The phytoavailability of potassium to small grains as influenced by edaphic and environmental factors
by Robert Olson Miller
A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in
Crop and Soil Science
Montana State University
© Copyright by Robert Olson Miller (1988)
Abstract:
Soil characteristics and rhizosphere conditions greatly influence plant available potassium (K).
Research in Montana has shown crop response to K fertilizers on soils testing high in ammonium
acetate extractable K (Kex). The objective of this research was to use an in-vitro technique to
determine: (1) plant available K on Montana soils and its relation to soil properties; (2) the influence of
temperature and water potential on K uptake; and (3) the influence of K additions on plant available K.
Soil characteristics which were found to be strongly related to plant available K (R2 0.93) are: clay
content, Kex diffusion gradient coefficient, and cation exchange capacity. Spring wheat in these studies
utilized a portion of Kex, but quantities differed across soils. This data suggests that spring wheat
utilizes significant quantities of soil K from nonexchangeable and K-mineral sources.
Spring wheat K uptake increased exponentially with temperature with little or no K absorbed at 8° C.
Water potentials alone had little influence on K uptake. The interaction with temperature suggests that
K uptake was not limited by water potential (water content) until temperature exceeded 16° C. Thus
until spring wheat K demand reached a critical K demand K uptake was not limited by water potential.
Potassium additions increased spring wheat K uptake nonuniformly across soils. Greatest K uptake
occurred on the Kevin soil and the least on the Beaverton. Data on soil rhizosphere Kex indicated K
additions enhanced the availability of Kex supplies in the near rhizosphere (0 - 0.5 mm). Soil Kex flux
data indicated that K additions did not necessarily increase Kex utilization.
These results indicate that phytoavailable K is governed primarily by three soil factors and that
environmental water potential play important roles as regulators. Spring wheat utilizes soil K forms
other than that explained by Kex in the rhizosphere, and that the quantity utilized is highly soil
dependent. THE EHYTOAVAIIABIHTY OF POTASSIUM TO SMALL GRAINS AS
INFLUENCED BY EDAPHIC AND ENVIRONMENTAL FACTORS
by
Robert Olson Miller
A thesis submitted in partial fulfillment
of the requirements for the degree
of
Doctor of Philosophy
in
Crop and Soil Science
MONTANA STATE UNIVERSITY
Bozeman, Montana
November 1988
APPROVAL
of a thesis submitted by
Robert Olson Miller
This thesis has been read by each member of the thesis committee
and has been found to be satisfactory regarding content, English
usage, format, citations, bibliographic style, and consistency, and
is ready for submission to the College of Graduate Studies.
Date
Chairperson, Graduate Committee
Approved for the Major Department
Date
Approved for the College of Graduate Studies
/2.//O - Z g ? Date
Graduate Dean
(c) COPYRIGHT
by
Robert Olson Miller
1988
All Rights Reserved
iii
STATEMENT OF PERMISSION TO USE
In presenting this thesis in partial fulfillment of the
requirements for a doctoral degree at Montana State University, I agree
that the Library shall make it available to borrowers under rules of
the Library.
I further agree that copying of this thesis is allowable
only for scholarly purposes, consistent with "fair use" as prescribed
in the U.S. Copyright Law.
Requests for extensive copying or
reproduction of this thesis.should be referred to Ifiiiversity Microfilms
International, 300 North Zeeb Road, Ann Arbor, Michigan 48106, to whom
I have granted "the exclusive right to reproduce and distribute copies
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and distribute by abstract in any format."
Signature
Date
Q- C
iv
VITA
The author, Robert Olson Miller, was b o m on August 12, 1955, in
Lincoln, Nebraska, to Russell H. Miller and Beatrice Miller.
He
received his primary and secondary education in Springfield, Nebraska.
He attended the University of Nebraska 1973-1981, where he completed
his Bachelor of Science in 1978 and Master of Science in 1981 in
agronomy.
He married Annette J. May on June 20th 1981.
From January
1982 until July 1984 he worked as a Research Associate in the
Horticulture sciences Department of Texas ASM University.
Bob and
Annette have one son, Jason D. Miller.
He began study and research toward the Fh.D. in the fall quarter
of 1984 at Montana State University.
v:
ACKNOWLEDGMENTS
The author wishes to extend his sincere appreciation to his
advisor and friend. Dr. Earl 0. Skogley, without whose efforts,
guidance, support, and humor this dissertation would not have been
possible.
I would also like to thank the members of my committee. Dr. Hayden
Ferguson, Dr. Ralph Olsen, Dr. Rick Engel, and Dr. Richard Stout, for
their advice, guidance and encouragement lending a great contribution
to this dissertation.
A special thanks to Gordon Williamson at
Technical Services for cooperation in the fabrication of equipment and
Carol Bittinger, Computer Services, for help with statistics.
Thanks also to friends Jae Yang, Thomas Deluca, and Stuart Georgitis
for their time and assistance through the course of my doctoral
program.
I would like to thank the Department of Plant and Soil
Science for its truly appreciated financial support.
My parents, Mr. Russell Miller and family deserve special thanks
for their loving support.
My deepest love and appreciation to my caring friend and loving
wife, Annette May Miller, the inspiration in my life.
A special thanks
to my son Jason, whose humor helped complete this thesis.
TABLE OF CONTENTS
TABTE OF CONTENTS.............
TTST OF TABLES..........................................
vi
vii
TTST OF FIGURES.................................................... xii
ABSTRACT.... ...................................................... xiii
INTRODUCTION..................................
I
Definitions..................................................
3
LITERATURE REVIEW..................................................
5
Soil K Ehytoavailability.... .................................
Temperature and Phytoavailable K.............................
Soil water Potential and K Availability............
Study of Ehytoavailable K ....................................
5
7
9
10
MATERIAIS AND METHODS.......
12
Methods Development....................
Calculations.............................
Physical and Chemical Methods................................
12
14
15
RESULTS AND DISCUSSION............................................
17
Methods Developmait Study (MD)..........
Fhytoavailability of K on Montana Agricultural Soils (KRTS)...
Temperature and Moisture Influences on K Phytoavailability
(TMS)........................................................
Effects of K Rate on Soil and Plant K (KRS)..................
17
20
39
52
SUMMARY AND CONCLUSIONS.......
65
LTTERATURE CITED.........
73
APPENDICES........................................................
80
Appendix A:
Appendix B:
Location description, physical and chemical
characteristics of twenty Montana soils.........
81
Correlation matrix for properties of twenty
Montana soils.................................
98
vii
U S T OF TABLES
Table
1.
Page
The influence of spring wheat plant density on mean net K
uptake from the Edgar soil series after 96 hours............
18
The influence of spring wheat seedling age on net mean K
uptake on the Edgar soil series after 96 hours..............
18
Mean (n=3) net accumulation of K by spring wheat seedlings
as influenced by time of soil contact on the Edgar soil
series......................................................
19
Selected physical properties of twenty Montana soils
used in the ERTS study......................................
21
Selected chemical properties of twenty Montana soils
used in the PETS study.......................................
22
6 . Analysis of variance for net K uptake by spring wheat on
twenty Montana soils maintained at a water potential of -33
Epa, after 96 hours..........................................
22
2.
3.
4.
5.
7.
Mean net (n=4) plant K uptake by spring wheat seedlings
after 96 hours of growth on twenty Montana soils
maintained at a water potential of -33 Fpa...................
23
8 . Analysis of variance for soil Eex concentration for five
rhizosphere distances and twenty Montana soils...............
24
9.
10.
11.
12.
13.
Mean soil Eex concentration at five rhizosphere distances
for twenty Montana soils after 96 hours maintained at a soil
water potential of - 33 Ipa, mean of four replications.......
25
Regression equations between Eex concentration (Y) and
rhizosphere distance (D) on twenty Montana soils.............
26
Estimated Eex diffusion gradient coefficient d [EexJZdD
diffusion distance (D^), soil Eex flux (SEex), and Eex
effective diffusion coefficient (Dc) on twenty Montana
soils........................................................
29
Mean net plant K flux, soil K flux (SEex), difference
(umol) and % Eex utilized by spring wheat seedlings after
96 hours growth on twenty Montana soils......................
301
*
3
Linear regression model equations between the amount o
K absorbed by spring wheat (umol pot-1) and physical
and chemical characteristics for twenty Montana Soils.
32
viii
IIST OF TARTBS—OCMTOMIED
Table
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
Page
Malticollinearity detection of regression model 8 with
dependent variable plant K uptake and independent variables:
clay, d[Kgx]/dD, and CEC.....................................
34
Changes in IID soil solution K concentration as related to
rhizosphere distance for spring wheat for the Amsterdam
soil after 96 hours..........................
35
Regression of Kex concentration gradient (d[Kex]/dD), (umol
cm-3 cm-1) as dependent variable (Y) and independent
variables: Kex; CACO3 ; and saturated paste Ca................
37
Analysis of variance for net plant K uptake as influenced
by temperature (TEMP) and water potential (KPA) on four
Montana soils (SOIL)................
40
Mean neta K uptake (umol pot-1) by spring wheat as
influenced by temperature (C) and soil water potential
(Kpa) on four Montana soils................................ ..
41
Calculated QlO for K uptake by spring wheat on four Montana
soils for temperatures 8 to 24 C, at a water potential of
of -12 Kpa........................................
42
Regression equations of dependent variable K uptake (umol)
(Y) and independent variables: water potential (Kpa) and
temperature (T) for four Montana soils.......................
44
Analysis of variance table for Kex (umol cm-3) at five
distances (D) in the rhizosphere of spring wheat as
influenced by temperature (TEMP) for four Montana soils
(SOIL).......................................................
47
Mean (n=3) soil Kex concentration (umol cm-3) in the
rhizosphere of spring wheat as a function of distance (mm)
and influenced by temperature (C) on four Montana soils
maintained at a water potential of - 33 Kpa..................
48
Regression equations of dependent variable soil Kex (Y) and
independent variables: rhizosphere distance (D) and
temperature (T) for four Montana soils at - 33 Kpa...........
492
*
4
Volumetric water content at three water potentials for four
Montana Soils.......................................... .....
50
ix
EEST
of
TATOt Fsktmtinijed
Table
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
Page
Mean (n=3) plant K uptake by spring wheat as influenced by
K additions as KCL on four Montana soils at 24 C and -33
Kpa..........................................................
53
Analysis of variance table for plant K uptake (umol pot-1)
by spring wheat as influenced by K addition (KRATE) for
four Montana soils (SOIL), 24 C and water potential
- 33 Kpa.
I....................................
53
Regression equations for dependent variable plant K uptake
(Y) and independent variable potassium addition (KRATE) for
four Montana soils, 24 C and water potential - 33 Kpa........
54
Analysis of variance table for Kex concentration (umol
cnf3) in the rhizosphere of spring wheat as influenced
by distance (D) and K addition (KRATE) on four Montana
soils (SOIL).................................................
54
Mean (n=3) rhizosphere Kex concentration as influenced by
rhizosphere distance (D) and K rate, for four Montana
soils, temperature 24 C and water potential -33 Ipa..........
56
Regression equations between rhizosphere distance (D) and
Kex (Y) at five rates of K addition for four Montana soils,
temperature 24 C and water potential - 33 Ipa................
57
Initial soil Kex concentration, diffusion gradient
(d[KexJZdD) and diffusion distance for four Montana soils,
temperature 24 C andwaterpotential -33 Ipa...................
60
Mean Kex plant, soil arid difference flux values as
influenced by five K additions on four Montana soils, 24 C
and water potential of - 33 Ipa..............................
62
Soil extractable Cl and electrical conductivity (EC) on
four Montana soils...............................
63
Multiple linear regression model for the influence of
temperature (T), water potential (KPA), and estimated
phytoavailable K index (ERKE) on spring wheat K uptake.......
68
Soil series, texture and location description of twenty
Montana soils............................
823
*
6
Soil series name and classification and family of twenty
Montana soils................................................
83
X
IZ ST OF TAHTFS-OCMTIMJED
Table
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
Page
Exchangeable cation concentrations for twenty Montana
soils as determined by 1.0 N ammonium acetate........... •....
84
Soil pH, organic matter, calcium carbonate and electrical
conductivity of twenty Montana soils.........................
85
Soil particle size analysis as determined by pipette (Gee
and Bauder, 1986) on twenty Montana soils....................
86
Saturated paste pH, cation concentration and potassium
activity ratio (AR) of twenty Montana soils..................
87
Exchangeable and nonexchangeable soil potassium as
determined by magnesium chloride and sodium tetraphenyl
boron, and nitric acid respectively..........................
88
Soil extractable phosphorus as determined by Bray and Olson
extraction methodologies for twenty Montana soils............
89
Soil solution cation concentration on a solution basis and
potassium activity ratio (AR) of twenty Montana soils as
determined by immiscible liquid displacement (Mubarak
and Olson, 1976).............................................
90
Soil solution cation concentration and potassium activity
ratio (AR) of twenty Montana soils at 0.33 Epa on a soil
mass basis as determined by immiscible liquid displacement
(Mubarak and Olsen, 1976)........ ............ ...............
91
Moisture contents of twenty Montana soils at - 0.15
- 0.33,- 0.66 and - 1.00 Kpa water potential....... .........
92
Moisture contents (gm Kg”1) of twenty Montana soils at
- 2.00, - 5.00, and - 15.00 Epa water potential..............
93
Soil, silt, and clay for twenty Montana soils as
determined by hydrometer (Gee and Bauder, 1986)..............
94
Available water at four water potential ranges for twenty
Montana soils................................................
954
*
9
Cation exchange capacity and mineralogy percentages
of the clay fraction of twenty Montana soils
provided by Bernard Schaff, method of Jackson (1958).........
96
xi
EEST OF TftBEES-CXMFENUED
Table
50.
51.
Page
Soil extractable NO3, Cl, and S for twenty Montana
soils........................................................
975
1
Correlation matrix for twenty soil characteristics on
twenty Montana soils........................................
99
xii
LIST OF FIGURES
Figure
1.
2.
3.
4.
5.
Page
Schematic of method for growing wheat seedlings on
soil columns separated by a nylon screen.....................
13
Accumulation of K by twenty five spring wheat seedlings
on the Edgar soil series at five time intervals.
......... ;.
19
Relationship of plant K uptake [dependent variable - Y]
and soil extractable K by NH4OAC (Kex) on twenty
Montana soils............................
24
Changes in the concentration of Kex as a function of
distance in the rhizosphere of spring wheat for
four Montana soils........................
28
Potassium uptake QlO for spring wheat seedlings on four
Montana soils at a water potential of -12 Kpa................
41
6.
Response function of plant K uptake (umol pot-1)
1
temperature, and soil water potential; soil series
Amsterdam....... *.......... ................................
45
7.
Response function of plant K uptake (umol pot-1),
temperature, and soil water potential; soil series
Beaverton..........
8 . Response function of plant K uptake (umol pot-1),
temperature, and soil water potential; soil series Edgar.
9.
10.
11.
12.
13.
14.
45
...
46
...
46
Response surface of mean Kex concentration as influenced by
rhizosphere distance and K addition, soil series Amsterdam.
.
58
Response surface of mean Kex concentration as influenced by
rhizosphere distance and K addition, soil series Beaverton.
.
58
Response function of plant K uptake (umol pot-1),
temperature, and soil water potential; soil series Kevin.
Response surface of mean Kex concentration as influenced by
rhizosphere distance and K addition, soil series Edgar.......
59
Response surface of mean Kex concentration as influenced by
rhizosphere distance and K rate, soil series Kevin...........
59
Model of phytoavailable K in the rhizosphere of spring wheat
for Montana soils...... .....................................
71
xiii
ABSTRACT
Soil characteristics and rhizosphere conditions greatly influence
plant available potassium (K). Research in Montana has shown crop
response to K fertilizers on soils testing high in ammonium acetate
extractable K (Kex). The objective of this research was to use an
in-vitro technique to determine: (I) plant available K on Montana
soils and its relation to soil properties; (2) the influence of
temperature and water potential on K uptake; and (3) the influence of
K additions on plant available K.
Soil characteristics which were found to be strongly related to
plant available K (R2 0.93) are: clay content, Kex diffusion gradient
coefficient, and cation exchange capacity. Spring wheat in these
studies utilized a portion of Kex, but quantities differed across
soils. This data suggests that spring wheat utilizes significant
quantities of soil K from nonexchangeable and K-mineral sources.
Spring wheat K uptake increased exponentially with temperature with
little or no K absorbed at 8 C. Water potentials alone had little
influence on K uptake. The interaction with temperature suggests that
K uptake was not limited by water potential (water content) until
temperature exceeded 16 C. Thus until spring wheat K demand reached a
critical K demand K uptake was not limited by water potential.
Potassium additions increased spring wheat K uptake nonuniformly
across soils. Greatest K uptake occurred on the Kevin soil and the
least on the Beaverton. Data on soil rhizosphere Kex indicated K
additions enhanced the availability of Kex supplies in the near
rhizosphere (0 - 0.5 mm). Soil Kex flux data indicated that K
additions did not necessarily increase Kex utilization.
These results indicate that phytoavailable K is governed
primarily by three soil factors and that environmental water
potential play important roles as regulators. Spring wheat utilizes
soil K forms other than that explained by Kex in the rhizosphere,
and that the quantity utilized is highly soil dependent.
I
INTRODUCTION
Soil potassium (K) can be characterized by four major indices: (I)
I
Soil solution K (KsoI); (2) exchangeable K (Kex); (4) nonexchangeable K
(Knex); and (4) mineral K (Km^n).
Soils are relatively high in total K
but only a small relative proportion is found in solution' form, which
is available to plants.
Replenishment of solution K at the soil-root
interface is dependent on rates of release from other forms and ion
transport in the rhizosphere.
Research in Montana over the past twenty years has shown crop
response to K fertilizers on soils testing "high" in NH4OAC-BXtractable
K (Skogley, 1976).
Similar results have been noted for many crops
around the world (Talibudeen et al. 1978).
This is due to the fact
that the NH4OAC procedure does not measure factors relating to crop K
demand, soil K release equilibria, and K transport in the rhizosphere.
A method using intact plants to study soil K release and transport at
the soil-root interface using in-vitro techniques would aid the
development of a reliable K soil test that is sensitive to these
factors which control K availability.
Nutrient phytoavailability can be separated into two components,
absorption characteristics of plant roots and the capacity of the soil
to supply nutrients.
Factors influencing soil nutrient capacity are
(I) quantity and form of nutrient present, and (2) the chemical
equilibria of the soil system affecting the replenishment (intensity)
2
of a given nutrient in the soil solution.
Such relationships have been
used extensively in describing solution cation activity in inorganic
systems.
Nutrient absorption and uptake is dependent on the nutrient status
in the plant/ morphological characteristics of the root system, root
age and influx characteristics, and rhizosphere environment.
Nutrient
acquisition occurs via three mechanisms, interception, mass flow, and
diffusion.
Interception results from direct contact between a root and
a soil nutrient.
Mass flow is the movement of a nutrient to the root
via the convective flow of soil water, the result of transpiration.
\
Diffusion, is the movement of a nutrient down the chemical potential
gradient established by the plant at the soil-root interface.
Work of
Barber (1962) and Barber (1972) has established that diffusion, and
mass flow to a lesser extent, are the major mechanisms by which
nutrients are acquired by plant roots.
In many instances the constraints of the rhizosphere environment
limit soil nutrient transport and plant uptake.
both plant biochemistry and soil chemistry.
Temperature affects
Soil water potential in
the rhizosphere affects soil nutrient availability and transport, plant
physiology, and soil-root contact.
Several methods have been proposed to study the soil-root
interface in an attempt to describe nutrient availability.
However,
physical limitations and the complexity of the processes involved have
impeded research.
Recently Kucheribuch and Jungk (1982) described a procedure for
studying soil K concentration gradients in the rhizosphere of rape.
3
Plant roots are separated from the soil by a flat nylon screen which
prohibits root penetration but permits root hairs to make contact with
the soil surface.
Such a system allows the rhizosphere to be treated
as a plane and, with microsampling techniques, be analyzed according to
traditional soil testing procedures.
Accurate information can thus be
obtained depicting plant nutrient availability and absorption in
addition to the status of soil rhizosphere K.
The objectives of this study were to:
(I) determine those soil
physical and chemical properties related to phytoavailable K; (2)
research the effects of temperature and soil water potential on plant K
uptake; and (3) evaluate the influence of K additions on K
phytoavailability and K dynamics in the rhizosphere.
The in vitro
method of studying the soil-root interface provides detailed
information on both phytoavailable K and K dynamics within the soil
rhizosphere.
Definitions
A list of abbreviated terms used in describing phytoavailable K
are as follows:
%ex
Soil extractable K, by I N Ammonium acetate, pH 7;
kSoI -
Soil solution K concentration determined by
immiscible liquid displacement (IID);
kUGX ~
Soil nonexchangeable K concentration, determined by
sodium tetraphenyl boron;
Kmin ~
Soil mineral K, associated with micas and feldspars;
D -
Rhizosphere distance perpendicular to the soil-root
interface;
4
d[KexJZdD - Rhizosphere Kex diffusion gradient coefficient;
Dc SKex -
Effective diffusion coefficient for Kex in rhizosphere;
Distance of estimated K depletion in the rhizosphere;
Calculated soil flux of Kex removed by plants.
5
U rEERAIURE REVIEW
Soil K Fhvtoavailabilitv
Soil K can be divided into four major forms: K solution, that
portion of K dissolved in the soil solution; K exchangeable, that
portion which is readily exchangeable for other cations; K
nonexchangeable, which is not readily exchangeable and is released
slowly to the solution; and K bearing minerals (Mclean and Watson,
1985).
Each of the solid phases tends to be in equilibrium with K in
solution.
Ehytoavailable K is described as that K fraction in the soil which
is accessible to plant roots for absorption, and involves aspects of
both soil characteristics and plant nutrient absorption (Bertsch and
Thomas 1985).
Soil solution K is a reflection of the parent material
and the degree of weathering that has occurred.
Feldspars and Micas
are the dominant K minerals which contribute to and control the
dynamics of soil solution K (Sparks and Haung, 1985).
Interfacial
reactions are the most significant means by which K is weathered from
feldspars.
Micas, such as muscovite, undergo zonal weathering which
results in the release of K from interlayer positions.
Thus, the stage
of weathering determines the equilibrium each mineral phase has with
the soil solution and with each other.
The equilibrium between solution phase and solid phase K indices
dictates the availability of soil potassium.
Beckett (1964) described
6
K availability in terms of a quantity and intensity ratio (Q/I). He
plotted the amounts of K adsorbed or desorbed against the activity
ratio for K in solution, and was thus able to predict the capacity of a
soil to maintain solution K.
Such a method could be used to make K
fertilizer recommendations. However, it was shown by Rasnake (1973)
that Q/I curves change with fertilization, and thus have limited
applications.
Both physical processes, such as freezing and thawing and wetting
and drying, and biological activity affect the release or fixation of K
from the soil solution.
Cook and Hutcheson (1960), reported that the
drying of soil samples increased exchangeable K
concentrations.
Song
and Haung (1983), in a review of the physical chemistry of soil K,
reported several instances where rhizosphere organic acids increased K
release from micas.
Thus, soil solution K is affected by physical
processes and amount of biological activity as well as chemical
processes.
Ultimately the phytoavailability of potassium is not only
dependent on the amount of K in the soil and the capacity of the soil
to replenish solution K. It is also dependent on the absorption
characteristics of plant roots, which are determined by overall
nutrient requirements, type of root system, physiology, and growing
conditions (Olsen, 1968 and Barber 1985b). Nutrient acquisition occurs
via three mechanisms, interception, mass flow, and diffusion.
Interception results from direct contact between a root and a soil
nutrient.
Mass flow is the movement of a nutrient to the root via the
convective flow of soil water, the result of transpiration.
Diffusion,
7
is the movement of a nutrient down the chemical potential gradient
established by the plant at the soil-root interface.
Work of Barber
(1962), Nye et al. (1975), and Nye and Tinker (1977) has established
that diffusion and, to a lesser degree, mass flow are the major
mechanisms by which nutrients are transported to plant roots.
Temperature and Fhvtoavailable K
Temperature effects on nutrient availability can be divided into
two components: (I) Plant aspects and (2) soil aspects.
Plant aspects
can be further separated into direct and indirect effects.
Temperature
indirectly influences ion absorption by affecting growth rate,
translocation, and transpiration.
It directly influences the kinetics
of physical and biological processes.
Nobel (1974) estimated a QlO of
I to 2 for physical reactions and 2 to 4 for bioltigical reactions.
With respect to water absorption, a physical process, Markart et al.
(1979) found the QlO for water absorption by soybeans increased from
1.3 to 13 between temperatures of 14 and 9 C.
phase change in plasmaletnma membrane lipids.
This was attributed to a
Ion absorption was found
by Carey and Berry (1978) using solution culture to be strongly
inhibited at .10 C, resulting in a change in QlO from 15 to 8 below this
temperature.
Similar results were found for P by Barber (1985a), where
P uptake by fescue cease! when temperature was lowered to 10 C .
The influence of temperature on cereal root system growth and
morphology has been reported by Abbas Al-Ani-ani and Hay (1983).
Root
systems of wheat increased in length and in number of seminal axes as
temperature rose from 5 to 25 C . Nye and Tinker (1977), have found
8
that the mean angle of maize roots to the horizon was smallest at a
temperature of 17 C.
temperature.
The angle increased with increases in
Thus temperature determines the size and morphology, of
the root system, in addition to its three dimensional orientation in
the soil.
Physical effects of temperature on soil aspects can easily be seen
in terms of effects on ion diffusion and soil solution viscosity.
As
temperature decreases ion diffusion decreases according to the StokesEinstein equation.
Viscosity also increases with decreasing
temperature and the combined effect results in a 22 % decrease in
diffusion of K for a temperature change from 25 to 15 C (Barber 1985a).
Temperature also influences the vapor pressure and surface tension of
water, therefore soil water movement is modified as temperature
changes.
Temperature affects soil chemical reactions by influencing cation
ion solution activity, cation bonding energies and extent of the double
layer (Barber, 1985a). These reactions ultimately determine
solubility, solution speciation and the stability of the soil system to
chemical change (Yang, 1987).
Sparks and Leibhardt (1982) found K
selectivity coefficients decreased with temperature, indicating
decreased K sorption with higher temperatures.
In many instances
temperature changes affect physical and chemical processes as a unit.
A decrease in temperature results in decreased solubility, but
precipitation is inhibited by decreased diffusion. Thus the system can
be considered a physiochemical process which is very sensitive to
9
temperature change and which influences nutrient availability (Sutton,
1969).
Soil Water Potential and K Availability
Water potential is defined as the chemical potential of water
with respect to pure water at the same temperature, expressed in terms
of energy.
Equivalent water potential in different soils implies equal
free energy levels, but different volumetric and /or gravimetric water
contents (Nye and Tinker, 1977).
As water potential decreases (more
negative), resistance to water withdrawal increases.
As with
temperature, the influence of water potential (ie. water content) can
be divided into plant and soil aspects.
Danielson (1967) reviewed the
effects of soil water content and found that root to shoot ratios
increased with decreases in water content.
This was attributed to an
increased root system and decreased shoot growth associated with drier
soils. Hsieh et al. (1972) found similar results for maize. Mackay and
Barber (1987), evaluated the effects of water potential on root hair
growth on c o m and found that increasing water potential, from
- 175
to - 7.5 Kpa, resulted in cessation of root hair growth behind the root
cap.
Reversing water potential (decreasing it) resulted in new root
hair formation.
In another experiment, Mackay and Barber (1983) found
the total root length with root hairs and root hair density increased
as soil moisture content decreased from 32 to 22 percent.
With soil
drying, root hair growth increased, with respect to length and density,
to maintain liquid continuity with the soil.
Water potential (water content) has great significance with
10
respect to physical and chemical processes.
Decreases in water
potential result in the physical draining of soil pores of ever
decreasing diameter, and a decrease in water film thickness over the
surface of particles.
This reduction in the continuity of water films
decreases the mobility of ions subjected to chemical gradients (Nye and
Tinker, 1977).
Thus nutrient diffusion is impeded by increased
tortousity as soil becomes drier (Wamcke and Barber, 1972).
Bertsch and Thomas (1985), reviewed the influence of soil water
content on soil chemical processes.
As water content decreased, ion
speciation in the solution changed because the activity ratio (AR) must
be maintained, as demonstrated by results of Mengel and von
Braunschweig (1972).
With increased water potential solution ion
concentration decreases, the result of dilution accompanied by a net
adsorption divalent cations and desorption of monovalent cations (Moss,
1963).
With decreased water potential the opposite reaction occurs,
resulting in a decrease in solution monovalent ions such as K.
Thus K
availability decreases with reduced water potential due to slowed
diffusion, a physical process and the AR mechanism, a chemical process.
Study of Phvtoavailable K
Soil tests of plant available K traditionally have relied on
correlation between a K extractable index based on cation displacement
and K response to K additions (Feigeribaum and Hagin, 1967).
This
'Index1 value of soil then implies a level of phytoavailable soil K.
Reitemeier et al. (1947) studied K availability based on
greenhouse, Neubauer, and laboratory methods using fourteen soils.
11
Their results indicated a relatively high correlation between K uptake
by clover and electrodialysis of K, as well as Neubauer extractable K.
The Neubauer technique was developed by Thomtoii (1935) to study
nutrient accumulation and involves growing plant seedlings in soil for
one to
to three weeks followed by nutrient uptake assessment.
The
technique has been modified numerous times for specific experiment
purposes (Masses, 1973.).
Research in methods of evaluating soil changes in nutrient
concentration were first described by Brown et al. (1964), using ion
exchange resins.
This method involved mating a resin against a soil
column and thin slicing the soil at micrometer distances from the resin
at the end of the experiment.
Several papers have since used this
methodology to study K, P and N availability (Vaidyanathan and Nye,
1966).
Kuchenbuch and Jungk (1982) described a method combining the
Neubauer technique with that of Brown et al. (1964).
seedlings are grown on nylon screen.
In it, plant
Root hairs grow through the
screen and make contact with the soil but roots do not.
Potassium
depletion gradients are then studied to determine K diffusion in the
rhizosphere.
This technique has many advantages for the purpose of
studying spring wheat phytoavailable K, and was adapted for use in the
studies reported here.
12
MATERIALS AND METHODS
To evaluate the influence of soil properties and environmental
factors on K phytoavailability four experiments were initiated. These
were: Methods Development (MD); Ehytoavailability of K on Montana
agricultural soils (KEdS); Terrperature and moisture influences on plant
and soil K (IMS); and Effects of K rate on soil and plant K (KERS).
In
the MD study, techniques were developed using spring wheat seedlings to
evaluate plant available soil K.
In the PKTS study plant available
soil K dynamics were assessed on twenty Montana soils to identify soil
characteristics important to K availability.
The influence of
temperature and water potential on plant K availability were
investigated in the IMS study, and in the EERS- study the affect of K
additions on plant K uptake and Kex concentration gradients were
evaluated.
Methods Develonment
A modification of the method of Kudheribuch and Jungk (1982), was
employed to determine plant K uptake.
Nylon cloth, 325 mesh, 38
percent porosity, and 40 urn thickness (Nitex Co. Zurich, Switzerland)
was cemented to one end of a plexiglass cylinder, 4.5 cm ID and 1.5 cm
in height.
The cylinders were washed with a 5 percent solution of
sodium hypochlorite to reduce the possibility of contaminating molds
CIRhizopus Sp.)
The nylon covered end of the cylinder was then placed
13
on a agar media consisting of 0.065 % agar purified (nutrient free) and
2 uM CaSO4 .
Various numbers of spring wheat seeds (Triticum aestivum
L. cv. Pondera,)
were placed in the cylinder, on the screen and
allowed to germinate/grow for 5 days at 22 C under etiolated
conditions.
An identical cylinder, but with no screen was filled with
soil wetted to a water potential of approximately - 33 Kpa to a bulk
density of 1.25 gm cm-3.
This cylinder containing soil was then placed
on a high flow moisture plate maintained at a potential of - 33 Kpa.
The cylinder containing the germinated seeds (referred to as a pot) was
then placed on the soil column so that the nylon screen separated the
seed from the soil (Figure I).
Figure
Root hairs but not roots penetrate the
I. Schematic of method for growing wheat seedlings on soil
columns separated by a nylon screen.
14
nYlon screen into the upper layer of the soil.
The system including
the high flow plate was covered with a plexiglass chamber.
Relative
humidity in the chamber was regulated to near 100 percent to minimize
mass flow of water from the soil to the plants.
The photoperiod was 14
hr and light intensity was 12 Wm-2.
v
The plants were left on the soil column from one to eight days.
At the end of each uptake period soil columns were thin sectioned,
using a modified micrometer and thin slicing knife, at five planar
distances representing mean distances of 0.25, 0.75, 1.5, 2.5, and 4.0
mm away from the nylon screen.
Moisture content and exchangeable
cations (as extracted by 1.0 N NH4OAC) were determined on each soil
thin section sample.
Whole spring wheat plants were removed from the
upper cylinder/pot and placed in digestion tubes for total K analysis
by the method of Havlin and Soltanpour (1980).
Control pots containing
spring wheat plants were grown parallel without soil and used to
calculate net K uptake.
Calculations
The quantity of a substance diffusing from a source across a
plane to a sink of constant concentration is given by Crank (1956) and
Vaidyanathan and Nye (1966):
M t = 2 (C1-C2) ((Dc)Vrr)0 *5
[1]
where M t = amount diffusing across the soil surface from
zero to time t.
C1 = initial concentration of ions in the soil.
C2 = constant concentration at the soil-sink interface.
15
(Dc) = the effective diffusion coefficient for the system
within the limits of C1 and C2 .
If the ion sink maintains C2 at or near zero concentration, then
the effective diffusion coefficient can by calculated :
Dc = (Mt)2Y /4 (C1)2 t
[2]
Physical and Chemical Methods
Physical and chemical analyses were performed as follows:
(1) particle size analysis by hydrometer method (Gee and Bauder, 1986) ;
(2) particle size distribution by pipette (Gee and Bauder, 1986);
(3) moisture retention curve by pressure plate (Peters, 1965);
(4) percent CaCO3 by gravimetric loss (U.S. Salinity Lab, 1954);
(5) percent organic matter (Sims and Haby, 1970);
(6) soil pH and conductivity by 2:1 dilution (U.S. Salinity Lab, 1954) ;
(7) extractable K, Na, Ca, and Mg, by 1.0 N NH4OAc extraction and
atomic absorption analysis (Bower et al., 1952);
(8) extractable K by 0.5 N MgCl and 0.5 N NH4OAc (Rich, 1964);
(9) soil extractable K by sodium tetraphenyl boron (Scott and Reed,
1960);
(10) soil extractable K by 1.0 N HNO3 (Mclean and Simon, 1958) ;
(11) saturated paste pH, K, Ca, and Mg extraction and analysis by atomic
absorption (U.S. Salinity Lab, 1954);
(12) soil solution K, Ca, Mg, NO3 , and Cl by extraction by immiscible
liquid displacement (Mubarak and Olson, 1979) and determination of
K , Ca, and Mg by atomic absorption, NO3 by Cd reduction (Willis,
1980) and Cl by ferric cyanide reduction;
16
(13) soil sulfate by acetate soluble SO4 (Bardsley and Lancaster, i960)
(14) available phosphorus by NaHOO3 (Olsen et al., 1954) and modified
Bray #1 (Smith et al., 1957);
(15) extraction of NO3-N in soils (Sims and Jackson, 1971) and
analysis by Cd reduction (Willis, 1980);
(16) plant tissue K, Ca, and Mg by 15:1 nitric-perchloric digest
(Havlin and Soltanpour, 1980), analysis performed by atomic
absorption;
(17) clay mineralology, illite, vermiculite, and montmorillinite
(Jackson, 1958).
17
RESULTS AND DISCUSSION
Methods Development Study
Fhytoavailable K can be best described by a plant model which
simulates K uptake and transport in the rhizosphere.
Techniques for
studying the soil-root interface have, in the past, proved quite
difficult.
Kudheribuch and Jungk (1982) have described a method for
studying fhizospheric soil.
Using modifications of this technique
a simple, accurate, and reproducible method is described for studying
both soil Kex concentration gradients and plant K uptake.
Spring wheat
was chosen for this study, due to its seedling growth characteristics
and importance as a major crop on the Northern Great Plains.
To study phytoavailable K, plant seedlings must exhibit high
demand for K, and growth conditions must be optimal with respect to
root/soil contact.
The objectives of the method development study (MD)
were: (I) determine the plant density required to cover the soil-root
interface (ie. nylon cloth) with roots; (2) determine seedling age
(hours after germination) for maximum K uptake; and (3) assess the rate
of plant K accumulation by spring wheat from soil columns to determine
the time frame for subsequent studies.
Results of studies to determine the influence of plant density on
I
net K accumulation are presented in Table I.
increased with increasing plant density.
Accumulation of K
Although high plant densities
favored greater uptake, low populations are desirable to minimize plant
root competition.
Twenty-five seeds provide sufficient root mass to
18
cover the nylon screen.
Seedlings germinated for 120 hours had a mean
root length of 30 cm and produced sufficient root mass to cover greater
than 75 percent of the screen area.
It was observed that root hairs
protruded through the nylon screen less than 150 um, and thus soil
penetration was limited.
The effect of seedling age on net plant K accumulation is
presented in Table 2.
Young seedlings exhibited lower K uptake than
Table I. The influence of spring wheat plant density on mean net K
uptake from the Edgar soil series after 96 days.
Plant Population (plants pot-1)
25
35
45
15
------------- K uptake umol pot-1 ------------22.Ia
35.6
46.4
52.3
a Means of 2 replications.
older ones, with maximum accumulation occurring at approximately 150
hours.
This suggests younger seedlings (< 48 hours) have near
sufficient K reserves to meet demand while older seedlings (>192 hours)
have decreased net accumulation, probably the result of depleted
endosperm reserves and slowed metabolism.
Table
2. The influence of spring wheat seedling age on net K uptake on
the Edgar soil series after 96 hours.
48
Seedling Age, Hours After Germination
96
150
192
-------------K uptake umol pot- 1 -------------10.5
28.5
34.5
18.2
19
The net accumulation of K by spring wheat as influenced by time
of soil contact is presented in Table 3.
Accumulation from zero to 96
hours was linear and averaged 0.44 umol K hour-1 pot-1 (Figure 2).
The
rate of K accumulation increased at a decreasing rate for periods longer
Table
3. Mean (n=3) net accumulation of K by spring wheat seedlings as
influenced by time of soil contact on the Edgar soils series.
Oa
24
Time
48
(hours)
96
150
192
---------------- K uptake umol pot-1 ----------------0.0
12.1
21.0
42.1
52.9
55.7
a Initial K content of 25 wheat seedlings germinated for 150 hours, 42.1
umoles.
Time (days)
Figure 2.
Accumulation of K by 25 spring wheat seedlings on the Edgar
soil series at five time intervals.
20
than 96 hours.
Thus K accumulation by spring wheat from 0 to 96 hours
has reached a steady state condition.
These results indicate 25 spring wheat seedlings which have
been germinated for 120 hours provide sufficient K demand for use as
a biological sink for soil K during growth periods of 96 hours.
Soil thin sectioning of the rhizosphere, data not shown, indicated
Kex concentration profiles extending from the soil-root interface to a
distance of 0.5 mm after 96 hours.
Thus spring wheat plants provide a
good model for studying both phytoavailable K and soil movement of Ke x .
Fhvtoavailable of K on Montana Agricultural Soils (FKTS)
Twenty soils were collected from majors agricultural areas from
throughout Montana where previous field fertility research had been
conducted.
Soils were air dried and physically and chemically
characterized according to established methods (see page 15).
In the FKTS study, soil columns 4.5 x 1.5 cm were prepared with
each of the twenty soils.
Columns were replicated four times and
placed on a one bar moisture plate with water potential maintained at
- 33 Kpa.
Twenty-five spring wheat seedlings germinated for 120 hours,
prepared as previously described, were placed on soil columns for 96
hours. Plant K uptake and soil rhizosphere Kex concentration profiles
were determined as described previously.
Selected physical and chemical properties of those soils used in
the FKTS study are presented in Table 4 and Table 5 respectively.
Soil organic
matter (CM) ranged from
ranged from H O to 477 gm Kg-1 of soil.
1.27 to 5.41 % and clay content
Soil pH ranged from 5.62 to
8.34 and Kex concentration (mass basis) ranged from 0.619 to 2.115 cmol
21
kg-1 on the twenty soils.
In general these soils represent the broad
spectrum of characteristics upon which spring wheat is produced in
Montana and the Northern Great Plains.
Analysis of variance results. Table 6, indicated significant
(p>0.0001) differences between soils in plant K uptake.
Table
Mean plant K
4. Selected physical properties of twenty Montana soils
used in the EKTS study.
Soil
Series
CE
%
Sand
-
Silt
g Kg 1
Clay
-
- 33 Kpaa
%
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
2.37
3.22
5.37
3.19
1.78
182
246
196
199
342
536
303
463
503
473
281
451
341
297
184
24.61
26.78
27.07
26.11
18.26
Cherry
Chinook
Creston
Edgar
Evanston
3.13
1.97
5.41
1.40
2.05
232
572
446
409
352
453
256
420
350
356
314
170
134
240
290
24.78
14.97
21.06
16.17
20.83
Flathead
Fort Collins
Gerber
Kevin
Manhatten
4.80
1.27
2.62
3.13
2.40
576
506
206
269
202
313
333
316
386
576
HO
160
477
344
220
22.79
14.65
27.38
22.37
23.34
Rothiemay
Round Butte
Stryker
Tanna
Vamey
4.26
2.39
3.58
1.92
1.68
342
139
149
439
596
353
640
570
340
203
304
220
280
220
200
23.21
31.40
33.36
18.11
15.18
2.89
0.11
2.95
0.12
330
19
5.7
31
407
21
5.2
35
262
17
6.4
28
22.63
0.58
2.58
0.97
N=4
Mean
STD DEV
CV %
ISD (0.05)
a Soil water content by pressure plate, -33 Kpa and 1.3 gm cm 3 .
22
Table 5.
Selected chemical properties of twenty Montana soils
used in the EKTS study.
Soil
Series
PH
(Isl)
CEC
cmol kg-1
CACO3
%
cmol Kg ■*-
5.47
0.72
0.49
0.66
0.17
1.43
1.92
0.823
1.74
0.955
0.57
0.96
0.24
1.16
0.81
1.36
1.40
0.619
0.887
1.32
1.08
1.85
1.31
0.73
0.51
1W
,
Xsol^
uM
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
8.24
7.93
5.62
7.34
6.62
22.5
22.6
25.1
23.9
9.3
Cherry
Chinook
Creston
Edgar
Evanston
7.35
8.34
5.69
6.81
6.35
28.8
10.4
13.5
10.9
13.9
Flathead
Fort Collins
Gerber
Kevin
Manhatten
7.18
6.13
6.78
6.92
8.15
14.1
7.6
30.7
13.7
20.1
0.25
0.26
0.72
0.42
4.04
0.877
0.988
2.05
2.11
1.89
1.31
1.17
0.95
1.88
0.84 ,
Rothiemay
Round Butte
Stryker
Tanna
Vamey
7.54
6.05
7.88
8.24
8.13
20.9
10.6
14.4
13.9
16.8
1.60
0.28
2.06
3.70
5.03
1.48
0.778
0.822
0.942
1.11
1.17
0.57
0.86
2.28
0.61
—
1.92
0.17
9.21
0.25
1.28
0.014
1.14
0.021
1.22
0.031
2.54
0.044
N=4
Mean
STD DEV
C.V. %
LSD (0.05)
7.17
0.087
1.28
0.13
0.44
11.33
0.13
0.14 '
0.34
a KsoI, determined by IID on soil, water content - 33 Kpa.
Table
6 . Analysis of variance for net K uptake by spring wheat on
twenty Montana soils maintained at a water potential of
-33 Kpa, after 96 hours.
Source
DF
Sum of
Squares
Mean
Square
Soil
Error
Corrected Total
19
60
79
9564.31
525.98
10090.30
503.38
8.77
F Value
Pr > F
57.42
0.0001
23
Table
7. Mean net (n=4) plant K uptake by spring wheat seedlings after
96 hours of growth on twenty Montana soils maintained at a
water potential of -33 Kpa.
Soil Series
K umol
Soil Series
K umol
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
32.25
56.34
27.12
42.16
31.95
Flathead
Fort Collins
Gerber
Kevin
Marihatten
20.87
35.94
52.52
52.21
38.64
Cherry
Chinook
Creston
Edgar
Evanston
32.84
17.28
22.62
40.41
44.46
Rothiemay
Round Butte
Stryker
Tarma
Vamey
49.40
35.32
44.11
34.65
22.24
Mean
Std Dev
CV %
ISD (0.05)
36.67
2.96
8.07
4.19
uptake for each soil is presented in Table
7.
Potassium uptake
ranged from 17.24 to 56.34 umoles pot-1 after four days for spring
wheat.
Means separation (ISD) indicated that the twenty soils could be
readily separated, and according to their ability to provide.
phytoavailable K.
A regression of the standard K soil test (I N
NH4OAc) and plant K uptake indicated a low correlation (Figure 3).
These results are in accordance with Skogley and Haby (1981), who found
regression coefficient in the field for K response of R2 = 0.32 .
Results of ANOVA on rhizosphere soil Fex concentrations at five
planar distances indicated high significance in SOIL, DIST and the
interaction term (Table
8).
Thus spring wheat seedlings, grown on
these soils induced significant differences in Kex between rhizosphere
distances and between soils.
24
Soil mean rhizosphere concentrations (volume basis), Table
9,
indicated that Kex concentration varied greatly between soils at any
given distance.
Cn all soils there was a significant reduction in
Kex concentration in the near rhizosphere (0.25 mm) as compared to
both greater distances and initial soil Kex concentration.
K6X
Figure
Table
Soils high
( c m o l k g ' 1)
3. Relationship of plant K uptake [dependent variable - Y) and
soil extractable K by NH4CAc (Kex) on twenty Montana soils.
8 . Analysis of variance for soil Kex concentration for five
rhizosphere distances and twenty Montana soils
Source
DF
Sum of
Squares
Mean
Square
SOIL
DIST
S0IL*DIST
Error
Corrected Total
19
4
76
330
439
8226.62
865.60
114.10
59.40
9265.74
432.98
216.40
1.51
0.180
F Value
Pr > F
2405.41
1202.12
8.33
0.0001
0.0001
0.0001
25
Table
9. Mean soil Kex concentration at five rhizosphere distances for
twenty Montana soils after 96 hours maintained at a soil water
potential of -33 Kpa, mean of four replications.
Rhizosphere Distance
mm
Amsterdam
Kex (umol cm 3)
Bear Raw
Beaverton
Bozeman
Chanta
0.25
0.75
1.50
2.50
4.00
10.41
11.70
12.55
13.75
14.36
13.60
15.46
16.69
18.01
19.77
6.68
7.53
8.01
8.38
8.77
13.63
14.63
16.01
17.19
18.31
8.68
9.23
9.60
10.19
11.10
std
Initial3
0.14
15.11
0.12
22.63
0.09
8.68
0.21
19.83
0.33
11.35
Chinook
Creston
Edgar
Cherry
Evanston
0.25
0.75
1.50
2.50
4.00
8.82
11.30
12.44
13.84
14.92
11.30
12.50
12.66
12.98
13.12
3.83
4.32
5.08
5.89
6.48
5.32
6.31
7.16
8.10
8.99
9.34
11.11
11.70
12.74
13.55
std
Initial
0.38
16.68
0.14
14.57
0.12
8.10
0.12
9.95
0.19
16.37
Gerber
Kevin
Flathead
0.25
0.75
1.50
2.50
4.00
std
Initial
Ft. Collins
Marihatten
5.08
6.65
8.24
8.89
9.86
6.92
7.79
8.42
9.19
9.76
17.26
18.64
20.27
21.24
21.98
18.14
20.08
20.84
22.23
23.42
12,84
15.10
16.34
17.79
18.49
0.41
10.70
0.35
10.80
0.21
24.05
0.15
25.65
0.17
21.82
Rothiemay
Round Butte
Stryker
Tanna
Vamey
0.25
0.75
1.50
2.50
4.00
9.61
12.06
13.63
14.73
16.08
5.02
5.80
6.46
7.20
7.81
4.85
5.99
6.84
' 8.04
8.91
7.57
8.84
9.25
10.14
10.87
8.95
10.34
11.22
12.20
12.68
std
Initial
0.31
18.10
0.14
9.44
0.24
10.42
0.25
11.70
0.58
13.22
a Initial concentration of Kex at time=0
26
Table 10. Regression equations between Kex concentration (Y) and
rhizosphere distance (D) on twenty Montana soils.
Soil Series
R 2 **
Equation
8.4 + 0.137(D0 *5)
Amsterdam
Y =
Bear Paw
Y = 11.4
+
0.145(D0-5)
Beaverton
Y
+
F
P>F
-
6 .68E—4 (D)
0.99
617
.0001
-
2.38E-4 (D)
0.99
1049
.0001
0.088(D0 *5 ) - 5.77E-4 (D)
0.98
345
.0001
Bozeman
Y = 11.8 + 0.113(D0,5) - 1.61E-4 (D)
0.99
436
.0001
Chanta
Y =
8.3 + 0.017(D0 *5 )
-
4.07E—4 (D)
0.87
54
.0001
Cherry
Y
=
5.5
+
0.240(D0 *5)
-
1.46E-3 (D)
0.96
211
.0001
Chinook
Y
=
10.8
+
0.073(D0 -5 )
-
5.77E—4 (D)
0.92
96
.0001
Creston
Y
=
2.8
+
0.058(D0 *5 )
+
5.10E-6 (D)
0.98
789'
.0001
Edgar
Y
=
3.9
+
0.091(D0 *5)
-
1.75E-4(D)
0.99
1108
.0001
Evanston
Y
=
7.2
+
0.153(D0 *5)
-
8.65E-4(D)
0.97
283
.0001
Flathead
Y =
2.3 + 0.196(DO'S) - 1.23E—3 (D)
0.91
81
.0001
Fort Collins
Y =
5.6 + 0.087(D0 '5) - 3.34E—4 (D)
0.94
165
.0001
Gerber
Y = 14.4 + 0.193(D0 '5) - 1.15E-3(D)
0.96
267
.0001
Kevin
Y = 16.0 + 0.151(D0 '5) - 5.56E-4(D)
0.98
370
.0001
Manhatten
Y =
9.3 + 0.251(DO'S) - 1.68E-3(D)
0.99
929
.0001
Rothiemay
Y =
6.1 + 0.253(D0 -S) - 1.53E-3(D)
0.97
. 256
.0001
Round Butte
Y =
3.8 + 0.077(D0 -S) - 2.35E-4(D)
0.97
316
.0001
Stryker
Y =
3.2 + 0.105(D0-S) - 2.47E-4(D)
0.98
256
.0001
Tanna
Y =
6.2 + 0.100(D0 -5) - 4.14E-4 (D)
0.94
152
.0001
Vamey
Y =
6.4 + 0.189(D0 -5) - 1.72E-3 (D)
0.92
98
.0001
=
5.5
a. Units for Kex (Y) are umol cm-3; Distance D, mm(10~3).
** Regression values based on mean of four observation at each
distance.
27
in Fexz in general, exhibited the greatest change in Kex between
distances of 0.25 and 4.00 ram.
Multiple regression analysis (SAS Institute, 1987) of rhizosphere
Kex concentration (Y), with respect to distance (D), indicated that Kex
was best described as a
two variable equation using distance and
square root of distance, equation [3] (Table 10).
Y = C1 + C2 (D) + C3 (D0-5)
The equation was:
[3]
On all twenty soils highly significant regressions were found
(P>0.0001). Regression.coefficients for the square root term (D®*^ are
approximately 1000 times greater than the term for distance alone.
This indicates the diffusive movement of Kex closely follows Pick's
first and second laws of diffusion (Nye and Tinker, 1977). The distance
term (D) reflects correction term for Kex concentration for Kex at
greater rhizosphere distances.
Using the regression equations for Kex, an overall Fex diffusion
gradient coefficient (U(Kex)ZdD) can be determined from the second
derivative of each equation in Table 10.
Thus d[Kex]/dD represents the
change in Kex concentration at any rhizosphere distance from the soildistance (equation 3), the extent of depletion in rhizosphere Kex was
calculated. Table 11.
Thus, the maximum distance of Kex diffusion
could be compared between soils.
This distance (Dl) ranged from 3.3 ram
to 10.1 ram and averaged 5.2 ram on the twenty soils.
Generally soils
which exhibited high plant K uptake had the greatest rhizosphere
diffusion distances.
Kudhenbuch and Jungk (1982), using rape, found
that the distance of K depletion increased with fertilizer additions.
28
V Amsterdam
O Tanna
X Beaverton
X Creston
Rhizosphere Distance (mm)
Figure
4. Changes in the concentration of Kex as a function of distance
in the rhizosphere of spring wheat for four Montana soils.
Symbols represent observed data points and lines represent
estimate d[Kex]/dD.
Intergrating equation [3] for each soil front the soil-root
interface to the estimated distance limit of diffusion (D^), and
subtracting the initial concentration of Kex an estimate of the amount
of soil Kex flux (SKex) was calculated (based on a soil column cross
sectional area of 15.5 cm and 96 hours).
Soil Kex flux ranged from 3.6
to 82.6 and averaged 45.2 nmol m-2 s-1 pot-1 over all soils.
The SKex
estimate represents the amount of Kex which was removed from each soil
by spring wheat seedlings in 96 hours.
A poor relationship was found
between SKex and plant K uptake (R2 = 0.28).
The final term Dc , Table 11, represents the estimated effective
diffusion coefficient for Kex calculated by equation [2] (Vaidyanathan
and Nye, 1968).
Diffusion terms reported in the literature are for K
29
alone, while these values represent Kex, based on the estimated values
d [KexJZdD and SKex. Among soils, Dc varied by two orders of magnitude.
Dc was the lowest on the Beaverton soil and greatest on the Creston soil
series.
Thus, on the Creston soil Kex diffusion was 146 times faster
Table 11. Estimated K^x diffusion gradient coefficient d[Kex]/dD
diffusion distance (D1), soil Kex flux (SKex), and Kex
effective diffusion coefficient (Dc) on twenty Montana soils.
Soil Series
CltKexJZdD
umol cm 2 cm I
Dl
mm
Flux SKex
nmol m 2 s
Dc
cm2 s
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
O .0864a
0.1390
0.0411
0.1112
0.0600
6.4b
8.1
3.3
6.3
4.5
28.9C
82.6
3.6
46.7
17.0
2.27e-6d
8.24e—6
1.19e-7
3.43e—6
1.41e-6
Cherry
Chinook
Creston
Edgar
Evanston
0.1227
0.0240
0.0644
0.0847
0.0854
6.8
3.8
8.3
6.0
7.9
59.0
33.7
42.9
32.4
80.3
7.74e-6
2.52e—6
1.74e-5
6.62e—6
1.49e—5
Flathead
Fort Collins
Gerber
Kevin
Marihatten
0.0975
0.0907
0.1005
0.1135
0.1128
6.4
5.1
7.0
10.0
5.5
35.3
33.5
70.9
70.0
68.4
6.71e—6
5.OOe-6
5.lie—6
4.48e-6
5.40e—6
Rothiemay
Round Butte
Stryker
Tanna
Vamey
0.1301
0.0637
0.0936
0.0703
0.0398
6.8
10.1
7.1
3.6
6.4
66.7
65.3
44.4
13.6
28.0
8.46e—6
1.74e-6
1.21e-5
9.89e-7
2.59e-6
0.0866
6.5
45.2
5.86e-6
Mean
a. Estimate of d [KexJZdD based second derivative of regression equation
of rhizosphere distance and Kex.
b. Estimates for Dl based on Kex depletion gradients and initial Kex
concentrations.
d. Estimates of SKex flux based on integration Kex depletion gradients,
a cross sectional area of 15.5 cm2 and 96 hours.
c. Dc estimate determined from equation.I (Vaidyanathan and Nye, 1966).
30
than on the Beaverton soil.
These diffusion coefficient values are
considerably larger than those reported by Rowell et al. (1967) and
Barber (1985a).
This is due to (I) the fact this system used intact
plants rather than resins which could result in differing effective
diffusion gradients and (2) these results are for Dc of Kex and not K
ions alone.
Comparisons of net plant K uptake and calculated SKex are
presented in Table 12.
Differences between plant and soil K flux
Table 12. Mean net plant K flux, soil K flux (SKex), difference (umol)
and % Kex utilized by spring wheat seedlings after 96 hours
growth on twenty Montana soils.
Soil Series
Plant K
Flux
SKex
Flux
Delta K
Flux
Kex Utilized
%
------ nmol m 2 s 1 pot -I
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
61.7
107.8
51.9
80.7
61.1
28.9
82.6
3.6
46.7
17.0
32.6
25.3
48.3
33.9
44.1
46.9
76.6
7.0
58.0
27.9
Cherry
Chinook
Creston
Edgar
Evanston
62.8
32.8
43.1
77.4
85.1
59.0
33.7
42.9
32.4
80.3
3.8
0.6
0.4
44.8
4.6
93.9
102.3
99.1
41.8
90.1
40.0
68.8
100.6
100.0
74.0
35.3
33.5
70.9
70.0
68.4
4.6
35.2
29,5
30.8
5.6
88.5
48.7
70.5
69.0
92.5
94.7
67.6
84.5
66.3
42.5
66.7
65.3
44.4
13.6
28.0
27.8
1.3
40.0
52.7
15.5
70.4
96.3
52.6
20.5
63.5
70.1
45.2
23.9
65.6
Flathead
Fort Collins
Gerber
Kevin
Manhattan
Rothiemay
Round Butte
Stryker
Tanna
Varney
Mean
31
are represented by Delta K flux; that portion of K taken up by spring
wheat that is not accounted for by changes in the Kex.
This is better
shown by the term Kex utilized (%) which represents SKex flux divided
by Plant K flux.
Only on six of the twenty soils did SKex account for
more than 70 % of the total K taken up by spring wheat seedlings.
Qn
six of the soils, SKex flux accounted for less than 50 % of the plant K
uptake.
For the Beaverton soil only 7 % of the K absorbed by the plant
was due to SKex flux.
These differences between plant K SKex flux
clearly demonstrate that Kex does not adequately predict phytoavailable
K on these soils.
Stepwise linear regression (SAS Institute, 1987) was employed to
select an optimum subset of soil physical and chemical characteristics
which best explain variation in K uptake by spring wheat.
Soil
physical characteristics which were used in model selection were:
%
sand, %silt, % clay, organic matter (CM), % CAG03, % coarse silt, %
medium silt, % fine silt, % clay by pipette, available water capacity, .
% illitic clay, % vermiculitic clay, and % montmorillinitic clay.
Soil chemical characteristics were: pH, EC, NO3 , Cl, Bray-P, Olsen-P,
S, K extractable, Ca extractable, Mg extractable, Na extractable,
potassium absorption ratio, IID solution K Ca, Mg, K activity ratio,
nonexchangeable K (sodium tetraphenyl boron and nitric acid),
extractable K (MgCl), paste pH, paste K, Ca and Mg concentration,
paste K activity ratio and ratio of KexZto solution K.
Additional
calculated variables included were: ^(Kex)ZdD, distance of diffusion
(D), and effective diffusion coefficient for Kex (Dc).
32
Variable selection was carried out using forward and maximum R
selection methods (Freund and Littell, 1986).
Models were selected on
the basis of significance, coefficient of determination and
of regression coefficients.
Models explaining plant K uptake using one
to five independent variables are listel in Table 13.
Models 1 - 5
represent those soil properties which individually indicate high
Table 13. Linear regression model equations between the amount of K
absorbed by spring wheat (umol pot-1) and physical and
chemical characteristics for twenty Montana soils.
Equations3
Model
R2
_ 16.4 + 2.62 (ILL)
0.72
0.59
0.55
0.42
0.38
F
P>F
.0001
.0001
.0001
.002
.003
I
2
3
4
5
Y
Y
Y
Y
Y
6
7
Y
21.2 — 0.58(CEC) + 3.28(ILL)
Y = 11.5 + IlSfd(KexVdX) + 1.95 (ILL)
0.79
0.78
29
.0001
.0001
8
Y = 8.53 4* 1.08(CIAY) - 0.98(CEC) +
194 Cd(KexVdX)
0.93
71
.0001
Y = 16.3 + 2.61(ILL) - 0.59(CEC) +
IlOfd(KexVdX)
0.85
31
.0001
0.94
55
.0001
0.90
35
.0001
0.96
68
.0001
9
10
11
12
a
@
Y
Y
=
=
=
=
13.2
13.5
23.1
17.5
+
+
+
+
0.90 (CLAY)
267 Cd(KexV dX)
@
175(FINE SILT)
15.I (Kex)
5.74 + I.09(CIAY) - I.00(CEC) +
189 Cd(KexVdX) + 0.OS(SILT)
'
11.4 + 0.93 (CLAYPIP) - 1.09(CEC) +
0.77(FINE SILT) + 208Cd(KexVdX)
Y = 2.82 + 0.91(CLAY) - I.15(CEC) +
205 (d[Kex]/dX) + 0.14 (SILT) + 0.69 (MONT)
46
25
22
13
11
32
Independent variables: ILL, % illitic clay; CLAY, % clay hydrometer;
d[Kex]/dD, diffusion gradient coefficient; FINE SILT, fine silt
particle size fraction; CEC, cation exchange capacity; SILT, % silt
by hydrometer; and CIAYPIP, clay particle size by pipette,
(![KexVdD, Kex Diffusion Gradient Coefficient, estimated from Kex
depletion gradients.
33
correlations with plant K uptake.
Models 6 through 12 represent those
equations with multiple independent variables.
Spring wheat. K uptake was highly correlated to % illitic clay
(ILL) Viiiich accounted for 72 percent of the variation in K uptake.
Individually clay content, d[Kg^]/dD and fine silt particle size
accounted for 59, 55, and 42 percent, respectively, of the variation in
plant K uptake.
illitic clay.
The best two variable models both included percent
A model including percent clay, d[Eg^]/dD and CEC
independent variables accounted for 93 % of the variation in plant
K uptake.
Model 12 indicated that 96 percent of the variation in plant
K uptake was accounted for by percent clay, dfE^j/dD, CEC, percent
silt and percent montmorillinitic clay.
However, not all regression
coefficients were significant for this model.
The best three-variable model, 8 , was selected as the best model
and was tested for multicoll inearity.
The existence of
multicoll inearity results from intercorrelation between independent
variables and it would lead to inflated variances in predicted values
and coefficient estimates that are nonsignificant or have incorrect
sign.
The statistics used to test for multicollinearity were: (I)
relative significance of coefficient estimates, (2) test for variance
inflation (VIE) and (3) analysis of structure matrix (Table 14).
All
regression coefficients estimates were highly significant (E>0 .0001) .
The VIF test indicated that significant multicollinearity existed for
variables with VIF greater than 14.36, of which none were found among
the variables.
Eigenvalues values indicate little linear dependence
between variables (bound of condition numbers less than 10).
Thus
34
Table 14. Multicollinearity detection of regression model 8 with
dependent variable plant K uptake and independent variables:
clay, d[Kex]/dD, and CEC
Dependent Variable: K Uptake
Source
Model
Error
C Total
Sum of
Squares
2224.7
166.3
2391.1
DF
3
16
19
Root MSE
Dep Mean
Variable
INTERCEPT
CIAY
d[Kex]/dD
CEC
3.22
36.66
R-square
C.V.
Parameter
Estimate
DF
I
I
I
I
T for HO:
Parameter=O
2.51
0.116
27.46
0.160
Variance
Inflation
I
0.00
2.27
1.34
2.11
F Value
71.327
Prob>F
0.0001
0.9304
8.79
Standard
Error
8.53
1.07 .
194.15
-0.98
Variable I)F
INTERCEPT
CLAY
I
I
d[Kex]/dD
I
CEC
Mean
Square
741.5
10.3
Prob > |T|
3.396
9.281
7.068
-6.147
0.0037
0.0001
0.0001
0.0001
Test
1/(1-0.9304)
14.36
Collinearity Diagnostics
Number
Eigenvalue
Condition
Number
1
2
3
2.10623
0.61890
0.27487
1.00000
1.84477
2.76815
Var Prop Var Prop Var Prop
PdAY
SMPE3QD CEC
0.0796
0.0535
0.8669
0.0915
0.8767
0.0318
0.0810
0.1498
0.7693
multicollinearity test indicates there were no significant
interdependence between independent variables with regard to plant K
uptake for model 8 and suggest this is a good regression model.
For
models 10 - 12 some degree of multicollinearity was found between
independent variables.
35
To investigate the contribution of Ksol to plant K uptake, an
experiment was conducted to determine Ksol flux in the soil rhizosphere
(Table 15).
Results, using the Amsterdam soil and the same
experimental conditions as used in the twenty soil study indicated that
Ksol flux accounted for 0.77 m o l e s K pot-1, or less than 4 percent of
Table 15. Changes in IID soil solution K concentration as related to
rhizosphere distance for spring wheat for the Amsterdam soil
after 96 hours.
0.25
0.75
Rhizosphere distance (mm)
1.50
2.50
4.00
6.00
---------------------- ItM---------------------0.13
0.210
total K uptake.
0.24
0.28
0.39
0.47
Thus, Ksol flux alone is relatively unimportant in
overall spring wheat K uptake, at least in the early stages of plant
growth and when mass flow is minimal.
Results of this study indicate spring wheat plants utilize
other than that extracted by I N RH4OAC.
soil K
Furthenirare, the amount of
plant K obtained from sources other than Kex was highly soil dependent.
It is hypothesized that plants are capable of utilizing K from Knex and
Kmln soil forms in the near rhizosphere (0.25 mm).
Evidence to support
this hypothesis includes the extreme depletion of Ksol in the near
rhizosphere (Table 15) and slow transport of Kex from greater distances
(Table 11).
In addition, spring wheat plants are capable of utilizing
K in these forms in time periods as short as 96 hours.
Reitemeier et
al. (1947) reported Ladino clover utilized Knex on A l a b a m soils.
Recently Richards, Bates and Sheppard (1988) reported that K uptake by
36
alfalfa was related to Knex on Ontario soils.
Kudhenbuch and Jungk
(1984) suggested that as much as 60% of the K taken up by rape was due
to Knex.
The results of this experiment further support this
hypothesis.
A significant relationship is evident by the coefficient of
determination, between plant K uptake and percent illitic clay, and
also fine silt, 5 - 2 um (Table 12).
Illitic clay (hydrous mica) which
contains interlayer or nonexchangeable K, ranged from 2.7 to 14.7
percent for the twenty soils.
Chute and Quirk (1967) have reported
that K diffusion from illitic clay (<2 um) was ten times slower than
that from silt size particles.
von Reicheribach and Rich (1969)
indicated that K could be removed more easily from coarser particles
(fine silt) than finer particles.
This information further supports
the hypothesis that nonexchangeable K is available to spring wheat
seedlings and that it probably released from predominately fine silt
and clay sized particles.
In describing phytoavailable K according to a mechnistic approach,
Barber (1985a) and Cushman (1982) have presented results showing the
effective diffusion coefficient (Dc) for K is often most limiting.
However K diffusion alone is not necessarily the most limiting factor
in this model.
Results of this study are based on Correlation of soil
variables with phytoavailable K and not direct cause and effect
relationships.
However, if one uses strictly a quantity and intensity
approach, transport processes do not play a major role in K
availability.
Instead the capacity of a soil to replenish Kso^ is of
major importance.
37
These results suggest quantity and intensity relationships
account for a majority of K availability.
Regression model 8 (Table
13) involving clay, (^[KexVdD, and GEC accounted for 93 % of the
variability in plant K uptake and had no significant
multicollinearity (Table 14).
Each of these variables influences Dc,
but they also have a major role in
quantity and intensity relations,
as follows:
(1) Clay represents a potential capacity of a soil to supply K
through increased CEC and clay-sized K bearing minerals (both
primary and secondary).
Further, clay highly influences the
soil volumetric water content (VWC).
to have high VWC at -33 Kpa.
Soils high in clay tend
Increased VWC will generally
increase KsoI as well as K diffusion (Barber 1985a).
(2) The Kex diffusion gradient coefficient (^[KexVdD) is
positively related with plant K uptake, and appears to
represent K diffusion in the rhizosphere since fit changes
with the square of the distance.
In addition, it accounts for
factors that limit Kex movement in the rhizosphere such as
CaOO3, as indicated by the negative coefficient for CaCO3 in
Table 16.
Table 16. Regression of Kex concentration gradient (d[KexIZdD), (umol
I cm“3 cm--*-) as dependent variable (Y) and independent
variables: Kex; CACO3 ; and saturated paste Ca.
Model
I Y =
Equation
2.6E-2 + 4.9E-2(Kex) - 5.8E-3(CaCO3) l.lE-4(pasCa)
■
R2
0.70
F
P>T
12.2
.0002
38
(3) The importance of CEC in the K phytoavailability model appears
contradictory due to the negative coefficient.
However, CEC
accounts for the resistance within the soil to supply K
through diffusion.
High CEC implies high K exchange capacity,
increased K affinity and thus restricted K movement (trans­
port) .
Furthermore, CEC is highly regulated by organic
matter (CM) content, and exchange sites on CM have been found
to have low affinity for K.
This translocates into relatively
small increases in K capacity with increased CEC due to CM.
These results are similar to those found by Jaworski and
Barber (1958) who found a negative regression coefficient
for CEC in a linear regression equation for K uptake by
alfalfa.
The interrelation of these variables for various soils is
apparent.
The Beaverton has relatively high clay content (341 g
Kg-1) suggesting a high potential to supply K.
capacity
Cation Exchange
and d[Eg^]/dD on this soil, however, both indicate low
phytoavailable K, as was indicated by low spring TAheat K uptake (27.12
umol pot-1).
The Creston soil has a clay content of 134 g Kg-1, a
value of 0.0644 for d[Kex]/dD, and a CEC of 13.5 cmol(-) Kg-1.
For the
Creston soil these values represent low K potential, a low to moderate
d[Kex]/dD, and low CEC, and thus little resistance to K movement
relative to K uptake.
The Stryker soil series, with a clay content of
280 g Kg-1, d[Eg^]/dD of .0936, and CEC of 14.4 cmol(-)Kg-1 has
moderately high K potential, moderate d[Kex]/dD and low CEC, resulting
39
in moderately high K uptake (44.11 umoles pot-1).
Overall, these results show that the amount of Kex used by spring
wheat seedlings is soil dependent and poorly related to total K uptake,
ViMle % illitic clay was hic^ily correlated with K uptake.
Spring wheat
plants are capable of utilizing K from soil sources other than Kex.
Fhytoavailability was best described by a multiple linear regression
equation including the variables percent clay, Kex diffusion gradient
coefficient and CEC. Apparently these variables were most highly
related to plant K uptake, and thus most influential in soil K supply
and transport in the rhizosphere.
Temperature and Moisture Influences on K Fhytoavail ability (TMS)
In the TMS study, plant K uptake was determined at five
temperatures and three soil water potentials on four soils in a split
plot design.
Temperature and water potential were main plots and soils
as subplots.
The factor combinations used are described below, with
three replications.
a. Temperature: 8 , 12, 16, 20, and 24 C
b. Water Potential: - 12 - 33 - 70 KPa
c. Soils Series: Amsterdam, Beaverton, Edgar, and Kevin
A high flow ceramic moisture plate with attached water column was
employed in this study to regulate water potential.
An isotemperature
plate was attached to the upper surface of the ceramic moisture plate.
It consisted of an aluminum plate containing access holes 4.8 cm ID and
2.0 cm in height in which soil columns were to be placed.
Within the
aluminum plate were conduit tubes, which when connected to a constant
40
temperature water bath would maintain soil columns at a constant
temperature +-1.0 C.
Soil columns, 4.5 x 2.0 cm (BD 1.25 gm cm--5) were prepared for
each of the soil series and placed into the isotemperature plate access
holes.
Pondera wheat seedlings, (0.75 gm) five days old, were placed
on soil columns for four days. Plant K uptake, and soil rhizosphere Kex
concentration profiles were determined as described previously.
Analysis of variance of the TMS study for net plant K uptake is
presented in Table 17.
Main plot effects, temperature, water potential
plant K uptake were affected by these treatments.
Sub plot effects and
Table 17. Analysis of variance for net plant K uptake as influenced
by temperature (TEMP) and water potential (KPA) on four
Montana soils (SOIL).
Dependent Variable: K uptake (umol pot-1)
Source
Model
Error
Corrected Total
DF
59
120
179
Sum of
Squares
25652.0
128.9
25780.9
Mean
Square
434.78
1.04
C.V.
8.11
Source
DF
Anova SS
Mean S
4
2
8
Error a
16
24.7
1.5
3
12
6
24
3971.2
1344.7
70.5
272.3
1323.5
112.2
11.5
11.1
56.3
1.2
Error b
48 .
P>F
404.66
.0001
Root MSE
1.036
TEMP
KPA
KPA*TEMP
SOIL
S0IL*Tenp
S0IL*KPA
SOIL*KPA*TEMP ■
18880.0
150.6
1112.9
F Value
4720.0
75.3
139.1
K uptake Mean
12.77
•F Value
3146
48.9
90.1
1093.8
93.5
10.3
9.2
P>T
.0001
.0014
.0001
.0001
.0001
.0031
.0001
41
- O- Kevin
-S - Beaverton
Amsterdam
-Q- Edgar
Temperature ( C )
Figure
5. Potassium uptake QlO for spring wheat seedling on four
Montana soils at a water potential of -12 Kpa.
Table 18. Mean neta K uptake (umol pot-1) by spring wheat as influenced
by temperature (C) and soil water potential (Ipa) on four
Montana soils.
Soil
Series
Water
Potential
(Ipa)
Temperature
8
12
16
(C)
20
24
umol pot 1
Amsterdam
12
33
70
0.5
1.1
0.6
3.8
3.9
3.9
8.7
7.5
11.4
17.9
18.3
12.7
31.6
33.2
18.9
12
33
70
- 2.2
- 1.1
- 0.4
2.3
3.2
3.5
3.7
6.2
5.4
11.4
11.5
12.3
22.7
20.4
15.8
12
33
70
1.4
1.1
0.7
2.1
2.6
3.1
9.6
9.0
11.5
14.3
13.8
16.2
33.9
29.2
21.7
12
33
70
2.1
2.0
1.8
7.1
10.6
10.4
15.3
20.2
21.7
31.5
30.9
27.5
52.1
43.6
31.2
Beaverton
Edgar
Kevin
42
their interaction were all highly significant (P=O-Ol) indicating
interactions were also highly significant.
Thus, soil and these
environmental factors had a major impact on plant potassium uptake.
The dynamic effects of temperature are noted by the large Mean square
term associated with this variable.
It is further depicted in the
mean plant K uptake values (Table 18).
Temperature increases resulted in an exponential increase in K
uptake by spring wheat across all soils (Table 18, Figure 5).
At 8 C,
statistically there was no net K uptake on any soil over that of the
control plants (grown in the absence of soil). However, trends
indicated greater K uptake by spring wheat on the Kevin soil than the
other three, and an actual loss of plant K from plants grown on the
Beaverton soil.
The influence of low temperature on plant K uptake is
also illustrated by data presented in Table 19 (Figure 5).
Clearly,
Table 19. Calculated QlO for K uptake by spring wheat on four Montana
soils for temperatures 8 to 24 C, at a water potential of
of -12 Kpa.
Temperature
Range C
Amsterdam
Soil Series
Beaverton
Edgar
8 - 12
43
498
26
63
12 - 24
6.1
8.0
7.0
3.8
Kevin
QlO
there is major change in the QlO for K uptake between 12 and 8 C on
three of four soils in this study.
Similar results have been presented
by Carey and Berry (1978) with barley.
They observed a sharp
discontinuity in the QlO for Rb uptake occurring at 10 C.
These results
for K using a soil system and spring wheat support their findings.
43
The influence of water potential on K uptake is less dramatic as
illustrated by the data in Table 18.
Below 16 C water potential
differences had little or no influence on plant K uptake on any of the
four soils.
However, at temperatures of 20 and 24 C, decreasing water
potentials resulted in reduced K uptake.
Thus, it was not until
higher temperatures had stimulated plant growth and K demand that water
potential had a significant influence on K uptake.
This effect was
most pronounced on the Kevin and least on the Beaverton soils.
Generalized linear regression models for plant K uptake as
influenced by temperature and water potential are presented in Table
20.
The generalized form of the equation was:
Y = C1 + C2 (a(T)b ) - C3 (a(T)b ) (Ipa)2 + C3 (T) (Epa)
[4]
Where a and b are coefficients associated with the power equation for
temperature and Epa is water potential.
Assumptions were made in
setting the boundary conditions for the equations.
The most
important of these was that K uptake at any one temperature is a
theoretical upper limit at the highest water potential, and decreased
with decreases in water potential.
The derived model would be a
linear type, containing the exponential effects of temperature and
the quadratic effects of water potential.
Coefficients of multiple determination (R2) indicate more
than 95 % of the variability in K uptake could be explained by
independent variables temperature and water potential.
Negative
coefficients for the linear temperature by quadratic water potential
term indicate the reduction in K uptake with this variable interaction.
44
Table 20. Regression equations of dependent variable K uptake (umol)
and independent variables: water potential (Kpa) and
temperature (T) for four Montana soils.
Soil Series
Equation
R2
F
P>T
Amsterdam
Y = -1.4 + 1.0(7.4E-4)(T3 *4) I .4E—4(7.4E—4)(T3 *4) (Kpa)2 +
6 .4E-3(T)(Kpa)
0.98
704
.0001
0.97
446
.0001
+ I.2 (2 .OE-3)(T3 -O) I.IE-4(2.OE-3)(T3 -0) (Kpa)2 +
4.5E—3 (T) (Ipa)
0.95
287
.0001
Y = -1.2 + 0.91(5.OE-3)(T2 -9) 1.4E-4 (5.0E-3) (T2 -9) (Ipa)2 +
1.4E-2 (T) (Ipa)
0.96
326
.0001
Beaverton
Y = -2.4 + 1.0(8.2E-4)(T3 *2) I.2E-4(8 .2E-4)(T3 -2) (Kpa)2 +
5.6E-3 (T) (Kpa)
Edgar
Y = -1.6
Kevin
number of observations per soil, 45.
In addition, differences in K uptake across soils can be seen by
comparing variable coefficients for the Kevin and Edgar soils.
Surface response models of plant K uptake on these four soils as
influenced by temperature and water potential are shown in Figures 6
- 9.
These figures indicate that the model is not exact, as K uptake
at 8 C does increase with decreased water potential.
This, however,
is the result of mathematical computation and is relatively unimportant,
since most plant growth occurs at higher temperatures.
Rhizosphere Kex concentrations were determined on a reduced data
set which consisted of main effects, soil, temperature and distance,
45
Figure
6 . Response function of plant K uptake (umol pot-1),
temperature, and soil water potential; soil series
Amsterdam.
Figure
7. Response function of plant K uptake (umol pot 1J,
temperature, and soil water potential; soil series Beaverton.
„
K uPlato.
P°‘'
46
8 . Response function of plant K Lptake (umol pot”1),
temperature and soil water potential; soil series Edgar.
K uptake, umoi pot1
'igure
vtelBr Potential
Figure
9. Response function of plant K uptake (umol pot 1),
temperature and soil water potential; soil series Kevin.
47
at a single water potential of - 33 Kpa. Analysis of variance
indicated that all main effects were highly significant (E>0 .0001).
Interaction effects were all highly significant (E>0.0001) with the
exception of SOIL*TEMP*D
(Table 21).
Mean rhizosphere Kex concentration indicated little change in
concentration with distance at low temperatures (Table 22).
As
temperatures increased from 12 to 24 C there was a rapid reduction in
near rhizosphere (0.25 mm) Kex.
In general this is seen across all
soils, but the amount of change in Kex was soil dependent.
Generalized regression models were developed and indicated that
Kex concentration was influenced primarily by the interaction square
Table 21. Analysis of variance table for Kex (umol cm-3) at five
distances (D) in the rhizosphere of spring wheat as influenced
by temperature (TEMP) for four Montana soils (SOIL).
Dependent Variable: Kex
Source
Model
Error
Corrected Total
Source
HEP
TEMP
EEP*TEMP
SOIL
D
S0IL*D
SOIDfcTEMP
TRMPfcD
SOTTl
fcTRMPfcD
DF
Sum of
Squares
Mean
Square
111
188
299
7537.18
149.23
7686.42
67.94
0.79
F Value
85.04
C.V.
7.21
Root MSE
0.886
P > F
0.0001
KVOL Mean
12.28
DF
Anova SS
Mean SS
F Value
P > F
2
4
8
3.2
220.21
1.61
1.6
55.05
0.20
8.0
272.50
0.4520
0.0001
3
4
12
12
16
48
6858.98
242.97
19.62
109.78
66.01
17.83
2286.32
60.74
1.63
9.14
4.12
.0.37
2910.83
77.33
2.08
11.65
5.25
0.47
0.0001
0.0001
0.0198
0.0001
0.0001
0.9986
48
root of distance and temperature (Table 23).
The generalized form of
the equation was:
Y = C1 - C2 (D). - C3 (T) + C4 (T) (D)0 *5) - C5 (T)2 (D)0 -5
[5]
The effects of temperature were most pronounced for the Kevin soil and
Table 22. Mean (n=3) soil Kex concentration (umol cm-3) in the
ihizosphere of spring wheat as a function of distance (mm)
and influenced by temperature (C) on four Montana soils
maintained at a water potential of - 33 Kpa.
Soil
Series
Distance
(mm)
Temperature (C)
8
12
16
■ un>o_L CIU
20
24
■■
Amsterdam
0.25
0.75
1.50
2.50
4.00
13.34a
13.86
14.00
13.98
14.11
0.25
0.75
1.50
2.50
4.00
7.99
8.19
8.26
8.28
8.29
0.25
0.75
1.50
2.50
4.00
0.25
0.75
1.50
2.50
4.00
13.01
13.47
13.63
14.08
14.28
11.22
12.70
13.26
13.58
14.01
10.47
12.27
12.91
13.55
13.93
9.55
11.15
11.85
12.50
14.11
7.94
8.07
8.28
8.25
8.36
6.92
7.18
7.40
7.64
8.05
6.51
6.90
7.24
7.69
8.03
5.78
6.37
6.91
7.56
8.24
9.18
9.30
9.40
9.55
9.70
8.57
8.88
9,30
9.54
9.68
7.07
7.92
8.35
9.08
9.49
6.59
7.61
8.13
8.86
9.45
6.18
7.25
7.88
8.39
9.52
20.92
21.57
22.08
22.43
22.80
20.27
20.81
21.93
22.16
22.80
17.30
18.15
19.53
20.41
21,97
15.50
17.11
18.04
20.55
22.44
13.52
16.44
17.67
. 19.31
„ 21.87
Beaverton
Edgar
Kevin
49
least for the Beaverton soil.
For all soils the coefficient of multiple
determination and F value indicated high significance.
This model type
for rhizosphere Kex is reasonable when these results are compared to
plant K uptake.
Table 23. Regression equations of dependent variable soil Kex (Y) and
independent variables: rhizosphere distance (D) and
temperature, (T) for four Montana soils at - 33 Kpa.
Soil Series
Equation
P>T
Amsterdam
Ya = 15.6 - 4.7E-4(D) - 0.33(T) +
6.3E-3(D0 *5) (T) - 6.3E-7(D0 *5) (T2)
.97
150
.0001
.97
150
.0001
.97
151
.0001
.95
90
.0001
Beaverton
Y = 9.3
- 1.3E-3 (D) - 0.18(T) +
2.0E-3(D0 *5) (T) + 2.8E-7(D°*5) (T2)
Edgar
Y = 10.6 - 2.IE—4 (D) - 0.25(T) +
4.1E—3 (D0 *5) (T) - 3.2E-7(D0 *5) (T2)
Kevin
Y = 23.6 - 1.0E-4(D) - 0.54(T) +
8 .8E-3(D0 '5) (T) - 1.2E-6(D0 *5) (T2)
a units: Kex of umol cm 3 ; D, distance mm; and T, temperature C.
Plant K uptake was influenced by temperature in accordance with
published nutrient research conducted under both field and greenhouse
conditions (Nielsen et al. 1960; Nielsen et al., 1961; and
Smith, 1971).
Differences across soils in plant K uptake reflected
inherent differences in soil capacities to replenish solution K
in the rhizosphere.
Decreases in temperature have been shown by Yang
50
(1987) to increase the selectivity of exchange sites for K.
Although
decreases in temperature would have pronounced effects on both K
release reactions and transport, the effects of temperature on the
biological system are much more significant (Rovira and Bowen, 1973).
Thus, at low temperature there is a large reduction in biological K
demand, and less of an effect on chemical and physical processes
associated with K availability in the rhizosphere.
Similar effects of
temperature on ion absorption have been demonstrated by Ching and
Barber (1979) for c o m and by Nye and Tinker (1977).
The effects of water potential, and associated volumetric water
content (VWC), are less distinct (Table 24).
decrease in K uptake with decreases in VWC.
Clearly there is a
Even though the number of
data points are limited and skewed to the moist end of the plant
available VWC range, these results indicate a major impact of decreased
Table 24. Volumetric water content at three water potentials for four
Montana soils.
Water Potential
(Kpa)
Amsterdam
- 12
- 33
- 70
0.4OOa
0.301
0.242
Soil Series
Beaverton
Edgar
0.425
0.347
0.279
— 3 <~m—3
dll
0.250
0.206
0.141 ,
Kevin
0.313
0.275
0.236
a Determined at a BD. 1.25 gm cm
VWC on plant available K.
Kuchenbuch, Claassen and Jungk (1986),
evaluated the effects of VWC on K uptake by onions and concluded that
decreasing VWC from 0.4 to 0.1 cm3 cm-3 decreased the effective
diffusion coefficient for K one order of magnitude.
In their study
they found K uptake by onions decreased according to a curvilinear
51
response function.
Similar results for K transport have been presented
by Barber (1985a), Nye and Tinker (1977), and Claassen and Jungk (1984).
Reductions in VWC result in a more tortuous diffusion path, increased
ionic strength, and decreased soil-root contact.
The present study was
not conducted in a manner to allow determination of the contribution of
each component.
However, the significant shifts in K uptake that are
evident between soils at the
same water potential, but dissimilar VWC,
does indicate that other soil properties (i.e. clay type, CEC) play an
important role in influencing phytoavailable K.
This is best seen in
comparing the Beaverton and Kevin soil series, which differed much more
in other soil properties and K uptake by plants grown on them than they
do in VWC.
It should also be pointed out that the current study was
conducted under conditions of minimal mass flow, which may have reduced
the magnitude of influence of water potential on K movement and uptake.
The interaction of temperature and moisture on K diffusion to ion
exchange resins have been documented by Schaff and Skogley (1982).
These results from experiments in which intact plants were used under
carefully controlled conditions provide further evidence of such
interactions.
Overall K uptake was not limited by VWC (within the
water potential range of -12 to -70 Kpa) until temperature exceeded
approximately 16 C on all soils (Table 22).
At greater temperatures
plant demand for K increased, and transport in the rhizosphere (i.e. K
diffusion) then became limiting (Figures 6 - 9).
Rhizosphere soil Kex concentrations closely reflect the influences
of temperature on plant K uptake.
The effects of temperature on K
transport in the rhizosphere have been discussed by Barber (1985a).
52
But in regard to changes in Kex the greatest influence is that directly
related to plant K demand.
Thus temperature governs the magnitude of
the chemical potential gradient induced by the plant which affects
rhizosphere soil Kex depletion gradients.
Effects of K Rate on Soil and Plant K (KRS)
In the KRS study, 200 grams of four soils were equilibrated with
one of five rates of K as KCL, in a complete factorial design.
Montana soils Amsterdam, Beaverton, Edgar, and Kevin were used with K
added at equivalent rates of 0, 50, 100, 200, and 400 Kg K Ha-1 on a
field basis, applied in a 20 ml aliquot.
Each soil was brought to a
moisture content equivalent to a water potential of - 33 Kpa and
allowed to equilibrate for 24 hours.
Prepared soils were packed into
cylinders (4.5 X 1.5 cm, BD 1.25 gm cm-3) and placed on a high flow
ceramic moisture plate.
- 33 Kpa.
Water potential was adjusted and maintained at
Pondera wheat seedlings five days old (0.75 gm), were placed
on the columns for 96 hours.
Plant K uptake and Kex concentration
profiles were determined as described previously.
Spring wheat seedlings generally increased their K uptake
(umol pot-1) with greater soil K application on all four soils (Table
25) . However, soils did not respond equally to K additions as indicated
by the significant interaction between SOIL*KRATE for K uptake (Table
26) . As K rate increased from 0 to 400 Kg ha-1, K uptake increased 24,
13, 14, and 7 umol pot-1 on the Amsterdam, Beaverton, Edgar, and Kevin
soil series respectively.
This is a 74 percent increase on the
Amsterdam soil, while only a 14 percent increase in K uptake on the
Kevin soil.
53
Table 25. Mean (n=3) plant K uptake by spring wheat as influenced by K
additions as KCL on four Montana soils at 24 C and -33 Kpa.
K Rate
Kg ha-1
Soil Series
Beaverton
Edgar
Amsterdam
Kevin
------- umol pot -I
0
50
100
200
400
32.24
36.30
42.21
46.55
56.21
32.30
35.32
38.58
43.01
48.92
38.21
43.95
49.92
56.32
52.14
54.54
53.91
55.62
58.41
62.04
4.15
4.62
3.85
5.21
LSD(0.05)
Table 26. Analysis of variance table for plant K uptake (umol pot-1)
by spring wheat as influenced by K addition (KRATE) for four
Montana soils (SOIL), 24 C and water potential - 33 Kpa.
Dependent Variable: K uptake
Source
Model
Error
Corrected Total
DF
Sum of
Squares
21
100
119
10906.9
84.9
10991.8
Mean
Square
519.8
0.87
Root MSE
1.49
F Value
599.30
C.V.
3.19
P > F
0.0001
K uptake Mean
46.60
Source
DF
Anova SS
Mean S
F Value
P > F
SOIL
KRATE
SOIL*KRATE
3
4
12
5614.3
4280.5
875.1
1871.4
1070.1
72.9
843.56
482.36
32.87
0.0001
0.0001
0.0001
Linear regression equations (SAS Institute, 1987) between plant K
uptake and K addition on four Montana soils are presented in Table 27.
All regression models indicate that K uptake was best explained by
quadratic function of K rate on the Amsterdam, Beaverton, and Edgar
soil series.
The generalized form was:
Y = C1 + C2 (X) + C3 (X2)
[6]
54
Table 27. Regression equations for dependent variable plant K uptake
(Y) and independent variable potassium addition (KRATE)
for four Montana soils 24 C and water potential - 33 Kpa.
Soil Series
Equation
R2
F
P>F
0.97
447
.0001
Y = 28.7 + I.IE-I(KRATE) - 1.4E-4(KRATE2)
0.96
288
.0001-
Y = 37.8 + I.SE-I(KRATE) - 2.8E-4(KRATE2)
0.94
188
.0001
Y = 53.8 + 2.IE-2 (KRATE)
0.78
95
.0001
'
Amsterdam
Ya = 32.2 + 9.OE-2 (KRATE) - 7.8E-5(KRATE2)
Beaverton
Edgar
Kevin
a Units: plant K uptake (Y), umol pot-1; KRATE, Kg ha-1.
Table 28. Analysis of variance table for Kex concentration (umol cm-3)
in the rhizosphere of spring wheat as influenced by distance
(D) and K addition (KRATE) on four Montana soils (SOIL).
Dependent variable: Kex
Source
Model
Error
Corrected Total
DF
Sum
Squares
Mean
Square
101
200
299
9329.58
18.20
9347.79
94.23
0.09
Source
DF
Anova SS
SOIL
KRATE
D
S0IL*KRATE
S0IL*D
KRATE*D
SOIL*KRATE*D
3
4
4
12
12
16
48
8204.67
341.38
664.55
41.76
50.78
11.71
14.70
F Value
Pr > F
1026.20
0.0001
Root MSE
0.301
C.V.
2.24
Kpx Mean
13.44
Mean S
. F Value
Er > F
2734.89
85.34
166.13
3.48
4.23
0.73
0.31
30042.65
937.52
1825.03
38.23
46.49
8.04
3.37
0.0001
0.0001
0.0001
0.0001
0.0001
0.0001
0.0005
55
Plant K uptake on the Kevin soil series indicated a linear response
function.
These results for the first three soils are comparable with
those of Nemeth (1975) using alfalfa which indicated K uptake generally
followed a quadratic response.
Statistical analysis of rhizosphere soil Kex concentration are
presented in Table 28.
Main effects of SOIL are highly significant
(pcO.OOOl) as are KRATE and D.
The dramatic effects of SOIL and D are
evident by the large Mean Squares for both terms.
Interaction
combinations also show high significance (P< 0.001).
Rhizosphere Kex concentration decreased with distance from the
bulk soil to the soil-root interface for all soils and K rates (Table
29).
As mean planar D decreased from 4.00 to 0.25 mm Kex concentration
on the Amsterdam decreased 3.85 umol cm-3, 26 percent, at the zero K
rate.
Differences between 0.25 and 4.00 mm Kex concentrations
increased with increasing K rate.
The relationship of Kex concentration with respect to distance
(D) could best be described by a square root function (Table 30), and
was highly significant across K rates and soils (P<0.006). The equation
had the general form:
Y = C1 + C2 (D0 -5)
[7]
For the Amsterxfem soil, as K rate increased the slope of the diffusion
gradient coefficient (d[Kex]/dD), representing change in Kex
concentration with distance, increased and was significant at the 0.05
level.
Kex.
Higher K rates, therefore increased the diffusion gradient of
This effect was noted on the Amsterdam and Beaverton soils.
56
Table 29. Mean (n=3) rhizosphere Kex concentration as influenced by
rhizosphere distance (D) and K rate, for four Montana soils,
temperature 24 C and water potential -33 Kpa.
Soil
Series
Distance
(mm)
0
50
K rate (Kg ha"-1)
100
200
400
- umol cm ^
Amsterdam
0.25
0.75
1.50
2.50
4.00
10.61
11.57
12.29
13.40
14.46
10.27
11.48
12.73
13.83
14.94
10.18
11.81
12.82
14.46
15.61
10.94
12.39
13.79
15.18
16.77
12.44
14.08
15.76
17.35
19.27
0.25
0.75
1.50
2.50
4.00
6.46
7.44
8.06
8.44
8.89
6.37
7.47
8.36
8.95
9.39
6.86
7.88
8.86
9.69
10.20
7.88
8.79
9.33
10.19
10.88
9.34
10.24
10.97
12.11
13.23
0.25
0.75
1.50
2.50
4.00
7.30
8.25
8.67
9.10
9.44
6.58
7.58
8.32
9.10
9.73
6.48
7.63
8.45
9.29
10.10
7.59
8.48
9.20
10.20
11.00
10.14
10.91
11.52
12.18
13.08
0.25
0.75
1.50
2.50
4.00
17.99
19.57
20.52
21.53
23.76
17.56
20.98
21.78
22.90
24.09
19.35
21.88
22.58 24.13
25.26
19.91
21.56
22.88
24.01
25.80
20.33
21.88
22.65
24.41
26.04
Beaverton
Edgar
Kevin
The diffusion gradient coefficient for the Edgar soil increased
with low K rates, but decreased at higher K rates.
For the Edgar
soil this decrease was highly significant between coefficients (P<
0.0001).
For the Kevin soil d [KexJZdD showed no significant changes
57
Table 30. Regression equations between rhizosphere distance (D) and
Kex (Y) at five rates of K addition for four Montana soils,
temperature 24 C and water potential - 33 Kpa.
Soil
Series
Ka
Rate
Equation
R2.
F
P>T
Amsterdam
0
50
100
200
400
Y
Y
Y
Y
Y
=
=
=
=
=
9.30 + 0.0811(D0 *5)
8.77 + 0.0994(D0 *5)
8.49 + 0.1149(D0 *5)
9.02 + 0.1229(D0-5I
10.15 + 0.1441(D0 *5)
0.997
0.997
0.993
0.999
1.000
974
1059
416
55734
61913
.0001
.0001
.0003
.0001
.0001
0
50
100
200
400
Y
Y
Y
Y
Y
=
=
=
=
=
5.87
5.62
5.89
6,97
7.97
+
+
+
+
+
0.0513(D0 -5)
0.0637(D0 -5)
0.0720(D0 *5)
0.0698 (D0 •5)
0.0822(D0*5)
0.964
0.960
0.971
0.994
0.995
80
72
133
489
628
.0029
.0035
.0014
.0002
.0001
0
50
100
200
400
Y
Y
Y
Y
Y
=
=
=
=
=
6.86
5.67
5.41
6.46
9.19
+
+
+
+
+
0.0435(D0 *5)
0.0664(D0 -5)
0.0757(D0 -5)
0.0726(D0 *5)
0.0609(D0 *5)
0.945
0.989
0.992
0.997
0.998
51
274
379
1058
1911
.0055
.0005
.0003
.0001
.0001
0
50
100
200
400
Y
Y
Y
Y
Y
=
=
=
=
=
16.18
16.50
17.98
18.28
18.43
169
60
76
271
305
.0010
.0058
.0032
.0005
.0004
Beaverton
Edgar
Kevin
+
+
+
+
+
0.1153(D0 -5)
0.1271(D0 -5)
0.1196(D0-5)
0.1190(D0-5)
0.1188(D0-5)
0.983
0.949
0.962 '
0.989
0.990
a K rates applied as KCl, Kg ha"1.
b units: distance (D) mm x(10"3) and Kex (Y) umol cm"3 .
with increasing K rates.
'
Thus on the Kevin soil, K rate did not
influence the Kex diffusion gradient coefficient.
A graphic representation of the influence of K rate on Kex
concentration with respect to distance is presented for these four
soils in Figures 10 - 12.
For the Edgar, and to a lesser extent on the
Amsterdam and Beaverton soils, an important feature is indicated in the
58
Figure 10. Response surface of mean Kex concentration as influenced by
rhizosphere distance and K addition, soil series Amsterdam.
Figure 11. Response surface of mean Kex concentration as influenced by
rhizosphere distance and K addition, soil series Beaverton.
59
Figure 12. Response surface of mean Kex concentration as influenced by
rhizosphere distance and K addition, soil series Edgar.
Figure 13. Response surface of mean Kex concentration as influenced by
rhizosphere distance and K rate, soil series Kevin.
60
mean surface response figures.
With the first K addition the Kex
concentration of the first rhizosphere distance decreased.
The effect
of increased Kex depletion as a function of K rate was significant
for two of the three soils and represents a priming effect that low
K additions has on potential rhizosphere K depletion.
Initial soil Kex concentration and d[Kex]/dD values for each soil
and K rate are listed in Table 31.
By substituting the initial Kex
concentration (time=zero) into the regression equation an estimate was
Table 31. Initial soil Kex concentration (Kex), diffusion gradient
(d[Kex]/dD) and diffusion distance for four Montana soils,
temperature 24 C and water potential -33 Kpa.
Soil
Series
K rate
(Kg Ha-1)
Kex
(umol cm-3)
^[KexV d D
Diffusion3
distance (mm)
Amsterdam
0
50
100
200
400
11.52
15.27
16.32
17.42
20.89
0.0811
0.0994
0.1149
0.1229
0.1441
4.2
4.3
4.6
4.7
5.4
0
50
100
200
400
8.93
9.72
10.89
11.77
12.84
0.0513
0.0637
0.0720,
0.0688
0.0822
3.5
4.1
4.8
4.9
5.5
0
50
100
200
400
9.81
10.41
10.92
11.74
13.95
0.0435
0.0664
0.0757
0.0757
0.0609
4.6
5.1
5.2
5.3
6.1
0
50
100
200
400
22.94
23.64
24.27
25.53
27.15
0.1153
0.1271
0.1196
0.1190
0.1188
3.4
3.2
2.9
3.6
5.1
Beaverton
•
Edgar
Kevin
a Diffusion distance (mm) calculated from equation of d[Kex]/dD
and initial Kex.
61
made on the extent into the rhizosphere to vSiich Kex was depleted.
These results indicate that increased K rates, in general, increased the
diffusion distance of Kex. With no added K, Kex diffusion distances
ranged from 3.4 to 4.2 mm, while at the highest K rate it ranged up to
5.1 to 6.1 mm across soils.
This effect suggests that recently added K
is more mobile in soils than native K.
By intergrating the regression equation representing Kex as a
function of distance, from the soil-root interface to the estimated
distance of diffusion, the estimated soil Kex flux can be calculated.
SKex flux in general increased with increasing K rate for all
soils (Table 32).
Only on the Beaverton soil at the highest K rate did
SKex flux actually decrease.
A comparison of the difference between plant and soil flux (Delta
K Flux) indicates that K additions resulted in increased discrepancies
between the two values.
However, examining the values for % Kex
utilized (Table 32), there is a trend toward increased utilization of
Kex as K rate increased.
Amsterdam and Kevin soils.
This trend was clearly evident on the
Qn the Beaverton and Edgar soils the % Kex
utilized initially increased with K additions, but decreased at higher
K levels.
These results indicate that adding moderate amounts of K to
soils generally increased the availability (plant utilization) of Kex
in the rhizosphere of spring wheat.
In summary, four points can be made from the results of the KRS
study. They are: (I) plant K uptake as influenced by K additions
responded according to quadratic functions; (2) diffusion gradients of
Kex (d[Kex]/dD) were highly influenced by K rate and there were no
62
Table 32. Mean Kex plant, soil and difference flux values as influenced
by five K additions on four Montana soils, 24 C and water
potential of - 33 Kpa.
Soil
Series
K
Rate
Plant
Flux
Kg ha-1
SKex
Flux
'■
Delta K
Flux
^ex
Utilized
nmol ItT 2 s-1 -
(%)
Amsterdam
0
50
100
200
400
61.9
69.6
80.9
89.2
107.7
21.8
27.5
36.0
38.8
56.9
40.0
42.0
45.1
50.3
50.7
35.2
39.6
44.4
43.6
52.9
0
50
100
200
400
52.1
67.7
73.9
82.4
93.7
10.7
16.8
23.8
24.1
20.5
41.8
50.8
50.1
58.2
73.2
20.4
24.8
32.3
29.3
21.9
0
50
100
200
400
73.2
84.1
95.6
107.9
99.9
13.5
23.8
28.4
27.3
28.6
• 59.7
60.3
67.3
80.5
78.0
18.4
28.4
30.3
25.3
21.9
0
50
100
200
400
104.5
103.3
106.6
111.9
118.9
22.3
22.3
23.2
26.6
45.6
82.0
81.0
83.3
85.3
73.2
21.4
21.6
21.8
23.8
38.4
Beaverton
Edgar
Kevin
consistent trends across soils; (3) Kex depletion in the near
rhizosphere (0.25 ram) was enhanced by K additions; and (4) small K
additions increased Kex utilization on soils initially, but higher
levels affected soils differently.
Spring wheat K phytoavailability responded to K fertilizers
according to accepted theories.
However, of the total plant K flux,
only 18 - 50 % was explained by fluxes of soil Kex.
These results
are consistent with those of Kuckeribuch et al. (1986) who have shown a
major portion of K uptake by rape was not explained by soil fluxes of
63
Kex.
Therefore, a majority of plant available K came from soil K forms
other than Kex, most probably from Knex and Km^n . Although no direct
evidence for this was obtained in this experiment, these results
strongly suggest these K forms are plant available.
Further, even with
the addition of K fertilizer, and concurrent enhancement of the Kex,
plants continue to utilize K other than Kex on a majority of soils.
The depression effect of low K rates on soil Kex in the near
rhizosphere (< 0.5 mm), and related influence on d[Kex]/dD for the
Amsterdam, Beaverton and Edgar soils , are not easily explained.
are three hypothesis for this phenomenon.
There
They are: (I) plant
deficiency of chloride on these soils, thus a subsequent stimulation by
KCL additions; (2) a priming effect of K additions on the Knex and Km^n
in the near rhizosphere; and (3) an increase in ionic strength in the
soil solution due to Cl which facilitates K dissolution from Knex and
Kmin forms.
Although chloride concentrations are lower on the Edgar and
Beaverton soils (Table 33), these results do not seem completely
plausible, due to the low requirement of Cl by spring wheat (Fixen
1986).
The priming effect is a possibility, but this research provides
Table 33. Soil extractable chloride and electrical conductivity (EC)
on four Montana soils.
Soil Series
Amsterdam
Beaverton
Edgar
Kevin
Chloride
EC
mg kg-1
S Hf'
49.7
33.6
32.6
48.8
15.5
8.5
6.2
12.5
64
no tangible evidence for support.
The influence of added K on ionic
strength may, however, be an important relationship.
Mclean and Watson
(1985), postulated that 'mass flow triggered' diffusion flew may
increase K availability.
In this process, mass flow of 'ions' to the
near rhizosphere leads to an excess of major Cations
in the soil solution.
plant absorption.
(ie. Ca, Mg, Na)
Potassium is removed from the solution because of
The result is stimulated removal of K from the
rhizosphere due to increased ionic strength. In the PRS study, mass
flow was near zero, therefore KCL additions were the main mechanism
enhancing soil K dissolution.
Supporting evidence for this hypothesis
is the low EC values reported for the Edgar and Beaverton soils
relative to the other two soils (Table 33).
Kuchenbuch and Jungk
(1984) have reported similar results with the application of other
fertilizer salts.
Additional research is needed to elucidate this ■
process as a mechanism of stimulating K release in the rhizosphere.
65
SUMMARY AND CONCLUSIONS
Soil characteristics and rhizosphere environment conditions
greatly influence the phytoavailability of K.
Soil characteristics
which are strongly related to plant available K are: clay content, Kex
diffusion gradient coefficient, and cation exchange capacity. Spring
wheat in these studies utilized part of Kex, but quantities differed
across soils.
Potassium was obtained from other K forms, presumably
Knex and KmJjn in the near rhizosphere over Kex at greater distances.
Potassium from these soil forms is thus apparently plant available,
within time periods of hours, to spring wheat seedlings.
Release of
Knex appears to depend on the characteristics of the soil solution and
the experimental conditions.
Temperature had a large dynamic influence on spring wheat K
uptake.
8 C.
Little or no K was absorbed by wheat seedlings across soils at
Increasing temperature caused an exponential increase in K uptake
to the highest experimental treatment (24 C). Temperature affected
plant metabolism and nutrient absorption more than K equilibria and
transport in the soil.
Water potential had little influence on K uptake until temperature
reached 16 C on any soil.
This interaction is highly significant and
indicates that K absorption is not limited by transport until K demand
exceeds a certain threshold (when mass flow is near zero). Until that
critical demand is reached, all phytoavailable K is obtained from the
near rhizosphere.
With increased temperature there is increased demand
66
on K at greater rhizosphere distances.
Potassium additions increased spring wheat K uptake nonuniformly
across soils (Table 25).
Soils with low plant K uptake (< 40 umol
pot-1) at the zero K rate level never reached maximum K absorption with
K additions, as did soils with higher zero rate levels.
Data on soil
Kex rhizosphere K concentrations indicated K additions enhanced the
availability of Kex supplies in the near rhizosphere.
occurred on two of four soils.
This effect
Generally as K rate increased, wheat
utilized a greater portion of Kex over other soil K forms, but was soil
dependent.
Spring wheat phytoavailable K is very sensitive to K soil
equilibria, as governed by several soil parameters.
But the role of
environmental factors is critical in regulating both plant K demand and
soil K supply processes.
Thus to develop a general overall model for
predicting K requirement and uptake by spring wheat seedlings it would
be necessary to combine the effects of these two major systems.
The
present study was not designed to be a mechanistic approach which
accounts for individual components of both systems, such as K
selectivity coefficients and the effects of temperature on MichaelisMenten kinetics.
Such an approach requires multiple formulas for both
soil and plant parameters, each with several variables.
The approach used in this study was to consider the system as a
Vihole, identify those soil components which are relatively strongly
influential in plant K availability and uptake, and determine or
calculate the strength of the relationship.
Although correlation does
not imply cause and effect, it does suggest components which in the
67
overall system influences plant available K.
The use of intact spring
wheat seedlings provides a stronger basis that other less direct
methods for correlating plant K uptake directly to soil components.
Soils can be compared based on differences in soil K quantity and
intensity characteristics and soil-root interface effects.
With this approach, multiple regression equations from the ERTS
and the TMS studies were combined into an overall equation which
predicts spring wheat phytoavailable K as influenced by soil and
environmental factors (Table 34).
Such a model is limited, since it is
restricted to soil factor limits inherent in the twenty soils and
within the experimental conditions.
Furthermore, only four soils were
used in this model, so it can be considered as a "first approximation"
only.
Multiple linear regression models were prepared by calculating the
predicted plant K uptake (EPKI) and combining it to the original model
developed in the TMS study.
Since there was significant interaction
between temperature and water potential with soils, cross variables
containing EEKE were added to the model.
Results of forward stepwise
regression resulted in a highly significant model containing four
variables (Table 34).
The equation took the generalized form:
Y = -C0 + C1 (EPKI) + C2 (EPKE) (Kpa) - C3 (Kpa2) (3.0E-4 (T2 *9)) +
C4 (EPKE)(3.OE-4(T2 •9))
[9]
As in the TMS study the temperature factor (T) was incorporated in
cross effects both as linear and exponential components.
Water
potential (Kpa) occurs in two variables as a linear and as a
quadratic term.
The term with water potential squared and
68
temperature exponential retained its negative coefficient from the
original model in the TMg study.
All variables in the model had
significant regression coefficients.
This model predicts 94 % of the variation in plant K uptake by
spring wheat seedlings on these four soils.
Such an empirical model
within the experiment boundary conditions of soil and environment
relates soil and environmental factors to plant K availability.
Such a
model has the potential to help one predict K uptake by spring wheat
seedlings on numerous soils across a wide range of growing conditions.
Table 34. Multiple linear regression model for the influence of
temperature (T), water potential (KPA), and estimated
phytoavailable K index (EEKI) on spring wheat K uptake.
Dependent Variable: Plant K uptake umol pot--*Analysis of Variance
Source
DF
Model
Error
C Total
4
175
179
Root MSE
Dep Mean
C.V.
Variable3
INTERCEP
EPKE *TT
KPA*KPA*TT
KPA*T
EEKI
Sum of
Squares
24465.62
1464.67
25930.30
2.89
12.81
22.58
Parameter
Estimate
DF
I
I
I
I
I
-5.88475
1.65e-2
—8.31e—5
7.49e-3
0.10218
Mean
Square
6116.40
8.36
F Value
Brob>F
730.790
0.0001
R-square
Adj R-sq
0.9435
0.9422
Standard
T for HO:
Error
Barameter=O
0.982695
0.000352
0.000008
0.001241
0.023184
-5.9
46.7
-9.4
6.0
4.4
Brob > |T|
0.0001
0.0001
0.0001
0.0001
0.0001
a Variable description: REST, estimated phytoavailable K index; KPA,
soil water potential Kpa; T, temperature C; and
TT, exponential temperature component TD=
5.OE-S(T)2 *91.
69
Further refinements can be added as more soils and conditions are
studied.
Further research is needed to correlate this method of assessing
soil fertility (using intact seedlings under controlled growth
conditions) with K uptake of plants grown under greenhouse of field
conditions.
Such results could be employed to help predict plant K
requirements, which on the Northern Great Plains appear to be highly
seasonally dependent (Skogley and Haby, 1981 and Veeh and Skogley,
1986).
Although determining these soil characteristics would be
impractical on a yearly basis, it would prove useful in establishing
baseline data on major soil series cropped to spring wheat.
Further,
with refinement of proper techniques, other plant species could be
included, as has been done here with spring wheat and previously with
rape.
Results of the KRS study provide an estimate of the upper limit of
spring wheat K demand under these growing conditions.
The results
further elucidated the soil phenomenon of Kex release in the near
rhizosphere, triggered or primed by addition of KCL. Although the
process is yet unclear, the hypothesis of diffusion aided mass flow
may provide an explanation for this effect.
Since the plasma membrane of a root hair acts as an ion selective
membrane, ion absorption is specific.
Potassium and nitrate are
absorbed while calcium and other multivalent cations are excluded.
These ions remain in the soil solution and accumulate if mass flow
becomes significantly great.
With the experimental conditions in this
study, mass flow was minimal and yet calcium and magnesium did
70
accumulate.
At the same time as K was being removed from the soil-root
interface soil solution a counter ion gradient of protons entered the
rhizosphere.
Increased proton concentration would be expected to
influence K exchange and the weathering of soil minerals.
These
effects were not directly accounted for in the present studies.
The two processes, divalent cation accumulation and proton efflux,
radically alter the ionic strength and ion speciation in the near
rhizosphere soil solution.
Other researchers (Sparks ,1980; Yang,
1987; and Jardine and Sparks, 1984) have described K release
thermodynamically using soil solution analysis.
However, none of these
researchers have examined the soil system under conditions where: (I) K
in solution was undergoing continuous depletion; (2) solution divalent
cation concentration is static or increasing; and (3) proton
concentration is increasing.
Such an experiment, although extremely
difficult to design, would yield a wealth of information about soil K
equilibria and K phytoavailability.
An overall model of phytoavailable K for Montana soils, as
summarized by this research is presented in Figure 14.
It suggests
that as much as 80 percent of plant K uptake is the result of K release
in the near rhizosphere (<0.5 mm) from Knex and Kmin forms.
The quantity of K released (Twenty Montana soil study) was highly soil
dependent indicating either inherent differences in the quantity of K
in these forms for a specific soil and/or the .rate of release form
these forms.
Other researchers (Reitemeier et al., 1988; Bertsch and Thomas,
1985; Barber and Mathews (1962); and Talibudeen et al., 1978) have
71
PHYTOAVAILABLE POTASSIUM
„
2
10
Log Distance (um)
3
10
10
'
10
10
H----- 1----- h
5
t
Root Surface
Root Hair
0 - 8 0 % of K uptake
Zone of K release from
nonexchangable forms and
K - minerals
20 - 90 % of K uptake
Zone of K release from
exchangeable forms
< 5 % of K uptake
Zone of K depletion of solution K
Figure 14.
Model of phytoavailable K in the rhizosphere of spring
wheat for Montana soils.
suggested K release from illite and K minerals is plant available,
however none have actually quantified plant and soil K fluxes.
It is
my hypothesis that K is released from micas, hydrous micas, and the
surfaces of feldspars of particle sizes ranging from 10 to 0.5 um in
the near rhizosphere and accounts for a significant portion of plant K
uptake.
Potassium release is due to (I) intense biological depletion
of soil solution K; (2) root exudation of protons and organic acids;
and (3) accumulation of divalent cations in the soil solution in the
near rhizosphere.
The total quantity of K and more importantly rate of
K release is governed by the quantity of K-minerals and extent of
chemical weathering which has occurred.
72
Evidence for support of this hypothesis can be divided into plant
and soil aspects.
Plant roots are capable of depleting K in the soil
solution (Table 15).
Nye and Tinker (1977) reviewed the literature and
reported that in the rhizosphere plant roots of many species exude
organic compounds and that roots are capable of reducing the pH at the
soil root interface to a value of 4.0.
In terms of soil. Song and Haung (1983) found that in the
presence of citric and oxalic acids, K release from K-bearing minerals
and K dissolution increase and the weathering sequence was biotite >
microcline = othoclase > muscovite.
von Reichenbach and Rich
(1969) have found that the rate of K release was faster from soil
particles 2 - 5 urn, intermediate for particles 5 - 20 urn and slowest
for particles less than 0.2 urn.
In general Montana soils, in
comparison to soils of the midwest and southern United States, have
been weathered less.
This is due to the ustic moisture and frigid
temperature regimes which results in decreased chemical weathering of
silt and coarse clay sized K-bearing minerals.
Thus in the presence of
a plant root, K is more likely on these Montana soils to be released
from micaceous and feldspar materials in the near rhizosphere.
Any
soil test which measures phytoavailable K must be able to assess K
release rates from these soil K-bearing minerals in order to provide a
useful means of predicting small grain K requirements.
73
LL'I'EHMURE CITED
74
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80
APPENDICES
APPENDIX A
location Description, Ehysical and Chemical
Characteristics of Twenty Montana Soils
82
Table 35. Soil series, texture and location description of twenty
Montana soils.
Soil Series
Texture
Amsterdam
silt loam
Gallatin
Bear Paw
clay
Chouteau
Beaverton
silty clay loam
Gallatin
Bozeman
silty clay loam
Gallatin
Chanta
loam
Prairie
Cherry
clay loam
Garfield
Chinook
sandy loam
Broadwater
Creston
loam
Flathead
Edgar
loam
Rosebud
Evanston
clay loam
Chouteau
Flathead
sandy loam
Flathead
County
Fort Collins loam
Rosebud
Gerber
clay
Cascade
Kevin
clay loam
Pondera
Manhatten
silt loam
Gallatin
Rothiemay
clay loam
Teton
Round Butte
silt loam
Lake
Stryker
silty clay loam
Flathead
Tanna
loam
Stillwater
Vamey
sandy clay loam
Madison
location Description
NE 1/4, Sec 7,
T2N, R5E
SW 1/4, Sec 12,
T28N, R15W
SE 1/4, NE 1/4, Sec
T2S, R 6E
SW 1/4, Sec 31,
T2S, R5E
SW 1/4, Sec 20 r
T21N, R52E
NW 1/4, Sec 4,
T19N, R34E
SW 1/4, SW 1/4, Sec
T5N, R2E
SE 1/4, Sec 33,
T29N, R20W
NE 1/4, Sec 20,
T6N, R24E
SW 1/4, Sec 34,
T29N, R5E
SW 1/4, SW 1/4, Sec
T29N, R22W
SE 1/4, Sec 15,
T6N, R41E
NW 1/4, Sec 10,
T22N, R8E
NW 1/4, Sec 8 ,
T29N, R2W
SW 1/4, Sec 7,
TIN, R3E
SE 1/4, Sec 26,
T22N, R2W
SE 1/4, NE 1/4, Sec
T22N, R21W
NW 1/4, SW 1/4, Sec
T30N, R22W
NW 1/4, Sec 21,
T3N, R20E
NE 1/4, Sec 9,
T3S, RlW
22,
35
15,
32,
17,
83
Table 36. Soil series name and classification and family of twenty
Montana soils.
Soil Series
Soil Taxonomic Classification
Amsterdam
Typic Cryoborolls
Fine-silty
Bear Baw
Typic Argiborolls
Fine, Montmorillinitic
Beaverton
Typic Argiborolls
Loamy-skeletal, mixed
Bozeman
Badhic Argiborolls
Fine silty
Chanta
Aridic Haploborolls
Fine-loamy over sand, mixed
Cherry
Typic Ustpchrepts
Fine-silty, mixed, frigid
Chinook
Aridic Haploborolls
Coarse, loamy, mixed
Creston
Udic Baploborolls
Coarse-silty, mixed
Edgar
Ustollic Cairiborthids
Fine-loamy
Evanston
Aridic Argiborolls
Fine-loamy, mixed
Flathead
Bachic Udic Haploborolls
Coarse-loamy, mixed
Fort Collins
Ustollic Haplargids
Fine-loamy, mixed, mesic
Gerber
Udorthentic Chramusterts
Fine, Montmorillinitic, frigid
Kevin
Aridic Argiborolls
Fine, Montmorillinitic
Manhatten
Typic Calciborolls
Coarse loamy
Rothiemay
Aridic Calciborolls
Fine-loamy, mixed
Round Butte
Xerollic Natragids
Fine, mixed frigid
Stryker
Aquic Eutrdboralfs
Fine-silty, mixed
Tanna
Aridic Argiborolls
Fine-montmorillinitic
Vamey
Aridic Argiborolls
Fine-loamy, mixed
84
Table 37. Exchangeable cation concentrations for twenty Montana soils
as determined by 1.0 N ammonium acetate.
Soil Series
K
Ca
Mg
Na
cmol Kg 1 ---Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
1.426
1.919
0.825
1.742
0.955
4.812
2.319
2.062
2.129
0.757
2.756
3.919
4.090
3.763
2.890
0.039
0.061
0.076
0.052
0.067
Cherry
Chinook
Creston
Edgar
Evanston
1.364
1.398
0.619
0.887
1.323
1.337
4.268
1.434
0.859
0.925
3.412
2.178
1.372
3.317
3.702
0.049
0.062
0.056
0.028
0.061
Flathead
Fort Collins
Gerber
Kevin
Marihatten
0.877
0.988
2.049
2.115
1.890
1.722
0.431
2.380
1.208
4.707
2.140
2.640
6.730
3.407
2.707
0.128
0.038
0.061
0.049
0.056
Rothiemay
Round Butte
Stryker
Tanna
Vamey
1.483
0.778
0.822
0.942
1.110
3.125
1.096
2.948
3.547
4.448
3.057
1.137
6.603
1.913
2.214
0.081
0.103
0.708
0.038
0.029
1.276
0.014
1.14
0.021
2.326
0.031
1.35
0.044
3.197
0.036
1.14
0.052
0.194
0.094
4.78
0.006
N=4
Mean
STD DEV
CV %
ISD (0.05)
85
Table 38. Soil pH, organic matter, calcium carbonate and electrical
conductivity of twenty Montana soils.
Soil Series
PH
(1:1)
CM
CACO3
EC
%
%
S nfl
Amsterdam
Bear Baw
Beaverton
Bozeman
Chanta
8.24
7.93
5.62
7.34
6.62
2.37
3.22
5.37
3.19
1.78
5.47
0.72
0.49
0.66
0.17
15.5
13.4
8.5
13.8
8.4
Cherry
Chinook
Creston
Edgar
Evanston
7.35
8.34
5.69
6.81
6.35
3.13
1.97
5.41
1.40
2.05
0.44
11.33
0.13
0.14
0.34
10.0
14.1
35.6
6.2
11.5
Flathead
Fort Collins
Gerber
Kevin
Manhatten
7.18
6.13
6.78
6.92
8.15
4.80
1.27
2.62
3.13
2.40
0.25
0.26
0.72
0.42
4.04
16.5
8.0
26.6
12.4
14.0
7.54
6.05
7.88
8.24
8.13
4.26
2.39
3.58
1.92
1.68
1.60
0.28
2.06
3.70
5.03
35.0
11.8
64.5
12.4
15.9
2.89
0.11
2.95
0.12
1.92
0.17
9.21
0.25
Rothiemay
Round Butte
Stryker
Tarma
Vamey
N=4
Mean
STD DEV
CV %
ISD (0.05)
7.17
0.087
1.28
0.13
17.7
4.20
23.73
5.95
-
86
Table 39. Soil particle size analysis as determined by pipette (Gee and
Bauder, 1986) on twenty Montana soils.
Soil Series
< 50
Particle Size Fraction (um)
50 - 20
20 - 5
5-2
■
gm Jxy
> 2
—— —
Amsterdam
Bear Baw
Beaverton
Bozeman
Chanta
161
202
140
171
356
338
99
244
277
290
194
175
225
195
154
80
162
58
69
37
224
359
328
286
162
Cherry
Chinook
Creston
Edgar
Evanston
216
700
493
527
360
212
90
194
170
169
218
58
161
91
147
119
28
46
27
86
233
122
104
182
234
Flathead
Fort Collins
Gerber
Kevin
Marihatten
565
552
182
306
210
121
178
130
133
415
163
104
120
169
151
54
27
98.
108
74
95
136
467
282
146
Rothiemay
Round Butte
Stryker
Tanna
Vamey
338
113
106
476
618
179
252
141
131
61
140
389
459
128
66
87
125
156
71
26
253
119
136
193
226
34.0
0.75
6.5
3.8
19.8
1.07
5.4
2.2
17.6
1.01
4.8
1.9
N=3
Mean
STD DEV
CV %
ISD (0.05)
7.7
0.40
5.2
0.9
21.5
1.01
4.7
1.8
87
Table 40. Saturated paste pH, cation concentration and potassium
activity ratio (AR) of twenty Montana soils.
Soil Series
PH
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
8.41
8.17
6.12
8.70
7.32
10.6
29.5
4.1
18.8
19.5
Cherry
Chinook
Creston
Edgar
Evanston
8.26
8.59
5.42
7.71
6.52
Flathead
Fort Collins
Gerber
Kevin
Marihatten
Rothiemay
Round Butte
Stryker
Tanna
Vamey
N=4
Mean
STD DEV
CV %
ISD (0.05)
K
Ca
----mg L--*-
Mg
AR
48.5
64.8
23.9
57.5
23.6
4.3
11.0
6.0
8.4
11.1
0.104
0.200
0.039
0.143
0.142
18.8
39.4
35.2
14.0
23.9
21.7
47.2
284.6
29.4
38.5
6.9
7.1
33.0
10.7
12.9
0.170
0.326
0.131
0.102
0.158
8.69
6.91
8.19
7.73
8.29
28.4
24.5
21.3
39.9
22.5
149.9
18.0
56.1
38.7
56.3
24.8
10.3
14.3
10.3
4.6
0.128
0.187
0.131
0.291
0.210
7.56
6.63
8.45
8.28
8.94
24.8
19.7
23.8
13.6
11.3
207.8
32.9
306.2
65.1
61.4
21.0
4.6
49.5
6.9
3.3
0.113
0.201
0.075
0.109
0.114
7.74
0.116
1.50
0.16
22.2
1.48
6.68
2.10
13.7
1.25
9.53
1.77
0.174
0.058
4.41
0.012
81.6
5.58
6.83
7.89
88
sI
I
Table 41. Exchangeable and nonexchangeable soil potassium as determined
by magnesium chloride and sodium tetraphenyl boron, and
nitric acid respectively.
HNO3
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
4.154
7.002
2.219
6.232
3.684
3.68
3.90
2.34
4.88
3.10
14.40
15.12
13.81
16.68
14.70
Cherry
Chinook
Creston
Edgar
Evanston
5.510
6.409
2.559
3.704
4.215
3.29
1.94
0.95
3.30
5.69
16.78
13.81
12.56
15.09
15.95
Flathead
Fort Collins
Gerber
Kevin
Marihatten
4.072
4.488
6.838
8.855
6.389
0.55
3.15
4.15
4.88
3.38
14.61
14.83
17.23
15.62
16.48
Rothiemay
Round Butte
Stryker
Tanna
Vamey
3.894
6.041
2.805
3.411
3.486
2.05
2.30
0.88
3.11
1.37
15.09
12.74
12.74
14.85
13.81
4.798
0.307
6.42
0.255
2.95
0.15
5.10
0.32
14.02
1.57
11.2
0.62
M 3Cl2
I
Soil Series
N=4
Mean
STD DEV
CV %
ISD (0.05)
89
Table 42. Soil extractable phosphorus as determined by Bray and
Olson extraction methodologies for twenty Montana soils.
Soil Series
BRAY P
OISON P
---------mg Kg-1 — --------
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
37.0
136.3
118.7
80.5
43.8
10.6
53.4
40.5
31.2
17.4
Cherry
Chinook
Creston
Edgar
Evanston
41.1
28.2
113.1
37.5
54.6
20.7
30.0
40.2
10.9
29.9
Flathead
Fort Collins
Gerber
Kevin
Manhatten
117.5
61.5
72.5
92.6
96.6
21.4
25.2
33.9
43.5
11.7
Rothiemay
Round Butte
Stryker
Tanna
Vamey
101.8
78.8
70.7
48.7
96.3
41.5
31.1
28.6
14.7
31.0
N=4
Mean
STD DEV 1
CV %
ISD (0.05)
76.4
2.84
3.72
18.3
28.4
0.37
1.31
1.44
90
Table 43. Soil solution cation concentration on a solution basis and
potassium activity ratio (AR) of twenty Montana soils as
determined by immiscible liquid displacement (Mubarak and
Olson, 1976).
Soil Series
K
Ca
Mg
AR
---- m m o l ----Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
0.57
0.96
0.24
1.16
0.81
11.06
8.16
26.94
20.14
3.13
1.56
2.10
17.25
0.88
2.33
0.160
0.300
0.037
0.254
0.349
Cherry
Chinook
Creston
Edgar
Evanston
1.08
1.85
1.31
0.73
0.51
16.16
10.26
35.77
' 5.55
8.83
4.15
2.40
10.12
3.69
1.33
0.239
0.520
0.194
0.242
0.160
Flathead
Fort Collins
Gerber
Kevin
Manhatten
1.31
1.17
0.95
1.88
0.84
16.87
4.05
10.24
8.28
9.02
5.28
3.76
4.22
4.08
1.26
0.278
0.421
0.251
0.536
0.263
Rothiemay
Round Butte
Stryker
Tarma
Vamey
1.17
0.57
0.86 ,
2.28
0.61
40.42
5.18
30.95
5.20
12.82
9.09
1.30
23.97
2.09
1.45
0.167
0.224
0.116
0.844
0.162
1.05
0.023
2.23
0.21
16.91
6.30
3.73
3.89
N =4
Mean
STD DEV
CV %
LSD (0.05)
4.97
0.181
3.63
1.14
0.285
0.008
3.41
0.051
91
Table 44. Soil solution cation concentration and potassium activity
ratio (AR) of twenty Montana soils at 0.33 Bpa on a soil mass
basis as determined by immiscible liquid displacement
(Mjbarak and Olsenz 1976).
Soil Series
K
Ca
Mg
AR
enrol Kg-1 —
.Amsterdam
Bear Paw _
Beaverton
Bozeman
Chanta
0.0140
0.0258
0.0066
0.0304
0.0149
0.272
0.218
0.729
0.526
0.057
0.0384
0.0565
0.4675
0.0230
0.0426
0.025
0.049
0.006
0.041
0.047
Cherry
Chinook
Creston
Edgar
Evanston
0.0267
0.0277
0.0277
0.0119
0.0106
0.400
0.153
0.753
0.089
0.183
0.1031
0.0360
0.2134
0.0598
0.0278
0.037
0.063
0.028
0.030
0.023
Flathead
Fort Collins
Gerber
Kevin
Marihatten
0.0298
0.0172
0.0261
0.0422
0.0197
0.384
0.059
0.280
0.185
0.210
0.1205
0.0552
0.1156
0.0915
0.0295
0.042
0.051
0.041
0.080
0.040
Rothiemay
Round Butte
Stryker
Tanna
Vamey
0.0273
0.0179
0.0287
0.0413
0.0093
0.938
0.162
1.032
0.094
0.194
0.2114
0.0410
0.8007
0.0379
0.0221
0.025
0.039
0.021
0.113
0.020
0.0228
0.0005
2.19
0.004
0.346
0.012
3.54
0.022
0.129
0.004
3.29
0.029
0.038
0.0012
1.94
0.0071
N=4
Mean
STD DEV
CV %
ISD (0.05)
92
Table 45. Moisture contents of twenty Montana soils at - 0.15
- 0.33,- 0.66 and - 1.00 Kpa water potential.
Soil Series
-0.15
Water Potential
(KPa)
—0.33
—0. 66
-1.00
'O
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
32.33
29.36
34.69
33.83
23.16
24.61
26.78
27.07
26.11
18.26
21.01
22.89
24.03
22.85
14.20
18.48
20.69
18.64
19.29
12.71
Cherry
Chinook
Creston
Edgar
Evanston
29.43
20.80
29.43
20.20
23.13
24.78
14.97
21.06
16.17
20.83
22.25
13.40
18.06
17.32
15.54
18.40
11.98
15.29
12.45
15.60
Flathead
Fort Collins
Gerber
Kevin
Marihatten
30.70
17.83
29.93
25.26
34.03
22.79
14.65
27.38
22.37
23.34
19.13
11.68
24.95
20.01
19.74
16.26
10.39
23.76
16.03
18.96
Rothiemay
Round Butte
Stryker
Tanna
Varriey
25.76
37.43
37.20
21.26
19.40
23.21
31.40
33.36
18.11
15.18
20.72
26.51
28.96
15.33
14.31
19.26
22.41
24.89
15.17
12.84
27.76
1.03
3.72
1.71
22.62
0.58
2.58
0.97
19.25
0.59
3.05
3.54
17.48
0.76
4.32
2.96
N=3
Mean
std dev
CV %
ISD (0.05)
93
Table 46. Moisture contents (gm Kg 1J of twenty Montana soils at
- 2.00, - 5.00, and - 15.00 Kpa water potential.
Soil Series
- 2.00
Water Potential (I^a)
- 5.00
- 15.00
%
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
17.38
21.00
21.63
19.61
10.68
14.32
17.55
17.19
15.92
8.18
12.76
15.88
16.62
15.36
8.06
Cherry
Chinook
Creston
Edgar
Evanston
16.71
11.17
14.06
11.29
15.45
12.54
9.62
10.31
9.55
11.54
11.16
8.81
9.60
8.37
10.88
Flathead
Fort Collins
Gerber
Kevin
Manhatten
15.17
9.21
24.36
17.57
15.56
11.13
7.83
20.65
13.57
12.66
10.92
6.59
18.91
11.89
12.15
19.31
15.65
. 21.31
13.11
11.63
15.43
10.21
14.18
10.65
11.09
14.47
8.68
11.34
9.44
11.04
16.09
0.36
2.22
0.59
12.70
0.57
4.45
0.93
11.60
0.72
6.19
1.19
Rothiemay
Round Butte
Stryker
Tanna
Vamey
N=4
Mean
STD DEV
CV %
ISD (0.05)
94
Table 47. Soil, silt, and clay and for twenty Montana soils as
determined by hydrometer (Gee and Bander, 1986).
Soil Series
Sand
Silt
Clay
gm Kg 1
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
182
246
196
199
342
536
303
463
503
473
281
451
341
297
184
Cherry
Chinook
Creston
Edgar
Evanston
232
572
446
409
352
453
256
420
350
356
314
170
134
240
290
Flathead
Fort Collins
Gerber
Kevin
Marihatten
576
506
206
269
202
313
333
316
386
576
HO
160
477
344
220
Rothiemay
Round Butte
Stryker
Tanna
Vamey
342
139
149
439
596
353
640
570
340
203
304
220
280
220
200
330
19
5.7
31
407
21
5.2
35
262
17
6.4
N=3
Mean
STD DEV
CV %
ISD (0.05)
28
95
Table 48. Available water at four water potential ranges for twenty
Montana soils.
Soil Series
0.33-15.00
0.33-5.00
0.33-2.00
0.33-1.00
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
11.85
10.90
10.45
10.74
10.20
10.29
9.23
9.88
10.18
10.08
7.23
5.77
5.43
6.50
7.58
6.13
5.09
4.09
6.82
5.55
Cherry
Chinook
Creston
Edgar
Evanston
13.61
6.15
11.46
7.80
9.95
12.23
5.35
10.75
6.61
9.28
8.06
3.80
7.00
4.88
5.38
6.37
2.99
5.77
3.71
5.23
Flathead
Fort Collins
Gerber
Kevin
Manhatten
11.86
8.06
8.47
10.48
11.18
11.66
6.82
6.73
8.80
10.67
7.61
5.44
3.02
4.80
7.77
6.53
4.26
3.62
4.34
6.14
Rothiemay
Round Butte
Stryker
Tanna
Vamey
8.74
22.72
22.02
8.67
4.14
7.78
21.19
19.18
7.45
4.09
3.90
15.74
12.05
5.00
3.55
3.95
8.32
8.47
2.93
2.33
10.97
4.42
7.48
1.35
9.91
4.09
7.98
1.31
6.52
2.99
10.05
1.08
5.131
1.881
20.03
1.69
N=3
Mean
STD DEV
CV %
ISD (0.05)
\
96
Table 49. Cation exchange capacity and mineralogy percentages
of the clay fraction of twenty Montana soils,
provided by Bernard Schaff, method of Jackson (1958).
Soil Series
Illite
Vermiculite
gm Kg 1
Montmorillinite
—
CEC
cmol Kg 1
Amsterdam
Bear Paw
Beaverton
Bozeman
Chanta
9.7
14.7
6.1
8.5
5.8
5.0
10.4
5.2
7.2
4.7
12.8
11.7
12.7
12.1
4.8
22.5
22.6
25.1
23.9
9.3
Cherry
Chinook
Creston
Edgar
Evanston
11.1
3.4
3.5
7.1
9.2
7.7
1.8
2.5
4.2
7.5
5.6
6.9
2.9
10.9
7.6
28.8
10.4
13.5
10.9
13.9
Flathead
Fort Collins
Gerber
Kevin
Manhattan
2.5
5.0
15.0
12.3
5.7
1.3
2.6
7.7
5.7
4.2
3.2
6.5
20.1
10.4
9.4
14.1
7.6
30.7
13.7
20.1
Rothiemay
Round Butte
Stryker
Tanna
Vamey
9.9
4.6
9.7
7.1
4.3
5.0
5.2
5.8
4.6
2.6
13.1
3.2
5.6
6.9
12.2
20.9
10.6
14.4
13.9
16.8
97
Table 50. Soil extractable NO3 , Cl, and S for twenty Montana
Soil Series
NO3
Cl
—
S
mg Kg- 1 ----
Amsterdam
Bear Baw
Beaverton
Bozeman
Chanta
3.7
19.9
8.7
9.8
8.1
49.7
47.3
33.6
41.0
26.9
8.0
12.3
7.5
6.5
2.5
Cherry
Chinook
Creston
Edgar
Evanston
5.5
6.1
72.6
8.8
24.1
35.4
25.1
33.5
32.6
41.0
3.5
13.3
8.2
2.5
4.5
Flathead
Fort Collins
Gerber
Kevin
Manhatten
49.9
9.9
22.4
15.7
6.4
28.7
27.2
23.2
48.8
19.8
8.0
2.7
4.2
5.7
9.2
Rothiemay
Round Butte
Stryker
Tanna
Vamey
103.7
7.1
220.3
5.7
7.8
122.3
31.5
87.0
33.9
34.0
15.0
5.5
34.2
6.0
8.5
19.4
0.5
2.3
2.6
41.7
2.0
4.8
4.5
7.5
0.5
6.5
1.9
N=4
Mean
STD DEV
CV %
ISD (0.05)
soils.
98
APPENDIX B
Correlation Matrix for Properties of
Twenty Montana Soils
99
Table 51. Correlation matrix for 28 soil properties on 20 Montana soils.
CORR
K Uptake
^ex
caO x
MGex
N^ex
PAR
CM
CaOO3
pH
EC
NO3
Cl
Bray-P
Olsen-P
Sulfur
^sol
caSOl
Gs o I
m
-33 Ypa H2O
Sand %
i
Silt %
Clay %
CEC
Illite %
Verm %
Mont %
d[Kex]/dD
K Uptake
%ex
caC X
1.0000
0.6223
0.6223
-0.1914
0.5862
0.1315
0.3502
-0.0987
-0.4252
0.0340
0.1650
0.1118
0.4187
0.1471
0.3378
0.1125
0.2468
0.0552
0.0577
0.4077
-0.5651
0.0979
0.7677
0.3084
0.8480
0.7689
0.4917
0.7455
1.0000
-0.1914
0.2595
0.2595
0.3660
-0.2558
0.4684
-0.1427
0.1235
0.3863
-0.1295
-0.2965
0.0558
0.1053
0.2562
-0.0802
0.3155
-0.1826
-0.3337
0.1364
-0.3300
-0.1176
0.6593
0.5225
0.6864
0.5365
0.6341
0.5764
-0.0270
0.0701
-0.4744
-0.0697
0.7948
0.7964
0.2173
0.0217
0.1477
-0.0088
-0.1791
0.4018
0.0464
0.1034
0.0116
-0.0099
0.0240
-0.0431
0.0141
0.2814
-0.0315
-0.1652
0.3334
-0.1411
1.0000
m Gg x
0.5862
0.3660
-0.0270
Naex
1.0000
0.1315
-0.2558
0.0701
0.5315
0.5315
-0.2948
0.0838
-0.2067
0.0445
0.4591
0.3635
0.2707
0.0026
0.1964
0.4098
0.0360
0.3532
0.5522
0.4886
-0.4919
0.0510 '
0.7096
0.4971
0.6947
0.5685
0.5432
0.3413
-0.5260
0.2141
-0.0243
0.1441
0.8136
0.8272
0.4609
0.0275
0.0405
0.8752
0.1514
0.5825
0.8505
0.5390
-0.2881
0.3556
0.0218
-0.1014
0.0867
0.0576
-0.2290
0.0588
1.0000
100
Table 51— Continued.
CORR
K Uptake
1Nex
caOsX
M9ex
Naex
PAR
CM
CaCO3
pH
EC
NO3
Cl
Bray-P
Olsen-P
Sulfur
Ksol
caSol
Mgsoi
-33 Epa H2O
Sand %
Silt %
Clay %
CEC
Illite %
Verm %
Mont %
d[Kex]/dD
PAR
0.3502
0.4684
-0.4744
-0.2948
-0.5260
1.0000
-0.2006
-0.3116
-0.2491
-0.5121
-0.4729
-0.1920
0.0544
0.2281
-0.5573
0.2346
-0.4770
-0.6329
-0.1050
-0.0657
-0.0036
0.1074
-0.1208
0.1911
0.2337
-0.0810
0.4028
CM
-0.0987
-0.1427
-0.0697
0.0838
0.2141
-0.2006
1.0000
-0.3056
-0.3025
0.4095
0.4867
0.3185
0.6827
0.4991
0.2991
0.2139
0.7764
0.5327
0.4806
-0.1680
0.1490
0.0834
0.3480
-0.0157
0.0010
-0,0743
0.1459
CaCO3
-0.4252
0.1235
0.7948
-0.2067
-0.0243
-0.3116
-0.3056
1.0000
0.6847
0.0157
-0.1292
—0.0661
-0.3549
-0.2093
0.2717
0.0367
-0.1621
-0.1409
-Oi3319
0.3141
-0.2222
-0.2242
-0.0936
-0.2536
-0.3718
0.0713
-0.4541
pH
.
0.0340
0.3863
0.7964
0.0445
0.1441
-0.2491
-0.3025
0.6847
1.0000
0.1459
-0.0038
0.2114
-0.1911
-0.2650
0.4070
0.3070
-0.0885
-0.1180
-0.0853
0.0863
-0.1625
0.0608
0.1664
0.1733
0.0288
0.1944
0.1725
EC
0.1650
-0.1295
0.2173
0.4591
0.8136
-0.5121
0.4095
0.0157
0.1459
1.0000
0.9536
0.6292
0.1905
0.2346
0.8485
0.2840
0.7731
0.7589
0.4695
-0.1859
0.1857
0.0671
0.0674
0.1561
0.0039
-0.0383
0.1406
101
Table 51— Continued.
CORR
K Uptake
kGX
caGX
MSex
N^ex
PAR
CM
CaOO3
PH
EC
NO3
Cl
Bray-P
Olsen-P
Sulfur
Hsol
^aSol
Mg50I
-33 Kpa H2O
Sand %
Silt %
Clay %
CEC
Illite %
Verm %
Mont %
d[K^]/dD
NO3
0.1118
-0.2965
0.0217
0.3635
0.8272
-0.4729
0.4867
-0.1292
-0.0038
0.9536
1.0000
0.6435
0.2324
0.2384
0.8199
0.2420
0.8001
0.8034
0.4090
-0.1079
0.1932
-0.0642
-0.0894
0.0414
-0.0602
-0.2268
0.1406
Cl
0.4187
0.0558
0.1477
0.2707
0.4609
-0.1920
0.3185
-0.0661
0.2114
0.6292
0.6435
1.0000
0.1728
0.3285
0.6278
0.2047
0.6876
0.4886
0.3292
-0.2188
0.0844
0.2409
0.1197
0.3406
.0.1981
0.1513
0.4056
Bray-P
0.1471
0.1053
-0.0088
• 0.0026
0.0275
0.0544
0.6827
-0.3549
-0.1911
0.1905
0.2324
0.1728
1.0000
0.6607
0.1820
0.0867
0.4069
0.2262
0.3440
-0.0639
-0.0643
0.1782
0.2401
0.0340
' 0.0882
0.1092
0.2662
Olsen-P
0.3378
0.2562
-0.1791
0.1964
0.0405
0.2281
0.4991
-0.2093
-0.2650
0.2346
0.2384
0.3285
0.6607
1.0000
0.2221
0.1968
0.3796
0.2320
0.2938
-0.0993
-0.2510
0.4593
0.1994
0.3367
0.3503
0.2155
0.1535
Sulfur
0.1125
-0.0802
0.4018
0.4098
0.8752
-0.5573
0.2991
0.2717
0.4070
0.8485
0.8199
0.6278
0.1820
0.2221
1.0000
0.2197
0.6683
0.7703
0.4499
-0.1808
0.1798
0.0660
-0.0035
0.1013
0.0242
-0.0780
0.0797
102
Table 51— Continued.
CORR
K Uptake
^ex
caB X
^ex
Naex
PAR
CM
CaCO3
PH
EC
NO3
Cl
Bray-P
Olsen-P
Sulfur
Kgol
caSOl
M g 5Oi
-33 Kpa H2O
Sand %
Silt %
Clay %
CEC
Illite %
Verm %
Mont %
dEIW/dD
Ksol
0.2468
O .3155
0.0464
0.0360
0.1514
0.2346
0.2139
0.0367
0.3070
0.2840
0.2420
0.2047
0.0867
0.1968
0.2197
1.0000
0.1381
0.0344
0.1331
0.0092
-0.0813
0.0841
0.0276
0.2540
0.0790
-0.1269
0.3854
c a Sol
M g 5Oi
-33 Kpa
SAND %
0.0552
-0.1826
0.1034
0.3532
0.5825
-0.4770
0.7764
-0.1621
-0.0885
0.7731
0.8001
0.6876
0.4069
0.3796
0.6683
0.1381
1.0000
0.7939
0.5397
-0.2850
0.2636
0.1283
0.3290
0.0902
0.0589
0.0296
0.1719
0.0577
-0.3337
0.0116
0.5522
0.8505
-0.6329
0.5327
-0.1409
-0.1180
0.7589
0.8034
0.4886
0.2262
0.2320
0.7703
0.0344
0.7939
1.0000
0.5404
-0.3167
0.3006
0.1332
0.0969
0.0838
0.0396
-0.0679
-0.0320
0.4077
0.1364
-0.0099
0.4886
0.5390
-0.1050
0.4806
-0.3319
-0.0853
0.4695
0.4090
0.3292
0.3440
0.2938
0.4499
0.1331
0.5397
0.5404
1.0000
-0.8309
0.6524
0.5141
0.4888
0.4399
0.5533
0.1024
0.3781
-0.5651
-0.3300
0.0240
-0.4919
-0.2881
-0.0657
-0.1680
0.3141
, 0.0863
-0.1859
-0.1079
-0.2188
-0.0639
-0.0993
-0.1808
0.0092
-0.2850
-0.3167
-0.8309
1.0000
-0.7702
—0.6367
-0.5213
-0.5821
-0.7003
-0.2791
-0.4161
.
103
Table 51— Continued.
CORR
K Uptake
%ex
Caex
M-fex
Naex
PAR
CM
CaCO3
PH
EC
NO3
Cl
Bray-P
Olsen-P
Sulfur
^sol
c a SOl
M=Tsol
-33 Kpa H2O
Sarxi %
Silt %
Clay %
CEC
Illite %
Verm %
Mont %
dCNexl/dD
Silt %
Clay %
0.0979
-0.1176
-0.0431
0.0510
0.3556
-0.0036
0.1490
-0.2222
. -0.1625
0.1857
0.1932
0.0844
-0.0643
-0.2510
0.1798
-0.0813
0.2636
0.3006
0.6524
-0.7702
1.0000
-0.0015
0.0805
-0.0100
0.1900
-0.2477
0.1301
0.7677
0.6593
0.0141
0.7096
0.0218
0.1074
0.0834
-0.2242
0.0608
0.0671
-0.0642
0.2409
0.1782
0.4593
0.0660
0.0841
0.1283
0.1332
0.5141
-0.6367
-0.0015
1.0000
0.7200
0.9247
0.8682
0.7369
0.4951
CEC
Illite
0.3084
0.5225
0.2814
0.4971
-0.1014
-0.1208
0.3480
-0,0936
0.1664
0.0674
-0.0894
0.1197
0.2401
0.1994
-0.0035
0.0276
0.3290
0.0969
0.4888
-0.5213
0.0805
0.7200
1.0000
0.6169
0.5908
0.6550
0.4288,
0.8480
0.6864
-0.0315
0.6947
0.0867
0.1911
-0.0157
-0.2536
0.1733
0.1561
0.0414
0.3406
0.0340
0.3367
0.1013
0.2540
0.0902
0.0838
0.4399
-0.5821
-0.0100
0.9247
0.6169
1.0000
0.8680
0.6123
0.6693
VERM
0.7689
0.5365
-0.1652
0.5685
0.0576
0.2337
0.0010
-0.3718
0.0288
0.0039
-0.0602
0.1981
0.0882
0.3503
0.0242
0.0790
0.0589
0.0396
0.5533
-0.7003
0.1900
0.8682
0.5908
0.8680
1.0000
0.4140
0.5854
104
Table 51— Continued.
CORR
K Uptake
^ex
caGX
m Zb x
Naex
PAR
CM
CaCO3
PH
EC
NO3
Cl
Bray-P
Olsen-P
Sulfur
1Ssol
caSol
Mgsol
-33 Kpa H2O
Sand %
Silt %
Clay %
CEC
Illite %
Vem %
Mont %
d[Kex]/dD
MONT
0.4917
0.6341
0.3334
0.5432
-0.2290
-0.0810
-0.0743
0.0713
0.1944
-0.0383
-0.2268
0.1513
0.1092
0.2155
-0.0780
-0.1269
0.0296
-0.0679
0.1024
-0.2791
-0.2477
0.7369
0.6550
0.6123
0.4140
1.0000
0.2329
d[%ex]/dD
0.7455
0.5764
-0.1411
0.3413
0.0588
0.4028
0.1459
-0.4541
0.1725
0.1406
0.1406
0.4056
0.2662
0.1535
0.0797
0.3854
0.1719
-0.0320
0.3781
-0.4161
0.1301
0.4951
0.4288
0.6693
0.5854
0.2329
1.0000