e e d e d
to o b ta in
( a c c u m u l a t i v e f lu x p e r d ay )
v e r s u s q u a n tity o f K a c t u a l l y s u p p lie d
t o o b ta in
........................................
46
R e s u lts of s im p le lin e a r c o r r e l a t i o n '
r e l a t i n g p l a n t u p ta k e o f p o t a s s i u m to
■ c h e m i c a l a n d d if f u s io n t e s t s . . . « .......................
48
C o m p a ris o n s b e tw e e n c h e m ic a l d e te r m in ' a t io n s a n d d if f u s io n d e t e r m i n a t i o n s o f
l a b i l e P , (C + C ), s o l u t i o n P , (C ) ,
a n d (R + l) „ S. . . ° .
52
S lo p e o f p h o s p h o r u s a d s o r p t i o n i s o t h e r m
fro m c h e m ic a l d e te rm in a tio n s a s d e ­
p ic te d in te x t . . . . . . . . . . . . . .
. . .
54
C o m p u te d q u a n t i t i e s o f p h o s p h o r u s s p ik in g
n e e d e d to o b t a i n
( a c c u m u l a t i v e flu x
p e r d a y ) v e r s u s q u a n t ity .o f s p ik in g a c t u a l l y
s u p p l i e d to o b ta in
58
v iii.
I
L I S T O F F IG U R E S
F ig u re
1.
D if f u s io n c e l l s h o w in g : A - D i m e n s i o n s
B - C e l l i n o p e r a t i o n C - M e th o d o f e x ­
t r a c t i n g r e s i n . . . . . ...................... . . . . . .
2. .
3.
4.
5»
Page
35
C o m p u te d s o l u t i o n c o n c e n t r a t i o n o f
c h l o r i d e a s r e l a t e d to d i s t a n c e f r o m
s i n k , a f t e r d if f u s in g o n e d a y . . . . . . . . .
.40
A d s o r b e d p o t a s s i u m c o n c e n t r a t i o n (C )
f o r s o i l s . C o m p a r i s o n i s m a d e b e tw e e n
tw o s p ik in g r a t e s to c a l c u l a t e C
s
44
R e la tio n s h ip s b e tw e e n p la n t p o ta s s iu m .
u p t a k e a n d o n e - d a y a c c u m u l a t i v e d if f u s iv e
f lu x
49
. Relationships between plant phosphorus
c o n t e n t a n d s o i l q u a n t ity a s m e a s u r e d
b y t h r e e m e th o d s . . . . . . . . . . . . . . . .
■ Z/ /
I
I
ix
.
56
.
/
' INTRODUCTION
L ite r a tu r e Review
A lthough th e d if f u s io n p r o c e ss was e x p la in e d on a s c i e n t i f i c b a s is
by F ic k more than a cen tu ry a g o , i t was o n ly s in c e 1950 th a t i t was
r e c o g n iz e d a s an im p ortan t phenomenon r e g u la t in g th e tr a n s p o r t o f many .
n u t r ie n t io n s to p la n t r o o t s .
In a d d itio n to th e academ ic in t r ig u e
a s s o c ia t e d w ith t h i s r e l a t io n s h i p , v a lu a b le a p p lic a t io n s may be im p le­
m ented.
These in c lu d e th e measurement and r e g u la tio n o f s o i l f e r t i l i t y ,
and p rob ab ly p la n t management and g e n e t ic s e le c t io n .,
In 1855 F ic k , a m ed ica l p h y s i o lo g is t a t th e U n iv e r s ity o f Z u rich,
was ' th e f i r s t to show how th e h e a t flo w eq u a tio n s d ev elo p ed by F o u rier
co u ld be a p p lie d to d i f f u s i o n .
Thus, . even though o n ly a co m p a ra tiv ely
few a n a l y t i c a l s o lu t io n s ( o f d i f f u s i o n - l i k e phenomena) were known th en ,
th e fundam ental p r i n c i p l e ( s ) were e s t a b lis h e d .
"It ^is n o t s u r p r is in g
th a t i t took such a lo n g tim e fo r a g ro n o m ists to r e c o g n iz e th e s i g n i f i ­
can ce o f t h i s . • F i r s t , th e q u a n tity o f s o lu t io n flo w (som etim es termed ..
' t r a n s p ir a t io n , v is c o u s , or mass flo w ) co u ld a ls o c o n c e iv a b ly accou n t
fo r la r g e q u a n t it ie s o f Io n s b e in g tr a n s fe r r e d to p la n t r o o t s - w h ich ,
I
•
was a v a lid assum ption fo r c e r t a in n u t r ie n t s .
-
T his tr a n s f e r p ro cess
was b e lie v e d to be accom panied by a ren ew al o f s o lu t io n io n s from,
m in era l r e s e r v e s , an oth er p la u s ib le p r o c e s s i
These two f a c e t s were
fir m ly lin k e d to g e th e r by Cameron (1911) in one o f th e f i r s t d e t a ile d
works d e a lin g w ith th e s o i l s o l u t i o n . ,
2
S in ce th en , a g r e a t d e a l o f s p e c u la t io n has e x is t e d on how to
m easure th e a c t i v i t y o f s o i l s o lu t io n s so th a t d ir e c t in t e r p r e t a t io n s
co u ld be made.
For exam ple, H oagland, in h is f i r s t le c t u r e g iv e n a t
Harvard U n iv e r s ity under th e P ra th er L ectu resh ip (1 9 4 4 ), to ld o f the
background o f th e ! i n i t i a l work in C a lif o r n ia p r io r to 1920.
He s a id
"much had been w r it t e n about th e s o i l s o lu t io n and c o n tr o v e r sy had n o t
ceased .
I t was ap p aren t t h a t ex p erim en ta l ev id e n c e was most inadequate^
G e n e r a lly , ch em ica l a n a ly s is had been made on f i e l d sam ples o f s o i l
under no adequate c o n t r o l."
To o b ta in b e t t e r c o n t r o l, he to ld how 13
s o i l s from th e S ta te w ere s e le c t e d and tw o-ton sam ples o f each were
sent to Berkeley for s o i l solution analysis while being cropped.
had been done fo r 27 y e a r s a t th e tim e o f th e L e c tu r e sh ip .
c lu d in g remarks about th e s e s t u d ie s were ". . . i t
T his
Some con­
has become apparent
th a t s o i l s o lu t io n s can o f t e n be more d i l u t e than th o se o f our o r i g in a l
s e t o f s o i l s , and s t i l l p la n t s w i l l n o t n e c e s s a r ily f a i l to absorb
adequate amounts o f n u t r ie n t v io n s .
Thus th e co n cep t o f esu p p ly in g
power8 and th e i n t e r r e l a t i o n o f th e s o l i d to th e liq u id ph ase o f the
s o i l became c o n s id e r a t io n s o f paramount s ig n if ic a n c e and th ey are so
to d a y ."
A n u t r ie n t o f p a r t ic u la r c o n s id e r a tio n in th e s e remarks was
p h osphorus.
I t had been found to be below one ppm in many s o lu t io n
sa m p les, even a t th e b eg in n in g o f th e cro p p in g p e r io d .
A ls o , p otassiu m
was low - u s u a lly l e s s than 20 ppm.
Byers e t . a l (1938) ex p ressed s im ila r th ou gh ts in 1938 in w r it in g
ab ou t th e s o i l s o lu t io n , and s p e c u la te d on methods o f e x t r a c t in g 88. , »:
3
none o f w hich i s w h o lly s a t i s f a c t o r y .
When such s o i l e x t r a c t s are
o b ta in e d , i t i s g e n e r a lly found th a t th e c o n c e n tr a tio n o f th e s o lu b le
s a l t s in th e s o lu t io n i s l e s s than i s req u ir ed in a r t i f i c i a l n u t r ie n t
s o lu t io n s to produce co rresp o n d in g r e s u l t s . . . .
I t seems th a t p a rt
.
.
'
o f th e s e r e l a t io n s a re to be a sc r ib e d to th e p resen ce o f c o l l o i d s in
th e s o i l s .
In g e n e r a l, th e c o n c e n tr a tio n o f any s o lu t io n i s u s u a lly
g r e a t e s t in th e f il m a d ja c e n t to any s o l i d s u r fa c e „ . .
Thus, th e y ,
a s d id H oagland, q u e stio n e d why th e e x tr a c te d s o i l s o lu t io n i s to o low
to a cco u n t fo r proper p la n t grow th, and p rop ose th a t e x t r a c t io n methods
do n o t d u p lic a t e what a p la n t r o o t may e n c o u n t e r .•
More recent d a ta by Barber (1962), and Barber (1 9 6 8 ), s t i l l ,in d icate,
la r g e d if f e r e n c e s in measured a c t i v i t i e s o f s o i l s o lu t io n s fo r v a r io u s
p r o d u c tiv e s o i l s .
T his f a c t s u b s t a n t ia t e s th e im p r a c t ic a lit y o f u sin g
a v era g es fo r draw ing c o n c l u s i o n s F o r p h osphorus, Olsen^ e t a l (1962)
con clud ed (w ith a p p lic a b le l i t e r a t u r e q u o ta tio n s n o t shown h e r e in )
’’F e r t i l e s o i l s u s u a lly c o n ta in 0 .2 to 0 .3 ppm P in th e s o i l s o lu t io n ,
and a corn p la n t ta k es up 250 to 350 g o f w ater p er g o f d ry m a tter. ,
I
Thus, v is c o u s flo w o f w ater used by th e p la n t would su p p ly 2 to 4% o f
th e t o t a l P taken up by th e p la n t ; ”
Barber e t a l (1 9 6 2 ), a f t e r study-r
in g 145 p red om in an tly m idw est s o i l s and by u sin g th e same rea so n in g a s
O lsen e t a l (1 9 6 2 ), concluded t h a t o n ly one p e r c e n t o f th e phosphorus
and 10 p e r c e n t o f th e p o ta ssiu m co u ld be tr a n s fe r r e d to th e r o o t by mass
flo w a lo n e .
R esearch on o th er n u t r ie n t s , summarized in th e more r e c e n t
r ev iew by O lsen and Kemper (1968) in d ic a te d th a t u s u a lly th e tr a n sp o r t
I
1
•
V /
^
'
.
I •
1
.
.
'
.
. X
4
.^r o n J m anganese, boron , cop p er, z i n c , molybdenum and som etim es n i t r o ­
gen and s u lf u r must be supplem ented by m echanism (s) in a d d itio n to mass
flo w .
E arly a ttem p ts to d e s c r ib e th e means ( in a d d itio n to mass flo w ) by
w hich io n s were tr a n s fe r r e d to r o o t s have c r e a te d an array o f i n t e r e s t ­
in g c o n c e p ts .
One w hich provoked much thought and c o n tr o v e r sy was th a t
o f " c o n ta c t exchange" w hich was developed by Jenny and O v e r str e e t (1939)
in 1939,
They proposed th a t exch a n g ea b le s o i l c a t io n s , and a l s o c a t io n s
on th e p la n t r o o t s u r f a c e , moved about in an o s c i l l a t i n g volum e.
These
volum es o v erla p p ed , and whenever a neighbor pair o f io n s sim u lta n e o u sly
happened to be c l o s e s to each o t h e r - s origin al a ttra ctiv e s i t e than
,
I
t h e ir own, th ey traded ,s i t e s .
In t h i s manner io n s exchanged between
p la n t r o o t s and charged s o i l p a r t i c l e s - and by a s im ila r a c t io n ,
betw een s i t e s on s o i l p a r t i c l e s a t w i l l .
From t h is co n cep t i t was co n - ,
elu d ed th a t th e s o i l s o lu t io n was n o t n e c e s s a r y to a cco u n t fo r th e
t r a n s f e r o f io n s .
Bray (1 9 5 4 ), how ever, argued "A s i n g l e r o o t , to be
f u n c t io n a l, must se c u r e many tim es th e amounts o f n u t r ie n t s th a t are to
be found on th e im m ediate s u r fa c e o f a c la y m in eral p a r t i c l e w ith which
i t may be in c o n t a c t .
R eg a rd less o f w hether th e r o o t and c la y s u r fa c e s
a re so c l o s e t h a t c o n ta c t exch an ge, a s p o s tu la te d by Jenny and
O v e r str e e t (1939) can ta k e p la c e , th e amount o b ta in ed from th e im m ediate
c o n ta c t would be sm a ll and i n s u f f i c i e n t to make th e r o o t f u n c t io n a l.
The s i g n i f i c a n t so u rce o f n u t r ie n t s to th e r o o t su r fa c e comes from
movement or d if f u s i o n i n t o th e f ilm o f w ater betw een th e r o o t s u r fa c e
5
and th e s o i l s u r fa c e ,"
B ra y 's c o n c lu s io n d id n o t s p e c if y a llo w a n ce s
fo r th e ren ew al o f io n s on th e c la y exchange s i t e by c o n ta c t exchange
w ith o th e r c la y m a t e r ia l, even i f he d id c o n s id e r t h i s in h i s comput­
a t io n s ;
However, Brown (1953) had j u s t com pleted an exp erim en t th a t
showed th a t io n tr a n sfe r , w ith o u t li q u i d f ilm media was n o n - e x is t e n t
,
under th e c o n d itio n s he im posed.
He had con verted p a r t o f a s o i l
sam ple to H -cla y and e n c lo se d i t in a perm eable membrane.
T his was
th en b u ried in th e n a tu r a l p o r tio n o f s o i l so th a t ion. exchange cou ld
ta k e p la c e betw een th e two sa m p les.
With s o i l w ater c o n te n ts s im ila r .
to th o se where p la n t r o o t s t h r iv e , io n exchange was r a p id .
H o w ev er,.
. when the water content.was reduced to near w iltin g point, the quantity
.. th a t exchanged a ls o d e c r e a se d toward z e r o .
s o lu t io n was n e c e s s a r y fo r t r a n s f e r .
f e r t o "m igration" and " d iffu s io n " .
T his in d ic a te d th a t th e
Brown (1953) a s c r ib e d th e tr a n s­
Thus, Brown's s ta te m e n ts , l i k e
B r a y 's , fa v o red d if f u s io n over c o n ta c t exch an ge,
At about t h i s same
tim e , Husted and Low (1954) p u b lish ed r e s u l t s which a l s o in d ic a te d th a t
io n movement was dependent b n .th e s o lu t io n p h a se, and d eriv ed a
s o lu t io n fo r s o i l io n t r a n s f e r w hich fo llo w e d P ic k 's d if f u s io n la w s.
Perhaps th e m ost c o n v in c in g d a ta to d i s p e l . t h e c o n ta c t exchange th eory
was p rovid ed by O lsen and Peech (1960) who measured p la n t uptake a t Rb+
. and Cat+ from b o th th e su sp e n sio n and:e q u ilib r iu m d ia ly z a t e .
A lthough
th ey v a r ie d th e r e la t iv e : c o n c e n t r a t io n s in th e p h ases to ex trem es; th e ^
r a t e o f Rbt and Ca"*"*" uptake from b oth p h a ses was th e same,
A d i f f e r e n t p r o c e s s th a t has b een e n v is io n e d a s a l s o c o n tr ib u tin g
&
6
v.
to io n uptake i s i n i t i a t e d b y . th e a c i d i f y in g a c t io n o f p la n t r o o t s .
It
\
was p o s tu la t e d th a t th e s o lu t io n a c t i v i t y n ear th e r o o t was enhanced
above th a t measured in s o i l , e x t r a c t s .
CO2 , H^CO^ may be form ed,
For exam ple, a s th e r o o ts e x c r e te
Or i f H+ io n s a re e x c r e te d to p r e s e r v e e l e c t ­
r i c a l n e u t r a li t y ( in c a se more c a t io n s a re absorbed than a n io n s ) , the
,
s o i l s o lu t io n pH would d e c r e a se .
q u e n t ia l a c t i v i t y d if f e r e n c e s ,
A pH d e c r e a se would p ro v id e co n se­
From Donnan e q u i l i b r i a i t can be
c a lc u la t e d th a t a pH d e c r e a se o f o n e .u n it would in c r e a s e th e s o lu t io n
p o ta ssiu m by a f a c t o r / 1 0 , w h ile th e ca lciu m would in c r e a s e by a f a c t o r
<.
o f 3Z 10.
Nye (1968) has argued th a t perhaps j u s t th e r e v e r s e s i t u a t io n
, may exist?
He sta te s "It i s widely ,believed that roots make nutrients
more a v a ila b le by ren d erin g t h e ir environm ent more a c id ."
By u sin g th e
d a ta o f Cunningham (1 9 6 4 ), where 62 common p la n t s p e c ie s were s tu d ie d ,
he reason ed t h a t , on th e a v e r a g e , more a n io n s than c a t io n s were taken up
from th e s o i l - when c o u n tin g n itr o g e n uptake a s NO" r a th e r than NH^.
Nye sp e c u la te d from th e s e d a ta th a t r o o t s e x c r e t e HCOg (n o t H+) , which
a
ten d s to r a i s e th e p H .• As an in d ic a t io n o f t h i s , he p o in te d out th a t i t
\
.
i s normal fo r p la n t s grow ing in n u t r ie n t m edia to in c r e a s e th e pH v a lu e
when th e n itr o g e n i s a p p lie d a s NO » v B ecause o f th e d i f f i c u l t i e s
'
/
3
r I . en cou n tered in m easuring a c t u a l pH changes near r o o t , s p e c u la t io n o n ly
(.
’
. ■ has. dom inated.
.
T h erefo r e, i t must be, con clud ed th a t t h i s typ e o f
1
■
e x p lo r a tio n i s in c o n c lu s iv e and more s p e c i f i c e v id e n c e . i s need ed .
Coupled w ith t h i s need i s a l s o a need fo r d eterm in in g more about
th e e x a c t n a tu re o f th e s e v e r a l com plexing a g e n ts th a t a p la n t may
•1
'
7
e x c r e te .
To stu d y th e e f f e c t s , E lgaw hary:e t a l (1970b) used a simu­
la t e d r o o t made o f porous c er a m ic: tu b in g which th ey embedded in the
s o il.
Complexing m a te r ia ls were mixed w ith w a ter and p a ssed through
t h i s "root" w hich a c te d a s a s in k fo r i o n s . . EDTA9 a t IO- 3 M concen­
t r a t io n , in c r e a se d z in c uptake by a f a c t o r o f 17 o v e r .w a te r a lo n e .
Other m a te r ia ls in c r e a se d z in c uptake l e s s , b u t were s t i l l h ig h ly
e ffe c tiv e .
As to th e a c t u a l m a te r ia ls e x c r e te d by p la n t r o o t s , R ovira
(1962) was a b le t o i s o l a t e o n ly sm a ll amounts o f c h e la t in g a n io n s as
c i t r a t e and l a c t a t e from w heat r o o t s .
Thus i t was concluded by Hale
e t a l (1 9 7 1 ), b eca u se o f la c k o f c o n c lu s iv e evidence^ th a t th e impI i car-'
tio n s in m in era l n u t r it io n o f p la n t s a re unknown,■
From th e p r e v io u s l i t e r a t u r e c i t e d h e r e in i t has been p o in ted ou t
th a t mechanisms such a s c o n ta c t exch an ge, a c i d i f y in g a c t io n o f r o o t s ,
or t h e ir com plexing ex u d a tes have f a i l e d to e x p la in th e la r g e d i f f e r ­
e n c e s betw een s o i l s o lu t io n " co n cen tration and p la n t uptake by mass flo w .
E vid en ce p o in t in g toward d if f u s io n i s more c o n c lu s iv e , a s w i l l be shown. ■
The f i r s t work in s o i l io n d if f u s io n d id n o t r e l a t e to th e p la n t
r o o t r o l e in th e p r o c e s s .
Emphasis was p la c e d .o n d if f u s i o n o f f e r t i l i z e r
m a te r ia ls once th ey had been added to th e s o i l , or to th e t h e o r e t i c a l
b a s is o f s o i l d if f u s io n i t s e l f .
I n i t i a l w orkers in th e s e s t u d ie s
in c lu d e d Chernov (1 9 3 9 ), Brown (1 9 5 4 ), Husted and Low (1 9 5 4 ), K lute and
L etey (1958) and M arsh all (1 9 5 8 ),
However, in th e e a r ly 1960*s B o u ld in .
(1961) and O lsen e t a i'( 1 9 6 2 ) i n i t i a l l y proposed th e im portance o f
d i f f u s i o n fo r tr a n s p o r tin g io n s to p la n t r o o t s . ' In t h e ir p u b lic a t io n s
- -
I
' '
'
,
I,
,
.
/ .
.
:
■
Z
'
,
l ' \
\
I
1 -•
-
i
I
. 1
.1
*
- I
‘
"
.
.
.
8
i t was p o in ted o u t th a t th e r o o t must red u ce th e s o lu t io n c o n c e n tr a tio n
o f io n s a t th e r o o t - s o i l boundary an d . th ey so lv e d m ath em atical m odels
in d ic a t in g th e e x t e n t .
A q u it e c o n v in c in g p o r tr a y a l o f th e r o o t s in k -
d i f f u s i v e flo w mechanism was p ro v id ed about t h is same tim e by Barber
(1962) w ith a u to ra d io g ra p h s.
He used a tech n iq u e o f growing p la n ts in
s o i l s la b e le d w ith a r a d io a c t iv e is o t o p e .
X -ray f ilm was p la ce d c l o s e
I
to th e a c t i v e r o o t s so th a t th e d ev elo p ed f ilm would d e p ic t th e is o t o p e
d is t r ib u t io n about them.
U sing t h i s m ethod, Barber la b e le d a s o i l w ith
a sm a ll amount o f Rb- 8 6 .
The r e s u lt i n g a u to ra d io g ra p h s showed th a t
th e r e was d e p le t io n o f t h i s m a te r ia l in th e r o o t v i c i n i t y a s s o c ia t e d
with plant uptake.
As time of uptake progressed, the s o i l zone of
d e p le t io n w idened.
To tr y to en su re th a t th e d e p le t io n was n o t a s s o c i­
a te d w ith a s o i l w ater g r a d ie n t in th e r o o t a r e a , th e p la n t s were
w atered d a i l y .
In an oth er p o r tio n o f t h i s g e n e r a l stu d y he a p p lie d
e x c e s s ( t o p la n t uptake) S r-9 0 to an agar r o o t m edia, grew p la n t s , and
added H oagland1s s o lu t io n afe a so u rce o f n u t r ie n t s .
In t h i s system the
is o t o p e i n i t i a l l y c o l le c t e d around th e r o o ts by mass f lo w . 1 A fte r the
r o o t s were c a r e f u l ly p u lle d ou t o f th e agar th e S r-90 d if f u s e d away
from th e p r e v io u s area o f c o n c e n tr a tio n .
T h erefo r e, i t was ev id en ced
th a t a r o o t was ca p a b le o f in d u cin g a c o n c e n tr a tio n g r a d ie n t, e it h e r by
red u cin g or by in c r e a s in g th e n e a r -r o o t io n c o n c e n tr a tio n .
From th e n , d if f u s io n became a cce p te d a s an im p ortan t mechanism fo r
..
'
V
p la n t n u t r it io n ,- and th e i n i t i a l s o i l d if f u s io n s t u d ie s took on new
,f
1 r
'
im portance as- th ey ./h elp ed 1t o .d e p ic t th e b a s ic p r o c e s s .
/
-O
Vl .
9
As y e t , t h i s d is c u s s io n has been d ev o ted to th e way th a t s o i l
d i f f u s i o n became e s t a b lis h e d r a th e r than to t h e . t h e o r e t i c a l developm ent
o f th e p r o c e s s i t s e l f .
As d if f u s io n o f io n s in s o i l encom passes a broad
f i e l d , th e r e w i l l be em phasis p la ced on th e sco p e o f th e h y p o th e sis and
ex p erim en ta l work to be g iv e n h e r e in .
Where io n or m atter tr a n s p o r t r e s u l t s from Brownian m otion i t i s
termed d if f u s i o n .
Brownian m otion i s random, so i f a c o n c e n tr a tio n
g r a d ie n t i n i t i a l l y e x i s t s th e m otion r e s u l t s in red u cin g th e g r a d ie n t
w hich in turn r e s u l t s in a n e t t r a n s f e r o f m atter to th e r e g io n o f
i n i t i a l l y low er c o n c e n tr a tio n .
To some, th e a c t u a l n e t tr a n s fe r sh ou ld
e x i s t b e fo r e th e term d if f u s io n may be im p lie d .
Even s o , many s o i l s
exp erim en ts have invoked th e i n i t i a l c o n d itio n th a t one zone o f a s o i l
c o n ta in e d la b e le d m a te r ia l added w h ile th e a d ja cen t zone had an eq u a l
amount o f n o n la b eled m a t e r ia l.
The t r a n s f e r o f la b e le d and n o n la b eled
m a te r ia l in t o each o t h e r ’ s zone has been stu d ie d and i s termed d if f u s io n ,
alth ou gh th e r e was no n e t tr a n sfe r , o f th e g e n e r a l io n ,
P ic k ’ s f i r s t . l a w d e s c r ib e s th e d if f u s io n p r o c e ss fo r a ste a d y s t a t e
c o n d it io n , and a s amended fo r a s o i l an ion i s
-
J =' -D I6(dC /dx)
(I)
where
J = th e f lu x o f su b sta n c e c r o s s in g a s o i l u n it a rea p e r p e n d ic u la r to flo w d ir e c t io n p er tim e, ■
(meq, grams. , , , ) (cm- ^) (sec"7"*-)
0 = th e v o lu m e tr ic s o i l w ater c o n te n t (d im e n s io n le s s )
i.,
.
■
- ' .
■
.
.
"
.
,
: .'
i
..
C =• s o i l s o lu t io n c o n c e n tr a tio n (meg, grams . •. ) (cm"3)
x = sp a ce v a r ia b le (cm)
D = d if f u s io n c o e f f i c i e n t (cm^) ( s e c
I
= im pedence. f a c t o r , d u e .to s o i l p a r t i c l e s in t e r f e r in g w ith
:
aqueous d if f u s io n (d im e n s io n le s s )
There i s some am b igu ity r eg a r d in g term s in th e l i t e r a t u r e .
Concen­
t r a t io n has som etim es been used to d en o te th e am ount.per volume o f s o i l ,
in e f f e c t com bitiing C and 6;
s o lu t io n c o n te n t.
As j u s t shown, C w i l l alw ays r e f e r to
By u se o f th e denoted terms combined w ith D in
e q u a tio n ( I ) , J w i l l r e f e r to a u n it area o f s o i l .
"I" in c lu d e s a
com b in ation o f im pedence f a c t o r s w hich a re t o r t u o s i t y , reduced f l u i d i t y
and e l e c t r o s t a t i c r e p u ls io n fo r a n io n s (o r , in th e c a s e o f c a t io n s ,
n e g a tiv e a d s o r p tio n ).
These th ree f a c t o r s th a t p ro v id e th e o v e r a ll
im pedence term a r e i ( in th eo ry ) m u lt ip lie d by each o th er to d eterm ine
' r
' th e impedence v a l i / e . - However, in p r a c t ic e i t has been n e c e s s a r y to
measure t o t a l im pedence, then se p a r a te v a lu e s o f th e c o n tr ib u tin g
f a c t o r s - u s u a lly by assum ing v a lu e s o f a t l e a s t one o f th e f a c t o r s . '
The v a lu e s o f ”1" (e x c e p t p o s s ib ly fo r H+ ) w i l l b e v le s s than I (which
i s th e v a lu e o f an aqueous s o lu t io n a lo n e where 0 = I ) .
D are l i t e r a t u r e v a lu e s fo r d i l u t e aqueous s o lu t io n s .
The v a lu e s o f
I t may be n oted
th a t some p u b lic a t io n s have r e fe r r e d to a d if f u s io n c o e f f i c i e n t . f o r
s o ils
(o r D a s an e f f e c t i v e d if f u s io n c o e f f i c i e n t ) w hich was a co m b in -'
e
,
a t i o n o f ( D )(I ) or (D )(I)(O ) in com parison to eq u a tio n ( I ) .
The u s e .o f a t o r t u o s it y f a c t o r , , acknowledged from th e o i l in d u str y
11
l i t e r a t u r e by P o rte r e t a l (1 9 6 0 ), in c o r p o r a te s th e in c r e a se d path
le n g th an io n must t r a v e l to reach i t s f i n a l d e s t in a t io n w ith the
reduced p ath area in w hich to t r a v e l .
p ro p o se, th e s e two f a c t o r s a re r e l a t e d .
As can be shown by th e model they
T h e r e fo r e , th e t o r t u o s it y
f a c to r th ey d e s c r ib e i s (L/L )^ . L sta n d s fo r th e e f f e c t i v e d is ta n c e an
1
6
io n t r a v e ls w h ile
d en o tes th e t o t a l d is t a n c e i t t r a v e ls in i t s
■
to r tu o u s p a th .
'
T his f a c t o r i s dependent on w ater c o n te n t, s o lu t io n
f i s c o s i t y and i o n i c - c l a y i n t e r a c t io n s .
are n o t in d ep en d en t o f each o th e r .
F u rth er, th e s e o th e r f a c t o r s '
For exam ple, red u cin g th e w ater
c o n te n t in c r e a s e s th e a v era g e s o lu t io n v i s c o s i t y (a s th e s o lu t io n i s
more viscous near surfaces) and causes diffusion to take place in
r e g io n s c l o s e r to c la y p a r t i c l e s where th ey become s u b j e c t to e l e c t r i c a l
fo rce s.
S in c e an an ion i s r e p e lle d away, from th e c la y ch a rg e, i t does .
n o t e x p e r ie n c e as much in f lu e n c e from in c r e a se d v i s c o s i t y as a c a t io n ,
b u t i t does e x p e r ie n c e th e e f f e c t i v e pathway red u c tio n to a g r e a te r
e x te n t.
With c h lo r id e , w hich i s n o t a p p r e c ia b ly ad sorb ed , P o r te r e t a l .
(1960) found t h a t th e p rod u ct o f th e t o r t u o s it y tim es reduced f l u i d i t y ,
tim es e l e c t r o s t a t i c r e p u ls io n was l i n e a r l y r e la t e d to v o lu m e tr ic w ater ■
c o n te n t.
The p rod u ct term had v a lu e s e x t r a p o la t in g to 0 when 0. was
reduced to near 15 atm osp h eres.
R o w ell e t a l (1967) o b ta in ed very
s im ila r r e s u l t s to th o se o f .P o r t e r e t a l and denoted th e s i m i l a r i t y in
1 . 1
.
t h e i r w r it in g s by p l o t t i n g b o th s e t s o f d a ta on one graph.'
■
'
A f u n c t io n a l r e la t io n s h ip th a t was d eriv ed by Kemper and van Sch aik
(1966) i s
.
Die = Daeb0
(2)
A
• . ■•
T
I J•
. • >
, I1
t
ii*
1X
'
i .i i
"
I .
'
. i n - ' ! i. 'i
. - x: . i-i i i ' ,
v ; ■! 11;
' I
.
,
11 •
'
' • ii
'
. : i
;
. '
x ___
; i
12
where "a" and "b” a r e e m p ir ic a l c o n s ta n ts w ith "a" b e in g r e la t e d to the
s u r fa c e a rea o f th e s o i l s t u d ie d .
O lsen and Kemper (1968) l a t e r con­
clu d ed t h a t , fo r th e o v e r a l l work done, th e r e was r e a so n a b le agreem ent,
when "b" was e q u a l to 10 and "a" ranged from 0 .0 0 5 to 0 .0 0 1 f o r sandy
loam to c la y s o i l s .
When phosphorus d if f u s io n was measured under s e v e r a l w a ter con­
t e n t s , Mahtab e t a l (1971) found a f a i r l y lin e a r r e l a t io n s h ip betw een
w ater c o n te n t and impedance v a lu e s as o th e r s had w ith c h lo r id e .
However, O lsen e t a l (1965) and a l s o R ow ell e t a l (1967) found more
cu rv a tu re in th e form o f a h y p e r b o lic f u n c t io n ,
O lsen e t a l a t t r ib u ­
ted th e d if f e r e n c e betw een phosphate and c h lo r id e to a d so r p tio n o f th e 1
p h o sp h a te.
That i s , a s th e s o lu t io n phosphate i s adsorbed a t low ered
w ater c o n t e n t s , i t s t o t a l s o lu t io n c o n c e n tr a tio n per volume o f s o i l
becomes l e s s .
In .co m p a riso n , th e t o t a l c h lo r id e c o n c e n tr a tio n per
volume rem ained th e same.
Low (1962) has rep o rte d th a t w a ter ta k e s on " q u a s i- c r y s t a llin e "
p r o p e r tie s a t c l o s e p r o x im it ie s to c la y s u r f a c e s .
These reduced
m o b ility e f f e c t s were measured by Kemper e t a l (1964) and th e f lu id i t y ,
found to be 0 .0 5 (a s compared to I fo r norm al w ater) in th e f i r s t la y e r
o f a C a -cla y and 0 .0 3 on a N a-c la y .
The m o b ility in c r e a se d r a p id ly by
th e th ir d w ater la y e r b u t w a s. s t i l l a f f e c t e d at.40& from th e c la y .
For c a tio n s ,' Bear (1964) d e p ic t s th a t th e d is t r ib u t io n o f io n s
■
r
from a c la y s u r fa c e f o llo w s th e p r o p o sa l o f S te m in 1923 fo r a d ou b le
la y e r .
The d is t r ib u t io n i s r e l a t i v e to th e io n ic dim ension o f th e io n ,
13
in a d d itio n to th e f o llo w in g th e e a r l i e r p r o p o sa ls o f Gouy and Chapman,
and H elm h o ltz.
A djacen t to th e c la y a la y e r o f c a tio n s (S te r n la y e r ) i s
c o n cen tra ted and th e r e th ey r a r e ly exchange p o s i t i o n s .
N ext to th e
S tern la y e r a l e s s t i g h t l y h e ld and co n c e n tr a te d la y e r e x i s t s where th e
c a tio n s a re termed ex ch a n g ea b le .
s o lu t io n .
Away from t h is la y e r i s th e b ulk
In com parison to th e s te a d y s t a t e eq u a tio n g iv e n f o r a n ion s
(e q u a tio n I ) „ O lsen and Kemper (1968) show th a t w ith c a t io n s th e r e i s a '
c o n tr ib u tio n from s o l u t i o n , and
■ jCfrom, solution) ^ ‘ (™C/RT) dS/dx
CS)
where
E s the gas constant
T = a b s o lu te tem perature
dp/dx = th e d r iv in g f o r c e , where
p = pq + RT In a + zFi|), and a
• is a c t i v i t y , z i s v a la n c e , F i s Faraday, and
i s th e phase
e le c t r ic p o te n tia l.
Other n o t a t io n i s th e same as used f o r eq u a tio n ( I ) .
The s o i l s u sp e n sio n d r iv in g f o r c e , d y /d x , has been c o n t r o v e r s ia l.
W hile i t has been argued th a t th e g r a d ie n t in th e ch em ica l p o t e n t ia l
( c a ll e d the, d a/d x th e o r y ) d e p ic t s th e d r iv in g f o r c e , Khasawneh (1 9 7 1 ),
in r e v ie w , s t a t e s th a t th e more r e c e n t body o f e v id e n c e su p p o rts th e
d y/d x (e le c tr o c h e m ic a l p o t e n t ia l) th eo ry as argued by F rere and A xley
I
(1964) ,* L agerw erff (1960) and O lsen (1 9 6 8 ).
With c a t io n s , R ow ell e t a l (1967) and P a t e l e t a l (1963) found
n e a r ly th e same h y p e r b o lic curve r e l a t i n g impedance f a c t o r s to v o lu m e tr ic
w ater c o n te n t a s .was found by most w orkers w ith phosphorus.
The r e l a t i v e c o n tr ib u tio n to d if f u s io n w ith in th e adsorbed phase
has been co n sid ered to be minor fo r stro n tiu m and sodium by R ow ell e t a l
(1967) minor fo r sodium b y.M ott and Nye (1968) and minor fo r calciu m by
van S ch aik e t a l ■(1 9 6 6 ). . These l a t t e r a u th o rs found th a t sodium was '•
la r g e ly r e g u la te d by d if f u s io n in th e adsorbed ph ase on a N a -c la y ,
E l l i s e t a l (1 9 6 9 ), from u sin g e q u a tio n s th ey d ev elo p ed , con clud ed th a t
Mott, and N ye’ s (1968) f in d in g s c o in c id e d w ith t h e ir developm en t.
Con­
v e r s e l y , Elgawhary e t a l (1972) and B ole and Barber (1 9 7 1 ), w ith p la n t
uptake s t u d ie s w ith ca lciu m and. s tr o n tiu m , con clud ed th a t w ith d if f u s io n
o f th e s e i o n s , th ey w ere th e p o r tio n b a la n ced by n e g a tiv e c la y ch a rg es.
By u sin g th e e x p r e s s io n d ev elo p ed by E l l i s , e t a l (1 9 6 9 ), P h i l l i p s e t a l
(1972) p roposed th a t when o n ly a sm a ll f r a c t i o n o f th e s o i l c a tio n
exchange, c a p a c ity i s f i l l e d w ith an io n in q u e s tio n ,1 i t w i l l tend to
d iffu se primarily in the adsorbed phase.
Thus they calculated th a t
copper and presum ably manganese and z in c w i l l d if f u s e in th e adsorbed
p h a se ,
.
.
1
As t r a n s ie n t c o n d itio n s are more common in s o i l s - than s te a d y s t a t e ,
'
e q u a tio n s fo r th e s e w i l l be g iv e n .
Some s im p lif i c a t io n w i l l be made to
cop e w ith problem s found in l e s s than i d e a l s i t u a t i o n s , as in . s o i l s , b u t
\
no more than i s u s u a lly found in th e l i t e r a t u r e . For exam ple. Low (1962)
•
.
.
has d is c u s s e d th a t b oth c o - d if f u s io n ( a ls o term ed. s a l t d if f u s io n ) and
c o u n t e r - d if f u s io n a re assumed to be o p e r a tiv e in s o i l - p l a n t sy ste m s.
C o -d iffu s io n i s th e p r o c e s s w hereby, in o rd er to m a in ta in e l e c t r i c a l
/
/
15
n e u t r a l i t y , an a n ion and c a t io n move in th e same d ir e c t io n .
For coun­
t e r - d i f f u s i o n , e l e c t r i c a l n e u t r a li t y i s m ain tain ed by io n s o f l i k e .
ch arge t r a v e lin g in o p p o s ite d i r e c t i o n s .
The g e n e r a l eq u a tio n fo r
t r a n s ie n t c o n d itio n d i f f u s i o n ( P ic k 's secon d law) can be d eriv ed by u se
o f P ic k 's f i r s t law fo r an an ion and th e eq u a tio n fo r c o n t in u it y
9C /9 t = DK32C/9 x 2)
(4)
A nother way o f e x p r e s s in g t h is i s by m u ltip ly in g by 0 , and
9M /9t;= D 0I(92C/9 x 2)
(5)
where M i s th e q u a n tity d if f u s in g per u n it volume o f s o i l .
Gardner
(1965) has g iv e n a u s e f u l a n a ly t ic a l s o lu t io n fo r eq u a tio n (5) fo r p lan ar
d if f u s io n in a s e m i - i n f i n i t e sy stem .
They were d e r iv e d by assum ing th a t
th e i n i t i a l c o n c e n tr a tio n in th e s o i l i s u n iform , b u t a f t e r tim e zero
th e boundary i s m a in ta in ed a t a new c o n c e n tr a tio n , or
C = Cq , t = 0 , x> 0
(6)
C = Cr , t >0, x = 0
(7)
where C i s th e o r i g i n a l s o i l s o lu t io n c o n c e n tr a tio n , and C i s th e
o
■ ■■
.
r■
boundary (a s r o o t .or o th e r s in k ) c o n c e n tr a tio n .
c o n d itio n s
,
Then, s u b j e c t to th e s e
X
.
(C-Cr )/C 0-Cr ) = . e r f [X Z (Z )(D It)1 / 2 ] ■
. ( 8 )
w hich d e p ic t s th e s o lu t io n c o n c e n tr a tio n w ith v a ry in g t and x .
The r a t e
:
o f d if f u s i o n in t o th e s in k i s
D I( d C /d x )^ o= (C0-Cr ) D I/(irD It)
i
i
'
1 /2
(9)
16
I n te g r a t io n to show th e q u a n tity o f m a te r ia l d if f u s e d per u n it a rea ■'
u n t i l tim e p •t shows
1 /2 1 /2
M f t= 2 ( Co“ c r ) (DIGt) ' /H
(10)
where M = th e q u a n tity p er -u n it s u r fa c e a rea o f s o i l p er tim e.
E quation (10) has been used by N y e 'and co-w orkers- (1966b) fo r d if f u s io n ■.
o f b o th c a t io n s and a n io n s , and a v e r s io n o f i t was used by Warnche and
Barber (1972)„
In th e s e e q u a tio n s th e d if f u s io n c o e f f i c i e n t , D, was taken to be
c o n s ta n t.
I t i s known to vary w ith c o n c e n tr a tio n , b u t n o t a p p recia b ly
u n t i l c o n c e n tr a tio n s become la r g e r than a re.n o rm a lly found in s o i l
so lu tio n s.
For example, Kemper and van Sehalk sta te that a constant
d if f u s i o n c o e f f i c i e n t " w i ll be s u f f i c i e n t l y a ccu ra te f o r m ost p r a c t ic a l,
a p p lic a t io n s " .
I f o n ly two io n s were in v o lv e d in a d if f u s io n .p r o c e s s
in s o i l ( f o r c o - d if f u s io n or c o u n t e r - d if f u s io n ) a w e ig h tin g method to
o b ta in a m utual d i f f u s i o n c o e f f i c i e n t co u ld be used a s shown by Low
(1 9 6 2 ).
A lthough t h i s method cannot be a p p lie d to more com plex system s
where th e e x a c t a c t io n s o f th e many io n s a re unknown, i t d oes p ro v id e
i n s i g h t in t o th e g e n e r a l n a tu re o f th e d if f u s io n p r o c e s s .
is :
.
The eq u a tio n
,
D12 = D1D2 (Z1C1 t Z2C2) / (D1Z1C1 + D^z2C2)
(11)
when D1 2 i s th e m utual d if f u s io n c o e f f i c i e n t , C i s th e io n c o n c e n tr a tio n ,
/
z i s th e v a le n c e o f th e io n , and th e s u b s c r ip t s I and 2 r e f e r to the two
r e s p e c t iv e io n s .
From t h i s eq u a tio n i t may be seen th a t th e v a lu e o f
D ^ i s betw een D1 and Dg, and th a t th e io n p r e s e n t in low c o n c e n tr a tio n
.
.
'
.
.
■
r
■
17
w i l l la r g e ly c o n t r o l.D ^ . . Nye (1966a) has proposed th a t in d if f u s io n
to a zero s in k , th e a p p ro p ria te average d if f u s i o n c o e f f i c i e n t i s the
s e l f - d i f f u s i o n c o e f f i c i e n t , such as would be o b ta in ed from m easuring
th e r a t e th a t a la b e le d io n d if f u s e s co u n ter to an i d e n t i c a l u n la b eled •
io n .
F u r th e r , he b e lie v e d th a t io n s p r e s e n t in sm a ll c o n c e n tr a tio n s
. may be assumed to be moving in d ep en d en tly w ith t h e ir own d if f u s io n
c o e f f i c i e n t s , b e in g l i t t l e a f f e c t e d by o th er macrocomponents in th e
system .
,
A method o f d eterm in in g th e c o n t r ib u t io n from adsorbed io n s to
'
d i f f u s i v e f l u x , where they entey in t o a simultaneous r e v e r s ib le r e a c t io n
. with the solu tion phase, was f ir s t proposed by Olsen et a l (1962) in
1962.
The s o l i d p lu s s o lu t io n phase c o n tr ib u tio n fo r t h i s r e a c t io n
comes from th e d i f f e r e n t i a l eq u a tio n
(9 C /d t)0 + ( 3 S /9 t ) = DIG(9 2C/3 x 2)
(12)
where S i s th e q u a n tity o f io n per u n it volume o f s o i l e n te r in g in t o
th e d if f u s i o n p r o c e s s .
I f th e iso th erm betw een adsorbed and s o lu t io n
phase i s l i n e a r
S = RGC + c o n s ta n t
(13)
i
.
,
'
where R i s th e r a t i o o f io n s in th e adsorbed phase to th o s e in the
j s o lu t io n p h a se , per u n it volume o f s o i l .
A new eq u a tio n may be w r itte n
. ' by com bining e q u a tio n s (12) and (13)
.
9C /3.t'= .[ D l/ ( R + l) ] ( 9 2C /3x2)
,
(14)
The (R fl) term d e p ic t s th e s lo p e o f th e iso th erm fo r th e r a t i o o f the
(adsorbed + s o lu t io n p h ase) t o th e s o l u t i o n , o n ly , p h a se.
I t i s what
18
O lsen e t a l (1962) term ed a " c a p a c ity f a c t o r " .
D / (Rl-I) i s a n a lo g o u s to th e rm a l d i f f u s i v i t y .
In h e a t flo w e q u a t io n s ,
When in c lu d in g th e
c a p a c i t y f a c t o r ( R + l) , e q u a tio n s (8) (9) and (10) becom e, r e s p e c t i v e l y
C" Cr /C o~Cr = e r f { tx ( R + l) 1 / 2 ] / 2 ( D I t ) 1Z2 }
(15)
D I(d C /d x )x=0 = (Co-C r ) B I / [ ( r D I t ) / ( R + l ) ] 1 /2
(16)
Mt = '2 (C0-C r ) [D I0 t (R +l) J1 Z2Zrr1 / 2
(17)
I t may be n o te d t h a t , f r 0 m th e a d s o rb e d p o o l, th e c o n t r i b u t i o n to
th e d i f f u s i o n p r o c e s s i s enhanced by th e c a p a c ity f a c t o r o v er t h a t o f
n o t h a v in g th e a d so rb e d m a t e r i a l - b u t o n ly when r e l a t i n g C a s th e
• s o lu tio n c o n c e n tr a ti o n a s done h e r e .
In th e l i t e r a t u r e o f Nye and co­
w o rk e rs (1966b) and o t h e r s who ta k e th e c o n c e n tr a ti o n term to e q u a l th e
t o t a l d i f f u s i b l e c o n c e n tr a ti o n p e r u n i t volum e o f s o i l ,
th e y use term s
t h a t d e p i c t t h a t th e d i f f u s i o n p r o c e s s i s red u ce d by th e a d s o r p ti o n o f
io n s .
G ard n er (1972) h as d e r iv e d th e e q u a tio n s o f Nye e t a l i n term s
u sed h e r e i n and- shown them to be i d e n t i c a l , and v a r y in g o n ly i n how
i n d i v i d u a l s p r e f e r to w ork w ith them.
When th e a d s o r p ti o n is o th e r m i s n o t l i n e a r , a s shown i n e q u a tio n
(1 3 ) , f i n i t e d i f f e r e n c e m ethods a r e n e c e s s a r y to s o lv e th e c o n t r i b u t i o n
o f b o th so rb e d and s o l u t i o n p h a s e s .
■ im p o rtan t c o n s i d e r a t i o n .
T h is a s p e c t , th e n , becom es an
O lsen e t a l (1962) found th e am ount o f P t h a t
u n d erw en t i s o t o p i c d i l u t i o n w ith P-32 i n a 2 4 -h o u r r e a c t i o n was l i n e a r
th ro u g h o u t th e im p o r ta n t ra n g e o f c o n c e n tr a ti o n .
c a p a c it y f a c t o r ( s lo p e o f R +l) was a c o n s t a n t .
T h e r e f o r e , th e
As more f e r t i l i z e r P
was added th e s lo p e o f (R+l) d e c re a s e d ta k in g th e form o f a F r e u n d lic h
19
iso th e r m .
A ls o , i t was thought th a t th e s lo p e o f th e iso th erm would be
more v a r ia b le fo r a c id s o i l s w ith t h e ir g r e a te r an ion a d so r p tio n capa­
c ity ,
Nye (1966) has in d ic a t e d th a t th e a p p ro p ria te m easure o f t h e •
c a p a c ity f a c t o r i s a s t r a ig h t l i n e p a s s in g from th e p o in t (x=C0 , y =
.
t o t a l d i f f u s i b l e c o n c e n t r a t i o n ) , t o th e o r ig in in th e c a s e th a t th e
/ ^
iso th erm d is p la y s some cu r v a tu r e . With boron, a s w ith p h osp h oru s, th e
iso th erm has been found to be lin e a r ov er low c o n c e n tr a tio n s by B igger
'
and Fireman (1 9 6 0 ), K in gston (1 9 6 4 ), Okazaki and Chao (1 9 6 8 , and Sulaiman
and Kay (1 9 7 2 ), b u t f o llo w in g a F re u n d lich or Langmuir iso th erm a t h ig h - ■
er c o n c e n t r a t io n s .
These a u th o rs have n o t agreed on a d so r p tio n and.
d e so r p tio n c h a r a c t e r i s t i c s .
But t h i s m ight be ex p ected when c o n s id e r in g
th a t boron may; in a d d itio n to b ein g sorbed or. form ing co m p lex es, e n te r
in t o th e c la y l a t t i c e or p r e c i p it a t e w ith s e s q u io x id e s , a s was found b y;
Sims and Bingham (1^ 67, 1 9 6 8 ).
With c a t io n s , V aidyanathan e t a l (1968) found c e r t a in s o i l s had
f a i r l y lin e a r s o r p tio n iso th erm s fo r K.
B rew ster and T inker (1970) found
th a t most o f th e K iso th erm was l i n e a r , -b u t s im ila r to B e c k e t t 's fin d ­
in g s (1 9 6 4 ), th e r e were m in era l s o r p tio n s i t e s p a r t ic u la r to K o n ly
w hich were o p e r a tiv e a t a very low K s t a t u s ,'
Thus, a la r g e r r a t io o f K
i s sorbed a t low c o n c e n tr a tio n s as compared to th e r a t i o found a t in t e r ­
m ed iate or h ig h er t o t a l c o n c e n tr a tio n s .
From Brew ster and T in k e r 's ex­
perim ent (1970) Na and Mg had lin e a r is o th e r m s .
They s t a t e , though, „
th a t a s Ca i s th e major s o i l io n , th e a s p e c t .o f in c r e a s in g th e Ca .
.sorb ed phase w ith, in c r e a se d s o lu t io n ph ase c o n c e n tr a tio n would n o t be
20
.
/
.
/
I
f
I
p o s s i b l e , e x c e p t w ith v ery lim it e d s o lu t io n ch an ges.
have a lin e a r iso th erm by Elgawhary e t a l (1 9 7 0 a ).
Z inc was found to
With ir o n , O’Connor
e t a l (1971) found th a t th e s lo p e o f th e iso th erm in c r e a s e d w ith one
month’s tim e (from 1000 to 5 0 0 0 ), and th e r e fo r e in s te a d o f term ing the
s lo p e a ." c a p a c ity f a c to r " , s t a t e d th a t i t sh ou ld be used a s a " co rrec­
t io n fa c t o r " .
The in c r e a s e in th e s lo p e was a s s o c ia t e d w ith grad u al
p r e c i p it a t io n o f added ir o n a s amorphous ir o n o x id e s ,
Nye (1966) p o in te d ou t t h a t , to a v o id h y s t e r e s is p rob lem s, the
iso th erm s sh o u ld be determ ined under th e same c o n d itio n s a s d if f u s io n i s
•to o c c u r , in d ic a t in g th a t i f d i f f u s i o n to a s in k were to be s tu d ie d , a
d e s o r p tio n i s Ofhermiwould be p r e fe r r e d to an, a d so r p tio n is o t h e r m ,■ The
p roced u res used in d e so r b in g s o i l m a te r ia ls have u s u a lly c o n s is te d o f
s e q u e n t ia lly e x t r a c t in g p o r tio n s o f th e io n s and m easuring them to ­
g e th e r w ith new ly o b ta in ed e q u ilib r iu m s o i l s o lu t io n c o n c e n tr a tio n .
C o n v e rsely , B ar-Y osef e t a l (1972) p o in ted out th a t th e h y s t e r e s is
,
phenomena in th e a d s o r p tio n -d e s o r p tio n p r o c e s s w ith phosphorus a r i s e s
d u rin g d e s o r p tio n from d r a s t i c a l l y red u cin g the P c o n c e n tr a tio n .
/^
B ecause o f t h i s , th e r e i s d i s s o l u t i o n o f s i l i c a and an a l t e r i n g o f th e 1
a v a il a b l e P a d so r p tio n s i t e s on th e c l a y .
Thus, w ith th e s e opposing
v iew s and q u e s tio n a b le u n d ersta n d in g o f h y s t e r e s i s , i t ap p ears th a t
c o n c lu s io n s a t p r e s e n t would be prem ature.
As an o v e r a l l c o n s id e r a tio n ab ou t th e b u ffe r c a p a c ity term , when i t
i s o b ta in ed from 'an iso th erm , i t i s an approxim ation^ v a r y in g in e x a c t­
n e s s o f a p p lic a t io n among s o i l s , ,.and w ith io n ty p e .and c o n c e n tr a tio n
21
w ith in a s o i l .
Even w it h th e s e draw backs, how ever, t h i s f a c to r quant­
i t y has p ro v id ed c o n s id e r a b le needed r e s o lu t io n o f q u a n t it a t iv e , d i f f ­
u sio n p r o c e s s .
In /r e g a r d to o th er f a c t o r s c o n tr ib u tin g to d if f u s io n r e g u la t io n ,
O lsen and Kemper (1968) have s t a t e d "While th e osm otic movement and
e l e c t r i c a l p o t e n t ia l in c r e a se d by s a l t g r a d ie n ts are in t r i g u i n g , they
I
change th e s a l t d i f f u s i o n c o e f f i c i e n t s o n ly s l i g h t l y
th e s e item s w i l l n o t .b e d e t a il e d h e r e .
T h erefo re,
I o n -p a ir fo rm a tio n i s s t i l l
an oth er f a c t o r th a t d e s e r v e s m en tion , b u t f a l l s in t o t h i s same c a te g o r y .
Ion exchange r e s in s have been used in d if f u s io n s t u d ie s b ecau se o f
their a b ility to reduce a s o i l ion concentration a t a s o i l - r e s i n ■I n te r ­
fa c e .
V aidyanathan and Nye ( 1 9 6 6 ) ,: used b oth c a t io n and an ion exchange
r e s in s in paper s t r i p s a s s in k s fo r p la n a r d if f u s i o n s t u d ie s and o u t lin e
methods o f d eterm in in g a ccu m u la tiv e f l u x . ' They d id n o t compute a
c a p a c ity f a c t o r , b u t o b ta in ed o v e r a l l . p o t e n t i a l s fo r s o i l s to c o n tr ib u te
to d i f f u s i v e f lu x .
T his tech n iq u e was a ls o used by Warncke and Barber
(1972) in z i n c - s o i l in t e r a c t io n s t u d ie s w ith eq u a l s u c c e s s .
V aidyanathan and Nye (1 9 7 0 ), in . l a t e r s t u d i e s , r e j e c t e d th e u se o f an
an ion exchange r e s in paper fo r m easuring P d if f u s io n a s th ey assumed
th a t d if f u s io n through th e paper was r a t e li m it in g .
T h eir n e x t approach
(1971) to m easuring P d if f u s io n was by e v a lu a tin g impedance f a c t o r s
to g e th e r w ith th e c a p a c ity f a c t o r a s had been proposed by O ls e n .e t a l
(1962) p r e v io u s ly .
'
.
. . / •
■
In conclusion/,^-much work has gone in t o d eterm in in g how to measure
22
s o i l d if f u s io n and in t e r p r e t in g th e b a s ic p r o c e s s , b oth from s o i l and
from p l a n t - s o i l a s p e c t s ,
As i s n orm ally en cou n tered in p la n t and s o i l
r e s e a r c h , system s have n o t been i d e a l and a ls o much measurement has had
to be done by in d ir e c t m e th o d s,, As y e t , a p p lic a t io n o f d i f f u s i v e
mechanisms fo r d eterm in in g s o i l f e r t i l i t y s t a t u s and p la n t c o n tr ib u tio n
have been r e l a t i v e l y u n u t iliz e d e x c e p t in i s o l a t e d in s t a n c e s .
i f■
V■/ '
23
H y p o th e s e s
'
I t w a s h y p o t h e s i z e d t h a t b y m e a s u r i n g p l a n a r d i f f u s i v e f lu x f r o m a
s o i l to a n e x c h a n g e r e s i n s in k th e r e s u l t s c o u ld b e u s e d to d e p i c t th e
s o i l 's f e r t i l i t y s t a t u s , e s p e c i a l l y in r e g a r d to t h o s e n u t r i e n t s t h a t a r e
t r a n s p o r t e d to a p l a n t r o o t b y t h i s m e th o d .
S p e c ific a lly , th o s e a s p e c ts
t h a t c o u ld b e e s t i m a t e d b y t h i s m e th o d i n c l u d e th e f o llo w in g :
1.
T h e o r i g i n a l ( b e f o r e r e d u c t i o n b y s in k u p ta k e ) s o i l s o lu ti o n
c o n c e n tra tio n .
A l s o , th e c o n c e n t r a t i o n a f t e r t i m e = t a n d
d i s t a n c e = x f r o m th e a d s o r b i n g s in k .
2.
T h e s o i l a d s o r b e d ( a n d o t h e r s t a t e ) io n c o n c e n t r a t i o n th a t
c o n t r i b u t e d to d if f u s iv e f lu x b y e q u i l i b r i a , c a l c u l a t e d f r o m
th e m o d e l f o r a n i n s t a n t a n e o u s r e v e r s i b l e r e a c t i o n h a v in g a
lin e a r a d s o rp tio n is o th e r m .
3.
T h e e s t i m a t i o n o f t h e s lo p e o f a l i n e a r a d s o r p t i o n i s o t h e r m
( b u f f e r c a p a c i t y ) c a l c u l a t e d to go to th e o r i g i n f r o m I . a n d
. 2. , a b o v e .
4.
T h e im p e d e n c e v a l u e f o r a n i n d i f f e r e n t io n ( C l) f o r a n y s o i l
u n d e r c o n s id e ra tio n .
5.
.
F r o m t h e s e f i r s t f o u r (a b o v e ) q u a n t i t i e s , th e c a l c u l a t e d
q u a n t i t i e s o f a f e r t i l i z e r t h a t n e e d to b e a d d e d to a s o i l to
h a v e i t p r o v i d e a. f lu x r a t e e q u a l t o p l a n t n e e d s .
I t w i l l b e s h o w n i n th e " T h e o r e t i c a l C o n s i d e r a t i o n s " s e c ti o n .h o w
th e d e v e l o p m e n t o f e q u a t io n s (1 5 ), (16) a n d (17) ( s h o w n i n th e l i t e r a t u r e
i y-l
. I . .
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• 'I
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1
vi ,
.
-
-
-
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i t "
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24
r e v i e w p o r t i o n o f th e " I n t r o d u c t i o n " s e c t i o n ) c a n b e d e v e lo p e d to d e t e r m in e th e s e v a r io u s a s p e c t s .
W h ile i t m a y .b e n o te d th a t'^ th e i n t e g r a t e d
( o v e r t i m e ) p l a n a r f lu x h a s b e e n p r e v i o u s l y m e a s u r e d b y V a id y a n a f h a n
a n d N y e (1966^ a n d o t h e r s , th e s e p a r a t i o n o f a n y o f th e c o m p o n e n ts
s h o w n a b o v e h a s n o t b e e n p r e v i o u s l y a c c o m p l i s h e d u s i n g d if f u s io n :
th e o ry .
:' i ‘
. : i .<
I 11■ ’
25
'' E X P E R I M E N T A L M E T H O D S A N D M A T E R IA L S
T h e o r e t i c a l D e v e lo p m e n t
A m a j o r p o r t i o n o f th e b a s i c
s t u d i e s in s o i l d if f u s io n h a v e
b e e n to r e s o l v e h o w f u n d a m e n t a l p r i n c i p a l s o f d if f u s io n a p p ly to
' r
a s o il s y s te m .
/ T h e r e f o r e , th e l i t e r a t u r e r e v i e w s e c t i o n c o n t a in s
th e g e n e r a l e s t a b l i s h e d t h e o r y r e l a t i n g to t h i s s tu d y .
fro m
th is g e n e r a l e s ta b lis h e d th e o ry ,
P ro c e e d in g
a d e v e l o p m e n t w i l l b e g iv e n
to s h o w h o w th e c o m p o n e n ts t h a t c o n t r i b u t e to d if f u s iv e m o v e m e n t
( s o i l s o lu ti o n c o n c e n t r a t i o n ,
fa c to r,
s o i l a d s o r b e d c o n c e n tr a ti o n *
c a p a c ity
e t c . ) c a n b e s e p a r a t e d to c h a r a c t e r i z e a s o i l .
T h e q u a n t ity o f s o i l io n f lo w by d if f u s io n in a u n i d i r e c t i o n a l
s y s t e m to a c o n s t a n t s i n k o v e r a t i m e p e r i o d h a s b e e n g iv e n p r e . v io u s ly
M t = 2 (C o -
C r ) [ D i e t (R + l ) ] l / 2 /l7 1 /2
’
i s th e . s lo p e o f a n a d s o r p t i o n
.
In e q u a t i o n (1 7 ),
is o th e rm ,
th e
(17)
(R + I ) t e r m
a n d i s a s s u m e d to b e l i n e a r .
I t d e s c r i b e s th e a m o u n t
o f c h a n g e in t o t a l d i f f u s i b l e io n c o n c e n t r a t i o n ( s o lu ti o n p lu s a d ­
s o r b e d p h a s e ) p e r a m o u n t o f c h a n g e i n s o lu ti o n c o n c e n t r a t i o n w h e n
a c o n d i tio n i s i m p o s e d to c a u s e t h i s c h a n g e .
M a th e m a tic a lly
. (R + I ) = (A C q + A C s ) / A C o
w h e re
C
i s th e s o r b e d
(18)
1
( a n d / o r o t h e r - u n s p e c if ie d ) p h a s e . . If..,/
a f e r t i l i z e r o r o t h e r m a t e r i a l i s a d d e d to a s o i l ,
m a t e r i a l r e m a in s in d iffu s ib le f o r m ,
«...
,
,
,
‘‘x . . ‘ I 1 . . I,•I. .I v.,
r’ <
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I v. ,
.1 J i l V - W -
I i \
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I
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^
, I < I I
; X - « I . t. . W
I
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‘ ’ 1.
x . I I / I a
’ V. / I I I I / X I , j
- . - i
* ‘ w I i
W‘
I I '
I )t I I I V
•
th e n t h i s q u a n t i t y b e c o m e s
-' "
v I
I .1 I
1
"x < i ' •
I I l x i. I
v
X, / j
•
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i Vy <I
a n d if th e
:
h -
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(x . .
26
(A C q + A C g).
T h e q u a n t ity o f d if f u s iv e m o v e m e n t o v e r a t i m e p e r i o d
m a y b e r e w r i t t e n f o r a n u n f e r t i l i z e d s o i l a n d a l s o f o r a f e r t i l i z e d s o il
u s i n g th e t e r m s i n t h e r i g h t s i d e o f e q u a t io n (1 8 ), a n d e q u a t io n (17)
becom es
M t u " 2 (C 0 ~ C r ) ( D l6 t) 1 / 2 [(A C o+ A C s ) / A C o ] 1 / 2 /7T
w h ere
r e p r e s e n t s th e u n f e r t i l i z e d c o n d i tio n .
1 /2
(19)
W h e re f e r ti liz e r h a s
b e e n a d d e d , th e n ew s o lu tio n c o n c e n tr a tio n b e c o m e s C q + ACq , an d
M fcf = 2 (c 0 + A C o * C r )(D I9 t)1 / 2 [(A C o + A C s ) / A C o ] 1 z 2 Ztt1 / 2
u s in g
(20)
to r e p r e s e n t th e f e r t i l i z e d c o n d i tio n .
T he te rm
A C q c a n b e s o lv e d i n t e r m s o f C q b y d iv id in g e q u a tio n
(19) b y e q u a t io n (20)
M t u ZMt f = (G 0 - C r ) / ( C 0 + A G o - G r )
A ls o ,
(21)
s i m p l i f i c a t i o n m a y b e m a d e b y h a v in g C ^ g o t o >0 ’ ■( a s w a s fo u n d
to b e t h e . c a s e i n e x p e r i m e n t s d o n e ) a n d
M t u /M tf = V
t c O + A C o>
<2 2 > .
P e r h a p s i t w i l l a d d c l a r i t y , b e f o r e s o lv in g f o r (C q + A C q ) i n
t e r m s of C q , to in tr o d u c e a f a c to r " z " .
z Cq ; = Cq + ACq.
.
L e t z b e a q u a n t ity s u c h t h a t
T h e n e q u a t io n (22) m a y b e w r i t t e n a s
+ A c o) = 1 / z
= W
.
. <2 3 >
or
I
.■I
<
// ■ ■■
W I.
27
* =
.
(2 4 )
I
a n d r e v e r t i n g b a c k to t e r m s u s e d b e f o r e i n t r o d u c i n g z ,
A C 0 = [ (M t i ZMt u ) - I 3 C o
(2 5 )
If th e q u a n t ity o f f e r t i l i z e r a d d e d to a d if f u s io n s y s t e m i s
te rm e d
" K " , a n d w h ic h e q u a l s A C
m a y c o n t r i b u t e to d if f u s io n ) ,
+ AC
o
( w h e r e th e t o t a l ' a d d e d "
s
a n d u s i n g t e r m s j u s t d e f in e d
M t u = 2 C o ( D i e t ) l / 2 (K M t u ) l / 2 / [ C o (M t r M t u h ] l / 2
.
(26)
B y s q u a r i n g b o th s i d e s o f e q u a t io n (2 6 ) a n d s o lv in g
C o = (M t u )(M t f - M t u H77) M D ie tK
A ls o ,
fro m
.
(2 7 )
e q u a t i o n s (2 5 ) a n d (27)
A C o = [ ( M t f ZMt u ) - I j ( M t u )(M t f - M t u )(T r)M D ietK .
(28)
2
'
A C o = (M t f _ M t u r ( T r ) /4 D I 6 tK .
(29.)
or
F o llo w in g t h i s d e v e l o p m e n t ,
fro m
AC
(R +
I ) m a y b e e a s i l y d e n o te d
r e a l i z i n g i t i s e q u a l to K / A C q .
fro m
S u b s tit u tin g th e v a lu e o f
e q u a t i o n (2 9 ) in to t h i s e x p r e s s i o n
2
2
(R + I ) = 4 K D ie tZ (M t f - M fcu)^TT
T q s o lv e f o r C g , th e
m in in g la b ile
s a m e a n a lo g y w ill be u s e d a s i s w h en d e t e r ­
s o i l io n s
A 6 0 /A C S * C0 /C S
o r,
(30)
on re a rra n g in g -
'
...
■
^
'
C g = (C o ) ( A C g )Z A C o
'
(32)
an d a ls o
I I
, .
: 4 « . -
I l". . I
11
I xl ,
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.
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28
ACs = K - ACo
(33)
and
c S =
(C o ) ( K - A C o ) / A C o
(34)
T h e t e r m s i n t h e r i g h t h a n d s i d e o f e q u a t io n (34) h a v e b e e n fo u n d p r e v ­
io u s ly so th a t
. C s = M fcu C(K)/( M t f - M t u ) _ (M t f _ M t u )(7T )/4D I6tK ]
(35)
T h e u s e o f th e a n a l o g y i n e q u a t io n (31) d e p i c t s t h a t a s t h e s o r b e d
p h a s e o f a n i o n a p p r o a c h e s z e r o , th e s o l u t i o n p h a s e m u s t a l s o , a n d w ith
a lin e a r re la tio n s h ip .
m e re ly
T h e re fo re ,
(R + I ) f r o m t h i s r e l a t i o n s h i p i s
(C q + C g) / ^ .
F r o m t h e s e e q u a t i o n s , th e v a l u e s i n e q u a t io n (17) m a y b e s o lv e d ,
providing t h a t t o t a l ions transferred to a sink from a fertilized and u n ­
f e r tiliz e d s o il a r e m e a s u r e d .
, a n d tim e m u s t b e m e a s u r e d .
I n a d d i tio n , v o l u m e t r i c w a t e r c o n te n t (6),
D if f u s io n c o e f f i c i e n t s f r o m d il u te a q u e o u s
^ s o lu tio n e x p e r im e n ts m a y b e u s e d .
F o r C l " , K"**, a n d o r t h o p h o s p h a t e
i o n s t h e r e h a s b e e n r e p e a t e d a g r e e m e n t i n s o i l s l i t e r a t u r e , w ith
I
b e in g ,
’
D
■
r e s p e c t i v e l y ; I . 8 2 , I . 98 , a n d 0 . 5 X10” ^ c m 3 / s e c .
T h e im p e d ­
a n c e v a l u e m a y b e s o lv e d b y a d d in g a n io n a s c h l o r i d e , w h ic h i s n o t a d ­
s o r b e d b y th e c l a y a n d b e c o m e s
ACq.
I = (M fcf- M t u )3
F r o m e q u a t io n (29)
(T T )H D Q tK a
(36)
T h e t e r m " l a b i l e " u s u a l l y a s s o c i a t e d w ith th e a m o u n t o f s o i l io n
e x c h a n g in g w ith i t s i s o t o p e , h a s b e e n u s e d h e r e to a l s o i n d i c a t e th e
. t o t a l d i f f u s i b l e a m o u n t.
I
29
S o ils U s e d a n d G e n e r a l C h e m i c a l a n d P h y s i c a l A n a l y s i s
T w e n ty o n e
S ta te s ,
s o i l s a m p l e s w e r e g a t h e r e d f r o m th e . U n ite d
a n d r e p r e s e n t e d a w id e r a n g e o f c h a r a c t e r i s t i c s .
T hey
w e r e d r i e d f o r 3 d a y s i n a f o r c e d a i r d r i e r a t 60° C a n d s t o r e d
f o r f u t u r e p l a n t u p ta k e ,
c h e m ic a l an d p h y s ic a l a n a ly s is ,
a n d io n
d iffu s io n t e s t s .
To d e te rm in e th e ir g e n e ra l c h a r a c te r i s t ic s ,
w e re
d o n e i n i t i a l l y b y u s u a l r o u t i n e m e t h o d s a s fo u n d in m a n y
te x tb o o k s .
m e th o d ,
T h e s e i n c l u d e d t e x t u r a l a n a l y s i s b y th e h y d r o m e t e r
o r g a n i c m a t t e r c o n t e n t b y th e W a l ld e y - B la c k ( w ith o u t
e x t e r n a l h e a t ) m e th o d ,
w ith
ro u tin e ' te s t s
IN N H ^ O A c ),
e x c h a n g e a b le
C a,
M g,
c a tio n e x c h a n g e c a p a c ity ,
K a n d N a (e x tra c te d
an d a v a ila b le p h o s­
p h o r u s b y O l s e n 's N aH C O g t e s t (w ith c o l o r d e v e l o p m e n t i n a s c o r ­
b i c a c i d ) (1 9 6 5 ). S o il pH m e a s u r e m e n t w a s d o n e b y m i x in g 0 . 01 N
C a C lg a n d s o i l i n a 2 :1 r a t i o ,
a n d p l a c i n g th e pH m e t e r g l a s s
I
.
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s u p e r n a ta n t liq u id .
te rm in e
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e v i d e n c e d b y t h e i r '.pH v a lu e a n d a l s o b y th e
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as
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T a b l e I - R e s u l t s o f s o i l p h y s i c a l and" c h e m i c a l d e t e r m i n a t i o n s o n s o i l s u s e d in e x p e r i m e n t s .
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T o e s t i m a t e l a b i l e P , th e m e th o d i n i t i a l l y p r o p o s e d b y A m e r
e t - a l (1 9 5 5 ) a n d w h ic h w a s a l s o c o m p a r e d b y O ls e n (1 9 7 0 ) w a s u s e d .
F o r t h i s t e s t I g o f th e t h r e e r a t e s o f t h e s p ik e d s o i l t h a t w e r e u s e d to
e s tim a te la b ile
K w e re p la c e d in a 12 5 -m l E r le n m e y e r fla s k .
T o th is
I g o f llA m b e r l i t e 1 R A - 4 1 0 M a n io n r e s i n , w h ic h h a d b e e n p r e v i o u s l y
p u r i f i e d i n a c o l u m n r e g e n e r a t i o n p r o c e s s w ith I N
r e ta in e d on a 3 2 -m e s h s ie v e , w a s a d d e d .
HG I , a i r d r i e d a n d
T h e s a m p l e s w e r e th e n
p l a c e d u n d e r p a r t i a l v a c u u m to d e g a s th e r e s i n , s t o p p e r e d a n d p l a c e d
o n a h a n d s h a k e r f o r 24 h o u r s .
A f t e r t h i s s h a k in g p e r i o d , th e r e s i n -
s o i l - w a t e r s a m p l e w a s p o u r e d in t o a 6 0 - m e s h s i e v e .
T o o b ta in c o m ­
p l e t e t r a n s f e r o f s o i l a n d r e s i n , th e E r l e n m e y e r w a s p a r t i a l l y r e f i l l e d
w ith a d d i t i o n a l d i s t i l l e d w a t e r a n d a g a i n p o u r e d in t o t h e s i e v e .
The
s o i l w a s w a s h e d t h r o u g h th e s i e v e w ith a j e t o f d i s t i l l e d w a t e r , w h ic h
l e f t o n ly th e r e s i n .
T o c o l l e c t th e r e s i n f o r e x t r a c t i o n , a p i e c e o f f in e
. m e s h n y lo n f a b r i c w a s f a s t e n e d v e r y l o o s e l y o v e r th e to p o f a g r a d u a t e
c y l i n d e r w ith a r u b b e r b a n d s o t h a t th e r e s i n c o u ld b e r i n s e d o u t o f th e
s i e v e w ith d i s t i l l e d w a t e r i n t o t h e h o llo w f o r m e d b y th e n y lo n f a b r i c .
' r
A f t e r t r a n s f e r , th 4 n y lo n f a b r i c h o ld in g th e r e s i n w a s t i e d in t o a b a g .
T o p r e p a r e to e x t r a c t , t h e b a g g e d r e s i n w a s p o s i t i o n e d a t t h e b o tt o m
o f a 3 0 - m l s e p a r a t o r y f u n n e l (w h ic h h a d t h e to p p r e v i o u s l y c u t o ff), a n d
w a s h e l d t i g h t l y i n p l a c e b y a t e f l o n - c o a t e d s t i r r i n g r o d w h ic h i n t u r n
w a s a t t a c h e d to a s t r e t c h e d r u b b e r b a n d .
d o n e w ith 50 m l o f I N
v o lu m e tr ic fla s k .
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m o ly b d a te c o lo r d e v e lo p m e n t in a s c o r b ic a c id .
T h e s o il s o lu tio n c o n c e n tr a tio n o f K
and
P
( a s s o c i a t e d w ith
th e l a b i l e c o n c e n t r a t i o n j u s t d e s c r i b e d ) w a s d e t e r m i n e d a t t h e s a m e
s p ik in g r a t e s f r o m e x t r a c t s of n e a r s a t u r a t e d p a s t e o n s o i l s a m p l e s
u n d e r g o i n g d if f u s io n t e s t s .
T h e m e th o d o f p r e p a r i n g th e p a s t e s i s i n ­
c l u d e d i n th e s e c t i o n d e s c r i b i n g d if f u s io n t e s t s .
C o n c e n tra tio n of K
-i
i n th e e x t r a c t s w a s d e t e r m i n e d w ith a f l a m e p h o t o m e t e r .
P h o sp h o ru s
w a s d e t e r m i n e d , o n t h e e x t r a c t s b y a m m o n i u m m o l y b d a te c o l o r d e v e lo p ­
m e n t in a s c o r b ic a c id w h e r e th e r e w a s s u ffic ie n t c o n c e n tr a tio n f o r th is
te s t.
A n e x t r a c t i o n o f a m m o n i u m p h o s p h o m o ly b d a te in t o i s o b u t y l a l c o ­
hol was made on eictraets having ins.uffieient concentration for the
a s c o r b i c a c i d m e th o d .
'
'
V
■
33
C h e m i c a l D e t e r m i n a t i o n o f S o lu ti o n a n d S o r b e d C o n c e n t r a t i o n a n d
C a p a c ity F a c t o r s f o r P h o s p h o ru s a n d P o ta s s iu m
■
•/"
T h e d r i e d s o i l s a m p l e s w e r e i n i t i a l l y m o i s t e n e d w ith w a t e r to
h a v e 15 p e r c e n t w a t e r b y w e ig h t.
T h e y w e r e th e n s t o r e d in p l a s t i c
lin e d c o n ta in e r s a t fo u r d e g r e e s c e n tig r a d e f o r s ix w e e k s .
To d e te r­
m i n e i f w a t e r l o s s h a d o c c u r r e d a f t e r t h e r e f r i g e r a t i o n p e r i o d , th e
s a m p l e s h a d w a t e r c o n t e n t d e t e r m i n e d a n d a llo w e d f o r s p ik in g w ith
f e r t i l i z e r to b e d o n e o n a d r y w e ig h t b a s i s .
A n e u t r a l s o l u t i o n c o n t a in ­
in g 4 . 32 g K C 1, I . 4 5 g K H 2 P O 4 a n d 2. 89 g K 2 H P O 4 ' SH 2 O p e r l i t e r
w a s a d d e d a t r a t e s o f 0, 1 0 , a n d 20 m l p e r 100 g s o i l ( w h ic h h a d p r e v ­
io u s ly p a s s e d th r o u g h a 100 m e s h s ie v e ).
T h e s o il w a te r c o n te n t w as
t h e n i n c r e a s e d to p r o d u c e a s a t u r a t e d p a s t e a n d th e s o i l w a s m ix e d
, a n d a i r d r i e d a t o t a l o f f o u r t i m e s d u r i n g a tw o - d a y p e r i o d .
Tb e s ti­
m a te la b ile K , th e m e th o d of G ra h a m a n d K a m p b e ll ( I 9 6 8 ) w a s u s e d ,
w h e r e 1 . 0 g o f s o i l a n d 24 m l o f 0. 01 M C a C l 2 w e r e a d d e d to a c e n t r i ­
f u g e tu b e .
T h e m i x t u r e w a s s t o p p e r e d a n d p l a c e d o n a s h a k e r h a v in g
120 e x c u r s i o n s p e r m i n u t e f o r o n e - h a l f h o u r .
T h e n th e s a m p le w as
c e n t r i f u g e d a n d t h e s u p e r n a t a n t l i q u i d c o l l e c t e d in a 2 5 0 m l p l a s t i c
b o ttle .
S e v e n m o r e p o r t i o n s o f C a C l 2 .w e r e s e q u e n t i a l l y a d d e d , s h a k e n
a n d c e n t r i f u g e d a s b e f o r e a n d th e r e s u l t i n g e x t r a c t a d d e d to th e p l a s t i c
b o ttle .
T h e c o l l e c t e d v o l u m e w a s b r o u g h t, to 200 m l b y a d d in g a d d i t i o n a l
C a C l 2 s o lu ti o n .
P o t a s s i u m c o n t e n t o f th e e x t r a c t w a s d e t e r m i n e d b y
fla m e s p e c tro s c o p y ,
,
34
D e t e r m i n a t i o n o f S o lu tio n a n d S o r b e d C o n c e n t r a t i o n ,
B u f f e r C a p a c ity
A n d I m p e d a n c e V a lu e s b y D if f u s io n
F o r th e s e d e te r m in a tio n s ,
s o i l w a s u s e d f r o m th e
s a m e b u lk
c o n ta in e r s h a v in g th e s o il w a te r a n d r e f r i g e r a t i o n p r e tr e a tm e n t a s
f o r th e c h e m i c a l d e t e r m i n a t i o n o f p h o s p h o r u s ,
c a p a c ity f a c t o r s .
A ls o ,
th e
sam e
p o ta s s iu m and
s p ik in g s o lu ti o n a n d r a t e w a s
a p p l i e d to a 4 0 0 g ( d r y w e ig h t b a s i s ) s a m p l e .
T hese
s a m p le s
w e r e th e n m i x e d w ith d i s t i l l e d w a t e r to p r o d u c e a p a s t e t h a t w a s
s lig h tly l e s s w e t th a n a s a tu r a te d p a s te .
(T h e r e a s o n f o r t h i s
d e v i a t i o n f r o m a n o r m a l s a t u r a t e d p a s t e w a s to e n s u r e t h a t th e
solid portion of the samples would not shrink away from the resin
s i n k d u r i n g th e d i f f u s i o n p e r i o d ,
w h ic h w o u ld h a v e p r o d u c e d p o o r
•
T h e w e tt e d s o i l w a s t h e n p l a c e d in a
i
I
s o il- r e s in s in k c o n ta c t. )
s e a le d p la s tic b a g ,
' '
■
■
th e b a g w a s p l a c e d i n a r o u n d c a p p e d j a r ,
and
th e j a r p l a c e d o n a s lo w ly r e v o l v i n g r o c k t u m b l e r f o r 2 4 h o u r s .
I n t h i s m a n n e r th e b a g r o l l e d i n th e j a r a n d th e s o i l w a s m ix e d
w ith n o
s e p a r a t i o n o f li q u id f r o m
s o lid p h a s e ,
p r o b l e m w ith o t h e r m i x in g m e t h o d s a t t e m p t e d .
w h ic h h a d b e e n a
A f t e r t h i s m ix in g
a p o r t i o n o f th e s o i l s o l u t i o n w a s e x t r a c t e d u n d e r s u c t i o n in a
B u c h n e r f u n n e l a n d th e e x t r a c t s
tio n c o n c e n tra tio n - -
s a v e d f o r d e te rm in in g
s o i l s o lu ­
a s m e n tio n e d in th e s e c t i o n o n " C h e m i c a l
D e t e r m i n a t i o n o f S o lu tio n a n d S o r b e d C o n c e n t r a t i o n a n d C a p a c ity
F a c to rs fo r P h o sp h o ru s and P o ta s s iu m " .
w a s u s e d to f i l l th e d i f f u s i o n c e l l ,
T he o th e r p o r tio n o f s o il
sh o w n in F ig u r e
I.
In a d d i t i o n
t o m e a s u r i n g th e q u a n t i t y o f w a t e r a d d e d to th e s o i l f o r th e d if f u s io n
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YZZZA
F ig u re I .
D if f u s io n c e l l s h o w in g : A - D i m e n s io n s ( m o d e l s h o w n c o u ld h a v e s o i l c o lu m n
h e i g h t r e d u c e d to o n e - h a l f ) ; B - C e l l in o p e r a t i o n ; C - M e th o d o f e x t r a c t i n g
re s in .
A w o o d e n m a tc h c a n b e i n s e r t e d th r o u g h c a p h o l d e r to p u s h o u t
r e s in a f te r e x tra c tio n .
36
I • t e s t , th e , s o i l f i l l e d c e l l (o f k n o w n v o lu m e a n d t a r e w e ig h t) w a s w e ig h e d .
j
F r o m th is ,
( p e r c e n t b y v o lu m e ) w a s c a l c u l a t e d f r o m e s t i m a t i n g t h a t
th e s p e c i f i c g r a v i t y o f th e m i n e r a l p o r t i o n w a s 2. 65 a n d
I
P y = [ m l s o i l - ( m l s o i l - g w e t s o i l ) / I . 6 5 ] (m l s o i l / 1 0 0 )
U s in g t h i s s a m e i n f o r m a t i o n to c a l c u l a t e P
w
(37)
( p e r c e n t b y w e ig h t)
P w = 100 [ 2 . 65 ( m l s o i l - w e t s o i l ) ] / 2 . 65 (g w e t s o i l - m l s o il)
(3 8 )
a n d b u lk d e n s i t y w a s c o m p u te d f r o m
B D = P v ZPw
(39)
T w o r e p l i c a t i o n s w ith th e t h r e e s p ik in g r a t e s f o r e a c h s o i l w e r e
'd o n e .
.
W h e n f i l l i n g th e c e l l s , a v i b r a t i n g h a i r c l i p p e r w a s to u c h e d to th e
s i d e o f t h e c e l l w h ic h f a c i l i t a t e d g e t tin g th e s o i l p a c k e d w ith o u t a i r
b u b b le s .
T h e e x p o s e d s o i l a t th e to p o f t h e c e l l w a s s t r u c k o ff w ith a
s p a t u l a to p r o d u c e a s m o o t h g l i s t e n i n g s u r f a c e , a n d th e r e s i n s in k (d e ­
g a s s e d a n d p r e v io u s ly s to r e d in w a te r ) w a s p la c e d in c o n ta c t an d w as
c a p p e d a s s h o w n i n p a r t B o f F i g u r e I . ' A f t e r d if f u s io n o f i o n s w a s
a l lo w e d to t a k e p l a c e f o r 24 h o u r s , th e c a p w ith r e s i n s in k w a s r e m o v e d ,
a n d th e s o i l a d h e r i n g to t h e n y lo n m e s h w a s r i n s e d a w a y w ith a j e t o f ■
d is tille d w a te r.
show n in p a r t
E x t r a c t i o n w a s d o n e w ith 100 m l o f IjN
C
IHL^SO^. a s
of F ig u re I .
T h e r e s i n u s e d i n t h e s in k w a s a n e u t r a l m i x t u r e o f A m b e r l i t e
L<
I R - 120 H ( m e d i u m y p o r o s ity ) , a s t r o n g l y a c i d i c r e s in * a n d A m b e r l i t e
/ IR A -4 1 0 OH (m e d iu m p o r o s ity ) , a s tr o n g ly b a s ic r e s in .
th e r 6 s i n s w e r e s i z e d .
B e fo re u se ,
T h e I R - 120 H r e s i n w a s p u r i f i e d w ith I N H ^S O ^
w h ile th e b a s i c 1 R - 4 1 0 r e s i n w a s c o n v e r t e d f r o m th e C l”"to O H " ty p e b y
Cv
.
:
-V
v*
...
.1'
37.
IN
N aO H in s ta n d a r d r e s i n c o lu m n te c h n iq u e .
T o d e t e r m i n e th e p r o p o r ­
t i o n o f e a c h r e s i n to a d d to th e m i x t u r e , e n o u g h o f e a c h w e r e a d d e d to
p r o d u c e a n e u t r a l p H w h e n a s a m p l e , w a s p l a c e d in a t e n p e r c e n t N a C l
s o lu ti o n .
P o t a s s i u m c o n t e n t o f th e e x t r a c t w a s d e t e r m i n e d b y f l a m e e m i s s i o n ,
■/ ^
/
■
p h o s p h o r u s b y a m m o n i u m m o l y b d a te c o l o r d e v e l o p m e n t i n a s c o r b i c
/
■ acid, a n d c h l o r i n e b y a p o t e n t i o m e t r i c m e th o d .
T h i s m e t h o d in v o lv e d
t i t r a t i n g a s t a n d a r d 0 . 0 0 2 _N K C l s o l u t i o n i n I N H ^ S O ^ ( r e s i n e x t r a c ­
t i o n s o lu tio n ) w ith 0. 005 N A g N O ^ a n d d e t e r m i n i n g th e r e l a t i v e m i l l i ­
v o l t r e a d i n g ( s e t a t z e r o b e f o r e t i t r a t i n g ) w i t h e a c h i n c r e m e n t a d d i tio n
o f th e A g N O 3 .
A
Ag
r e f e r e n c e an d A g -A g -C l e le c tro d e w e re u se d .
J T h e i n f l e c t i o n p o in t o f t h e r e s u l t i n g g r a p h a g r e e d w ith th e c a l c u l a t e d
e n d p o in t a n d t h e u n k n o w n s w e r e t i t r a t e d to t h i s m i l l i v o l t e n d p o in t w ith
th e A g N O 3 s o l u t i o n . | •
/
38
I
D e t e r m i n a t i o n o f P l a n t U p ta k e f r o m S o ils
T h e N e u b a u e r s e e d l i n g m e th o d a s d e s c r i b e d b y V a n d e c a v e y e (1 9 4 8)
w a s f o llo w e d c l o s e l y , u s i n g t h r e e r e p l i c a t i o n s o f e a c h s o i l a n d s a n d
ch eck s.
B a r l e y (H o r d e u m d i s t i c h o n v a r P i r o l i n e ) w a s g r o w n f o r 17
d a y s i n a g r o w th c h a m b e r w ith f u ll l i g h t ( 5 0 0 -6 0 0 m i c r o e i n s t e i n s / m 3/
■ s e c w ith i n th e 4 0 0 - 7 0 0 n m w a v e le n g th r a n g e ) f o r 16 h o u r s a t 2 4 ° C a n d
w ith a n e i g h t - h o u r n i g h t t i m e o f 1 8 ° C .
T h e n th e e n t i r e p l a n t w a s h a r ­
v e s t e d , w e ig h e d a n d g r o u n d i n a U d y c y c lo n e m i l l .
T he TC A e x tra c ­
t i o n p r o c e d u r e f o r p h o s p h o r u s a n d p o t a s s i u m , a s o u tl in e d b y L e g g e t t
,
a n d W e s t e r m a n n (1 9 7 3 ), w a s u s e d .
P o t a s s i u m c o n t e n t o f th e e x t r a c t
w a s d e t e r m i n e d b y f l a m e p h o t o m e t e r , w h ile p h o s p h o r u s w a s d e t e r m i n e d
b y a m m o n iu m m o l y b d a te c o l o r d e v e l o p m e n t i n a s c o r b i c a c i d .
I
I
A ls o , th e s h o r t t e r m m e th o d o f D e M e n t, S t a n f o r d a n d B r a d f o r d
(1 9 5 9 ) w a s u s e d w ith 4 0 b a r l e y s e e d l i n g s g r o w n .
T w o r e p l i c a t i o n s of
" m i n u s K " a n d a l s o tw o r e p l i c a t i o n s o f " m i n u s P " t r e a t m e n t s w e r e
g r o w n p e r s o i l arid a l s o t h r e e s a n d c h e c k s .
T h e r o o t s a n d to p s w e r e
g r o u n d , e x t r a c t e d , a n d K a n d P c o n t e n t m e a s u r e d i n th e s a m e m e th o d
a s th e N e u b a u e r t e s t s .
39
R E S U L T S A N D I N T E R P R E T A T IO N S
I m p e d a n c e V a l u e s f r o m C h l o r i d e D if f u s io n
T h e q u a n t ity o f C l t h a t d if f u s e d to th e r e s i n , u s i n g t h e c e l l s h o w n
in F ig u re I , w as m e a s u re d .
I m p e d a n c e v a l u e s (w h ic h d e n o te th e r e l ­
a t i v e q u a n t ity o f d if f u s iv e f lo w i n s o i l s o l u t i o n a s c o m p a r e d to a n
a q u e o u s s o lu tio n of s i m i l a r c o n c e n tra tio n ) w e r e c a lc u la te d f r o m e q u a ­
t i o n (36) to a v e r a g e 0. 28 f o r th e v a r i o u s s o i l s u s e d .
T h e s ta n d a rd
d e v i a t i o n w a s 0. 1 1 , a n d t h e r a n g e w a s f r o m 0. 10 t o . 0 . 4 6 .
T hese
v a l u e s fo u n d w e r e i n g e n e r a l a g r e e m e n t w ith th o s e t h a t P o r t e r e t a l
(I9 6 0 ) o b ta in e d f r o m C l d if f u s io n .
P r e c i s i o n o f t h i s m e a s u r e m e n t w a s s u c h t h a t th e a v e r a g e d e v i­
a t i o n o f a s i n g l e s o i l s a m p l e v a l u e f r o m th e m e a n of r e p l i c a t e s (fo r
t h e s a m e s o il) w a s 3. 8 p e r c e n t .
F r o m c o m p a r i n g t h e im p e d a n c e
v a l u e s o f t h e v a r i o u s s o i l s to t h e i r b u lk d e n s i t y ( w ith in t h e d if f u s io n
c e l l ) , t e x t u r e , a n d o r g a n i c m a t t e r c o n t e n t, t h e r e w e r e n o a p p a r e n t
re la tio n s h ip s .
T h e s o i l w ith th e l o w e s t im p e d a n c e v a l u e (0. 10) w a s
A s to r ia c la y lo a m .
I t w a s a n e x t r e m e l y " f lu f f y " s o i l a n d h a d a b u lk
d e n s i t y o f o n ly 0. 76 w h ile u n d e r g o in g d if f u s io n .
T o c o m p u te th e t h e o r e t i c a l C l d i s t r i b u t i o n w ith i n a s o i l u n d e r ­
g o in g d if f u s io n , e q u a t io n (8) m a y b e u s e d .
F o r illu s tra tiv e p u rp o se s,
th e r e s u l t s a r e s h o w n i n F i g u r e 2 f o r th e D a y to n s o i l a f t e r 24 h o u r s .
T h i s s o i l h a d a n a v e r a g e im p e d a n c e v a l u e .
A s m a y b e n o te d f r o m F i g ­
u r e 2, d if f u s io n r e d u c e d th e i n i t i a l C l c o n c e n t r a t i o n (C q ) f o r a 2 - c m
s o i l d i s t a n c e f r o m th e r e s i n s in k d u r in g th e p e r i o d .
T he a v e ra g e quan­
t i t y o f C l a d s o r b e d i n 24 h o u r s b y t h e r e s i n s in k w a s 4 . 3 p e r c e n t o f th e
SOLN CONC - /xeq CIZcm^
x - cm (DISTANCE FROM RESIN SINK)
F ig u re 2.
C o m p u te d s o lu tio n c o n c e n t r a t i o n o f c h l o r i d e a s r e l a t e d to d is ta n c e f r o m s in k , a f t e r
d if f u s in g o n e d a y . A z e r o s in k i s a s s u m e d h e r e . C q w a s c a l c u l a t e d f r o m th e C l
s p ik in g d o n e .
41
i
a m o u n t a d d e d to th e s o i l i n th e s p ik in g s o lu ti o n .
It m a y a ls o be v is u ­
a l l y n o te d t h a t th e a r e a o f r e d u c e d c o n c e n t r a t i o n in F i g u r e 2 , a s c o m ­
p a r e d to th e t o t a l a r e a f o r a 1 5 - c m h ig h c e l l , a g r e e s w ith th e 4 . 3 p e r*
cen t of Cl a d so rb e d .
D if f u s io n a n d C h e m i c a l l y D e t e r m i n e d S o il. P o t a s s i u m
T h e r e p e a t e d 0 .0 1
C a C lg e x t r a c t i o n o f s o i l K , a s p r o p o s e d
b y G r a h a m a n d K a m p b e l l (1 9 6 8 ) w a s u s e d a s a n e s t i m a t e o f l a b i l e K .
I t h a d b e e n s h o w n b y th e a u t h o r s to v e r y c l o s e l y p r e d i c t K - 42 is o to p e
m e a s u r e d la b ile K .
F r o m c o m p a r i n g th e r e s u l t s o f th e C a C lg e x t r a c t
to th e IN N H ^ O A c e x t r a c t f o r e x c h a n g e a b le K ( T a b le I ) ,
i t w a s n o te d
t h a t th e C a C lg e x t r a c t p r o v i d e d s o m e w h a t l a r g e r v a l u e s .
T hese a v e r ­
a g e d 0 . 8 4 m e q K / l 0 0 g f r o m th e C a C lg e x t r a c t a n d 0 . 71 m e q K /lO O g
s o i l f r o m th e N H ^ O A c e x t r a c t .
S im ila r d iffe re n c e s w e re re p o rte d by
G r a h a m a n d K a m p b e l l (1 9 6 8 ), a n d th u s th e u s e o f t h e i r p r o c e d u r e
se e m e d ju s tifie d .
T h e r e s u l t s o f t h i s t e s t a r e s h o w n in T a b le
m a y b e c o m p a r e d to d i f f u s i o n - b a s e d e s t i m a t e s o f l a b i l e K .
2 , and
T h e d if f ­
u s i o n d a t a d e p i c t i n g l a b i l e K w e r e o b ta in e d f r o m m e a s u r i n g f lu x o f K
a n d C l to th e r e s i n s in k d u r i n g a m e a s u r e d t i m e t o g e t h e r w ith th e
v a l u e s n e e d e d to s o lv e e q u a t i o n s (27) a n d (3 5 ) f o r C q a n d C g , r e s p e c ­
t i v e l y - a s m e n tio n e d i n th e " M e th o d s a n d M a t e r i a l s " s e c t i o n .
\
A lth o u g h t h r e e r a t e s o f s p ik in g (0 , 1 0 , a n d 20 m i s s p ik in g so l*
u ti o n p e r 1 0 0 ,g s o il) w e r e u s e d , o n ly th e r e s u l t s f r o m th e 0 a n d 10 m l
'I
r a t e w e r e u s e d f o r i n c l u s i o n in T a b le 2 . A l s o , v a l u e s o f M ^ a n d M ^
t h e s e s p ik in g r a t e s a r e i n c lu d e d w ith o t h e r d a t a i n .'T ab le 3 .
It w as
42
T a b l e 2 - C o m p a r i s o n s b e t w e e n c h e m i c a l d e t e r m i n a t i o n s a n d d if f u s io n
. d e t e r m i n a t i o n s , o f l a b i l e . K , .(C + C ), a n d s o l u t i o n K , (C ).
. ' s o
o
S o il
'
C h e m i c a l M e th o d s
D if f u s io n M e th o d s
L a b ile K *
L a b ile K $
f ie q /c m 3
c Ot
C o*
JLleq/c m 3
J ie q /cm 3
J ie q /cm 3
1.7. 5
0 .4 1
2 3 .7
0 . 33.
A s to ria
1 .4
. 06
4 .8 .
C am as C re e k
8. 5
. 12
8. 7
. 14
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7. 8
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. 67
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I . 82
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P o rtn e u f
16. 9
. 28
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. 17
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. 39
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. 54
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1 5 .2
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18. 6
. 34
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2 .6
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21. 8
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L lo y d
, /
S t a n t o n 's C r o s s i n g
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.
. 33.'.;
'
;
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2. 0
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* F r o m G r a h a m - .E a m p b e ll m e th o d
t F r o m s o il s a tu r a tio n e x tr a c t
$ C o m p u te d a f t e r m e a s u r i n g K f lu x to r e s i n s in k .
.
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43
th o u g h t t h a t th e c a p a c i t y f a c t o r (R + l) m i g h t b e r e d u c e d a t h i g h e r s p i k ­
i n g r a t e s b e c a u s e , w ith a l i m i t e d q u a n t i t y o f e x c h a n g e s i t e s o n th e .
c l a y s , th e n e w e q u i l i b r i u m b e tw e e n ' s o r b e d a n d s o lu tio n p h a s e w o u ld
t e n d to m a i n t a i n a. g r e a t e r s h a r e o f K in s o lu ti o n .
F r o m 'r e c o m p u tin g !
f r o m th e h i g h e r t o g e t h e r w ith th e z e r o s p ik in g r a t e ( a s tw o r a t e s a r e
n e e d e d f o r o n e d e t e r m i n a t i o n ) , i t w a s fo u n d t h a t th e n e w a v e r a g e C g
v a l u e s w e r e r e d u c e d to 83 p e r c e n t o f t h e o ld v a l u e s .
L ik e w is e , th e re
w a s a n i d e n t i c a l i n c r e a s e i n th e n e w a v e r a g e G q v a l u e s ( a s m a t h e m a t ,
i c a l l y w o u ld b e e x p e c te d ) .
F ig u re
3 i l l u s t r a t e s th e C
v a lu e s , as
s
d e t e r m i n e d f r o m th e z e r o p l u s th e 10 m l s p ik in g r a t e v e r s u s t h o s e d e ­
t e r m i n e d f r o m th e z e r o p l u s t h e 20' m l s p ik in g r a t e .
B e c k e t t (1 96 4 ) h a s
e s t a b l i s h e d t h a t (R + l) v a l u e s d e c r e a s e w ith h i g h e r c o n c e n t r a t i o n s of .
K a d d e d , a n d s o th e r e s u l t h e r e m i g h t b e e x p e c te d .
T h e v a r i a t i o n a b o u t th e t r e a t m e n t m e a n f o r K d e t e r m i n a t i o n s
.4
o f th e r e s i n s in k e x t r a c t ( M ^ , . M ^ ) a v e r a g e d o n ly 2. 9 p e r c e n t . T h u s
t h e p r o c e d u r e a p p e a r e d to b e s u f f i c i e n t l y s i m p l e a n d w ith o u t i n h e r e n t
s o u r c e s o f e x p e r i m e n t a l e r r o r f o r a c c e p t a b l e p r e c i s i o n w h e n u s e d to
d e te rm in e
K
d if f u s io n .
T h e s i m i l a r i t y o f v a l u e s s h o w n i n T a b le 2
o b t a i n e d f r o m c h e m i c a l e x t r a c t i o n o f s o i l i t s e l f v e r s u s d if f u s io n u p ta k e
w a s a n e x c i t i n g s u r p r i s e , i n s p i t e o f th e o r i g i n a l h y p o t h e s i s s u g g e s tin g
t h a t a d if f u s io n m e c h a n i s m c o u ld b e u s e d to m e a s u r e s o l u t i o n a n d a d ­
s o r b e d i o n c o n c e n t r a t i o n (C q a n d C g).
T h e u s e o f e q u a t io n (30) m a y b e a r r a n g e d s o t h a t
■
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b e tw e e n tw o s p ik in g r a t e s to c a l c u l a t e C g .
C o m p a r is o n i s m a d e
45
and
K p r e d i c t s th e q u a n t ity o f s p ik in g n e e d e d to i n c r e a s e th e a c c u m u ­
l a t i v e f lu x o f a n o n s p ik e d s o i l (M^y ) to a n e w v a l u e ( M ^ ) .. I n o r d e r to
m a in ta in n o ta tio n ,
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t i o n s a r e n e e d e d K^. w o u ld e q u a l th e q u a n t ity n e e d e d .
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c h e c k w a s m a d e to d e t e r m i n e th e v a l i d i t y o f th e u s e o f th e d if f u s io n
e x p e r i m e n t s to d e t e r m i n e n e e d e d
' K^. n e e d e d to o b t a i n t h e
v a lu e s .
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f o u n d f r o m t h e lo w s p ik in g r a t e (10 m l
s p ik in g s o l u t i o n a d d e d p e r 100 g s o il) , o r w h e r e
w as a lre a d y know n.
T o d o t h i s , th e v a l u e s o f (R + l) a n d I w e r e u s e d f r o m th e r e s u l t s o f th e
diffusion cells having the high spiking rate together with the nonspiked
s o il.
T h e s e r e s u l t s a r e s h o w n i n T a b l e 3.
c o m p u te d
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r e c o g n i z e d t h a t t h e s e v a l u e s w e r e o b ta in e d e n t i r e l y f r o m th e d if f u s io n
e x p e rim e n ts.
T h e r e f o r e , w h ile i t d o e s n o t s u p p ly p r o o f o f t h e u tility ,
o f th e m e th o d , i t d o e s m a k e a c o m p a r i s o n f r o m th e d a t a t h a t c o u ld h a v e
d is p ro v e n its u tility .
T h e r e la tiv e e ffic ie n c y of
to w a rd in c re a s in g
f lu x c a n b e c o m p a r e d f o r v a r i o u s s o i l s b y u s e o f t h i s m e th o d , w h ic h
v a r i e s l a r g e l y f r o m th e p o r t i o n o f K^. g o in g in to s o lu ti o n v e r s u s b e in g
a d so rb e d .
P l a n t P o t a s s i u m U p ta k e C o m p a r e d t o C h e m i c a l a n d D if f u s io n T e s t s
T h e r e s u l t s f r o m th e D e M e n t - S t a n f o r d s h o r t - t e r m t e s t (1959)
w e r e s o m e w h a t d i f f e r e n t t h a n th e N e u b a u e r t e s t .
S e v e r a l s im p le lin e a r
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m e t h o d s v e r s u s c h e m i c a l a n d d if f u s io n t e s t s .
The sq u a re d c o rre la tio n '
c o e f f i c i e n t v a l u e s (r3 ) a r e g iv e n i n T a b l e 4 .. 'I n th e D e M e n t - S ta n f o r d
m e th o d , p l a n t s a r e f i r s t p a r t i a l l y g r o w n i n a s a n d - n u t r i e n t s o lu tio n
K.
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g r o w i n s o i l f o r o n ly 6 d a y s .
I n c o m p a r i s o n , th e N e u b a u e r m e th o d
a l lo w s s e e d l i n g p l a n t s to g ro w i n l i m i t e d s o i l f o r 18 d a y s a n d c o m p l e t e l y
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e x h a u s t th e
T h e r e f o r e , th e D e M e n t- S ta n f o r d m e th o d m e a s ­
u r e s a n i m m e d i a t e l y a v a i l a b l e s u p p ly w h ile t h e N e u b a u e r m e th o d t e n d s
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to c o m b in e t h i s w ith th e r e s e r v e a m o u n t s . A s s e e n , th e N e u b a u e r
m e t h o d v a l u e s a n d t h e s o i l e x c h a n g e a b le
c o r r e l a t e d ( r a - . 8 1 ),
K c o n t e n t w e r e f a i r l y w e ll
T h e g r e a t e r s o il e x tra c tio n
done b y Graham-*
Kampbell1S method, as c o m p a r e d to e x c h a n g e a b le K, r e s u l t e d in m u c h
r e d u c e d v a l u e s (r3 = . 3 9 ).
C o r r e l a t i o n b e t w e e n th e d if f u s io n m e th o d a n d
N e u b a u e r ’ s v a l u e s (r3 = . 54) w e r e i n t e r m e d i a t e to t h e c o r r e l a t i o n s j u s t
d e s c rib e d .
B y t h e o r y , t h e d if f u s io n m e th o d s h o u ld r e f l e c t i o n m o v e ­
m e n t f r o m a n in fin ite s o u r c e .
I n c o n t r a s t , t h e b a r l e y p l a n t s i n th e .
N e u b a u e r p o t s a r e e x p e c t e d to a l m o s t c o m p l e t e l y e x p l o it th e a v a i l a b l e
K so u rc e .
T h u s , th e p o o r c o r r e l a t i o n b e t w e e n th e d if f u s io n m e th o d a n d
N e u b a u e r 's m e th o d m i g h t b e a n t i c i p a t e d .
R e s u l t s f r o m th e d if f u s io n m e th o d h a d b e t t e r c o r r e l a t i o n w ith th e .
D e M e n t - S t a n f o r d c r o p p i n g e x p e r i m e n t ( r 3 = . 88) th a n a n y o f th e c h e m i c a l
e v a lu a tio n m a d e .
T h u s th e d if f u s io n m e t h o d a p p e a r e d to b e v a l u a b le
f o r d e p i c tin g s h o r t - t e r m u p ta k e b y p l a n t s .
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f lu x .
50
b e e n h a n c e d b y th e s q u a r e r o o t o f th e c a p a c i t y f a c t o r .
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c a p a c i t y f a c t o r s w e r e e s t i m a t e d f r o m c h e m i c a l d a ta , m u l t i p l i e d b y th e
s o l u t i o n c o n c e n t r a t i o n , a n d ’ th e r e s u l t i n g p r o d u c t v a l u e s c o r r e l a t e d .
I
w ith D e M e n t- S t a n f o r d v a l u e s .
T h e r e s u l t i n g c o r r e l a t i o n c o e f f ic ie n ts
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b y c o m p a r i n g s o l u t i o n c o n c e n t r a t i o n a l o n e to th e D e M e n t - S t a n f o r d r e ­
s u lts .
T h e r e f o r e , n o b e n e f i t w a s fo u n d b y u t i l i z i n g t h i s c o n c e p t w h e n
th e c a p a c i t y f a c t o r w a s t a k e n f r o m th e c h e m i c a l m e th o d s o u tlin e d a t
th e b o t t o m o f T a b l e 4 .
T h e r e d u c t i o n i n s o lu ti o n
K
c o n t e n t n e x t to a n e w r o o t i n a s o i l
c a n b e d e t e r m i n e d f r o m e q u a t io n (15).
I t w a s fo u n d t h a t m o s t o f th e
s o i l s w o u ld h a v e th e s o l u t i o n c o n c e n t r a t i o n r e d u c e d to a d e g r e e to a b o u t
0 . 4 c m a t t h e e n d o f a d a y a n d a b o u t d o u b le t h i s in t h r e e d a y s .
In th is
c a lc u la tio n i t w a s a s s u m e d th a t th e p la n t r o o t g e o m e tr y w a s th a t of a n
in fin ite c y lin d e r .
E q u a t i o n (15) i s th e f i r s t t e r m o f a s e r i e s s o lu ti o n
f o r a c y l i n d e r , a n d th u s a n a p p r o x i m a t i o n .
red u ce d ,
T o k n o w th e p e r c e n t o f C q
w o u ld a l s o n e e d to b e k n o w n - - th e f i g u r e o f 0 . 4 c m d e n o t e s
t h e e f f e c t i v e s o i l s o l u t i o n v o lu m e a b o u t th e r o o t in r e g a r d to p o t a s s i u m .
D i f f u s i o n a n d C h e m i c a l l y D e t e r m i n e d S o il P h o s p h o r u s
R e s u l t s o f a v a i l a b l e p h o s p h o r u s d e t e r m i n a t i o n s b y O l s e n 's
NaHCOg m e t h o d w e r e g iv e n i n T a b l e I .
v a r i a t i o n i n th e s o i l 's
T h e s e d a ta p o in t to th e la r g e
P 0 E x t r e m e - v a l u e s w e r e 3 a n d H O p p m -P 0
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la b ile
P
w a s n o t e d t o b e r e l a t e d to O l s e n 's t e s t ( r = O0 9 7 , w h e n e l i m ­
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i n a t i n g o n e o b v io u s ly b a d p o in t) w h e r e th e r e s i n e x t r a c t e d a b o u t tw o
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ppm
P , a s d id L lo y d e v e n a t th e lo w s p ik in g r a t e .
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B y h a v in g th e e s t i m a t e o f l a b i l e
P , w h ic h h a s b e e n d e n o t e d a s
( C g + C q ), a n d b y k n o w in g th e s o lu ti o n c o n c e n t r a t i o n , (C q ), f u r t h e r
e s t i m a t e s o f th e c a p a c i t y f a c t o r ,
( R + l) , w e r e c o m p u te d . . I n th e f i r s t
c o m p u t a t i o n ( R + l) w a s l e t e q u a l (C q + C g) / C ^ - w h ic h w a s a l s o u s e d a s
a f i r s t a p p r o x i m a t i o n i n th e d if f u s io n e x p e r i m e n t w ith
P.
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c r e a s e d ( o r s o m e t i m e s e v e n p o s i t i v e ) d if f u s iv e f lu x f r o m i n c r e a s e d
r a te s of P
s p ik in g .
T h e a v e r a g e v a r i a t i o n f r o m th e t r e a t m e n t m e a n
v a l u e a v e r a g e d 8. 6 p e r c e n t f o r a l l s o i l s .
B e c a u se of th is v a r ia tio n
a n d e r r a t i c d i f f u s i v e r e s p o n s e f o r t h e f iv e s o i l s i n p a r t i c u l a r , t h e i r
v a l u e s o f C q , C ^ a n d ( R + l) a r e n o t i n c l u d e d i n th e d if f u s io n d a t a .
th e o t h e r s o i l s , c o m p a r i s o n a r e s h o w n i n T a b l e 5.
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T h e v a lu e s in th is
t a b l e w e r e t a k e n f r o m th e n o n - s p i k e d s o i l s a n d th e lo w s p ik in g r a t e .
U s in g t h e s e , th e r3 v a l u e r e l a t i n g c h e m i c a l l y d e t e r m i n e d C q to d if f u s io n
C q w a s 0. 6 6 .
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a n d (R + l) to d if f u s io n m e t h d s w e r e 0. 33 a n d 0. 2 5 , r e s p e c t i v e l y .
O t h e r m e th o d s o f a p p r o x i m a t i n g (R + l) f r o m d if f u s io n w e r e t r i e d ,
b u t c o r r e l a t i o n s W e re n o t a s g o o d a s t h o s e j u s t s h o w n .
52
T a b l e 5 - C o m p a r i s o n s b e t w e e n c h e m i c a l d e t e r m i n a t i o n s a n d d if f u s io n
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A r e a s o n b e l i e v e d p a r t l y r e s p o n s i b l e f o r th e d e v i a t i o n i n d if f u s ­
io n r e s u l t s f r o m c h e m i c a l r e s u l t s (if a s s u m i n g th e c h e m i c a l d e t e r m i n ­
a t i o n s to b e m o r e c o r r e c t ) w a s th e l a c k o f l i n e a r i t y i n th e a d s o r p t i o n
is o th e rm s .
F r o m c h e m i c a l d a t a th e c a l c u l a t e d s l o p e s f o r s o lu ti o n
c o n c e n t r a t i o n s b e tw e e n : (I) 0 to C ,
o’
(3)
c Io w s p ik in g r a t e to
(2)
x '
C
o
to C n
^
and
lo w s p ik in g r a t e ,
C h ig h s p ik in g r a t e a r e s h o w n i n T a b l e 6 ‘
m e t h o d o f c o m p u tin g ( I ) w a s th e s a m e a s w a s u s e d in T a b l e 5.
c o m p u tin g (2) a n d (3 ), ( A C s o r f e e d +
w ere u sed .
solation)
/
The
For
s o l a t i o n H g u re s
It is r e a d ily a p p a re n t th a t F r e u n d lic h - I ik e a d s o rp tio n is o ­
t h e r m s a r e b e in g a d h e r e d to .
T h i s ty p e o f i s o t h e r m h a s b e e n a s s o c ­
iated with acid s o i l s b y O ls e n a n d Kemper (1 9 6 8 ).
Fox and
Kamprath
(1 9 7 0 ), f r o m a c i d s o i l s , h a v e p l o t t e d t h e s o l u t i o n c o n c e n t r a t i o n o n a lo g
s c a l e v e r s u s t h e a d s o r b e d c o n c e n t r a t i o n o n a l i n e a r s c a l e a n d o b ta in e d
s tra ig h t lin e s .
T h e c o n s t a n t v a l u e s O l s e n a n d W a ta n a b e (1 9 7 0 ) fo u n d
w e re fro m c a lc a re o u s s o ils .
A ls o , a d d in g to o m u c h p h o s p h o r u s s p ik in g
s o l u t i o n c o u ld b e e x p e c te d to m a k e th e i s o t h e r m f l a t t e n i n t h a t a r e a o f
th e c u r v e .
H o w e v e r , i f f e r t i l i z e r a p p l i c a t i o n r a t e f i g u r e s a r e to b e
d e t e r m i n e d f r o m d i f f u s i o n d a t a , i t s e e m s l o g i c a l t h a t t h e d if f u s io n e x ­
p e r i m e n t s s h o u ld b e d o n e a t , a t l e a s t , t h e s e r a t e s . . T h e p r o b l e m o f
c o r r e c t l y s o lv in g C Q, C g , a n d (R + l) v a l u e s , w h e r e c u r v a t u r e e x i s t s ,
c o u ld b e r e s o l v e d i f t h e r e w e r e a n a l y t i c a l s o lu ti o n s - - o r e v e n a p p r o x ­
im a tio n s .
W ith o u t t h e s e , f i n i t e d i f f e r e n c e m e th o d s n e e d to b e u s e d in
c o n j u n c tio n w ith a c o m p u t e r .
\ '/
54
T a b l e 6 - S lo p e o f p h o s p h o r u s a d s o r p t i o n i s o t h e r m f r o m c h e m i c a l
d e te r m in a tio n s a s d e p ic te d in te x t.
S lo p e ( R + l) B e tw e e n S o lu tio n C o n c e n t r a t i o n s
S o il
O to C
O
C to C
lo w s p ik in g
Q
H o w . s p ik in g to
h ig h s p ik in g
A m s te rd a m
560
23
- 470
C am as C re e k
620
168
18
2140
520
194
D ru m m er
830
188
199
F ra n k fo rt-B ry c e
730
22
18
M in id o k a
230
H
37
P o r tn e u f s u b s o il
190
302
. 47
Sagem oor
308
60
142
S t a n t o n 's C r o s s i n g
460
942
T ra c y ,
760
; 547
W a h lu k e
170
16
W h itn e y
HO
14 .
W illia m s
200
35
W in c h e s te r
510
25
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i... u
I
'!
C,
: i-
•
75
-2. 7
29
5 5
P l a n t P h o s p h o r u s U p ta k e C o m p a r e d to C h e m i c a l a n d
D if f u s io n T e s t s
T h e N e u b a u e r t e s t f o r p h o s p h o r u s , a l th o u g h fo u n d to g iv e r e p e a t a b l e r e s u l t s , w a s n o t s i g n i f i c a n t l y r e l a t e d to o t h e r s o il o r p l a n t d e t e r m ­
i n a t i o n s . . J n f a c t , th e c o r r e l a t i o n c o e f f i c i e n t r e l a t i n g i t to th e D e M e n tS t a n f o r d s h o r t - t e r m u p ta k e t e s t w a s
n o t in c lu d e d h e r e in .
O.
T h e re fo re , its ’ r e s u lts a re
T h e D e M e n t - S t a n f o r d t e s t i t s e l f w a s b e l i e v e d to
c o n t a i n s o m e i n h e r e n t e r r o r a s i t a d j u s t e d d i f f e r e n t s o i l s to v a r y i n g
m o i s t u r e t e n s i o n s d u r in g t h e t i m e th e s o i l a n d p l a n t s w e r e t o g e t h e r .
A
s e c o n d D e M e n t - S t a n f o r d t e s t w a s d o n e a n d a t t e m p t s w e r e m d d e to c o m ­
p e n s a te f o r th is .
■T h e s h a p e
o f th e c u r v e s r e l a t i n g p e r c e n t
P
i n th p y p la n ts to s o il
q u a n t i t i e s ( O ls e n P , " l a b i l e " P , a n d d if f u s io n P ) w e r e l o g a r i t h m i c .
T h e r e f o r e , a l o g a r i t h m i c t r a n s f o r m w a s m a d e o n th e in d e p e n d e n t v a lu e
of s o il
P.
i n F i g u r e 5.
R e s u l t s o f th e t h r e e r e g r e s s i o n s a n d c o r r e l a t i o n s a r e 's h o w n
T h e b e s t c o r r e l a t i o n s w ith p l a n t u p ta k e w e r e f r o m O l s e n 's
N a H C O ^ t e s t (r3 = . 70} w ith th e " l a b i l e " P t e s t (r3 = . 58) b e i n g i n t e r m e d ­
ia te .
T h e p o i n t s f r o m tw o s o i l s f o r d i f f u s i o n - m e a s u r e d
P
w e re not
in c lu d e d in F ig u r e 5 a s t h e i r r e p lic a tio n d e v ia tio n w as la r g e .
th e y b e e n i n c l u d e d , t h e r
H ad
v a l u e v /o u ld h a v e r e m a i n e d a b o u t t h e s a m e
■as th e v a l u e o f . 5 2 , s h o w n .
T h e c u r v i l i n e a r a p p r o a c h ( F i g u r e 5) w a s
th o u g h t j u s t i f i e d i n t h e s e p h o s p h o r u s u p ta k e s t u d i e s , a s i t i s c o m m o n ly
a c c e p t e d t h a t t h e r e i s d e c r e a s e d u p ta k e o f i n c r e m e n t s of a d d i t i o n a l
ab o v e th re s h o ld le v e ls .
P
F r o m a d if f u s io n a s p e c t , t h i s c o u ld b e b r o u g h t
a b o u t b y p l a n t r e g u l a t i o n o f th e
P
c o n c e n t r a t i o n a t th e r o o t - s o i l i n t e r f a c e .
PLANT P-
56
9- .0 4 3 9 + .0153 (log X)
PLANT P-%
Mfu - P - /ig Zcm2ZDAY
9- .0 2 6 + .0 2 0 3 (log
X)
PLANT P-%
OLSEN P - ppm
Y - . 0 2 8 + .0154 ( I ogX)
r2 - . 5 8
50
IOO
150
RESIN "LABILE" P - ppm
F ig u r e 5.
R e l a t i o n s h i p s b e tw e e n p la n t p h o s p h o r u s c o n te n t a n d
s o il q u a n tity a s m e a s u r e d by th r e e m e th o d s .
.
V >
57
If, f o r e x a m p le , a p la n t th a t i s a b u n d a n tly s u p p lie d w ith s o il
le t th e C
r
P
w e r e to
in c r e a s e ', th e n th e d iffu s iv e flo w w o u ld d e c r e a s e - - a s it is
• r.
t h o u g h t to b e p r o p o r t i o n a l to (C Q - C ^ ) .
J u d g i n g f r o m t h e r 3 v a l u e s i n F i g u r e 5, t h e d i f f u s i o n t e s t w o u ld
not be th e b e s t c h o ic e fo r d e te rm in in g th e so il
P
s ta tu s . ‘ H o w e v e r, th e
u s e o f t h e d i f f u s i o n t e c h n i q u e d o e s a l l o w f o r e s t i m a t i n g t h e a m o u n t of .
s p ik in g n e e d e d to b r i n g a b o u t a d e s i r e d f lu x i n c r e a s e p e r t i m e (e q u a tio n
40).
U sin g th e s a m e a p p r o a c h a s w a s u s e d f o r p o ta s s iu m , th e q u a n tity
•
o f s p ik in g w a s e s t i m a t e d th a t w o u ld b e n e e d e d to p r o v id e a d iffu s iv e
r a t e e q u a l to
(lo w r a t e s p i k i n g ) .
T h e e s t i m a t e s w e r e f a i,r ly a c c u r a t e
i n a b o u t o n e h a l f o f t h e c a s e s , t h e i r d e v i a t i n g l e s s t h a n 10 p e r c e n t f r o m
t h e k n o w n a m o u n t ( T a b l e 7).
In th e e x t r e m e c a s e h o w e v e r, th e e s ti m a t e
w a s o n l y 21 p e r c e n t of t h e t r u e v a l u e .
C h a n g e s i n f l u x r a t e p e r q u a n t i t y of P
sid e ra b ly .
sp ik in g a d d e d v a r i e d c o n - .
F o r e x a m p le , f r o m T a b le 5 it m a y b e c a lc u la te d th a t A s to r ia
n e e d e d 4 5 t i m e s a s m u c h p h o s p h o r u s a d d e d a s t h e W h i t n e y s o i l to c h a n g e
t h e d i f f u s i v e f lo w I jig P / c m ^ d a y .
T h e r e f o r e , th e d e v ia tio n s in c a l c u ­
l a t e d p h o s p h o r u s a s c o m p a r e d to th e v a l u e s a c tu a lly u s e d a p p e a r l e s s
s i g n i f i c a n t - - w h e n c o n t r a s t e d w i t h t h e r a n g e of r e l a t i v e e f f i c i e n c y t h a t
n e e d s to b e e s t i m a t e d .
F r o m e q u a t i o n (15), a n d b y u s i n g t h e s a m e r e a s o n i n g a s w a s u s e d
for
K, it c a n b e e s t i m a t e d th a t fo r a so il w ith a n o r m a l b u ffe r c a p a c ity
o f 5 0 0 , t h e r o o t w i l l r e d u c e t h e s o l u t i o n p h o s p h o r u s c o n c e n t r a t i o n to
d i s t a n c e s of o n l y 0. 04 c m i n a d a y .
T h is is th e s a m e d is ta n c e as r e ­
p o r t e d b y O l s e n a n d W a t a n a b e (1970) w i t h c o r n ...
5 8
T a b l e 7 - C o m p u t e d q u a n t i t i e s of p h o s p h o r u s ' s p i k i n g n e e d e d to o b t a i n
•
(a c c u m u la tiv e flu x p e r day) v e r s u s q u a n tity o f sp ik in g
a c t u a l l y s u p p l i e d to o b t a i n
S o il
.
C o m p u ted
M t£*
■M t u *
— At e q / c m 3 / d a y
A m ste rd a m
A sto ria /
I
I C am as C reek
■
■
Peq/ cm
8. 27 .
43
I . 03
0.95
51
5. 31
4 . 35
22 •
3.26
2.58
13. 17
1 1 .1 9
9.92
i l . 62
A c t u a l K.
S u p p lie d 3
-------89.
■
55
105
169
102
74
74
8.59
105 '
82
1 5 .6 0
5 .7 0
97 '
106
P o rtn e u f su b so il
7. 71
3.86
Sagem oor
8. 37
4. 46 ■
151
S ta n to n 's C r o s s i n g
I . 83
I . 36 .
46
108 •
T racy
2.29
I . 54
98
100
W ah lu k e
6. 12
2.3?
99
98
W h itn e y
21.19
15. 25
89
91
D oor
D ru m m er
F ra n k fo rt-B ry c e
M in id o k a
'
.
'
106
.
•
99
111
W illia m s
7. 33
5.38
73
100
W in c h e ste r
8.73
3. 57
73
115
* M e a su re d v a lu e s.
.
M ^ f r o m 0 a n d 10 m l s p i k i n g r a t e / l OOg
so il
t
V a l u e c o m p u t e d f r o m r e s u l t s o f 0 a n d 2 0 m l s p i k i n g r a t e / IOOg '
so il
SUMMARY
T w o m e t h o d s w e r e u s e d to d e t e r m i n e s o i l s o l u t i o n p o t a s s i u m c o n ­
c e n t r a t i o n s ; (a) t h e q u a n t i t y f r o m a s a t u r a t i o n e x t r a c t a n d (b) th e
q u a n t i t y a s e s t i m a t e d f r o m m e a s u r i n g d i f f u s i v e flo w i n t o a r e s i n s i n k .
T h e s e a m o u n ts w e r e n e a r l y e q u a l in m o s t s o i l s .
F r o m th e d iffu siv e
flo w m e a s u r e m e n t s , i t w a s c a l c u l a t e d t h a t t h e e q u i l i b r u m b e t w e e n
s o l u t i o n a n d a d s o r b e d p h a s e c l o s e l y a d h e r e d to t h a t of a n i n s t a n t a n e o u s
re v e rs ib le re a c tio n .
T h is r e s u l t im p lie d th a t th e " c a p a c ity f a c t o r " '
v a l u e (to d e n o t e th e r e l e a s e of s o r b e d i o n s to d i f f u s i v e flo w ) c o u l d
be u tilis e d .
I n t e r m s of q u a n t i t y of m a t e r i a l t r a n s p o r t e d ,
th e c a p a c ity
f a c t o r c o n c e p t d e n o t e s t h a t d i f f u s i o n i s e n h a n c e d p r o p e r ti o n a d ly to th e
s q u a r e r o o t of t h e a d s o r b e d p o o l - - a s c o m p a r e d to if o n ly t h e s o l u t i o n
c o n c e n tra tio n w ere, p r e s e n t.
T he to ta l q u an tity , ( s o lu tio n p lu s a d s o r b e d )
of p o t a s s i u m e n t e r i n g in t o d i f f u s i v e flo w w a s t h a t w h i c h h a s b e e n
n o rm a lly m e a s u r e d as " la b ile " p o ta ss iu m .
T he d iffu s io n c e ll, b u ilt for th is e x p e r i m e n t , w o rk e d w e ll w hen
p o ta s s iu rn an d c h lo rid e w e r e b ein g d e te r m in e d .
By c o m p a rin g d iffu sio n
f r o m a s o i l w h i c h h a d t h e s e m a t e r i a l s a d d e d , th e s o i l s o l u t i o n a n d
a d s o rb e d q u a n titie s and im p e d a n c e te r m s w e re c a lc u la te d .
A lso ,
c a l c u l a t i o n s d o n e to e s t i m a t e t h e q u a n t i t y of a d d i t i o n a l p o t a s s i u m t h a t
w o u ld b e n e e d e d to b r i n g a b o u t a p r e d e t e r m i n e d f l u x r a t e g a v e f a i r
e s tim a te s of th e a c tu a l q u a n tity n eed ed .
60
S h o r t - t e r m p la n t u p ta k e o f p o ta s s iu m w a s m o r e c lo s e ly c o r ­
r e l a t e d w ith th e a c c u m u la tiv e d iffu s iv e flu x (as m e a s u r e d f r o m th e
u s e o f t h e d i f f u s i o n c e l l ) t h a n w i t h d i r e c t s o i l e x t r a c t s m a d e to d e ­
te r m in e so lu tio n , e x c h a n g e a b le , o r la b ile p o ta s s iu m .
Q u a n titie s of la b ile an d so lu tio n p h o s p h o ru s , d e te r m in e d f r o m
c h e m i c a l e x t r a c t i o n , in d ic a te d th a t th e a d s o r p t i o n i s o t h e r m w a s n o t
lin e a r.
T h e r e f o r e , t h e m a t h e m a t i c s d e r i v e d to c a l c u l a t e s o l u t i o n a n d
a d s o rb e d c o n c e n tra tio n of p h o sp h o ru s f ro m m e a s u re d acc u m u la tiv e
d i f f u s i v e f l u x c a n b e c o n s i d e r e d o n ly a f i r s t a p p r o x i m a t i o n .
S h o rt- .
t e r m p la n t u p ta k e of p h o s p h o ru s w a s b e t t e r c o r r e l a t e d w ith m o s t c h e m ­
i c a l e x t r a c t s th a n d iffu s iv e flu x .
H o w e v e r , th e d iffu s io n m e a s u r e m e n t
(as w ith p o ta s s iu m ) p ro v id e d f o r e s tim a tin g t h e , q u a n tity of p h o s p h o ru s '
a s o i l n e e d e d to b r i n g a b o u t a p r e d e t e r m i n e d f l u x r a t e .
A s th e q u a n ­
t i t y o f p h o s p h o r u s n e e d e d to i n c r e a s e a u n i t f l u x r a t e v a r i e d m a n y ,
fo ld b e tw e e n s o i l s , . th e e r r o r a s s o c i a t e d w ith th e e s t i m a t e d p h o s p h o r u s
•
n e 'e d w a s b e l i e v e d to b e m o r e a c c e p t a b l e .
M u c h a d d i t i o n a l r e s e a r c h i s n e e d e d to m o r e c l e a r l y r e s o l v e
p r o b le m s a s s o c ia t e d w ith th e th e o ry a n d .e x p e rim e n ta l m e th o d s' u se d ,
a n d to r e s o l v e p r o b l e m s i n t r o d u c e d b y t h e e x p e r i m e n t i t s e l f .
In­
c lu d e d i s th a t o f o b ta in in g a b e t t e r k n o w led g e of th e f a c t o r s in v o lv ed
in th e ti m e la p s e b e t w e e n a d d in g a s p ik in g " m a te r ia l a n d s t a r t i n g th e
. d iffu s io n p r o c e s s .
A b e t t e r a t t a c k i s n e e d e d to d e t e r m i n e t h e c a ­
p a c ity f a c to r fo r p h o s p h o ru s , and in te r p r e tin g it m a th e m a tic a lly .
T h e v a r i a t i o n b e t w e e n r e p l i c a t i o n s i n p h o s p h o r u s f l u x to a r e s i n s i n k
■
.
"
.
■
.61
n eed s m o re c o n tro l..
needs
T h e t i m e i n v o l v e d i n d o i n g th e d i f f u s i o n t e s t
s h o r t e n i n g i f t h e m e t h o d w e r e to b e u s e d i n r o u t i n e a n a l y s i s .
C o r r e l a t i o n b e tw e e n r e s u l t s of fie ld f e r t i l i t y
s tu d ie s an d d iffu sio n
t e s t s a r e n e e d e d i f t h e d i f f u s i o n t e s t i s to b e a p p l i e d i n t h a t m a n ­
n er.
O th er p la n t n u tr i e n ts ,
b e sid e p h o sp h o ru s and p o ta s s iu m ,
th a t
a r e t r a n s p o r t e d to th e r o o t m a in ly by d iffu s io n m ig h t be e v a lu a te d
s i m u l t a n e o u s l y by. t h e d i f f u s i o n m e t h o d a n d t h u s m a k e t h e t e s t
m o re in c lu siv e .
62
R E F E R E N C E S C IT E D •
A m er,
F . , D . R . B o u l d i n , ■ C . A . B l a c k , a n d F . R . D uke..
1955.
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In: D ia g n o stic T e c h n iq u e s fo r C ro p s and
S o ils.
The A m e r ic a n P o ta s h I n s tit u te ,. W ash .
v a n S c h a i k , J . C . , W . D . K e m p e r , a n d S. R . O l s e n .
1966.
C o n t r i b u t i o n o f a b s o r b e d c a t i o n s to d i f f u s i o n i n c l a y - w a t e r
sy ste m s.
S o il S c i . S o c . A m e r . P r o c . 3 0 : 1 7 - 2 2 .
,
.
W a r n c k e , D . D . , a n d S. A . B a r b e r .
1972.
D iffu sio n of zin c in
s o i l s : I.. '.',The i n f l u e n c e o f s o i l m o i s t u r e .
S o il S c i. S oc.
A m e r . Pro/c-. 3 6 : 3 9 - 4 2 .
W a t a n a b e , F . S . , a n d S. R . O l s e n .
1965.
T e s t of a n a s c o r b ic
a c i d m e th o d f o r d e t e r m i n i n g p h o s p h o r u s in w a t e r a n d N aH C O g
- e x t r a c ts f r o m s o il.
S o il S c i . S o c . A m e r . P r o c . 2 9 : 6 7 7 - 6 7 8 .
.68
W a t a n a b e , F 1. S . , a n d S. R . O l s e n .
1962.
C o lo m e tric d e te rm in a
tio n of p h o s p h o r u s in w a t e r e x t r a c t s of s o il.
S o il S c i . 9 3 :
183-188.
■
A p p e n d i x A - R e s u l t s o f c h e m i c a l d e t e r m i n a t i o n s of s o i l p o t a s s i u m - ( s o i l b u l k d e n s i t y i s
i n c l u d e d f o r c o n v e r t i n g v o l u m e d a t a to a w e i g h t b a s i s i f d e s i r e d ) .
0 sp ik in g
BDt
S o il
S o ln K t L a b i l e K **
10 m i s s p i k i n g
p e r 100 g s o i l *
S o ln K t
*
t
$
**
1 .2 4
0. 76
1 .4 6
1 .2 0
1 .4 2
I . 02
I . 13
1 .2 3
I . 38
1 .4 8
I . 30
1 .3 7 .
I . 54
I . 50
I . 39
1 .3 9
I . 36
1 .2 6
1 .3 9
1 .2 8
1.60
S o ln K t
L a b ile
_
^
cm 3
g /cm
A m ste rd a m
■' —
A sto ria
C am as C reek
D a y to n
Door
D ru m m er
F ra n k fo rt- B ry ce
Jo ry
L lo y d
M in id o k a
P o rtn e u f
P o rtn e u f su b so il
Sagem oor
S ta n to n 's C r o s s i n g
T e to n ia
T racy
.
W ah lu k e
"
W h itn e y
W illia m s
W illa m e tte
W in c h e ste r
L a b i l e K **
20 m i s s p i k i n g
p e r 100 g s o i l *
.4 1 .
. 06
: .1 2
.4 7
. 10
.5 4
.4 6
. 34
.1 1
I . 82
. 28
. 19
.1 7
.0 4
. 39
.1 6
. 12
. 76
. 34.
.66
.3 3
17. 5
1 .4
8.5
7. 8
I. 3
8. 5
13. I
10. 2
7 .4
2 5. 5
16. 9
10. I
12. 9
5 .7
22.8
3. 8
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1 5 .2
18. 6
2.6
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I . 04
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1 .2
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2 .7 4
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. 61
.99
I . 30
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I . 78
1 .1 1
. 50
I . 13
22. 8
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1 3 .1
1 1 .9
5 .1 13. 3:
18. 9
1 5 .4
13. I
32. 3
22. 5
16. 6
20. 0
11. 8
—1 0. 3
11. 9
2 0. 0
2 5. 2
8 .4
2 9. 0
I . 84
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2. 56
2. 63
2. 33
2. I
I . 88
2. 21
2. 03
6. 10
1 .2 1
I . 56
I . 58
I . 26
I . 64
3. 27
I . 34
2.96
2. 06
I . 26
2.38
2 7 .0
7 .2
1 6 .2
1 6 .4
1 1 .2 .
-17.-5
2 2 .4 •
21. 2
18. 5
3 5 .7
26.3
. 2 2 .5
24. 5
1 6 .0
27. 6
1 5 .6
1 6 .4
24.3
3 0 .8
1 3 .4
33.9
T h e 10 a n d 20 m l s p i k i n g r a t e s h a d e q u i l i v a l e n t to 0. 9 4 a n d I . 82 m e q K a d d e d / 1 0 0 g
so il, r e s p e c tiv e ly .
B u l k d e n s i t y f i g u r e s t a k e n f r o m d i f f u s i o n c e l l d a t a , u s i n g e q u a t i o n (39).
S o lu tio n K v a lu e s w e r e f r o m so il s a tu r a tio n e x t r a c ts .
L a b ile K e s ti m a t e d f r o m C a C l^ e x t r a c t d e n o te d in te x t a s G r a h a m - K a m p b e ll m e th o d .
A p p e n d i x ' B - R e s u l t s of c h e m i c a l d e t e r m i n a t i o n s o f s o i l p h o s p h o r u s - ( s o i l b u l k d e n s i t y i s
i n c l u d e d f o r c o n v e r t i n g v o l u m e d a t a t o a w e i g h t b a s i s if d e s i r e d ) .
10 m i s s p i k i n g
p e r 100 g s o il*
0 sp ik in g
S o il
BDt
S o ln P t . L a b i l e P * *
*
t
$
. 07
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,0 4
. 76'
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.1 2
1 .4 2
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. 30
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. .06
0
I . 38
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1 .4 8
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I . 30
I . 37
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1 .5 4
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. 20
• I . 39
; 04
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. 12
I . 60
S o ln P t
L a b ile P**
u Si/ c m 3
g /c m
A m ste rd a m
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C am as C reek
D a y to n
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D ru m m er
F ra n k fo rt- B ry ce
Jo ry
L lo y d
M in id o k a
P o rtn e u f
P o rtn e u f su b so il
Sagem oor
S ta n to n ’s C ro s s in g
T e to n ia
T racy
W ah lu k e
' W h itn e y
Willia m s
W illa m e tte
W in c h e ste r
L a b ile P * *
S o ln P t
20 m i s s p i k i n g
p e r 100 g s o i l *
■ 39
•24
. 62
133
67
134
21 9
36
40
61
100
39
39
20
59
63
68
150
58
73
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0
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.8 2
,06
4 .0 5
T h e 10 a n d 20 m l s p i k i n g r a t e s h a d e q u i v a l e n t
re sp e c tiv e ly .
B u lk d e n s ity f i g u r e s ta k e n f r o m d iffu s io n c e l l
S o lu tio n P v a lu e s w e r e f r o m so il s a tu r a t io n
L a b ile P e s tim a te d f r o m r e s in e x tra c tio n a s
•
. 60
33
103
178
112
171
2-31
51
57
100
137
63
86
58
105
HO
94
171
80
101
114
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1.25
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1 .2 9
——
I . 69
4.21
2. 58
. 11
3.38
95
44
129
2 13
130
198
236
62
69
127
169
HO
114
. 92
135
124
129
175
130
119
145 '
to 72. 3 a n d 144. 5 /i e q P / g s o i l a d d e d ,
d a t a , u s i n g e q u a t i o n (39).
e x tra c ts.
d e n o te d in te x t.
71
A p p e n d i x G - C a l c u l a t e d i m p e d a n c e v a l u e s (I) a n d q u a n t i t y o f p o t a s s i u m
d i f f u s i n g to r e s i n s i n k , s u r f a c e (7. 9 2 c m ) p e r 2 4 - H o u r
p e r i o d (M t ) 1
• S o il
I*
0 sp ik in g
10 m l s p i k i n g
p e r 100 g s o i l t
/4»g JX/ I o'
O
CH J L / <-^*x XlT D
.A m ste rd a m .
.42
'15. 3 •
22. 8
A sto ria $
. 11
2 .1
5 .2
C am as C reek
.28
5. 9
D a y to n
.29
1 3 .3
Door
.46
4 .3
D ru m m er $
.2 6
F ra n k fo rt-B ry c e '
.
20 m l s p i k i n g
p e r 100 g s o i l t
33. 2
,
1 4 .4
. 5 0 .5
1 4 .6
'
. 2 5 .4
40. I
1 6 .3
35. 6
16.2
29.1
41. 5
.2 1
1 2. 3
1 8 .7
Jo ry
.1 2
' 6 .4
1 6 .1
2 2 .5
L lo y d
.1 4 '
1 .5
12. 2
26.8
M in id o k a
.2 8
27. 6
58.8
90.0
P o rtn e u f
.38
7. 6
1 4. 9
2 1 .8
P o rtn e u f su b so il
.4 3
■ 9.0
1 8 .8
32.2
Sagem oor
. 39
■ 6. 3
1 8 .6
S t a n t o n ' s C r o s s i n g . . 23
3. 6
' 7 .6
.
■
2 6 .7
,
"
'
.25.5
20.8
T e to n ia
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1 6 .5
2 5 .4
T racy $
.,36
.2.6
19. 6
47. 6
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. 35
2. 6
8.3
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. 33
1 6 ,4
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45.9
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. 15
8.8
16.8
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. 32
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18. I
.
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.
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'
17. 3
38. I
'* I m p e d a n c e v a l u e s c a l c u l a t e d f r o n d e q u a t i o n (36), a f t e r m e a s u r i n g
C l" d i f f u s i o n .
t T h e 10 a n d 20 m l s p i k i n g r a t e s c o n t a i n e d e q u i v a l e n t t o 0 .'9 4 .and
I . 82 m e q . K a d d e d / 1 0 0 g s o i l , r e s p e c t i v e l y .
$ S a m p l e s d if f u s e d f o r 40 h o u r s , r a t h e r th a n 24.
72
A p p e n d i x D - C a l c u l a t e d i m p e d a n c e v a l u e s (I) a n d q u a n t i t y o f p h o s p h o r u s
d i f f u s i n g to r e s i n s i n k s u r f a c e (7. 92 c m ) p e r 2 4 -h o u r
p e r i o d (Mfc)
S o il
0 sp ik in g
I*
10 m l s p i k i n g
p e r 100 g s o i l !
■ r*
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& ■*■ / 1• 0/ 9“
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.
66
.42
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7 .5
/ 9 A.
^
t ~
20 m l s p i k i n g
p e r 100 g s o i l !
T-, T- C
*
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92
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. 11
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. 28
34
42
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58.
75
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20
26
27
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. 26
89
• 1 04 .■
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. 21
68
78
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. 12
5. 7
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. 14 .
7 .2 '
M in id o k a
.2 8
45
1 24
. 2 16
P o rtn e u f
.3 8
88
82
130
P o rtn e u f su b so il
.4 3
31 •
61
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. 39
35
66
S t a n t o n ’s C r o s s i n g
. 23
10. 8
fT e t o n i a
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116
89
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. 36
12
18
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. 35
19
49
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. 33
121
168
2 17
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. 15
43
58
85
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. 32
39
14
29
W in c h e ste r
' . 24
28
69
168
'
* Im p ed an ce v alu es
m e a s u rin g C l"
t T h e 10 a n d 20 m l
a n d 144. 5 ^ g P
$ S a m p le s d iffu se d
108
120
85
1 0 .0
9.3
7 .2
9 .0
■
-
88 .
. 81
28.2
. 14.5
"
153
24
■
-
77
c a l c u l a t e d f r o m e q u a t i o n (36), a f t e r
d iffu sio n .
s p i k i n g r a t e s c o n t a i n e d e q u i v a l e n t t o 7 2. 3
a d d e d /g so il, r e s p e c tiv e ly .
f o r 4 0 h o u r s , r a t h e r t h a n 24.
V.
' .
' vv fuyg4
*
-
P 3T 9
M 383
c o p .2
i
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" a a s e « ;, T ru m a n W
S o il c h a r a c te r ! z a tio r
h y d if f u s io n
m e a s u re m e n ts
X A M K A N o A bom m em
O i - . u l c c x ^ V i '^ b y
- J - R .* t> - >v s c j ,
C/4i-r>i n c r A l
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