EFFECT OF RATE. PLACEMENT AND
SOURCE OF POTASSIUM 0N. YIELD
AND MINERAL CONTENT OF POTATOES
AND
PHQSPHORUS FQRMS Am EQUILIBRIA
iN SELECTED PERU’VM SGILS

Thesis fer the Degree of Ph, D.
MICHEGAN STATE UNIVERSITY
CARLOS VALVERDE S.
1970

_ ir— M ’

l-H"S'-§

This is to certify that the

thesis entitled
EFFECT OF RATE, PLACEMENT AND SOURCE OF

POTASSIUM ON YIELD AND MINERAL CONTENT
OF POTATOES AND PHOSPHORUS FORMS AND
EQUILIBRIA IN SELECTED PERUVIAN SOILS

presented by

CARLOS VALVERDE S.

has been accepted towards fulfillment
of the requirements for

Mo.— degree in _S_Q.il_S_C_ience

NJHHQ M0

ajor professor

Datecqilémq a 7} AC1 7 O

0-169

 

.H. in-" I

L r ammuc IV
'0“ 8 ”NY
390K HIDE" M2-

ABSTRACT
PART I

EFFECT OF RATE, PLACEMENT AND SOURCE
OF POTASSIUM ON YIELD AND MINERAL
CONTENT OF POTATOES

by Carlos Valverde S.

Three field experiments with potassium fertilization
of potatoes were conducted: one on Hodunk sandy loam in
1967 to determine the effects of rate and placement of K,
another on Hodunk sandy loam in 1968 to determine the
effects of rate, source and placement of K, and the third
on McBride sandy loam in 1968 to determine the effects of
rate and placement of K for Russet Burbank and Sebago
potatoes.

Yields of potatoes appeared to be related to the level
of exchangeable soil K, since the most marked response was
obtained in 1967 on Hodunk sandy loam at an exchangeable K
level of 135 pounds per acre, a lesser response on Hodunk
sandy loam in 1968 at a level of 160 pounds, and the least
response on McBride sandy loam at a level of 200 pounds K

per acre. The yields were decreased when rates of K applied

Carlos Valverde S.

were equal to or greater than 200 pounds banded or 400

pounds broadcast. The sources of K (KCl, K and K2CO

2304 3)
were all equally effective with respect to yields when the
K was applied broadcast at the level of 200 pounds K per
acre or less. The specific gravity and percent dry weight
of potatoes decreased as rate of K increased.

The concentration of K in petioles, leaves and vines
increased as the rate of K increased, while the concentra-
tion of Ca and Mg tended to decrease. On the other hand,
as the potato matured, K concentration in plants decreased
and Ca and Mg concentration increased.

Broadcast and banded applications of K were generally
equally effective with respect to yield and chemical compo-
sition of potatoes.

When potassium fertilizer was broadcast, exchangeable
K increased as the rate of K increased, but a comparison
of the level of soil K after cropping and of crop removal
with the rate of K application indicates that a considerable
portion of applied fertilizer K was either "fixed" by the

soil or leached from the plow layer.

Carlos Valverde S.

ABSTRACT
PART II

PHOSPHORUS FORMS AND EQUILIBRIA
IN SELECTED PERUVIAN SOILS

A laboratory study was conducted to characterize the
phOSphorus fractions in nine Peruvian soils and to evaluate
the phosphorus fixation and equilibria reactions in these
soils. Three of the soils were from the coastal area,
three from the mountains, and three from the jungle.

PhOSphorus in the coastal soils was primarily calcium
phOSphate, and adsorption maxima and strength of adsorption,
as determined using the Langmuir adsorption isotherm, were
directly related to the amount of free calcium carbonate in
the soils. PhOSphate potential determinations indicated
that phOSphorus solubility in these soils was controlled
mainly by octocalcium phOSphate.

In a mountain soil with a neutral reaction, calcium
phOSphate was again the dominant form of phOSphorus, but
phOSphorus solubility was governed by hydroxyapatite, and
the strength of bonding was much higher than on the coastal
soils. In two acid mountain soils, iron phOSphate was the

dominant form of phOSphorus, with considerable amounts of

Carlos Valverde S.

aluminum phOSphate present. PhOSphorus solubility was less
than that of strengite until 500 ppm P had been applied,
when variscite appeared to be governing phOSphorus avail—
ability.

PhOSphorus in strongly acid jungle soils occurred
mostly as iron and aluminum phOSphates, and phOSphorus
solubility was again less than that of strengite. In a
slightly acid jungle soil, phOSphorus solubility appeared
to be controlled by hydroxyapatite, even though iron and
aluminum phOSphates appeared to be the dominant forms of
phosphorus in this soil.

When that part of the total phOSphorus in the soils
extracted during the fractionation procedure is considered,
the data indicate that the jungle soils were the most severely
weathered, and that the coastal soils showed the least

weathering.

EFFECT OF RATE, PLACEMENT AND SOURCE
OF POTASSIUM ON YIELD AND MINERAL
CONTENT OF POTATOES

AND

PHOSPHORUS FORMS AND EQUILIBRIA
IN SELECTED PERUVIAN SOILS

By

Carlos Valverde Sudwwl

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Crop and Soil Sciences Department

1970

This thesis is dedicated to my wife and daughter

FLOR DE MARIA and KAREN

ii

ACKNOWLEDGMENTS

The author wishes to eXpress his most sincere appreci-
ation to Dr. E. C. Doll for his continuing interest, support
and patient guidance throughout the course of this investi-
gation and for his help in initiating the work in Peruvian
soils while he was in Peru.

Appreciation is also extended to Dr. R. L. Cook, Dr.

B. G. Ellis, Dr. B. D. Knezek, Dr. C. Pollard and Dr. L. S.
Robertson for their suggestions and for serving as members
of my guidance committee.

Acknowledgment is given to the members of the Soil
Test Laboratory, especially Mrs. Florence Drullinger and
Alyce Coryell, for their efforts in conducting the labora-
tory analyses, and to the American Potash Institute for
financial aid which made these analyses possible.

The writer would like to thank Mr. J. Oaks for his
assistance with the field experiments and Dr. M. L. Vitosh
for allowing me to work on the experiment in Montcalm County.

The author's stay at Michigan State University was made
possible through financial assistance from the Rockefeller
Foundation. Their continuous support is gratefully acknow-

.ledged.

iii

A special acknowledgment is given to the Agricultural
Experiment Station at LA MOLINA, who gave me the Opportunity

to complete my Ph.D. program.

iv

TABLE OF CONTENTS

Page

LIST OF TABLES . . . . . . . . . . . . . . . . . . . x

LIST OF FIGURES . . . . . . . . . . . . . . . . . . xiii
PART I. EFFECT OF RATE, PLACEMENT

AND SOURCE OF POTASSIUM ON YIELD AND
MINERAL CONTENT OF POTATOES

INTRODUCTION . . . . . . . . . . . . . . . . . . . . 2
LITERATURE REVIEW .'. . . . . . . . . . . . . . . . 4
Potassium Deficiency Symptoms in Potatoes . . . A
Effect of Rate of Potassium on Yields . . . . . A
Effect of Source of Potassium on Potato Yields 6

The Effect of Rate and Source of Potassium on
the Specific Gravity of Potatoes . . . . . . 7
Fertilizer Placement for Potatoes . . . . . . . 10

Effects of Rates and Sources of Potassium on

the Absorption of Potassium, Magnesium and
Calcium by Potato Plants . . . . . . . . . . 13

The Relation of Exchangeable Potassium to

Yields 0 O O O O O O O O O O O O O O O O O O 16

The Relation of Soil Test to the ReSponse to
Potassium Fertilizer . . . . . . . . . . . . l8
METI-I ODS AND MATERIALS 0 O O O O O O O O O O O O O O 20
Field Procedure . . . . . . . . . . . . . . . . 20

Rate and Placement of Potassium on Hodunk

Sandy Loam in 1967 . . . . . . . . . . . 20

Table of Contents. —- Cont.

Page

Rate, Source and Placement of Potassium
on Hodunk Sandy Loam in 1968 . . . . . . 22

Rate and Placement of Potassium on
McBride Sandy Loam in 1968 . . . . . . . 24

Laboratory Procedure . . . . . . . . . . . . . 25
Soil Analysis . . . . . . . . . . . . . . 25

Plant Analysis . . . . . . . . . . . . . . 27
Statistical Analysis . . . . . . . . . . . 27

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . 28

Rate and Placement of Potassium on Hodunk Sandy
Loam in 1967 . . . . . . . . . . . . . . . . 28

Yields of Potatoes . . . . . . . . . . . . 28
Specific Gravity . . . . . . . . . . . . . 28
Percent Dry Weight of Tubers . . . . . . . 31
Yield of Vines . . . . . . . . . . . . . . 31

Potassium Concentration in Petioles and

Leaves . . . . . . . . . . . . . . . . . 31
Potassium Concentration in Vines . . . . . 32
Potassium Concentration in Tubers . . . . 32
Potassium Uptake by Vines and Tubers . . . 3h
Calcium Concentration in Petioles and

Leaves . . . . . . . . . . . . . . . . . 34
Calcium Concentration of Vines . . . . . . 35
Calcium Concentration in Tubers . . . . . 35
Calcium Uptake by Vines and Tubers . . . . 35
Magnesium Concentration in Petioles and

Leaves . . . . . . . . . . . . . . . . . 35
Magnesium Concentration in Vines . . . . . 38

vi

Table of Contents. -- Cont.

Page
Magnesium Concentration in Tubers . . . . . 38
Magnesium Uptake by Vines and Tubers . . . 38
Exchangeable Soil Potassium . . . . . . . . 39
Exchangeable Soil Calcium . . . . . . . . . Ah
Exchangeable Soil Magnesium . . . . . . . . AA
Relation Between Yields and Soil Potassium AA

Rate, Source, and Placement of Potassium on
Hodunk Sandy Loam in 1968 . . . . . . . . . . 47

Yield of Potatoes . . . . . . . . . . . . . A7

Specific Gravity of Potatoes . . . . . . . 48

Potassium Concentration in Petioles . . . . 53
Potassium Concentration in Tubers . . . . . 56
Calcium Concentration in Petioles . . . . . 56
Calcium Concentration in Tubers . . . . . . 59
Magnesium Concentration in Petioles . . . . 59

Magnesium Concentration in Tubers . . . . . 62

Rate and Placement of Potassium on McBride Sandy
Loam in 1968 O O I O O O O O O O O O O O O O O 62

Yield of Potatoes . . . . . . . . . . . . . 63
Potassium Concentration in Petioles . . . . 63
Calcium Concentration in Petioles . . . . . 66
Magnesium Concentration in Petioles . . . . 67
SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . 7O
BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . 76
APPENDIX . . . . . . . . . . . . . . . . . . . . . . l3O

vii

Table of Contents. —- Cont.

Page

PART II. PHOSPHORUS FORMS AND
EQUILIBRIA IN SELECTED PERUVIAN SOILS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . 84
LITERATURE REVIEN I O O O 0 O O O 0 O O O O 0 O O O 86
PhOSphorus Fixation in the Soils . . . . . . . 86

Absorption of P by Clay Minerals . . . . . 86

Chemical Precipitation of P . . . . . . . 87
Determination of the Fixing Capacity of the
Soils . . . . . . . . . . . . . . . . . . . . 88
Forms of Inorganic PhOSphorus in Soils . . . . 90
Direct Observations . . . . . . . . . . . 90

Phase Solubility Diagrams . . . . . . . . 90
Soil Phosphorus Fractions . . . . . . . . 92

METHODS AND MATERIALS . . . . . . . . . . . . . . . 96

PhOSphorus Adsorption Capacity . . . . . . . . 96
PhOSphorus Potential . . . . . . . . . . . . . 98
Fractionation of Soil PhOSphorus . . . . . . . 99
Total Phosphorus in Soils . . . . . . . . . . . 99

RESULTS AND DISCUSSION . . . . . . . . . . . . . . . 100
PhOSphorus Adsorbing Capacity . . . . . . . . . 100
Coastal Soils . . . . . . . . . . . . . . 100

Mountain Soils . . . . . . . . . . . . . . 103

Jungle Soils . . . . . . . . . . . . . . . 103
PhOSphorus Potential . . . . . . . . . . . . . 10A
Coastal Soils . . . . . . . . . . . . . . 110

Mountain Soils . . . . . . . . . . . . . . 110

Table of Contents. -- Cont.

Jungle Soils .
Fractionation of Soil
Coastal Soils
Mountain Soils .
Jungle Soils .
SUMMARY AND CONCLUSIONS .
BIBLIOGRAPHY . . . . . . .

PhOSphorus

ix

Page
113
113
113
118
119
121
12A

LIST OF TABLES
PART I

Table Page

1. Yield, Specific gravity and percent dry weight
of tubers and dry weight of potato vines as
affected by rate and placement of K on
Hodunk sandy loam in 1967 . . . . . . . . . . 29

2. Significant differences of Sebago potato
yields as related to rate and placement of
K on Hodunk sandy loam in 1967 . . . . . . . 30

3. Potassium, calcium and magnesium concentra-
tions in petioles and leaves in early season
(69 days after planting) as affected by rate
and placement of K on Hodunk sandy loam in

1967 . . . . . . . . . . . . . . . . . . . . 33

4. Potassium, calcium and magnesium concentration
in vines (150 days after planting) and
tubers as affected by rate and placement of
K on Hodunk sandy loam in 1967 . . . . . . . 36

5. Uptake of potassium, calcium and magnesium by
potato vines and tubers as affected by rate
and placement of K on Hodunk sandy loam in

1967 . . . . . . . .... . . . . . . . . . . 37

6. Exchangeable soil K, Ca and Mg before planting
and at mid-season and late season (0, 70 and
170 days after planting reapectively) as
affected by rate and placement of K on Hodunk
sandy loam in 1967 . . . . . . . . . . . . . A0

7. Yield and Specific gravity of Sebago potatoes
as related to source, rate and placement of
K on Hodunk sandy loam in 1968 . . . . . . . 50

8. Significant differences of Sebago potato
yields as related to rate and placement using
potassium chloride (KCl) as a source of K
fertilization on Hodunk sandy loam in 1968 . 51

X

List of Tables. -- Cont.
Table

9. Significant differences of Sebago potato yields
as affected by sources and rates of K on
Hodunk sandy loam in 1968 . . . . . . . .

10. Potassium concentration (%) in petioles of
Sebago potato in early season, mid—season
and late season (60, 98 and 130 days after
planting reSpectively) as affected by source
and rate of K on Hodunk sandy loam in 1968 .

11. Percent of potassium, calcium and magnesium in
mature tubers as affected by source and rates
of K on Hodunk sandy loam in 1968 . . . . . .

12. Calcium concentration (%) in petioles of
Sebago potato in early season, mid-season
and late season (60, 98 and 130 days after
planting reSpectively) as affected by source
and rate of K on Hodunk sandy loam in 1968 .

13. Magnesium concentration (%) in petioles of
Sebago potato in early season, mid-season
and late season (60, 98 and 130 days after
planting respectively) as affected by source
and rate of K on Hodunk sandy loam in 1968 .

14. Yield of Sebago and Russet Burbank potatoes
as affected by rate, placement and time of
K on Mc Bride sandy loam in 1968 . . . . . .

15. Potassium concentration (%) in petioles of
Sebago and Russet Burbank potatoes in early
and mid—season (60 and 96 days after plant—
ing respectively) as affected by rate,
placement and time of K on Mc Bride sandy
loam soil in 1968 . . . . . . . . . . . . .

16. Calcium concentration (%) in petioles of
Sebago and Russet Burbank potatoes in early
and mid-season (60 and 96 days after plant—
ing reSpectively) as affected by rate,
placement and time of K on Me Bride sandy
loam soil in 1968 . . . . . . . . . . . . . .

1?. Magnesium concentration (%) in petioles of
ebago and Russet Burbank potatoes in early
and mid-season (60, and 96 days after plant-
ing reSpectively) as affected by rate,
placement and time of K on Mc Bride sandy
loam soil in 1968 . . . . . . . . . . . . . .

xi

Page

52

5h

57

58

60

64

65

68

69

List of Tables. -— Cont.
PART II
Table Page

1. Texture, pH, CaCO , organic matter, Olsen P,
exchangeable cagions (Ca, Mg and K) and
cation exchange capacity (CEC) of nine
Peruvian soils . . . . . . . . . . . . . . . 97

2. PhOSphorus adsorption data for the coastal,
mountain and jungle soils of Peru . . . . . 102

3. The pH, pH2P0 , phOSphate potentials and
lime potentials of the coastal soils as
affected by the application of P and after
wetting and drying 20 times . . . . . . . . 106

A. The pH, pH2P0 , phOSphate potentials and
lime potentials of the mountain soils as
affected by the application of P and after
wetting and drying 20 times . . . . . . . . 107

5. The pH, pH P0 , phOSphate potentials and
lime potentials of the jungle soils as
affected by the application of P and after
wetting and drying 20 times . . . . . . . . 108

6. Total P and inorganic P fractions in nine
Peruvian soils to which no P was applied
and after wetting and drying 20 times . . . 116

7. Total P and inorganic P fractions in nine
Peruvian soils to which 500 ppm P was
applied and after wetting and drying 20
times . . . . . . . . . . . . . . . . . . . 117

xii

LIST OF FIGURES
PART I

Figure Page

1. Exchangeable potassium before planting, at
mid-season and late season (0, 70 and 170
days after planting reSpectively) as
affected by rates of K applied banded on
Hodunk sandy loam in 1967 . . . . . . . . . . Al

2. Exchangeable potassium (1N NH OAc pH 7.0)
before planting, at mid-seaéon and late
season (0, 70 and 170 days after planting
reSpectively) as affected by rates of K
applied broadcast on Hodunk sandy loam in
l .

. . . . . . . . . . . . . . . . . . . A2

3. X-ray diffraction patterns for coarse clay
(0.2 — 2.0 u) of Hodunk sandy loam soil . . . A3

A. Mitscherlich reSponse curve relating yield to
exchangeable soil K (Hodunk sandy loam in

1967) . . . . . . . . . . . . . . . . . . . . A6

5. Relationship between soil test value and rate
of K application for expected 95% maximum
yield response (Hodunk sandy loam in 1967) . A9

6. Effect of rate and source of K in the K con-
centration in petioles at early season,
mid-season and late season 0 o o o o o o o o 55

7. Effect of rate and source of K in the Mg

concentration in petioles at early season,
mid-season and late season . . . . . . . . . 61

PART II

1. Langmuir isotherm regressions for Lambayeque
(coast); Casablanca (mountain); and Tingo
Maria (jungle) soils . . . . . . . . . . . . 101

xiii

List of Figures. —— Cont.
Figure Page

2. Phase diagram for phOSphate compounds in
selected Peruvian soils, as determined by
the phOSphate solubility diagram of Lindsay
and Moreno (1960) . . . . . . . . . . . . . . 109

3. PhOSphate and lime potentials of the coastal
soils in relation to those of pure calcium
phOSphate, as affected by P application and
after wetting and drying 20 times . . . . . . 111

A. Solubility phase diagram of Lindsay and
Moreno (1960) for the mountain soils as
affected by the application of P and after
wetting and drying 20 times . . . . . . . . . 112

5. Solubility phase diagram of Lindsay and
Moreno (1960) for the jungle soils as
affected by the application of P and after
wetting and drying 20 times . . . . . . . . . 11A

xiv

PART I

EFFECT OF RATE, PLACEMENT AND SOURCE
OF POTASSIUM 0N YIELD AND MINERAL CONTENT
OF POTATOES

EFFECT OF RATE, PLACEMENT AND SOURCE
OF POTASSIUM 0N YIELD AND MINERAL CONTENT
OF POTATOES

INTRODUCTION

Heavy rates of potassium fertilizer are generally
needed to produce optimum yields of potatoes. Considerable
field research has been done to evaluate the potassium
status of Michigan potato soils, but relatively few of
these experiments were conducted with irrigation and at
current yield levels. Control of fertilizer nutrient levels
and adequate evaluation of cation balance in soils becomes
highly important as fertilizer rates increase and production
becomes more intensive. Evaluation of nutrient levels in
petioles and leaves throughout the growing season is neces-
sary if reliable criteria are to be established for the
interpretation of plant analyses.

As higher rates of potassium fertilizers are applied,
the effects of the different sources of potassium need to be
re-evaluated, since the effects of anions applied with
potassium may be more critical at high fertilization levels.
The relative effectiveness of band and broadcast applications

needs to be determined at high rates of application.

2

The investigations reported herein were conducted to
determine the effects of rate, source, and placement of
potassium fertilizers on yields, Specific gravity, and levels

of potassium, calcium, and magnesium in potatoes grown under

1 rrigation.

LITERATURE REVIEW

Potassium Deficiency Symptoms in Potatoes

The deficiency symptoms for K in potatoes have been
fully reported (MC Murtrey, 19A8; Wallace, 1951; Cook, 1953;
Houghland, 196A; Ulrich and Ohki, 1966), and may be des-
cribed as follows: The growth of the plant is retarded and
the stalks (haulms) are Slender with the internodes some-
what Shortened. The leaves lose their smooth surface, are
reduced in Size, and tend to be flat or to curl backward
near the margins. The appearance of dark green foliage is
an early Sign of K Shortage. Then the older leaves become
yellowish, and a brown or bronze color develOpS, starting
from the tips and margins and gradually affecting the entire
leaves. Leaflets are cupped and crowded together. The
lower leaves dry up and collapse prematurely. The tuber
flesh is bluish and poorly developed. When a deficiency of

K is severe, the plants eventually die.

Effect of Rate of Potassium on Yields
The effects of rates of K on yields of potatoes have
been Studied in most of the potato producing areas (Brown,
1938 and 19A0; Ware, 1939; Prince e2 31., 19A0; Chucka
922;” 19M»; Jacob _e_t_ £11., 19A9; Terman e}; 31., 19A9, 1950:

1953 and 1963; Hawkins 22.2;~: 19A6; Nelson and Hawkins,
19A7; Lorenz at al., 195A; Harrap, 1960; Berger et a1.,
1961; Wilcox, 1961; Rowberry etflgl., 1963; Murphy and

Goven, 1965 and 1966; and Laughlin, 1966). The results
obtained by these authors indicate that response of potatoes
to K fertilizer varies with soil type, climate conditions,
and varieties used. In California, Lorenz gt a1. (195A)
indicate that potatoes did not respond to different rates of
K in most of the potato-producing areas with exception of
the peat soils of San Juaquin Delta, where applications as
high as 160 pounds of K per acre were needed, and the
Ripperdan fine sandy loams, the only mineral soils on which
yields were increased by K. Nelson and Hawkins (19A7)
reported that yields may be increased with applications of
K greater than 120 pounds per acre in North Carolina. In
Maine, Terman (1950) summarized 83 field experiments
involving potassium rates conducted from 1930 to 19A9, and
concluded that the greatest yield response was obtained with
the first 60-80 pounds of K20 per acre. The same author
(Terman, 1953) later reported Significant yield increases
with only 60 pounds K20 per acre.

In Ontario, Rowberry £3 31. (1963) reported that potatoes
growing in mineral soils responded to successive increments
of a 6-12—12 fertilizer up to 1,000 pounds per acre, with no
further increase when 1,500 pounds were applied. Timm and
Merkle (1963), in the major potato growing area of Pennsyl-

vania, reported increases in potato yields when 66 pounds of

K20 per acre was applied to soils in which the exchangeable
K was more than 200 pounds K per acre. Harrap (1960), at
Levington in Great Britain, found that the optimum K appli—
cations for the production of good quality potatoes varied
from soil to soil, and that the average optimum rate was

200 pounds K20 per acre. Wilcox (1961) in southwestern
Indiana observed linear increases in yields for rates of

K20 up to 150 pounds per acre. Higher rates of K20 resulted
in sharply decreased yields. In Michigan, Crabtree (1969)
reported Significant yield increases for rates of K20 up to

180 pounds per acre.

Effect of Source of Potassium on Potato Yields

In considering the effect on yields, the literature
indicates that the source of K does not usually affect
potato yields. Chucka gt 31. (19AA) in Maine, comparing
potassium chloride (KCl), potassium sulfate (K2SOA)’ potas—
sium nitrate (KNOB) and potassium metaphOSphate (KP03),
reported that the yields produced were approximately the
same with all sources.

Terman (19A9 and 1950), comparing KCl and KZSOA’ found
that yields were not affected although variable results were
obtained in individual experiments. Timm and Merkle (1963)
in Pennsylvania did not find statistically significant dif-
ferences in yields between either of these two sources, and
stressed that soil variability, moisture content and varietal

differences apparently affected potato yields as much as did

the source of K. In Ontario, Rowberry 22 31. (1963) did not
find any yield differences due to either of these sources of
K except at one location in 1958 and in 1960 where yields
were higher with K2SOA’ Recently in Maine, Murphy and Goven
(1965) in a three-year period found that the source of K had
no significant effect on yield of tubers and in 1966 these
same authors, summarizing data from 1956 to 1958, concluded
that source of K did not influence yield of potatoes, but
that potatoes fertilized with KCl tended to produce chips of
lighter color than did those fertilized with KZSOA or KN03.

There are some reports that potato yields on plots to
which KCl was applied were higher than those from plots to
which KZSOA was applied (Berger gt 31., 1961 and Wilcox
1961). Under greenhouse conditions, using solution culture
where the ions present were carefully controlled, Hart and
Smith (1966) determined that at the same level of K, the
percent dry weight of plant tops was higher when KZSOA was
used than when KCl was used. Lucas et'al. (195A) reported
that potato yields on organic soils in Michigan were Slightly,
and nearly Significantly, higher when K2804 was applied than
when KCl was applied. Doll and Thurlow (1965) indicate that
no consistent differences in yields were Obtained on mineral
soils between the chloride and sulfate forms of K fertilizers.

The Effect of Rate and Source of Potassium
on the SpecificICravity of Potatoes
The starch content of the potato tubers is important

because the quality of the tubers is related to the dry matter

content (starch, protein and other mineral constituents).

Studies by many investigators indicate that the Specific

gravity of the tubers indirectly measures the starch con—

tent. In Germany, Scheele et a1. (1936) from 5A0 potato

samples collected over a four year period, correlated

Specific gravity with dry matter and starch content and

reported correlation coefficients (r) of 0.937 and 0.9A7,

respectively. Dunn and Nylund (19A5) in Minnesota reported ~x'

a correlation coefficient (r) of 0.8686 between specific

gravity and dry matter for 260 samples from the Red River {II

valley. ““—
Early in 1912, Thatchter noted that the production 'W“

and storage of starch in potatoes and sugar beets was :11

directly related to a decreasing supply of.avai1ab1e soil K.

Mulder (1956) reported that K affected the rate of tuber

respiration more than N, P, Mg or Ca. Potassium-deficient

tubers have considerably higher reSpiration rates than tubers

grown with an adequate supply of K. McCollum.§£‘§l. (1958)

have pointed out that for maximum activity of pyruvic kinase,

magnesium (Mg) is required as well as K; this enzyme is

essential for the metabolism of carbohydrates. While the

above effects of K were noted for the experimental condition

reported, under field conditions, increasing rates of K

usually result in a reduction of the starch content and

consequently the Specific gravity of the tubers. The same

is true with the anion associated with the K fertilizer.

Houghland and Shricker (1933) in Virginia measured total

starch production in more than 300 samples of potatoes tubers
grown on a Norfolk sandy loam and an Arlington clay loam.
These authors found that in the majority of the cases, the
addition of K caused a Slight depression in the starch con-
tent of the tubers, and noted that this reduction was greater
when KCl was applied than when K2SOA was applied.

Results of subsequent research have usually indicated
that K fertilizers, particularly those containing chlorides,
lower the Specific gravity and that the higher the rate of
application the more the Specific gravity is lowered (Dunn
and Nylund, 19A5 - Dunn and Rost, 19A8; Terman, 19A9 and
1950; Harrap, 1960; Berger £3 31., 1961; Wilcox, 1961; Timm
and Merkle, 1963; Rowberry §§,al,, 1963). Murphy and Goven
(1959, 1965, and 1966) reported that as the rate of K was
increased from 0 to 250 pounds of K20 per acre, the Specific
gravity of the tubers was decreased linearly from 1.08A to
1.070, and that the yield was increased only by the first
50-pound increment of K. When sources of K were compared,
the Specific gravity was higher when K2804 and KNO3 were
applied than when KCl was applied, and chips made from pota—
toes fertilized with KCl were higher in color than chips
from potatoes fertilized with KZSOA’ Lucas eg‘al. (195A)
reported that potatoes grown on organic soils in Michigan
contained 13 percent less starch and were 6 percent lighter
in weight when KCl was applied than when the same rate of

K2SOA was applied.

10

The effect of ci'on the metabolism of starch formation
is not clear, but CI does result in a higher water content
in the tubers. Numerous reports in the literature indicate
that large and sometimes excessive amounts of 01- are readily
absorbed by potatoes. (Dunn and Nylund, 19A5; Dunn and Rost,
19A8; Knolewles and Cowie, 19A0).

Corbett and Gausman (1960) suggested that Cl may affect
potato tuber's quality by affecting the uptake of phOSphorus
(P). Along with these findings, Hart and Smith (1966) found
that P absorption at a particular Stage of plant development
was affected by source of K. On the other hand, Latzko(l955)
indicated that invertase, amylase and / glucosidase are

inhibited by C1- and increased by SOA

Fertilizer Placement for Potatoes

The potato plant does not have an extensive root system,
and it has a high K requirement. Data obtained in Maine
(Hawkins, 19A6) revealed that during the peak period of K
absorption (70 days after planting), as much as 6.A pounds
of K20 per acre per day were absorbed.

Cummings and Houghland (1939) studied 13 different
methods of K placement from 1931 to 1937 on typical potato
growing areas of Arostook County, Maine; on Long Island, New
York; in central New Jersey; on the eastern Shore of Virginia;
in northeastern Ohio and in western Michigan. Their results
indicate that placement of the fertilizer in a band immedi-

ately under, above or mixed with the soil around the seed

" p”—

11

resulted in delayed emergence of the Sprout and reduction in
yield. The placement of the fertilizer in bands 2 inches at
each Side and on the lower level of the seed consistently
produced relatively higher average yields than the other
side placements, both those nearer and those further from
the seed. The placement of the fertilizer in a band at only
one Side of the row gave lower yields than two bands, one on
either side of the seed. In general, fertilizer concentra—
ted in bands near the row was more effective than broadcast
fertilizer. A more detailed description of the results
obtained at Mancelona and Greenville in the Michigan area

is given by Grantham gt a1. (1939); these results indicate
that for equal amounts of commercial fertilizer, higher
yields were obtained when the fertilizer was applied in the
row than when it was applied broadcast.

In Maine on a Caribou loam, Chucka 22.§l- (19AA) com-
pared the placement of a 6-6-12 fertilizer applied as fol-
lows at a total rate of 2,000 pounds per acre: (1) all
applied in the row; (2) 1,500 pounds in the row and 500
pounds plowed down; (3) 1,000 pounds in the row and 1,000
plowed down; (A) 500 pounds in the row and 1,500 pounds on
the plowsole; (5) 2,000 pounds plowed down; (6) all applied
broadcast before plowing and (7) all applied broadcast after
plowing. The results indicated that the fertilizer applied
broadcast gave the highest yield, but not Significantly
higher, and that the other placements were comparable.
Similar results were reported for the same area by Hawkins

522 3;. (191.4).

12

Berger 23.§l- (1961) in Wisconsin compared the effects
of banded and broadcast applications of KCl and K2SOA, on P
uptake. Their results were summarized as follows:

(1) The same amount of KCl applied broadcast with

banded P and nitrogen (N) banded resulted in
higher P uptake than when the KCl was applied
banded.

(2) In most potato trials, P uptake was higher with
broadcast applications of either KCl or K2801+
than with comparable row applications.

(3) Broadcasting K resulted in higher Specific
gravity than with row applications.

(A) KZSOA is a better source of K than is KCl when
applied banded in the row With the P and N ferti—
lizer.

Nelson (1968) indicates that the modern trend on ferti-
lizer practices is to minimize Sizeable amounts at planting
in favor of large amounts broadcast and plowed down. Hawkins
(1965) reported that Sidedressing one half of the K either
as KCl or K280,+ resulted in Slightly better yields than when
all K was applied in side bands at planting. Sidedressing
three fourth's of the K when the plants were 3 to 5 inches
high, without irrigation, gave larger yields than when all
the K was banded at planting. Similar results were obtained
with chloride, sulfate, and nitrate of K although the best
yield, growth, and dry matter content was obtained with KNOB.

The same author (196A) compared applications of KCl either

l3

plowed down or broadcast after plowing with banded K at
planting, and obtained better early growth and as good or
slightly better yields with the plow down or broadcast

applications.

Effects of Rates and Sources of Potassium
_on tHe Absorption of Potassium, Magnesium
and CaICium—by Potato Plants

 

High rates of K applied to the soils can induce Mg
deficiency and lower the Ca content of plants in many crops
(Stanford gt al., 19A2; Boynton and Burrell, 19AA; MeHlich:
and Reed, 19A6;<Lugas and Scarseth, 19A7; McColloch 22.2l°’
1957). More Specific results of K inducing Mg deficiency
in potatoes have been reported by Hovland and Caldwell
(1960), D011 and Hossner (196A) and Adams and Henderson
(1962). Wallace e_t 21. (191.2) observed that K deficiency
symptoms were present on the leaves of potato plants grown
on plots where K was not applied, and Mg deficiency on
those grown where K was applied. Walsh and O'Donohoe (19A5)
reported that high rates of K induced severe Mg deficiency
which was reflected in a very low content of Mg in the
foliage while the tuber was affected only Slightly. They
also noted that the calcium (Ca) content of the foliage,
and to a lesser extent in the tubers, was lowered by K fert-
ilization.

Dunn and Rost (19A8) in Minnesota reported the results
of 23 field eXperiments which indicated that the application

of K increased the K content of potatoes grown on Ulen soils

.——.—~—

1A

and some Bearden soils and that the percentages of Ca, Mg
and S were not affected by K fertilization.

Ward (1959) grew potatoes in sand culture with various
levels of K ranging from complete deficiency to luxury con—
sumption. This resulted in increasing amounts of K in all
plant tissues and in decreasing amounts of Na, Ca, Mg, Fe,
and Cu. In certain tissues, particularly in the leaf and
stem, Mg content varied inversely with K content. The same
trend was noted with Ca, but was much less pronounced.
Roots and tubers did not Show these effects.

Tyler 23.2A- (1960), reported the results of A0 field
experiments and 73 field surveys from 1956 to 1960 in Cali-
fornia and concluded that the differences in K content
between K-deficient plants and those grown with sufficient
K fertilizer remain small until tuber growth commences.

Also in California, Lorenz (19A?) studied four treat-
ments on a HeSperia fine sandy loam: none, 50, 100 pounds
per acre of N as NHASOA with neither P or K and as a fourth
treatment, 125 pounds per acre each of P205 and K with the
highest rate of N. Leaf samples were first taken when the

plants were about Six inches high, and successive samples

were taken at approximately two week intervals until harvest.

From the analysis of the samples, it was concluded that the
K content of both plants and tubers decreased with age of
the plant and that the K application had no effect on the K

content of either plants or tubers at any stage of growth.

15

Wilcox (1961), in Indiana, applied 0, 75, 150 and 225
pounds per acre of K20 applied as KCl and as KZSOA' In order
to intensify the anion effect, N was applied as ammonium
sulfate [(NHA)ZSOA] with K2SOA and as ammonium chloride
(NHACl) with KCl. The analyses of leaves sampled at pre-

bloom stage Showed that as rate of K applications was increased,

K in the leaf tissue increased without any differential effect
due to associated anion. The Ca and Mg content of the leaf
decreased as the K rate increased. The Ca and Mg content of
the leaves tended to be higher when KCl was applied than when
KZSOA was applied.

Laughlin (1966), in the Matanuska Valley of Alaska from
1961 to 1963, compared sources and rates of K and soil and
Spray applications of magnesium sulfate (MgSOh). The foliage
and tubers were analyzed for N, P, K, Ca and Mg. In two of
the three years, K fertilizer increased the sum of the
cations (K + Ca + Mg) in the tubers and decreased the dry
matter, N, and P content, the Ca:Mg ratio of tubers, and the
content of Mg and the sum of cations in the tops.

Hossner and Doll (1968) indicate that with a soil Mg:K
ratio below 0.8 (expressed as me/lOO g), K induced Mg defic-
iency in potatoes grown on an acid sandy podzol in Northern
Michigan.

McColloch _e_t_ El. (1957) found that an exchangeable K:Mg
ratio, as lb/A, greater than 0.4 to 0.5 is suggestive of Mg
deficiency in citrus. They concluded that the exchangeable

K:Mg ratio appears to be a useful index in determining the

‘_-"—‘—‘

~ —s—.—..—

16

need for supplemental Mg, as have other workers with other
crops (Prince gg’gl,, 19A7; Walsh and(TDonohoe,l9A5).

Hovland and Caldwell (1960) explained the effect of K
in inducing Mg deficiency in soils as follows:

(1) The addition of K to soils may decrease the ease

of replacement of exchangeable Mg, thus lowering
Mg availability to the plants.

(2) Competition for exchange Sites on plant roots
caused by increasing levels of K, thus decreasing
the rate of Mg uptake.

(3) High amounts of K in the plants may in some way pre-
vent Mg from performing its functions.

Bear and Prince (19A5) postulated that each cation has
at least two functions in the plant, one which is unique to
that cation and the other(s) of the type that could be per—
formed by any of the three dominant cations—~K, Ca, and Mg.
Once the supply of each cation is adequate to meet the
specific need for it, then there can be a wide range in
ratios and quantities of cations that could be absorbed by

the plant to meet its total needs.

The Relation of Exchangeable Potassium to Yields

Usually, exchangeable K is used to predict the need for
K fertilizer. Bear §t_§l. (19AA) found that the amount of K
in the exchangeable form was a reliable index to the K sup-
plying power of the soil to alfalfa (Hardistan variety).
Stanford and Kelly (19A2) in Iowa found a close relationship

between the yield of corn and the amount of exchangeable K

17

in the soil. Hawkins 22.2l- (19A6), with potatoes in Maine,
reported that on soils containing more than 500 pounds of
exchangeable K20 per acre, little or no increase in yield
was obtained for more than 100 pounds of K20, which was the
maximum rate used.

In one of the more comprehensive reports, Tyler ggpal.
(1960) related K in the potato leaf petioles to exchangeable
K in the soil. Soils containing 100 ppm K usually resulted
in plant K values below A percent at late season, and the
soil then was considered deficient in K. Also, potato plants
growing in soils low in exchangeable (A6 ppm) K Showed a
narrow range of K concentration at early season. By mid-
season, the difference in plant K content between unferti-
lized plants and those which received A00 pounds of K20 per
acre was more than several fold the difference at early
season, and this difference remained large the rest of the
season.

Nelson and Hawkins (19A7) reported that in North
Carolina and in Maine, the K content of the leaves on potato
plants was related to the amount of exchangeable K in the
soil and to the amount of K applied. Terman (1950) concluded,
after summarizing 115 experiments in Maine, that few exper-
iments showed a yield response to more than lA0-200 pounds
of K20 and these responses were on soils low in exchangeable

K.

18

The Relation of Soil Test to the
Response to PotaSSIum Fértilizer

Crowther and Yates (19A1) adopted the Mitscherlich
standard curve equation with some modifications to determine
reSponse curves for the majority of arable crOpS in Great
Britain and northern Europe. Bray (19AA, l9A8, and 1956)
proposed the following modification of the Mitscherlich
equation so that soil test values could be used in predicting
the response to added increments of nutrients and to deter—
mine the rate required for maximum yield:

Log (A-y) = log A - (clbl-cx)
where A is 100 percent or maximum yield, y is the yield or
relative yield obtained at soil test value of bl, x is the
rate of nutrient required for maximum yield and £1 and g
are constants which are determined experimentally.

The constants in the Bray equation are being success—
fully used to determine P and K requirements for some crops,
(Arnold, 1953; Bray, 19A5; Melsted, 1967).

On potatoes, Smith and Sheard (1957) used the Bray
technique to evaluate ten extracting procedures for soil P
in trials conducted in various potato growing areas of south-
ern Ontario, over a period of three years.

MacKay'gt‘gl. (1959) reported the relationship of nitrate
N to potato yields at 21 experimental locations in Canada by
using the Bray'S modified Mitscherlich equation. A mean value
of‘gl for 58 individual tests was 0.0182. A close agreement

in the mean of 91 values was found for each of the two years,

19

for three varieties (Kennebec, Netted Gem and Sebago), and
for most of the potato Soils. Large yield increase would
be eXpected from applications of nitrogen applied to
potatoes grown on soils which tested 116 ppm N for mountain

soils or 6A ppm N for valley soils.

METHODS AND MATERIALS

Three field experiments were conducted to determine
the effects of rate, source, and placement of potassium (K)
fertilizer on yields, Specific gravity, and chemical com-
position of potatoes. Two experiments, one each in 1967
and 1968, were conducted on Hodunk sandy loam on the
M.S.U. Agricultural Experiment Station Farm at East Lansing,
and one experiment in 1968 on the Montcalm Experimental

Farm in Montcalm County

Field Procedure

Rate and Placement of Potassium
on Hodunk Sandy Loam in 1967

 

The experiment on Hodunk sandy loam in 1967 was con—
ducted to determine the effect of rate and placement of K
on yields, Specific gravity, and chemical composition of
potatoes. The experimental area tested pH 6.0, available
phOSphoruS (P) was 89 pounds per acre, and exchangeable
calcium (Ca), potassium (K), and magnesium (Mg) were 636,
135, and 131 pounds per acre, respectively. The plots were
laid out in a randomized block design with four replications,
and each plot consisted of A rows 32 inches apart and 23
feet long. The various rates and method of application of

K, applied as KCl, are given in Table 1. On all plots,

2O

21

65 pounds per acre of N as NHANO3 was broadcast and plowed
down prior to planting, as was the broadcast K on appropri-
ate plotS. An additional 60 pounds of N and AA pounds of

P per acre as A5 percent concentrated superphOSphate were
banded at planting in 2 bands located 2 inches on either
Side of the seed piece. On appropriate plots, banded K

was applied with the N and P.

Sebago potatoes (B-Size whole seed) were planted May
19, 1967 and harvested November 23, 1967.

Soil samples were taken from each plot of the experi-
ment on three different dates: (1) before fertilizers
were applied in the Spring, (2) on July 30, 70 days after
planting, and (3) on November 9, 170 days after planting.
At each sampling, at least 20 cores were taken midway
between the rows on each plot.

Petiole and leaf samples were obtained as described by
Tyler 33 31. (1960) by taking 50 to 60 petioles and leaves
from the center rows on each plot; the fourth or fifth
leaf from the growing tip of the plant was sampled. Generally,
the fourth leaf is the youngest fully developed leaf of the
plant. The petioles comprise that portion of the plant
between the stem and the base of the first leaflet, whereas
the leaf samples were made up of the leaves as removed from
the ends of the petioles.

The leaf and petiole samples were taken on July 28, 69
days after planting, when the plants were 1A to 18 inches

high. On November 9, ten complete plants were sampled

22

randomly from each plot, dried and weighed to calculate
total nutrient uptake. Plant samples were dried in a
forced-air oven at 650 C, and ground in a Wiley mill to
pass AO-mesh sieve for chemical analysis.

For Specific gravity determinations, 8 pounds of tubers
were randomly selected from each plot, washed thoroughly,
placed in a wire basket and suSpended in water from a hydro-
meter, and Specific gravity determined by the method des-
cribed by Smith (1950).

To obtain tuber samples for chemical analysis, ten
mature tubers were randomly selected from each plot, washed
with tap water, and then rinsed with distilled water. The
tubers were Sliced, and a one-pound sample taken for drying
so that the dry matter content could be determined. Samples
were dried in a forced-air oven at 650 C until a constant
weight was reached. After weighing, dried samples were
ground for analysis as described above.

Rate, Source, and Placement of Potassium
on Hodunk Sandy Loam in 1968

The experiment on Hodunk sandy loam in 1968 was con-
ducted to determine the effect of source, rate, and place—
ment of K on potato yields, Specific gravity, and chemical
composition. The experimental area tested pH 6.8, available
.P was 69 pounds per acre, and exchangeable Ca, K, and Mg
evere 966, 160, and 190 pounds per acre, reSpectively. The
IDlotS were laid out in a randomized block experiment with

1% replications as described for the 1967 experiment, except

——~"~

23

that the rows were 25 feet in length. The various potassium
rates and method of placement are listed in Table 7, and
potassium chloride (KCl), potassium sulfate (K2SOA) and
potassium carbonate (K2003) were used as sources of K.
In addition to theSe K treatments, four additional
treatments were included, three in which magnesium as
MgSOA°7H20 was banded on plots to which each of the three
sources of K were broadcast and one in which potassium- :~’“
magnesium sulfate [KZMg(SOh)2] was banded together with
supplemental KZSOA' 2;:i
As was described for the 1967 experiment, 65 pounds :WW-
of N and AA pounds of P were banded at planting on all plots, 'rrr
and the banded K and Mg treatments listed in Table 7 were ::__
banded with the N and P on appropriate plots. Sebago pota- *5"
toes were planted May 13, 1968, using B-Size whole seed,
and were harvested on October 10, 1968.
Petiole samples, obtained as described for the 1967
experiment, were taken 60, 98, and 130 days after planting,
or on July 13, August 21, and September 2A, respectively.
For the purposes of this discussion, the petiole samples
will be referred to as "early season", "mid-season", and
"late season", reSpectively. As has been pointed out by
Tyler e§_§l. (1960), "The length of the growing season for
potatoes varies widely even within the same district due to
environmental conditions, and it is advisable to classify
plants and Samples according to their physiological age

rather than to the time since planting." They consider

2A

"early season" plants to be from A to 6 weeks after emergence,
usually until the time of blossoming or the beginning of
tuber set. "Mid—season" is from blossoming or early tuber
set until the tubers are half grown, which is generally from
6 to 10 weeks after emergence. "Late season" is the time
tubers are half-grown until maturity.

Tuber samples were taken at harvest for determinations
of Specific gravity and total dry matter content and for
chemical analysis. The same procedures as described pre-
viously for the 1967 experiment were followed.

Rate and Placement of Potassium
on MEBride Sandy Loam in 1968

The experiment on McBride sandy loam in 1968 was con-
ducted to determine the effect of rate and placement of K
fertilizer on yield and chemical composition of Russet
Burbank and Sebago potatoes. The experimental area tested
pH 6.5, available P was 225 pounds, and exchangeable Ca, K,
and Mg were 950, 200, and 150 pounds per acre, respectively.
The plots were laid out in a Split plot design with four
replications; main plots were K treatments, and sub-plots
were varieties. Each plot consisted of 6 rows, 32 inches
wide and 50 feet long. Russet Burbank potatoes were planted
in three rows of each plot, and Sebago potatoes were planted
in the other three rows.

On all plots, 120 pounds of N was applied as NHANOB’
half of the N was broadcast before plowing and the other

half was banded at planting. Concentrated superphOSphate at

25

a rate to supply AA pounds P per acre was also banded at
planting on all plots. Potassium treatments, which are
listed in Table 1A, were either broadcast before plowing
or banded at planting with the N and P on appropriate plots.
The potatoes were planted on May 1 and 2, 1968, and were
harvested September 27, 1968.

Petiole samples were taken from each variety on each
plot 60 and 96 days after planting, or on July 2 and August
8. The sampling procedures described previously were fol—

lowed.

Laboratory Procedure

Soil Analyses

Soil samples were air-dried and ground to pass a 20-
mesh Sieve. Exchangeable cations (Ca, K, and Mg) were
extracted with 1.0 N NHAOAC adjusted to pH 7.0, using a 1:8
soil:Solution ratio and a one—minute extraction period.
Potassium in the extract was determined using a Coleman
Model 21 flame photometer, and Ca and Mg were determined
using a Model 290 Perkin-Elmer atomic absorption Spectro-
photometer; 1500 ppm La was added to the diluted extract for
Ca and Mg to eliminate interference from other ions as des-
cribed by Doll and Christenson (1966).

Available P was extracted for one minute using the Bray
P—l reagent (0.025 N HCl + 0.03 N NHhF) at 1:8 soil solution
ratio. Soil pH was determined in a 1:1 soil:water suSpen-

sion, using a glass electrode potentiometer.

26

To separate the clay from Hodunk sandy loam, a sample
of the soil was buffered at pH A.8 with a sodium acetate-
acetic acid buffer and then treated with H202 to destroy
organic matter, followed by leaching with more buffer and
then with water to remove the salts. The treated soil was
suSpended in water and the pH adjusted to the phenolphthalein
endpoint with NaOH. Dispersion was completed by Shaking the
soil suSpenSion for A8 hours on a reciprocating Shaker, with
periodic adjustments of the pH. The Sand fraction was
separated by decanting, and the clay fraction separated from
the Silt by sedimentation.

Oriented clay Specimens were prepared for X-ray dif-
fraction by depositing 25—30 mg of clay on ceramic plates.
Specimens were then Mg-Saturated and glycerol solvated.
Diffraction patterns were made with a Phillips-Norelco X-ray
unit using a copper source and nickle filter. Prior to heat
treatments of 3000 and 5500 C, the specimens were K-saturated
with l N KCl and washed free of chlorides. The X—ray dif-
fraction patterns indicated that kaolinite was the dominant
clay mineral, and that appreciable amounts of illite, ver-
miculite, a randomly stratified chlorite—vermiculite-
montmorillonite, and quartz were present. Cation exchange
capacity was 20.5 me/lOO g when determined by replacing Ca
with Mg, and was 11.A me/lOO g when determined by replacing
K with NHAI. Accordingly, the vermiculite content of the

clay was estimated at 5.9 percent.

27

Plant Analyses

 

For cation analyses of plant tissue, 0.5 grams of

oven dry ground plant tissue was ashed in a muffle furnace
at 5000 C for 1A hours. After cooling, 25 ml. of l N HNO3
was added, and the acid was evaporated to dryness on a hot
plate over a period of 2 to 3 hours. The residue was then
placed in a muffle furnace and reashed at 5250 C for 10
minutes. After cooling, the residue was dissolved in 25 ml.
of l N HCl, the resulting solution filtered into a 100 ml.
volumetric flask, and Ca, K, and Mg determined in the solu-

tion as described above for the soil extract.

Statistical Analyses

All the field and laboratory analysis data from the
East Lansing field experiments were subjected to analysis
of variance for a completely randomized block design. The
field and laboratory analysis data for the Montcalm field
experiment were subjected to analysis of variance using a
Split plot design with the K treatment as the whole plot and
potato variety as sub—plots.

Simple linear regressions were used in order to relate
Specific gravity to percent tuber dry matter weight, and to
evaluate the effects of rate, placement, and source of K on
the levels of the various nutrients in the petioles. The
least Significant differences (lsd) is used to denote the

statistical differences between treatments.

RESULTS AND DISCUSSION

Rate and Placement of Potassium on Hodunk
SandyILoam in7I967

An experiment was conducted on Hodunk sandy loam in
1967 to determine the effects of rate and placement of K
on yields, Specific gravity, percent dry weight of tubers,
and the K, Ca, and Mg contents of petioles, leaves, vines

(or tops) and tubers of Sebago potatoes.

Yields of Potatoes

 

In 1967, yields of potatoes on Hodunk sandy loam were
increased when K was applied (Tables 1 and 2); the highest
yields were obtained when 200 pounds of K per acre was
broadcast. The maximum yield, obtained when 200 pounds of
K was broadcast, was Significantly higher (0.01 level) than
when no K was applied. When A00 pounds of K was broadcast,
the yield was lower than when 200 pounds was broadcast, but
it was not Significantly lower. No statistically signifi-
cant differences were noted between comparable rates of
banded and broadcast K, but yields when K was banded were

consistently lower than when similar rates were broadcast.

Specific Gravity
The Specific gravity of the tubers decreased as the

rate of K increased (Table 1). For both the banded and the

28

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30

Table 2. Significant differences of Sebago potato
yields as related to rate and placement of K
on Hodunk sandy loam in 1967.

 

 

 

 

Treatments compared Probability level
Banded:
No K vs K (All rates) .01
50 vs 100 lbs and 200 lbs ns
100 vs 200 lbs and A00 lbs ns
200 vs A00 lbs ns
Broadcast:
No K vs K (All rates) .01
100 vs 200 lbs .01
100 vs A00 lbs .05
200 vs A00 lbs ns
Banded K vs broadcast K ns
200 banded vs 200 broadcast nS
lSd (.05) 63

lsd (.01) 82

 

31

broadcast treatments, the Specific gravity was lower (0.01
level) when K was applied at a rate of A00 pounds per acre

than when applied at 200 pounds.

Percent Dry Weight of Tubers

AS was the case with Specific gravity, the percent dry
weight of tubers decreased as the rate of both banded and
broadcast K was increased. The percent dry weight was
Significantly less when A00 pounds of K was banded than when
no K was applied or when 50 or 100 pounds was banded.

. Total dry matter produced per acre was directly related
to tuber yields (Table 1). Thus, even though increasing the
rate of K decreased the dry matter content of the tuber as
measured by either specific gravity or percent dry weight,
the total dry matter produced per acre was increased when

the yields increased.

Yield of Vines
The vine yields, in terms of dry matter per acre, were

not affected by rate or placement of K (Table 1).

Potassium Concentration in Petioles and Leaves

At mid-season (69 days after planting), the K concen-
tration in the petioles inoreased with each additional
increment of banded K and with each increment of broadcast
K up to 200 pounds per acre (Table 3). However, the increase
in petiole K when 50 and 100 pounds of banded K and 100
pounds of broadcast K were applied was not Significantly

higher than when no K was applied. No differences were

32

noted in the K content of petioles between comparable banded
and broadcast treatments, although petiole K when 100 and
200 pounds of K were broadcast was Slightly higher than when
the same rates were banded.

In the leaves, the K concentration also increased for
each additional increment of applied K for both banded and
broadcast treatments (Table 3), although the increased level
of leaf K when 50 and 100 pounds K were applied was not
Significantly higher than when no K was applied. No differ-
ences were apparent when banded and broadcast treatments
were compared. The concentration of K in the leaves was
only about one-third of that in the petioles for all com-

parable treatments.

Potassium Concentration in Vines

The K concentration in potato vines increased with
increasing rates of both banded and broadcast K (Table A),
although only in the 200 and A00 pound rates was the K con-
centration Significantly higher than that when no K was
applied. No differences in K concentration of the vines
were noted between Similar rates of banded and broadcast K.)

The level of K in the vines was lower than that of 9

either the petioles or leaves (Tables 3 and A) on comparable

treatments.

Potassium Concentration in Tubers
The K concentration in the tubers, calculated on a dry—

weight basis, increased with each increment of applied K

— -....-

33

Table 3.

Potassium, calcium, and magnesium concentrations in

petioles and leaves in early season (69 days after
planting) as affected by rate and placement of K on

Hodunk sandy loam in 1967.

 

 

Cation content (%)

 

 

 

 

 

 

Pounds K per acre Petioles Leaves
Banded Broadcast K Ca Mg K ,Ca Mg
0 0 6.59 1.0A 0.77 1.78 1.66 0.77
50 -- 7.3A 1.06 0.58 2.27 l.Al 0.68
100 -— 7.A5 0.9A 0.50 2.31 1.29 0.66
200 -- 8.67 0.91 0.A8 2.66 1.31 0.66
A00 -— 10.09 0.76 0.37 3.28 1.16 0.59
-— 100 7.6A 0.91 0.A6 2.37 l.A6 0.69
—- 200 9.A0 0.89 0.A7 2.65 1.25 0.66
-- A00 9.16 0.76 0.32 2.99 1.12 0.60
lsd (.05) 2.06 .15 .19 .39 .18 .07
lsd (.01) 2.81 .21 .27 .5A .25 .10

 

34

(Table A), and the increase when 200 and A00 pounds K were
applied was Significantly higher than when no K was applied.
Although not statistically Significant, K content of tubers
tended to be higher when K was banded than when K was broad-
cast.

The K content of the tubers was higher than that of
the vines (Table A) for comparable treatments, but was

lower than that of petioles and leaves (Table 3).

Potassium Uptakegby Vines and Tubers

The uptake of K per acre by both vines and tubers
increased as the rates of both banded and broadcast K
increased (Table 5). The K uptake by vines was higher (0.01
level) when A00 pounds of K was applied, both banded and
broadcast, than for any of the other rates of application,
and the uptake of K when A00 pounds was applied was higher
(0.01 level) when K was banded than when broadcast.

The uptake of K by tubers was higher than that of vines,
as would be expected because of both the higher dry matter
yields and the higher K content of the tubers. Recovery of
applied K tended to be low, only about 20 to 25 percent of
that applied when recovery is calculated as the difference
between K uptake when K fertilizer was applied and K uptake

when no K was applied.

Calcium Concentration in Petioles and Leaves
The Ca concentration in petioles at mid-season (69 days

after planting) decreased as the rate of K increased for

35

both banded and broadcast K applications (Table 3); however,(‘

1

this decrease was statistically significant only when 200 )
or A00 pounds K were applied. The effect of K on decreasing
Ca concentrations in the petioles was similar for both
banded and broadcast treatments.

The Ca concentration in the leaves also decreased with
increasing rates of K for both banded and broadcast appli-

cations (Table 3). The Ca concentration in the leaves was

consistently higher than that of the petioles.

Calcium Concentration of Vines

The Ca concentration of the vines decreased as the
rate of K increased, but this decrease was not statistically
significant except when A00 pounds of K was applied (Table

A). No differences due to placement of K were noted.

Calcium Concentration in Tubers
The Ca concentration in the tubers was not affected by
any of the K treatments, and the levels found were extremely

low, averaging 0.77 percent (Table A).

Calcium Uptake by Vines and Tubers
The uptake of Ca by vines and tubers was not affected
by either rate or placement of K (Table 5). The vines con-

tained about 10 times as much Ca as the tubers.

Magnesium Concentration in Petioles and Leaves
The magnesium concentration in petioles decreased as

rate of K increased (Table 3), and this decrease tended to

Table A.

36

Potassium, calcium and magnesium concentration in
vines (150 days after planting) and tubers as
affected by rate and placement of K on Hodunk
sandy loam in 1967.

 

 

Cation content (%)

 

 

 

 

 

 

Pounds K per acre Vines Tubers

Banded Broadcast K Ca Mg K Ca Mg
0 -— 0.51 2.26 1.01 1.58 0.07 0.11
50 -- 0.92 1.99 0.91 1.72 0.12 0.12
100 -- 0.85 1.93 0.8A 1.91 0.07 0.12
200 -- l.A2 1.90 0.78 2.1A 0.07 0.12
A00 -— 2.A8 1.63 0.71 2.A6 0.06 0.12
-— 100 0.86 2.09 0.93 1.88 0.07 0.11
-— 200 1.12 1.89 0.81 2.08 0.06 0.11
-- A00 2.1A 1.71 0.7A 2.25 0.06 0.12

lsd (.05) .5A . .38 .15 .25 ns nS
(.01) .7A .52 .21 .3A nS ns '

 

37

 

 

 

 

 

 

 

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38

be relatively greater when K was broadcast than when banded,
but not significantly greater.

The Mg concentration in the leaves decreased Signifi—
cantly as the rate of K was increased for both banded and
broadcast applications of K. No differences in Mg concen-
tration were noted due to band or broadcast placement of K.
The concentration of Mg in leaves was about the same as
that of the petioles when no K was applied, but the decrease
in Mg when K was applied was relatively greater in the peti—

oles than in the leaves.

\

Magnesium Concentration in Vines

The Mg concentration of vines decreased as the rate of
K increased for both the band and the broadcast applications
(Table A). This decrease in Mg concentration was statisti-
cally Significant for all rates of applied K except when 50
pounds was banded. The relative decrease in Mg concentration .
tended to be greater, but not Significantly greater, when K

was banded than when broadcast.

Magnesium Concentration in Tubers
The Mg concentration in tubers was not affected by K

rate or placement (Table A).

Egnesium Uptake by Vines and Tubers
The uptake of Mg by vines and tubers was not affected
t0? either rate or placement of K (Table 5). The total

turtake of Mg was slightly less than 20 pounds per acre, and

39

the vines contained approximately four times as much Mg as

the tubers.

Exchangeable Soil Potassium

In soil samples taken at mid—season (70 days after
planting), exchangeable K was not affected when fertilizer
K was banded, and the level of exchangeable K tended to be
lower than that before planting (Table 6 and Figure 1).

This indicates that the plants were absorbing soil K as well
as banded fertilizer K. On the other hand, the level of
exchangeable K on the plots where K fertilizer was broadcast
increased as the rate of K increased (Table 6 and Figure 2).
Whenever fertilizer K was broadcast, exchangeable K was
equal to or higher than the initial exchangeable K before
planting.

Exchangeable K at late season (170 days after planting)
showed more variation than the initial and mid-season
exchangeable K, and increased as the rate of either banded
or broadcast K was increased. However, only when A00 pounds
K was banded was the exchangeable K on any of the banded
treatments higher than the initial level of exchangeable K;
When K was broadcast, exchangeable K at 170 days was lower
than the initial level only when 100 pounds was broadcast.

The total uptake of K by vines and tubers (Table 6)

‘When no K was applied was about 30 percent greater than the

decrease in exchangeable K during the season (Table 3), indi—

oating either that a significant amount of non-exchangeable

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POUNDS EXCHANGEABLE K PER ACRE

 

 

120»

Al

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure l.

 

 

 

 

 

 

 

 

 

 

 

 

 

0 50 I00 200
POUNDS K HANDED PER ACRE

BEFORE PLANTING
MIDSEASON
LATE SEASON

400

1

 

E
nlillililllll;

Exchangeable potassium before planting, at
mid—season, and late season, (0, 70 and 170
days after planting, reSpectively) as
affected by rates of K applied banded on

Hodunk sandy loam in 1967.

A2

I90 A

IBO

 

ISO-

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[30

IZO-

 

 

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at

POUNDS EXCHANGEABLE K'PER ACRE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

o [00 .200 300 '
Romans K BROADCAST PER ACRE

 

BE FORE PLANTING 1:1-3’..-
MIDSEASON ‘
WWI?!

LATE SEASON
Figure 2. Exchangeable potassium (l‘N NHAOAC pH 7.0)
before planting, at mid—season, and late
season (0, 70 and 170 days after planting,
reSpectively) as affected by rates of K
applied broadcast on Hodunk sandy loam in 1967.

 

 

 

 

 

   

MINIW WWW

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UNCROPPED
I) Mg SATURATED

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\ (I A A N “AMI " .II II --INW
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l A» [12 [lo a g 4L
DE GREES 2 9
Figure 3. X-ray diffraction patterns for coarse clay (0.2 — 2.0 u)

of Hodunk sandy loam soil.

#4

K was released during the season or that a considerable
portion of the K absorbed by the plant came from below the
plow layer. On the other hand, when #00 pounds of K was
broadcast, exchangeable K was increased by 45 pounds, and
the vines and tubers contained 132.5 pounds; this leaves
22.5 pounds of the original #00 pounds which was either
fixed or leached below the plot layer. This soil would be
expected to fix and release K since illite and vermiculite

are important clays in this soil (Figure 3).

Exchangeable Soil Calcium

 

Exchangeable Ca in the soil during the growing season

was not affected by the K fertilizer treatments (Table 6).

Exchangeable Soil Magnesium
Exchangeable Mg during the growing season was not

affected by the application of K fertilizers (Table 6).

Relation Between Yields and Soil Potassium

In order to describe the relation between yields at the
initial level of soil K and the rate of K fertilizer, the
Mitscherlich equation (as given by Bray, l9u5) was used:

Log (A - y) = Log A - clbl

in which A was the maximum yield obtained (426 cwt/A or 100%),
y the yield when no K was applied (251 cwt/A or 59%), and
b1 the level of exchangeable K prior to applying fertilizer

(135 pounds/acre). The calculations are as follows:

= Log A _ Log (A - y) = 2.629h11552.2430h = 0.00287

c
1 —b1

#5

Using the preceding calculated value for 01 (0.00287), the
curve relating yield to exchangeable soil K was drawn
(Figure A). This curve relates yield only to level of soil
K, and indicates that maximum yields would be obtained at a
soil test level of about 400 pounds of exchangeable K.

In order to relate the rate of applied fertilizer K to
yields, the modified Misterlich equation proposed by Bray
(1945) was used:

Log (A — y) = Log A — (Clbl - cx)

in which 2 is the constant for fertilizer K and x is the
rate of fertilizer K. The following calculations were made,
equating the maximum yield (A) of #26 cwt. to 100%, equating
the yield for y of 333 cwt. to 78% when x or rate of K is
100 pounds broadcast, and using the same values of 0.00287

and 135 for £1 and bl reSpectively:

Log (100 - 78) = Log 100 - (0.00287 x 135 - 100 3)
0.34242 = 2.00000 - 0.38722 — 100 c

C = 0.27036

T00—_ = 0.00270

The complete equation then becomes:
Log (A - y) = Log A - (0.00287 bl - 0.00270 x)

For practical use, fertilizer recommendations were
developed to calculate the amount of fertilizer needed to
obtain a yield equivalent to 95% of the maximum possible
yield. Calculations were made using the above equation

from which:

46

L06 (A-v) = LOG A— 0. 00287 b.

400»

300'

ZOOr

IOOr

CWI/ACRE

 

 

 

0 5‘0 :00 :50 200 250 300 360 400 450 550

POUNDS EXCHANGEABLE K PER ACRE

Figure 4. Mitscherlich response curve relating yield to
exchangeable soil K (Hodunk sandy loam, 1967).

ud—‘. c

47

Log (100 — 95) = Log 100 — (0.00286 bl - 0.00270 x)

= 1.30103 - 0.00287 bl
0.00270

X

 

From this equation, the rate of fertilizer required to obtain
95 percent of the maximum yield (x) can be calculated for

any soil test level (bl)’ or a graph such as that shown in
Figure 5 can be constructed.

The soil test calibration developed here represents the
results of only one year at one location, and would not be
adequate for general fertilizer recommendations. However,
it does describe the response obtained at this location,
and illustrates a method that can be used to calibrate soil

tests.

Rate, Source, and Placement of Potassium on
Hodunk Sandy Loam in l968

Another experiment was conducted on Hodunk sandy loam
in 1968 to determine the effect of the effects of rate and
placement of KCl and rate of broadcast K2804 and K2C03 on
yields, Specific gravity, and chemical composition of peti-

oles of Sebago potatoes.

Yield of Potatoes

In 1968, the yields increased when K was applied (Table
7), and the highest yield was obtained when 200 pounds of K
was broadcast as KCl. When K as KCl was banded, yields

tended to be slightly lower than for the comparable broadcast

48

treatments, although these differences were not statisti-
cally significant (Table 8).

No significant differences in yields were noted due
to the different sources of K (Tables 7 and 9), but yields
tended to be higher when 200 and 000 pounds K were applied
as KCl than when the same rates were applied as K2804 or
K2C03.

When 40 pounds per acre of Mg was banded with 400
pounds of K broadcast as KCl, K2S04, or K2003, yields were
not different than those obtained when the same sources of
K were broadcast without banded Mg. When sulfate of potash-
magnesia was banded, and supplemented with K280,+ so that a
total of 400 pounds of K and 40 pounds of Mg were applied,
yields were not different from those obtained with compar—
able rates of the other sources of broadcast K when Mg was

applied, or when the same amount of K was banded as KCl

without Mg.

Specific Gravity of Potatoes

The Specific gravity decreased as the rate of K was
increased (Table 7); and when KCl was applied, the Specific
gravity was significantly lower (0.01 level) than when KZSOA
or K2C03 were applied.

It should be mentioned that the anion 003+2 will react
with soil hydrogen ions (H+) and form water and carbon
dioxide, and thus does not add to the salt content of the

soil. This may have had some effect which caused the

"‘.--

l
‘h “I“...

(X) POUNDS K FOR 95’]. MAXIMUM YIELD

500

400

300 '

200 -

 

A9

    

x . LOG A - LOG (A-Y)-0.00§§6 b
0.00270

   

 

[OO-
50 ICC 200 300 400
(h) K SOIL TEST
Figure 5. Relationship between soil test value and rate

of K application for expected 95% maximum
yield response (Hodunk sandy loam, 1967).

w..- -—

50

Table 7. Yield and specific gravity of Sebago potatoes as
related to source, rate and placement of K on
Hodunk sandy loam in 1968. '

 

 

 

 

 

 

Pounds K Pounds Mg
Source per acre per acre Yield Specific
of K Banded Broadcast Banded cwt/A gravity
None -- -- -- 404 1.083
KCl -- 100 -- 426 1.083
KCl —- 200 -- 477 1.079
KCl -- 400 -- 459 1.077
K01 -- 800 -- 435 1.075
K2804 -— 200 -- 426 1.082
K2804 -- 400 -- 416 1.079
K2804 -- 800 -- 441 1.079
K2003 -- 200 -- 434 1.083
K2003 -- 400 -- 454 1.079
K2003 -- 800 -- 438 1.082
K01 100 -- -- 416 1.083
KCl 200 -— -— 441 1.082
KCl 400 -- —— 450 1.080
K01 -- 400 40 469 1.077
K2804 -— 400 40 417 1.076
K2C03 -- 400 40 417 1.081
K2804Mg 400 -- 40 445 1.081
lsd (.05) 53 0.004

(.01) 70 0.005

 

51

Table 8. Significant differences of Sebago potato
yields as related to rate and placement
using potassium chloride (KCl) as a source
of K fertilization on Hodunk sandy loam in

 

 

 

 

1968.
Comparison Probability level

Banded:

No K vs K (All rates) ns

100 vs 200 lbs and 400 lbs ns
Broadcast:

No K vs K (All rates) ns

No K vs 200 .01

No K vs 400 .05

No K vs 800 nS

100 vs 200 lbs and 400 lbs ns

200 vs 400 lbs and 800 lbs ns
lsd (.05) 53
lsd (.01) 70

 

_4.-~_-

52

Table 9. Significant differences of Sebago potato yields as
affected by sources and rates of K on Hodunk sandy
loam in 1968.

 

 

 

Comparison Probability level
Sources:
No K vs K sources (All sources) ns
KCl VS K230]+ ns
KCl vs K2003 ns
K2804 VS K2003 nS

Rates and Sources:

200 lbs KCl vs 200 lbs K2804 and ns
200 lbs K C0
2 3

400 lbs KCl vs 400 lbs K2804 and ns
400 lbs K C0
2 3

800 lbs KCl vs 800 lbs K2804 and ns
800 lbs K2C03

200 lbs KCl vs 400 K280 .05

4

Sources and Magnesium:

400 lbs (All sources) vs 400 lbs (All sources) ns
+ 40 lbs Mg

 

lsd (.05) 53
lsd (.01) 70

 

53

differential reaction of K2003 with respect to decreasing

the Specific gravity.

Potassium Concentration in Petioles

The potassium concentration in the petioles at early
season (60 days after planting) increased as the rate of K
increased for all the K sources (Table 10). When 200 and
800 pounds of K per acre were applied broadcast, the K con-
centration was lower (0.01 level) when K2003 was applied
than when KCl or K280,+ was applied (Figure 6).

At mid—season (98 days after planting) the K concen—
tration was generally lower than that at early season (Table
10 and Figure 6), but the K concentration still increased
with increasing rates of K.

At late season (130 days after planting) the K con-
centration was generally lower than that obtained at mid-
season, although the K concentration still increased as the
rate of K increased (Table 10).

It is interesting to note that when K2804 was the source
of K, a fairly uniform increase in K concentration was noted
as the rate of applied K increased at each of the three
sampling dates, while K concentrations in petioles showed
more variability at early and mid-season when KCl and K2C03
were the sources of K. The K concentration in petioles was
not affected by K placement, although K in petioles tended
to be higher when K as KCl was banded at early season than
when broadcast, but it tended to be lower on banded treat-

ments at mid and late season.

‘9
-
‘—

54

Table 10. Potassium concentration (%) in petioles of Sebago
potatoes in early season, mid-season and late
season (60, 98 and 130 days after planting,
respectively) as affected by source and rate of K
on Hodunk sandy loam in 1968.

Fertilizer treatment Potassium content (%)

 

 

 

 

 

 

Pounds K Pounds Mg
per acre per acre

Source 60 98 130
of K Banded Broadcast Banded days days days
None -- -- -- 7.72 3.89 1.98
KCl -- 100 -- 9.01 5.67 2.15
KCl -- 200 -- 10.55 6.52 3.05
KCl -- 400 -— 10.50 8.33 5.06
KCl -- 800 -- 13.01 8.39 6.62
K2804 -- 200 —- 10.25 6.72 3.22
KZSOLP -- 400 —- 10.60 7.48 4.03
K2804 —- 800 —— 12.50 8.96 5.77
K2003 -- 200 -— 8.61 5.89 3.29
K2003 -- 400 -— 10.70 7.40 4.27
K2C03 -— 800 -- 10.55 7.96 5.31
KCl 100 —- -- 9.95 5.23 2.01
KCl 200 -- -- 10.75 6.55 2.76
KCl 400 -- —- 12.70 8.15 4.26
KCl -- 400 40 11.80 8.33 5.24
K230,P -- 400 40 10.35 7.63 4.52
K2C03 —- 400 40 10.30 6.61 4.05
KZSOhMg 400 -- 40 11.45 6.05 2.74
lsd (.05) lfl34. 1.12 1J02
(.01) 1.79 1.50 1.30

 

I

I31

0 ,
1
I

IN PETIOLES

POTASSIUM

96
a:
4+

 

 

55

_EARuv
SEASON

 

 

jMD-
SEASON

 

 

LATE
SEASON

 

Figure 6.

A
V

200

400 600 860

POUNDS K APPLIED PER ACRE

Effect of rate and source of K on the K concentra-

tion in petioles at early season, mid-season and

late season.

56

Applying Mg in the fertilizer band did not affect K
in petioles except that K was lower when sulfate of

potash-magnesia, supplemented by K2SO4’ was banded.

Potassium Concentration in Tubers

The K concentration of the tubers tended to increase
when K fertilizers were applied (Table 11), but no differ-
ences due to the different sources of K were noted.

No differences in K concentration in the tubers were
noted between banded and broadcast applications of KCl,

or when Mg was applied.

Calcium Concentration in Petioles

The Ca concentration in petioles at the early season
sampling (60 days after planting) was decreased when K
fertilizers were applied, but at the mid- and late season
samplings (98 and 130 days after planting), Ca concentra-
tion was not affected, even though it tended to be lower in
mid—season when K was applied (Table 12).

The Ca concentration in the petioles at early season
was lowest when K2804 was applied, but no differences were
noted between KCl and K2003. When KCl was banded, Ca in
petioles tended to be lower than when KCl was broadcast,
but this difference was not statistically significant.
Applying Mg in the fertilizer band did not affect Ca con-

centration in petioles.

57

Table 11. Percent of potassium, calcium, and magnesium in
mature tubers as affected by source and rates of
K on Hodunk sandy loam in 1968.

 

 

 

 

 

 

Pounds K Pounds Mg
per acre per acre Tubers, content in (%)

Source

of K Banded Broadcast Banded K Ca Mg
None -— —— -— 1.52 0.04 0.12 .fl‘
KCl -- 100 -- 1.59 0.03 0.16 :g:
KCl -- 200 -- 1.96 0.03 0.24 f
KCl —- 400 -- 1.91 0.03 0.20 75
K01 -— 800 —— 2.36 0.03 0.19 § f;
K2304 —- 200 -- 2.27 0.03 0.25 E;
K2804 —- 400 -— 1.99 0.04 0.21 _;::
K2304 -- 800 —- 2.44 0.04 0.29 :;;
K2C03 -- 200 —- 1.98 0.03 0.23 ;:if
K2C03 -- 400 -- 2.02 0.04 0.23 ”’
K2C03 -- 800 -- 2.00 0.04 0.20
KCl 100 —- -- 1.73 0.02 0.21
KCl 200 —— -- 1.85 0.05 0.21
KCl 400 -- -- 2.26 0.04 0.22
KCl -- 400 40 2.45 0.03 0.21
K2804 -— 400 40 2.11 0.04 0.12
K2C03 -- 400 40 1.72 0.04 0.14
KZSOAMg 400 -- 40 2.02 0.03 0.26

lsd (.05) .45 ns ns

(.01) .57 ns ns

 

58

Table 12. Calcium concentration (%) in petioles of
Sebago potato in early season, mid-season,
and late season (60, 98 and 130 days after
planting, reSpectively) as affected by source
and rate of K on Hodunk sandy loam in 1968.

 

 

Pounds K Pounds Mg Calcium content (%)

per acre per acre

Source 60 98 130
of K Banded Broadcast Banded days days days

 

 

 

 

None -- -- -- 1.77 1.42 1.17 £:::
K01 —— 100 -— 1.57 1.18 1.39 :22;:
KCl -- 200 -- 1.60 1.33 1.34 .Lp5f
KCl -- 400 —- 1.33 1.23 1.28 ;;;j
KCl —- 800 -— 1.38 1.18 1.28 31::
K250,P -- 200 —- 1.28 1.24 1.28 gig:
K250,F -- 400 -— 1.09 1.08 1.34 {3:3
KZSOA —- 800 —— 1.09 1.09 1.22 34::
K2003 -- 200 -- 1.62, 1.28 1.28 45,.
K2C03 -- 400 -- 1.47 1.23 1.45

K2003 —— 800 —- 1.28 1.14 1.39

KCl 100 -- -- 1.41 1.48 1.28

KCl 200 -- -- 1.24 1.13 1.39

KCl 400 —- -- 1.09 1.18 1.17

K01 -- 400 40 1.19 1.23 1.28

K2804 -- 400 40 1.28 1.08 1.45‘

K2003 -- 400 40 1.28 1.28 1.34

K2804Mg 400 -- 40 1.19 1.19 1.28

lsd (.05) .28 ns ns

(.01) .35 ns ns

 

59

Calcium Concentration in Tubers

The Ca concentration in the tubers was not affected by

either rate or source of K fertilizer (Table 11).

Magnesium Concentration in Petioles
The Mg concentration in petioles decreased as the rate
of K increased at each of the three sampling dates except 1
at the late season sampling when 100 pounds of K was applied :fp11417
as KCl (Table 13). SETT’W;
At the early season sampling, Mg in petioles tended to ,::“*w
be higher when KCl was applied than when K2801+ or K2003 was ~llfifif
applied, except when 200 pounds of K was applied as K2003 :~-*H=
(Figure 7). 111114
When KCl was banded at planting, Mg in petioles tended “”*‘7-
to be lower, but not significantly lower, than when KCl was
broadcast. Applying 40 pounds of Mg fertilizer in the band“)
at planting did not affect Mg levels in petioles.
At the mid-season sampling, Mg levels in petioles were
consistently higher than at the early season sampling, and
Mg concentrations in the petioles decreased as the rate of
K was increased. When K2804 was applied, Mg in petioles
was lower than when KCl or K2C03 was applied.
Again, Mg in petioles appeared to be slightly higher,
but not significantly higher, when KCl was banded than when
KCl was broadcast. The levels of Mg in petioles were not
increased when Mg fertilizer was banded at planting.
At the late season sampling, Mg in petioles was higher-

than for all comparable treatments at the mid-season

60

Table 13. Magnesium concentration (%) in petioles of
Sebago potato in early season, mid-season and
late season (60, 98 and 130 days after plant-
ing, respectively) as affected by source and
rate of K on Hodunk sandy loam in 1968.

 

 

 

 

 

 

 

Pounds K Pounds Mg Magnesium content (%)

per acre per acre
Source 60 98 130
of K Banded Broadcast Banded days days days
None -- -- -- 0.99 1.02 1.55
KCl -- 100 -- 0.83 1.08 1.66
KCl -- 200 -- 0.65 1.03 1.48
KCl -- 400 -- 0.63 0.82 1.37
K01 -- 800 -- 0.47 0.67 1.25
K2804 —— 200 —- 0.58 0.90 1.21
K2804 -- 400 -- 0.56 0.66 1.06
K2804 —- 800 —- 0.39 0.56 0.90
K2003 —- 200 -- 0.80 1.02 1.18
K2C03 -- 400 -- 0.53 0.77 0.99
K2003 -- 800 —- 0.44 0.65 0.89
KCl 100 -- -- 0.76 1.29 1.71
KCl 200 -- -- 0.49 1.01 1.39
KCl 400 -- -- 0.37 0.82 1.40
KCl -- 400 40 0.60 0.91 1.37
K2504 -- 400 40 0.57 0.64 1.04
K2003 -- 400 40 0.61 0.84 1.16
K2804Mg 400 -- 40 0.52 0.92 1.49
lsd ( 05) .27 .29 .28
( .36 .37 .37

—----,.-v-'

61

 

 

 

 

 

 

1.5-
L44
1.31
KCI '
n.2-
LI‘
'LATE 4 - ,
SEASON .-:::
LOJ H 'ZIT
III .........
_I 4 4-1.1.1..
9 0.8 . TWA]
.- ._::'*"'.-,_,-
w .11---. ,
0. EM
007‘
Z
MID-
§ 0'61 SEASON
3 .
3 as .
g _EARLY
04‘ SEASON
.2 .
0.3«
0.2.
0.1a

200 400 600 800
POUNDS K APPLIED PER ACRE

Figure 7. Effect of rate and sources of K in the Mg concentra-
tion in petioles at early season, mid-season and
late season.

62

sampling, and Mg levels again decreased as the rate of K
fertilizer increased. The level of Mg in petioles was
markedly higher when KCl was applied than when K2804 or
K2C03 was applied. No differences in petiole Mg levels
were apparent between banded and broadcast applications
of KCl. Petiole Mg was not increased when Mg fertilizers
were banded at planting. At no time was the uptake of Mg
either increased or decreased when sulfate of potash-
magnesia was used as a source of K and Mg.

It was apparent that at the late season sampling, the
anion accompanying the K in the fertilizer affected the Mg
concentration in the petioles, and the differences found
in the decrease of Mg in petioles due to the different K
sources were relatively greater than at the earlier

samplings.

Magnesium Concentration in Tubers
The Mg concentration in tubers was not affected by rate

or source of K fertilizer (Table 12).

Rate and Placement of Potassium on
McBride‘Sandy Loam in 1968

The experiment on McBride sandy loam in 1968 was con-
ducted to determine the effects of rate and placement of K
on yields, and the Ca, K, and Mg concentrations in petioles

of Sebago and Russet Burbank potatoes.

’4‘

l'~ .
r- -"._-_.4

iara-9.. pus-t-

63

Yield of Potatoes

The yields of both Sebago and Russet Burbank potatoes
were increased when K fertilizer was applied (Table 14),
but statistical analyses of the data do not indicate that
these differences are significant.

The highest yield of Sebago potatoes was obtained when
100 pounds of K was banded at planting, and the highest
yield of Russet Burbank potatoes was obtained when 200
pounds of K was banded. Higher yields were obtained with

Sebago potatoes than with Russet Burbank potatoes.

Potassium Concentration in Petioles

At the early season sampling (60 days after planting),
K in the petioles of Sebago potatoes was increased only when
200 pounds of K was banded at planting and when 400 pounds K
(300 pounds broadcast plus 100 banded) was applied (Table
15). In Russet Burbank petioles, K was increased by all
rates of applied K except when 50 pounds was applied (either
broadcast or banded). No consistent differences were noted
between banded and broadcast applications of K, but K in
petioles of Sebago potatoes tended to be slightly higher
when K was banded. No differences were apparent between
the K content of Sebago and Russet Burbank potatoes, although
the difference in K content between the low and the high
rates of K seemed to be greater in Russet Burbanks.

At mid-season (96 days after planting), the K concen-

tration in petioles of both varieties was lower than at the

 

." par-W“

64

Table 14. Yield of Sebago and Russet Burbank potatoes as
affected by rate, placement and time of K on
McBride sandy loam in 1968.

 

 

 

 

 

Pounds K per acre Sebago Russet Burbank :EE::;5
Yield Yield if .33;
Broadcast Banded Total cwt/A cwt/A tjjxjj
~»--_l.
0 0 0 268 218 13:}
o 50 50 304 247 £33
0 100 100 3 24 250 W-
0 150 150 316 246
0 200 200 318 272
300 100 400 294 252
50 0 50 316 262
100 0 100 317 248
200 0 200 307 250
lsd (.05) ns ns

lsd (0.5) treatment x variety ns ns

 

Table 15.

65

Potassium concentration (%) in petioles of Sebago
and Russet Burbank potatoes in early and mid-season
(60 and 96 days after planting, reSpectively) as
affected by rate, placement and time of K on McBride
sandy loam in 1968.

 

 

Potassium content (%)

 

 

 

 

 

 

Pounds K per acre Sebago Russet Burbank
60 96 6O 96
Broadcast Banded Total days days days days
0 0 0 10.20 6.56 9.21 5.99
0 50 50 10.13 6.01 9.98 6.92
0 100 100 10.26 7.33 10.50 7.58
0 150 150 9.93 7.09 10.89 7.97
0 200 200 11.97 8.24 13.64 8.99
300 100 400 11.41 8.93 11.82 10.12
50 0 50 9.65 6.62 10.00 7.22
100 0 100 10.00 7.09 10.99 8.65
200 0 200 10.02 6.87 11.59 9.24
IWean. 10.47 7.25 10.89 8.05
lsd (.05) .93 .73 .93 .73
(.01) 1.26 .99 1.26 .99
lsxi (.(35) 'treatment x variety ns .46 ns .46
(. 01) ns .63 nS .63

 

o
" .— uncow-‘Q

66

early season sampling, and differences in K content due to
K fertilizer treatment were more marked. The K content in
petioles of both varieties was increased when K was applied
except when 50 pounds K (either banded or broadcast) was
applied to Sebago potatoes. No differences were noted
between broadcast and banded applications of K. Except
when no K was applied, petiole K was higher in Russet Bur-
bank potatoes than in Sebago potatoes.

The differences in K concentration at early season and
mid-season indicate that the petiole K concentration is
related to the potato variety, and that these differences
due to variety tend to increase as the plant matures.

Also, at mid-season, the highest petiole K concentration
in the Sebago variety was obtained when the K was banded,
and in the Russet Burbank variety, the highest petiole K
was obtained when the K was broadcast. These tendencies
could very well be the effects of differences in the root
systems of the two varieties and/or in their ability to

absorb K from the soil.

Calcium Concentration in Petioles

The Ca concentration of the petioles was not affected
by rate or placement of K at either the early or mid—season
sampling date for either variety (Table 16). The petiole
Ca in both varieties was higher at mid-season than early
season. No differences were noted in petiole Ca between

the two varieties at the early season sampling, but petiole

th‘ -

 

 

67

Ca in Russet Burbanks at mid-season was higher than that

of Sebagos.

IMagnesium Concentration in Petioles

The Mg concentration in the petioles of the Sebago and
Russet Burbank varieties was not affected by either rate or
placement of fertilizer K at either the early or the mid-
season sampling (Table 17). However, the data tended to be
extremely variable; at mid-season, petiole Mg tended to
decrease in both varieties as the rate of K was increased,
eSpecially in the Sebago variety. When these results are
compared with those of the two experiments on Hodunk sandy
loam, the differences obtained here are greater than signi-
ficant differences on the other experiments.

The Mg in petioles of both varieties increased about

sevenfold from the early to the mid-season sampling. The

Mg concentration in petioles of both varieties at early sea-

son appears to be at or near the deficiency level, especially

for the Sebago variety. Doll and Hossner (1964) reported
Mg deficiency in Sebago potatoes when Mg concentration in

petioles was less than 0.15 percent.

 

 

 

 

68

180h316. Calcium concentration (%) in petioles of Sebago
and Russet Burbank potatoes, in early and mid-
season (60 and 96 days after planting, reSpect-
ively) as affected by rate placement and time of
K on McBride sandy loam in 1968.

 

 

Calcium content (%)

 

 

 

 

 

 

Pounds K per acre Sebago Russet Burbank
I
60 96 60 96 33:33 I;
Broadcast Banded Total days days days days .1 ”'32::
0 0 0 0.62 0.95 0.67 0.95 f. iii-E.
0 50 50 0. 67 1.00 0. 59 1. 22 17:1.
0 100 100 0.62 0.84 0.67 1.17 £113:
0 150 150 0.67 0.84 0.73 0.78 3:2:
0 200 200 0.67 0.84 0.56 0.84 7""
300 100 400 0.56 0.89 0.56 0.78
50 0 50 0.72 0.89 0.73 1.11
100 0 100 0.67 0.84 0.78 0.89
200 0 200 0.78 1.06 0.62 1.06
Mean 0.65 0.90 0.68 1.02
lsd (.05) ns ns ns nS
lsd ( . 05) treatment x variety ns ns ns ns

 

69

Tahkal7. Magnesium concentration (%) in petioles of Sebago
and Russet Burbank potatoes, in early and mid-
season (60, and 96 days after planting, reSpect-
ively) as affected by rate, placement and time of
K on McBride sandy loam in 1968.

 

 

Magnesium content (%)

 

 

 

 

 

 

Pounds K per acre Sebago Russet Burbank l
”J
60 96 6o 96 "7:: ".1 '
Broadcast Banded Total days days days days “1:;
0 0 0 0.09 1.10 0.18 1.28 E“:
0 50 50 0 . 07 1 . 13 0 . 11. 1 . 60 ‘_ ..t;';~_-_-"__'-}J
0 100 100 0 . 09 0 . 79 0 . 12 1 . 1.0 E)
0 200 200 0 .11 0. 72 0. 23 1. 26 :11;
0 250 250 0.16 0.77 0.12 1.23 9::
300 100 #00 0.13 0.50 0.16 0.84
50 0 50 0.13 0.93 0.18 l.AO
100 0 100 0.10 0.70 0.16 1.10
200 0 200 0.15 0.96 0.17 0.98
Mean 0.11 0.83 0.17 1.23
lsd (.05) ns ns ns ns
lsd (. 05) treatment x variety ns ns ns ns

 

 

SUMMARY AND CONCLUS IONS

EFFECT OF RATE, PLACEMENT AND SOURCE
OF POTASSIUM ON YIELD AND MINERAL
CONTENT OF POTATOES

Three field experiments with potassium fertilization

of potatoes were conducted: one on Hodunk sandy loam in

1967 to determine the effects of rate and placement of K,
another on Hodunk sandy loam in 1968 to determine the

effects of rate, source and placement of K, and the third

on McBride sandy loam in 1968 to determine the effects of
rate and placement of K for Russet Burbank and Sebago
potatoes.

Yields of potatoes appeared to be related to level of
exchangeable soil K, since the most marked yield response
was obtained in 1967 on Hodunk sandy loam at an exchangeable
‘K levefl.<xf 135 pounds per acre, a lesser reSponse on Hodunk
sandy'lxnnn in 1968 at a level of 160 pounds, and the least

reSponse on McBride sandy loam at a level of 200 pounds K

per acre; However, even though the potatoes were irrigated
at all three locations, both yields and relative response to

K fertilizers appeared to be affected by climatic conditions

as well as level of soil K.
Yields were not affected by the placement of the K

‘ertilizer, so that broadcast K appeared to be as effective

70

 

 

71

as did banded K. No significant yield differences were

noted between sources of K, although the highest yield was
obtained when KCl was applied on Hodunk sandy loam in 1968.
No differences were noted between Russet Burbank and Sebago
potatoes with respect to relative response to K fertilizer,
although actual yields were higher when Sebago potatoes

were grown than when Russet Burbanks were grown.

Exchangeable soil K on Hodunk sandy loam in 1967

decreased during the growing season on plots to which no

fertilizer K was applied. The level of exchangeable K on

plots to which K fertilizer was broadcast increased as the
rate of K increased; when 400 pounds K was broadcast,

exchangeable K at harvest was AB pounds more than the

initial level before planting. The level of exchangeable

soil K was not increased by band K applications except when
#00 pounds K was applied, and when lower rates of banded K
were applied, exchangeable soil K was less than that before
planting, indicating that substantial amounts of native

soil K as well as fertilizer K were being absorbed by the
plants.

In general, the Specific gravity and the percent dry

weight of the potatoes decreased as the rate of K fertilizer

was increased. When KCl was applied, the Specific gravity

decreased more than when K2801... and K2003 were applied, and
specific gravity tended to be highest when K2003 was applied.

Specific gravity and percent dry weight were significantly
correlated (r = 0.70).

 

 

72

The concentration of K in petioles, leaves, vines, and

tubers generally increased as the rate of K increased. The

K concentrations were neither significantly or consistently

affected by the placement (band or broadcast) of K ferti-

lizer.

No consistent differences in K concentration were

noted due to source of K, although K frequently tended to

be higher when KCl was applied and lowest when K2003 was

applied.

than Sebago potatoes.

Russet Burbank petioles tended to be higher in K

This varietal difference may have

been due to either a difference in root systems of the two

varieties, or to the smaller size of the Russet Burbank

plants which resulted in a greater accumulation of K in the

plant.

The concentration of K in the petioles was much higher

at the early season samplings, and then decreased rapidly

for the remainder of the growing season.

This illustrates

the need for evaluating the K status of the plant on the

basis of physiological age if petiole analyses are to be

used.

In 1967 on Hodunk sandy loam, the total uptake of K

per acre (vines + tubers) varied from 55 pounds per acre

when no K was applied to 135 pounds when #00 pounds K was

applied.

For maximum yields, about 110 pounds K was required.

These figures are lower than other previously reported data

(Rudgers, 1967)-

The Ca concentration in petioles, leaves, and vines

generally tended to decrease as the rate of K fertilizer was

73

increased, eSpecially at the early season sampling date.

Placement of K did not affect Ca concentration in the

plants. In the tubers, Ca concentration was not affected

No significant differences in Ca concentra-
In

by rate of K.

tion were noted due to source of K or potato variety.

1967 on Hodunk sandy loam, the total uptake of Ca by vines

and tubers was about 36 pounds per acre. The Ca concen- .

4 .
......

tration in petioles tended to increase as the potato plant .J.

II I -.-.-oo“l

generally decreased as the rate of K was increased. No con- ;r.l‘....-..__,..

sistent differences in Mg concentration were noted due to .-
" ».--n-...‘_,. .u‘

placement of K fertilizer. The Mg concentration of tubers -....-.-......

was not affected by K fertilization.

of potato petioles tended to increase as the plants matured.

The Mg concentration

On McBride sandy loam in 1968,'Mg in petioles at the early
season sampling was at or near previously reported deficiency

levels. The Mg concentration in petioles was not affected

by source of K fertilizer. Total uptake of Mg (vines +

tubers) was about 20 pounds per acre in 1967.

These experiments can be briefly summarized as follows:

The relative response of potatoes to K fertilizer

l.
was related to the level of soil K, although actual
yields were also affected by climatic factors.

2. Yields were decreased when rates of K applied were

equal to or greater than 200 pounds banded or 400

pounds broadcast. Chemical analyses of the plants

 

7A

imficate that this decrease in yield may be

mflated to a suppression of Mg uptake at high

levels of K .

Spmfific gravity and percent dry weight of potatoes
dmneased as the rate of K increased.

mnmentration of K in petioles, leaves, and vines
increased as the rate of K increased, while the
concentration of Ca and Mg tended to decrease.
Broadcast and banded applications of K were gener-
ally equally effective with respect to yield and
chemical composition of the potatoes.

As the potatoes matured, K concentration in plants
decreased, and Ca and Mg concentrations increased.
When fertilizer K was banded, levels of exchange-
able K before and after cropping indicated that

native soil K as well as fertilizer K was being

absorbed by the plant. No detectable effect of

banded K on level of exchangeable K between the

rtwns was observed except when #00 pounds K per acre
was banded.

Mflierl fertilizer K was broadcast, exchangeable K
iruxreased as the rate of K increased, but a com-
parison of the level of soil K after cropping and
of crop removal with the rate of K application indi-
cates that a considerable portion of applied ferti—

lizer K was either "fixed" by the soil or leached

from the plow layer.

9.

75

The total uptake (vines + tubers) of K ranged from
55 to 135 pounds K per acre, and the average uptake
of Ca and Mg was 36 and 20 pounds per acre, reSpec-
tively. These data are much lower than those pre-

viously reported from Michigan.

BIBLIOGRAPHY
PART I

Adams,IR, and Henderson, J. B. 1962. Magnesium availa-

bility as affected by deficient and adequate
levels of potassium and lime. Soil Sci. Soc.

Amer. Proc. 26:65-68.

Baum,.E.IL, Heady, E. 0., Blackmore, J. 1956. Methodo-

logical Procedures in the Economic Analysis of
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Bear, F. E., Prince, A. L., and Malcolm, J. L. l9hh. The

Berger, K. C., Potterton, P. E., and Hobson, E. L.

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1961.

Yield, quality and phOSphorus uptake of potatoes as
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Black, C. A. 1968. Soil-Plant Relationships, John Wiley

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R, PI. 1944. Soil—Plant Relations: I. The quanti-

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I2. H. 1948. Correlation of soil test with crop

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76

 

77

Bray,IL H. 1948. Requirements for successful soil tests.
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Brown,IL A. 1944. Soil Fertility Experiments with Potatoes.
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Carolus,ft In 1933. Some significant variations in the

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Chucka, J. A., Hawkins, A., and Brown, B. E. 1944. Potash #:;;:....-.'
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Corbett, E. G., and Gausman, H. W. 1960. The interaction 'ZLE,M

of chloride with sulfate and phosphate in the nutri- ,n~aaj
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J o 5 2: 9142—96 0 k; .:-,--__-... .

Crowther, E. M., and Yates, F. 1941. Fertilizer policy in
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Empire J. Exp. Agric. 9:77-97.

Cummings, G. A., and Houghland, G. V. C. 1939. Fertilizer
placement for potatoes. U.S.D.A. Tech. Bull., 669.

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IBucharest, Romania. 4:907-912.

Doll, 13. C., and Thurlow, D. L. 1965. Soil management
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DUIHI, L. 13., and Nylund, R. E. 1945. The influence of
:fertilizers on the Specific gravity of potatoes
grxnmn in Minnesota. Amer. Potato J. 22:275-288.

78

Dunn L.Il, and Rost, C. 0. 1948. Effect of fertilizers
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1939. Soil
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Harrap,IR E. G. 1960. Some aspects of the potash nutri
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Hart,'T.CL, and Smith, 0. 1966. Effects of levels and

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Hawkins, A., Chucka, J. A., and Brown, B. E. 1944. Ferti-
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Progress Bull. 438, p. 548.

Hawkins, A., Chucka, J. A., and Brown, B. E. 1946. Rate

of potash test. Maine Agric. Exp. Sta. Rept. of
Progress Bull. 442, p. 1 2.

Hossner, L. R., Doll, E. 0., and Thurlow, D. L. 1968. Effect
of magnesium fertilization on yield and magnesium
uptake by potatoes (Manuscript in press).

Houghland, G. V. C. 1964. Nutrient deficiencies in the

potato. Hunper Signs in CrOps a Symposium. Chapter
IV. David McKay Co., New York, pp. 223-225.

Houghland, G. V. C., and Shricker, F. A. 1933.
of potash on starch in potatoes.
Agron. 25:334—340.

The effect
J. Amer. Soc.

Hovleuui, D., and Caldwell, A. C. 1960. Potassium and mag-
:nesiunlrelationship in soils and plants. Soil Sci.

89:92-96.

Jackson, M. L. 1958. Soil Chemical Analysis. Prentice
Phill, Inc., Englewood Cliffs, New Jersey.

James, W. D. 1930. Studies of the physiological importance
of‘iflne mineral elements in plants. I. The relation-

shjqa of potassium to the prOpertieS and functions of
leaves. Ann. Botany. 44:173—198.

79

Jones, J. 0., and Plant, W. 1942. Note on the composition
of leaves from potato manurial experiment. Annual
Rept. Agric. Hort. Res. Sta., Long Ashton, Bristol,
Eng. ALP-[+5 o

Knolewles, F., and Cowie, G. A. 1940. Some effects of
fertilizer interactions on growth and composition
0% the potato plant. J. Agric. Sci. Camb. 30:159-
1 1.

Latzko, E. 1955. Relations between chloride and sulfate
nutrition, intensity of assimilation, enzyme activity,

carbohydrate metabolism, and quality of potatoes. .-n
Z. Pflanzenernahr. Dung. Bodenk. 68:49-55. efTZZ”
Laughlin, w. M. 1966. Effect of soil applications of "Kffi::1
potassium, magnesium sulfate and magnesium sulfate :ng::h~
Spray on potato yield; composition and nutrient 1 ;:3

uptake. Amer. Potato J. 43:403—411. kl:f“”1

Lorenz, 0. A. 1947. Studies on potato nutrition. III. I”;::fi.
Chemical composition and uptake of nutrients by Kern ::“””j
County potatoes. Amer. Potato J. 24:281-293. agllla

.-~.’-'

Lorenz, o. A., Bishop, J. 0., Hoyle, B. J., Zobel, M. P., 7”::;3
Minges, P. A., Doneen, L. D., and Ulrich, A. 1954. "ll/é‘
Potato fertilizer experiments in California. Calif.

Agric. Exp. Sta. Bull. 744.

Lucas, R. E., and Scarseth, G. D. 1947. Potassium, calcium,’/
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McCollum, R. E., Hageman, R. H., and Tyner, E. H. 1958.
Influence of potassium on pyruvic kinase from plant
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80

Mc Murstrey, Jr., J. E. 1948. Visual symptoms of malnu—
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’ O O

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potatoes to phOSphorus and potassium on soils having

different levels of these nutrients in Maine and
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Influence of rates of fertilizer and sources of

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wean!

81

Salmon, R. C. 1963. Magnesium relationships in soils and
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Determination of the starch and dry matter content
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Nutrient content of potato plants as affected by
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".C_.—b"‘

-‘a—-—Q

”.‘-\._.—c

82

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v.5, p. 72. .

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in some crop plants in relation to the level of
potassium nutrition. J. Agric. Sci. 35:254-263.

Ward, G. M. 1959. Potassium in plant metabolism. II.
Effect of potassium upon the carbohydrate and min-
eral composition of potato plants. Can. J. Plant
Sci. 39:246-252.

Ware, L. M. 1939. Fertilizer requirements of the potato
on different soils of Alabama. Amer. Potato J.
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0“)

77"“?!—

PART II

PHOSPHORUS FORMS AND EQUILIBRIA
IN SELECTED PERUVIAN SOILS

PHOSPHORUS FORMS AND EQUILIBRIA
IN SELECTED PERUVIAN SOILS

INTRODUCTION

The soils of Peru vary as much as those of any country
in the world because of the large differences in climate,
topography, parent material, and vegetation in the differ-
ent parts of the country. A comprehensive review of the
soils of Peru has been given by Drossdoff 23,31. (1960).
The formation of unavailable forms of phOSphorus is known
to occur when fertilizer phOSphoruS is applied, so that
phOSphorus fixation is significant in both alkaline and

acid soils.

Insofar as the writer knows, no comprehensive Study has

been conducted with Peruvian soils to characterize the fix—
ation of applied phOSphoruS and to determine the chemical
forms of soil phOSphoruS which govern its availability to
plants.

It is of considerable importance, therefore, to char-
acterize the phOSphoruS fractions and to evaluate the phos-
phorus fixation and equilibria reactions in Peruvian soils.

The study reported here was conducted to: (1) characterize

84

‘cu—u-su.

85

the different phOSphorus fractions in selected coastal,
mountain, and jungle soils of Peru, and (2) study the
capacity of these soils to fix added phOSphoruS by means
of adsorption isotherms, and (3) identify the compounds
formed when added P is fixed by these soils by means of

phOSphate potentials and solubility diagrams.

~'.
hfi—‘o

LITERATURE REVIEW

Phosphorus Fixation in Soils

The exact mechanism(s) involved in the fixation of
phOSphoruS (P) by soils is not well understood, but the
following three possibilities have been suggested: (a)
adsorption of P by the soil complex, (b) the P in solution
is precipitated thus becoming a part of the solid phase
(oldest theory),and (c) P immobilization due to microbial
uptake.

Since little is known about the role of the micro-
organisms in P immobilization and since their role in min—
eral soils does not appear of great importance, no discus-

sion of microbial action will be included.

Absorption of quy Clay Minerals
Kelley and Midgley (1943), Scarseth (1935), and Stout

(1939) all indicated a possible reversible exchange reaction

between phOSphate and hydroxyls at the edges of the clay
lattices. Murphy (1939) indicated that finely ground kao-

linite showed a very high retention of P, with the maximum

absorption occurring at pH 4. His conclusions were supported

by the decrease in P retention with increasing pH and the

release of P when soils were extracted with dilute NaOH.

86

87

Black (1942), Coleman (1945), Ellis and Truog (1955)
and Coleman (1960) all indicated that the fixation of P
by clay minerals is a result of the alteration of the clay

+3 +3

crystal by the P solution releasing of free A1 and Fe
which then precipitates the phOSphateS.
Fixation of P by hydrated oxides of Fe and A1 can
result from a Simple substitution of P for hydroxyl ions. 5
The theory that P is fixed by a system in which cations :7——;
are the linking force has been suggested. Ravikovitch I
(1934) indicated that a HZPOA-Ca-Clay system could be formed.
Wild (1953) found an increase in P fixation by clay either 5:11,
with monovalent or divalent cations, which could indicate pf~—ui
that the added P can react directly with Ca adsorbed on the ’”“'J

clay surfaces or with the surface ions of CaCO3 in neutral

or alkaline soils (Cole 23 31. 1953).

Chemical Precipitation of P

The chemical precipitation of P is the oldest theory
of ‘P fixation and has been described by Bradfield _ep §_1_.
(1935) who postulated three separate mechanisms that could
overlap each other. At pH 2 to 5, the retention is chiefly
due to the gradual dissolution of iron and aluminum oxides,
which then are reprecipitated aS phOSphates. At pH 4.5 to
7.5, P is fixed on the surface of clay particles, and at
pH 6 to 10, P is precipitated by divalent cations in the

soil solution.

88

Aluminum and iron phOSphateS could be present in the

soil as the isomorphus series variscite (aluminum phos-

phate), redondite (Ferrian-variscite), barrandite (aluminum-

 

strengite), or strengite (iron phOSphate), (Freed and
Shapiro, 1960).

In neutral or alkaline soils, P can be precipitated
by Ca in soil solution (Midgley, 1940; Freed and Shapiro,
1960). The nature of the intermediate CaP compounds formed
are not clearly defined but they are of the apatite struc-
ture (CaF)Cah(P04)3. Henwall (1957) indicated that apatite
is quite stable, and permits unusual types of substitutions
that could involve a large number of ions.

Determination of the Fixing Capacity
of the Soils

Determinations of the P-fixing capacity of soils are
usually made by either (1) measuring the decrease in the
concentration of aqueous P in equilibrium with soils, or
(2) measuring the amount of P extracted from soils equili-
brated with P compounds. Both principles are based upon

the concept that P concentrations at the interface between

the liquid and the solid system, a phenomenon called adsorp-

tion. Although adsorption is not clearly defined as a
specific P fixation mechanism, the amount of P taken up by
soils is proportional to the concentration.

It has been postulated by Russell and Prescott (1961),

Davis (1935), and Kurtz §§_§1, (1946) that the adsorption

89

of phOSphorus by soils can be described by the equation of

Freundlich.
35=KCn
m

Although the Freundlich isotherm is applicable to
large amounts of absorbed P, it is not possible to calculate
adsorption maximum. Olsen and Watanabe (1957), therefore,
prOposed the use of the Langmuir adsorption isotherm, based
in the kinetic theory of gases and used to describe gas
absorption on solids (Langmuir, 1918).

The equation as used in soils is:

= 5%3 + Kc

BIN

where EZE = mg of P absorbed per 100 g of soil,

p_= absorption maximum, 3 = equilibrium P concentration in
moles per liter, and K = a constant related to the bonding
energy of the absorbent for the absorbate. A linear form
of the equation is given by:

c _ l c
275 ‘ EB + B

in this form the SlOpe = l/b, and the intercept = 1/kb, or
K = Slope/intercept.

Olsen and Watanabe (1957), by using the Langmuir
isotherm, calculated the maximum absorption of P by acid as
well as by alkaline soils; they indicated that the acid
soils retained more P per unit of surface area and also held

the P with a greater bonding energy than alkaline soils.

90

The use of the Langmuir isotherm in soils of the Latin-

American tropics has been reported by Fassbender (1966).

Forms of Inorganic Phosphorus
in Soils

 

Three different procedures have been used to char-
acterize the forms of inorganic soil P: (1) direct obser-
vations using X-ray diffraction techniques, infrared Spec— I-
troscopy, electron microscopy, or DTA analysis, (2) the use
of phase diagrams based upon solubility product concepts; :3-m

and (3) extraction with different chemical solutions. ‘fmm§

Direct Observations --_i}'

 

The real contribution of the use of direct observations L~~u
appears to be questionable quantitatively, because of the zf‘*d'
difficulty of separating the P forms of the soils and the
actual danger of altering the P compounds by any physical
separation. Perhaps the most interesting use of this
technique in identifying the composition of products formed
by the addition of different fertilizers has been performed
by Lindsay §£_§1. (1962), who identified more than 30
crystalline products of variable composition as well as
colloidal precipitates in soils from Tennessee, Iowa and

Arizona.

Phase Solubility Diagrams

 

The use of solubility criteria of pure P compounds to
identify forms of P in soils has been used by Aslyng (1954),
Clarke and Peech (1955), Larsen and Court (1961), and

91

Lindsay and Moreno (1960). Aslyng (1954) plotted P poten—
tial (%pCa + pH2P04) against lime potential (pH — %pCa) of
soils and constructed a phase diagram for comparison with
known CaP compounds. He found that when large amounts of
superphOSphate are added, dicalcium and/or octocalcium
phOSphate are initially formed in calcareous soils, and
that these compounds are then Slowly converted to a more
basic CaP, presumably hydroxyapatite. Clarke and Peech
(1955) represented the solubilities of CaP in a single
solubility diagram in which pH2POI+ + %pCa and pH - %pCa
were used as coordinates; when a CaCO3 solid phase was
present, the chemical potential of lime (pH - %pCa)
depended upon the partial pressure of C02 in the atmosphere,
leading them to conclude that monocalcium phOSphate cannot
persist in soils and that hydroxyapatite is the probable
predominant solid phase in neutral and alkaline soils.

The use of the solubility product principle is based
on the assumption that a crystalline solid phase exists in
the soil as a result of the equilibrium attained between P
and the other reactive ions in the soil solution. These

2
+.K+.NH+.

other reactive ions are Fe+3, Al+3, Ca+2, Mg 4
H+, OH' and F‘. Lindsay and Moreno (1960) developed a solu-
bility diagram which includes the activity isotherms for
variscite, (AlPOh - 2H20), strengite (FePOh - 2H20),
fluorapatite [C310(PO4)6F2]’ hydroxyapatite [calO(PO4)6(OH)2]’

octocalcium phOSphate [CahH(P0)33H20], and dicalcium phOSphate

92

dihydrate (CaHPOLP . 2H20). The activity isotherms of
these compounds are represented on a Simple solubility

phase diagram in which pH2P04 is plotted against pH. The
+3

is limited

+3 is

assumption is made that the activities of Al
by the solubility of gibbsite, the activity of Fe
limited by strengite, the activity of F- by fluorite and

+2 is limited by a 0.005 11; Ca concentration.

that of Ca
Then by plotting the value for pH2PO4 and pH, it iS pos-
sible to locate a point for a given soil and determine the
forms of P controlling P solubility in the soil, assess
the relative stabilities of these compounds and predict

the transformations of fertilizer P when applied to the

soil.

Soil PhOSphoruS Fractions
Soil P exists in the following inorganic forms:
calcium phOSphates, aluminum phosphates, iron ph0Sphates

and occluded and reductant-Soluble phosphates.

Kittrick and Jackson (1956) have indicated that avail-

ability of P depends on the chemical form of various surface

P compounds in the soil.
The different inorganic P forms in soils have been

fractionated to determine the chemical forms of the native

soil P as well as to study the fate of applied P fertilizer
before and after cropping. The fractionation of the soil P
was studied by Fraps (1906), Dean (1938), and Williams (1950),

but in their procedures FeP and AlP are combined in the same

93

fraction. Since Turner and Rice (1954) fOund that neutral
ammonium fluoride dissolves AlP but not FeP, many extrac-
tants have been developed to characterize a specific P
fraction. For instance, it is assumed that the P extracted
from soils by the Bray and Kurtz method (1945) must be
largely AlP. Chang and Jackson (1957) develOped a soil P
fractionation procedure which uses different extraction
solutions to permit the fractionation of inorganic P into
AlP, FeP, CaP, reductant soluble FeP and occluded FeP and
AlP. This method has been extensively used: (1) to follow
the weathering process of the phOSphates in soils (Hsu,
1960; Chang and Jackson, 1958; Chang and Chu, 1961) and (2)
to determine the fate of applied P to soils and its avail-
ability to plants, (Hanley, 1962; Melton, 1964; Smith,
1965; Albany 2 31., 1964; Susuki pp 31., 1963). It appears
that in soils the weathering sequence of the phosphorus
compounds follow the order CaP, AlP, FeP and occluded P
(Chang and Jackson, 1958). In acid and calcareous soils

of Taiwan, Chu and Chang (1960) found that the AlP fraction

was not a dominant form in any of the paddy soils studied,

Sen Gupta and Cornfield (1962, 1963) studied P in calcareous

soils and found a decrease in the P fractions in the order
inert P, apatites, non-apatites, CaP, AlP, FeP and easily
replaceable P. They also found that none of the P forms

correlated with CaCO3 content in the soils studied. Many
studies have been conducted that indicate that AlP and FeP

are quite abundant in acid soils and CaP in alkaline or

'--....¢

94

calcareous soils (Chai Moo Cho and Caldwell, 1959; Chang
and Juo, 1963; Chu and Chang, 1960; Dahnke and Malcolm,
1964; Henwall, 1957; Kurtz, 1953; and Olsen, 1962;
Fassbender pp a1., 1968).

The fractionation procedure of Chang and Jackson has
been criticized in the light of subsequent findings con-
cerning the effects of the various extractants on pure
compounds and on soils; Specially in regard to the differ-
entiation between FeP and AlP (Fife, 1959a, 1959b, 1962
and 1963; Khin and Leeper, 1960; Saunders, 1953; and Smith,
1965); thus dicalcium ph0Sphate and some FeP may be dis-
solved by the neutral 0.5N NHAF, measuring the amounts of
AlP. Fife (1959) indicated that raising the pH of the
NHAF solution to pH 8.00 or above would decrease the con-
centration of the fluoroferrate complex formed. Glenn pp
a1. (1959) found a negligible amount of FeP removed by the

NHAF solution at pH 8.00 or above. It is also possible

that the extraction of CaP with 0.5N_H280LP following extrac-

tions with NHhF and HaOH may dissolve some of the occluded
phOSphate (Khin and Leeper, 1960). The suggestion was made
before by Glenn pp El. (1950) that the reductant soluble
and occluded FeP and AlP be extracted after the removal of
FeP with 0.1N|Na0H and before extracting CaP with 0.5K
H2SO4‘
Although the P-fractionation procedure of Chang and

Jackson has been criticized, it is without any doubt useful

in helping to characterize the P forms in the soil and thus

-..
"u—n-¢

95

has contributed greatly to the understanding of the chem-

istry of soil P.

METHODS AND MATERIALS

Nine representative Peruvian soils were selected for
a study involving the characterization of soil P and applied
P; three of these soils were from the coastal area, three
from the mountains, and three from the high jungle. The
location and characterization of these soils is given in
Table 1. In order to fix known amounts of P, duplicate
500 g samples of each soil were placed in plastic containers,
and rates of O, 50, 100, 200, and 500 ppm P added by apply-
ing the appropriate amount of a solution of H3P04 which con—
tained 2500 ppm P. After the P was added, enough distilled
water was added to give approximately a 1:1 soil:water sus-
pension, the mixture was thoroughly mixed, and dried in a
forced—air oven at 500 C. The samples were rewetted, mixed,
and dried 20 times, and soil samples for analyses were

taken after the lst, 5th, 10th, 15th, and 20th drying cycles.

Phopphorus Adsorption Cppacity
Langmuir adsorption isotherms were determined for each
soil as described by Olsen and Watanabe (1957). A series
of equilibrating solutions was prepared which contained from
1 to 12 x 10‘“ M KHZPOLP, each adjusted to pH 7.0 with KOH.

Five grams of soil (to which no P had been added) was

96

97

 

 

 

 

H.N om.o b.o N.H a o.o I 4.4 seas u u n cameos oases oases mmm
H.s 4H.o c.4 4.m N s.m u m.o ssoH spasm 0.4m 4.b4 b.0m cameos oaaaom can
m.m b4.o m.o N.N 4 o.m . m.4 sooa spasm o.mH 4.44 b.ms cameos sosom com mam
4.04 N4.o c.H 4.m m4 o.H . N.s anon o.o4 4.44 c.0m saoassoz osmososm 4mm
Ewoa
m.m 4m.o 4.4 b.m H m.m . 0.4 scab spasm o.pm 4.mm b.m4 saoasaoz osaoschoo mmm
m.o mm.o m.m m.m 44 H.m . c.4 soon o.4m 4.0m c.m4 saoassoz oosoasnnoo NNN
o.o4 04.0 4.N 4.4a s b.a a 4.m smog o.mm 4.44 o.s4 boooo osafioz on m
s.s4 om.o 4.4 4.NH m m.m 4c.m m.m sooa seas o.mm 4.0m p.sm onooo enactments o
«.84 00.0 m.4 m.ma OH 4.m m4.m H.m swab spasm o.m4 4.04 o.sa phooo oaoosonsoq 4
w ooa\ms 111w ooH\osII Edd IIIIoIIII I llfii
.o.m.o s 42 so a 2.0 moons ma osspxoe oaam scam poem mesa noaooooq oz
mcowpmo
mammowam£oxm

 

 

.maflom cmfi>5Lom mafia mo Aomov hpflomdmo

Am cam MS .mov MQOHme manmmmcmgoxo .m comao .poppme aflcmmho

o annexe coapmo paw

. Como .md .oQprme

.H oHQmB

 

98

shaken with 100 m1. of the appropriate equilibrating
solution for 24 hours on a reciprocating Shaker, and then
centrifuged until the supernatant liquid was clear. On
some soils, centrifuging did not clarify the solution; on

these soils, sufficient l N KCl was added to the superna-

tant liquid, after decanting, to flocculate the suSpended
material. 5
[”1“ fl
PhOSphorus in the supernatant liquid was determined _;f‘y

by the phOSphomolybdenum blue method in sulfuric acid, 14».
using SnCl2 as the reducing agent. This procedure is LEi)
described by Jackson (1958) and is referred to by him as £s_(
Phosphorus Method I. jr—4

The linear expression of the Langmuir isotherm ;__,

c 1 c

275=T+E

was used as is described in page 89 in the Literature Review

Phosphorus Potential

The phOSphorus potential was determined essentially as
described by Lindsay and Moreno (1960) and Withee and Ellis
(1965). Fifteen g of soil was agitated in 50 ml. of 0.01 M
CaCl2 for 24 hours on a reciprocating shaker, and the pH of
the suSpenSion was determined using a glass electrode
potentiometer. The solution was then centrifuged, and P
in the supernatant solution determined as described above.
In another aliquot, Ca was determined by means of versenate
titration, using murexide (ammonium purpurate) as an indi-

cator (Jackson, 1958).

99

Fractionation of Soil PhOSphorus

Soil ph0SphoruS was fractionated by the procedure of
Chang and Jackson (1957) as modified by Glenn 2; {311. (1959)
in that the pH of the NHAF extractant was increased to 8.2,
and the reductant—soluble P (NaZSOh-extractable) was removed
after FeP (NaOH—extractable) and before CaP (H2804—extractable).
PhOSphorus in the reductant-soluble fraction was not deter-
mined, so only data for bound P (NHhCl-extractable), AlP

(NH F—extractable), FeP, and CaP are given.

4
For each soil, two samples were fractionated: one to

which no P was added and which was taken after the first

drying cycle, and the other one to which 500 ppm P had been

added and which was taken after the twentieth drying cycle.

Total PhOSphorus in Soils
The total P content of each soil was determined by
fusing a sample with Na2003 as described by Jackson (1958),
and P in solution after the fused sample was dissolved in

0.1 N HCl was determined as described above.

RESULTS AND DISCUSSION

Phosphorus Adsorbing_Capacipy
The values for the maximum adsorption of P obtained
using the Langmuir isotherm varied greatly between the
different soils, as would be expected from the chemical
analyses given in Table 1. Typical regressions for three

of the soils are Shown in Figure 1.

Coastal Soils

The Lambayeque soil had the highest adsorption capacity
of the calcareous coastal soils (Table 2). The results of
Cole §p_§1. (1953) would suggest that P in this soil and in
the Casagrande soil was probably adsorbed on free CaC03,
since both of these soils contain free CaCO3. The adsorbing
capacity of the La Molina soil was lower than that of the
other two coastal soils, and it does not contain free CaC03.
Olsen (1953) reported that P adsorbed from dilute solution
by calcareous soils is probably all exchangeable with P32.
This implies that P is adsorbed in a monolayer and that the
concentration of this adsorbed P is likely to be within the
range of concentrations that follow the Langmuir isotherm.
Based upon the magnitude of the energy—of-adsorption con—
stant K (derived from the slope and intercept of the regres-
sion equation), the Casagrande soil adsorbed P with a greater

100

5

!?'?1i!iti;t

\Elilli

lOl

24M)—

0J8?-

LAMBAYEQUE

  
  

ou4

I

CASABLANCA
0.: 2
"lm

TINGO MARIA

 

 

l l l l

| 2 3 4
cmous P PER LITER x IO4)
Figure l. Langmuir isotherm regressions for Lambayeque,

coast)° Casablanca, (mountain); and Tingo Maria,
jungle) soils.

102

.AHO>0H

40.00 ps0oa0as0an sasmam **

 

 

004.4 00.00 *s 000.0 0040.0 0400.0 n s 4.4 04002 omsae
000.0 00.04 xx 000.0 0H00.0 0404.0 u s 0.0 o0a000
000.0 40.00 *x 000.0 0H0H.0 0H40.0 n s 0.4 sos00 000
000.4 00.04 xx 400.0 4400.0 0000.0 u 0 0.0 os0os0sm
000.4 04.04 ** 400.0 0000.0 0000.0 n s 0.0 000000000
000.0 00.00 *x 000.0 4000.0 0000.0 u s 0.4 0000400000
000.0 04.0H ** 040.0 0000.0 040H.0 n s H.0 0saHos 0a
000.0 0N.Hm ** 000.0 4040.0 4000.0 u s 0.0 00s0t00000
000.0 0H.04 ** 000.0 4400.0 0040.0 u s H.0 0000000s0q
M Qx\a\u A90 40H N pmpfla 909 m mmaoe .0 H mm coapmooq
games. 0.000%” mmmmwmmw ass. ” a
hmumqm coapdpompa madsflm

 

 

.spom mo mHHom meQSn 0cm Campasos .Hmpmmoo map pom 0900 coapdpompm mSLOQQmonm .m oanme

103

bonding energy than the Lambayeque or the La Molina soils.
The K values obtained are within the range of those

reported by Olsen and Watanabe (1957).

Mountain Soils

 

The Casablance and Cajabamba soils had a higher adsorb-
ing capacity for P than the Huancayo soil (Table 2). Both
of these soils are acid soils in which Al and Fe would be
expected to be important in the fixation of added P. Kurtz
§p_g1. (1946) and Low and Black (1950) suggest that P fix-
ation takes place in two stages, a rapid initial reaction
followed by a second relatively slow reaction. The pre—
dominant ions involved in P fixation in the acid Casablance
and Cajabamba soils are probably Al and Fe, while Ca is
probably the predominant ion in the Huancayo soil, Since

this soil has more exchangeable Ca and the pH is neutral.

Jungle Soils

The Tingo Maria soil had a maximum adsorbing capacity
of 56.23 mg P per 100 g soil, as compared with 28.04 and
18.20 for the San Ramon and Satipo soils, respectively (Table
2). The magnitude of the adsorption maxima values for the
San Ramon and Tingo Maria soils is higher than those reported
by Fassbender (1966) for three strongly acid soils of Costa
Rica, by Olsen and Watanabe (1957) for acid Davidson clay,
and by Woodruff and Kamprath (1965) for acid soils in North
Carolina. Comparing the acid Tingo Maria and San Ramon

soils, the higher adsorption capacity of the Tingo Maria

(!il'.’

104

soil is probably due to the higher clay content which would
result in a greater surface area for P adsorption and fix-
ation.

According to the findings of Coleman §§_§1. (1960),
the amount of P removed from solution by soils correlates
with the amount of exchangeable Al in the soil, and because
of the low pH of the San Ramon and Tingo Maria soils, this
may explain the higher level of P adsorption on these soils.
Because of severe weathering under conditions of high rain-
fall and temperature, it is possible that the actual fixing
capacity of the Tingo Maria soil could be even higher than
that obtained using the Langmuir isotherm, Since P fixation
has been Shown to increase with time (Hsu and Rennie, 1962;
Fassbender, 1966).

The Satipo soil gave a P adsorption maximum of 18.2 mg
per 100 g soil. This could be a reflection of the low con-
tent of clay and the Slightly acid reaction of this soil.

The K values of 4.199, 0.830, and 0.260 for the Tingo
Maria, San Ramon, and Satipo soils, reSpectively, are in
agreement with those reported for soils of Similar pH values

by Olsen and Watanabe (1957).

Ph0Sphorus Potential

 

The soil reaction (pH), the negative logarithm of the
phOSphate ion activity (pH2P04)’ the phOSphate potential
(pH2P04 + %pCa) and the lime potential (pH - épCa) for the

105

coastal, mountain, and jungle soils are given in Tables 3,
4, and 5, reSpectively.

In general, the pH2P04 and the phOSphate potential,
pH2P04 + %pCa, decreased as the rate of applied P increased,
which indicates that there is an increase in the solubility
of the compound or compounds controlling the phOSphate ion
activity and phOSphate potential in the soils. The decrease
in pH noted when high rates of P were added, particularly in
the La Molina, Cajabamba, Huancayo, San Ramon, and Tingo
Maria soils, is probably related to a lower buffering capac-
ity of these soils as compared to the other soils, so that
the pH was leached when P was added as H3PO4'

The forms of P in the untreated soils vary considerably
(Figure 2), as shown by the phosphate solubility diagram
constructed as described by Lindsay and Moreno (1960).

These differences are primarily due to differences in soil
pH between the various soils. The data plotted in Figure 2
indicate that the alluvial soils of the coast-—Lambayeque,
Casagrande, and La Molina--and the Huancayo soil from the
mountains are saturated with respect to hydroxyapatite and
undersaturated with reSpect to octocalcium ph0Sphate. Mean-
while, the acid soils of the mountain and jungle, except for
the Satipo soil, are undersaturated with reSpect to fluor-
apatite and strengite. The value plotted for the pH2P0A of
the Tingo Maria soil is a calculated value, since it was

not possible to detect any P in the equilibrium solution

after the soil was treated with 0.01 M CaC12. Data for the

lO6

 

 

 

Table 3. The pH, pH2P0 , ph0Sphate potentials and lime
potentials of the coastal soils, as affected by
the application of P and after wetting and drying
20 times.

Applied P pH2P04 +
Location ppm pH pH2P04 %pCa pH - épCa

Lambayeque O 8.0 7.15 8.21 6.93
50 8.0 6.81 7.41 7.39

100 8.0 6.44 7.03 7.40

200 8.0 6.33 7.33 6.99

500 8.0 6.07 7.07 7.00

Casagrande 0 8.3 7.61 -8.67 7.24
50 8.3 7.07 8.11 7.25

100 8.3 6.67 7.69 7.27

200 8.3 6.34 7.36 7.28

500 8.3 5.83 6.84 7.29

La Molina 0 8.3 7.65 8.70 7.24
50 8.2 7.12 8.15 7.16

100 8.2 6.93 7.95 7.18

200 8.0 5.24 6.25 6.99

500 7.4 5.24 6.25 6.40

 

107

Table 4. The pH, pH2P0 , ph0Sphate potentials and lime
potentials of the mountain soils as affected by
the application of P and after wetting and drying

 

 

 

20 times.
Applied P szPOI+ +
Location ppm pH pH2PO4 %pCa pH - épCa

Casablance O 5.0 7.17 8.23 3.91
50 5.0 6.99 8.10 3.89

100 5.0 6.58 7.67 3.91

200 5.0 6.38 7.45 3.92

500 4.9 5.75 6.8O 3.84

Cajabamba 0 5.6 7.90 09.02 4.48
50 5.6 '7.30 8.39 4.50

100 5.6 7.20 8.29 4.51

200 5.6 6.47 7.54 4.52

500 5.3 5.42 6.47 4.24

Huancayo O 7.7 7.08 8.14 6.63
50 7.6 6.63 7068 6055

100 7.6 6.35 7.37 6.57

200 7.4 5.82 6.83 6.39

500 7.0 4-94 5.95 5.99

 

108

Table 5. The pH, pH2PO , phOSphate potentials and lime
potentials of the jungle soils, as affected by

the application of P, and after wetting and drying

 

 

 

20 times.
Applied P pHZPOLF +
Location ppm pH pH2PO4 épCa pH - %pCa
San Ramon O 5.1 7.60 8.71 3.97
50 5.1 7.42 8.53 3.98
100 5.1 7.20 8.29 4.00
200 5.1 6.59 7.67 4.02
500 4.8 5.83 6.90 3.74
Satipo 0 6.7 7.51 8.59 5.61
50 6.7 7.29 8.35 5.63
100 6.7 6.68 7.74 5.64
200 6.7 6.01 7.04 5.66
500 6.6 5.17 6.19 5.57
Tingo Maria* 0 4.2 7.89 8.99 3.10
50 4.2 7.89 8.99 3.12
100 4.2 7.89 8.99 3.13
200 4.2 7.89 8.99 3.17
500 4.0 6.36 7.40 2.95

 

* In this soil to calculate the values pH PO4’ pH2P04 + %pCa
for 0, 50, 100 and 200 ppm P added, it as assumed that the
P of the equilibrium solution was 0.001 ppm Since it was
not possible to detect P in the equilibrium solution.

109

o LAWAYEQUE + CASABLANCA 0 SAN RAMON
A CASAGRANDE . CAJABAMBA a! SATIPO
0 LA MOLINA x HUANCAYO E] TINGO MARIA

 

 

 

sowmurv coco3 \' 4,

 

 

 

9 -
0.0003 AT" 602 I I
~ 0.0l ATM 602 ———'I
I
I0 1 1 1 l a L 1 1 I J 1 L 1 '
3 4 5 6 7 8 9
pH
Figure 2. Phase diagram for phOSphate compounds in

selected Peruvian soils as determined by the
phOSphate solubility diagram of Lindsay and
Moreno (1960).

llO

Satipo soil indicate oversaturation with respect to fluor-

apatite and undersaturation with reSpect to hydroxyapatite.

Coastal Soils

In calcareous soils, the use of the phOSphate potential
(pH2P04 + %pCa) and the lime potential (pH - %pCa) as pro-
posed by Aslyng gives the most precise evaluation of the
solubility of soil P compounds (Aslyng, 1954; Weir and 4
Soper, 1963; Withee and Ellis, 1965). In general, P in
these soils is more soluble than octocalcium phOSphate, but
less soluble than dicalcium phOSphate (Figure 3). Note that E

the P potentials decrease as the level of P applied increases,

[ i

‘ l

and that all the soils were oversaturated with reSpect to

1.1;:

octocalcium phOSphate, eSpecially when 200 and 500 ppm P

were added.

Mountain Soils

The P solubility data from the mountain soils are plot—
ted on the phase diagram shown in Figure 4, constructed as
described by Lindsay and Moreno (1960), since two of the
mountain soils (Casablanca and Cajabamba) are acid. The
pH2P04 values for these two acid soils decreased as the
level of applied P increased; when 200 ppm P or less was
applied, the soils are undersaturated with respect to both
strengite and fluorapatite. When 500 ppm P was added, both
soils became oversaturated with respect to strengite, and
the Casablanca soil was oversaturated with reSpect to

variscite. This would indicate that P solubility in these

111

1-0
‘9 “W586: 3‘ ’80
a. CA 0 -1 p
0 LA M0L1NA 4:200 ppm

 

a:
1

PHOSPHORATE POTENTIAL pH, PO44. I/2 pCo
“P 1'

 

 

 

 

Figure 3.

e 7
LIME POTENTIAL pH-I/Z pCo

PhOSphate and lime potentials of the coastal
soils in relation to those of pure calcium
phOSphates, as affected by P application and
after wetting and drying 20 times.

112

#0

+ CASABLANCA z-so

. CAJABAMBA 3-100 pme

x HUANCAYO 4 -200
5-500

 

 

 

 

 

4..
54..
‘. .
O /
0&1 6r-/'
I /
O. L
,.-‘|'-4
s +3
7—+2
1+1
8 l
5
Figure 4.

Solubility phase diagram of Lindsay and Moreno
(1960) for the mountain soils, as affected by
the application of P and after wetting and
drying 20 times.

113

two soils is related to variscite and strengite rather than
fluorapatite. Because of the high pH, P in the Huancayo

soil was oversaturated with respect of octocalcium phOSphate.

Jungle Soils

In the San Ramon soil, P activity appears to be governed
principally by strengite (Figure 5); for even though the
addition of P up to 200 ppm decreased the pH2POh, not until
500 ppm P was added was the soil oversaturated with reSpect
to variscite.

In the Slightly acid Satipo soil, P activity appeared
to be governed by fluorapatite and hydroxyapatite. In the
Tingo Maria soil, the P concentration in the equilibrium
solution could be measured only when 500 ppm P had been
added. The P compound that apparently governs P solubility
is apparently strengite except when the highest rate of P

iS applied.

Fractionation of Soil Phopphorus
The CaP, AlP, and FeP fractions were determined for
each of the nine soils on samples to which no P had been
added and on samples to which 500 ppm P had been added. All
samples were taken after the samples had been wetted and

dried 20 times.

Coastal Soils
In the coastal soils, CaP was the dominant P fraction,

although appreciable amounts of AlP were present. The

114

 

 

 

 

 

l-O
o SAN RAMON 2'_ 50
111 SATIPO 3-100
El TINGO MARIA 4-200
5-500
4 — / ’
/
/’
" ./
L //
/
5 — ox" s
9‘} «V ’9
_ 0‘ o‘ ’0
A? (99/ i-
«Q‘ ‘9
0/ so
EA
2‘.
.4
‘2 *5
O .
’2, a
7o
‘51
13
6‘
’3
’2
p 02 *|
+- 0'
8 l 1 1 1 I 1 1 1 i 4 1 1
4 5 6 7
pH
;Figure 5. Solubility phase diagram of Lindsay and Moreno

(1960) for the jungle soils, as affected by the
application of P and after wetting and drying
20 times.

115

bound P (or exchangeable P) and FeP fractions accounted
for a very small portion of the total extracted P (Table
6). From 50 to 60 percent of the total P in the soils was
extracted as these four forms. It Should be noted, however,
that part of the fraction extracted as AlP by this pro-
cedure could be derived from some of the more soluble cal-
cium phOSphates that might be expected to occur in these
calcareous soils (Glenn pp 31.,1959; Smith pp gl., 1957).
When 500 ppm P was added, the increase in P extracted
during the fractionation procedure followed the same trends
as those present before P was added (Table 7). When the
total P in the soil was assumed to be that present origin-
ally plus that added for the purposes of this study, the P
removed by the fractionation procedure was about 60 percent
of the total P for all three soils, indicating that a
larger prOportion of the applied P was extracted by the
fractionation procedure than that of native soil P. Con-
siderably more of the extracted P was present as bound P
after P had been applied than before P applications. Note,
however, that in the La Molina soil, the amount of CaP was
about the same after P was added as before, and that applied
P appeared to be present primarily in the bound P and AlP
fractions. This was the only coastal soil that did not
contain free Ca003, and it is probable that most of the
applied P was present as exchangeable P and as calcium

;phOSphates that are soluble in NHAF in this soil.

Am0o + mmm + m4< + mmv Mo SS0 0:4 mo 0 00 0090430400 **

116

 

 

 

 

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0.00 0.00 0.04 I 0.0 0.04 0.00 0.04 0.0 4 040 4.4 04002 00044
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4.0 4.04 0.44 4.0 0.00 0.00 0.0 0.00 0.00 0.0 000 0.4 00000 000
0.00 0.40 0.00 0.4 0.00 4.004 0.00 0.04 0.00 0.0 000 0.0 00000000
4.04 0.00 0.00 I 4.04 0.044 0.00 0.00 0.00 4 000 0.0 000000400
0.0 0.00 0.00 4.4 0.00 0.000 0.00 0.040 0.404 0.0 4004 0.4 0000400000
0.00 0.0 4.04 0.4 0.00 0.000 0.040 0.00 0.00 0.00 0044 4.0 004402 04
4.00 0.0 4.04 0.0 0.04 0.004 0.000 0.04 0.00 0.04 040 0.0 0000000000
0.00 0.0 0.00 0.4 0.00 0.000 0.040 0.0 0.004 0.0 0404 4.0 0000000004
1111111111 HIR_IIIIIIIII RF I I II Egg III I I
000 000 044 *00 0 40000 000 000 000 044 *00 0 00 00400004
40 40004

 

 

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117

Ammo + 000 + 044 + mmv MO 650 000 mo 0 00 0000420400 xx

 

 

 

 

 

 

 

404 40 02 0043 0000000000 0000000000 00000 n 00 x
4.0 0.00 0.00 0.0 0.00 0.000 0.00 0.044 0.000 0.04 0404 4.4 04002 00040
0.0 0.00 0.04 0.04 0.40 0.004 0.04 0.004 0.000 0.00 000 0.0 004000
0.4 0.00 0.00 0.4 0.00 0.000 0.0 0.004 0.000 0.00 000 0.4 00000 000
4.04 0.04 0.04 4.40 0.04 0.000 0.00 0.044 0.000 0.004 0044 0.0 00000000
0.4 0.00 0.40 0.4 0.04 0.040 0.40 0.004 0.000 0.00 0044 0.0 000000400
4.0 0.04 0.04 0.4 4.04 0.000 0.00 0.000 0.000 0.04 4004 0.4 0000400000
0.40 0.0 0.00 4.04 0.00 0.0004 0.000 0.00 0.000 0.004 0004 4.0 004402 04
4.00 0.0 0.00 0.04 0.00 0.000 0.044 0.00 0.000 0.004 0444 0.0 0000000000
0.00 4.0 0.00 0.0 0.40 0.0004 0.000 0.0 0.000 0.00 0404 4.0 0000000004

00 IIIIIIIIII 0 III I Ema
000 000 044 000 0 40000 000 000 000 044 x00 0 00 00400004
.HO HMPOB
00440000

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000400000 0 040000004

 

 

.0044000 003 Ema 000 00403 04 04400 004>500m

.00040 om 004000 000 0040003 00000 000

0040 04 000400000 0 040000004 000 0 40000

.0 04000

118

The relatively high levels of P in the coastal soils
are likely a reflection of the high rates of guano 92.l§l§§
that have been commonly applied annually to these soils
for centuries. The recovery of approximately 60 percent
of the total P by the fractionation procedure is in agree-
ment with data reported from calcareous soils (Hawkins and

Kunze, 1965).

Mountain Soils

 

In the acid Casablanca and Cajabamba soils, FeP was
the dominant mineral P fraction, and a considerable amount
of AlP was present in the Casablanca soil (Table 6). The
amounts of AlP and CaP were about the same in the Cajabamba
soil. In the neutral Huancayo soil, the amounts of AlP,
FeP, and CaP were about equal. No appreciable amounts of
bound P were noted in any of the mountain soils. The total
P in these mountain soils is relatively high and could be
a reflection of the high native fertility of these soils
and the relatively higher content of organic matter as
compared to the coastal and jungle soils. The recovery of
from 17 to 33 percent of the total P by the fractionation
procedure is less than that noted for the coastal soils,
and is indicative of a more advanced stage of weathering
(Chang and Jackson, 1958).

When 500 ppm P was applied to these soils, data indi-
cate that most of the applied P was recovered by the fraction-

ation procedure on all three soils (Table 7). Most of the

119

applied P appeared to be removed as AlP, although an
appreciable amount was present as bound P in the Huancayo
soil. No appreciable change in CaP was noted on any of
the soils.

The forms of P in the Huancayo soil were definitely
different than those in the more acid mountain soils, and
the distribution is also different from that in the more
calcareous coastal soils. This may in part be due to more
severe weathering in the mountains than in the coast. It
is interesting to note that the distribution of P in this
soil does not appear to follow the sequence of formation
and transformations of the various phOSphate Species in
accordance to the chemical principles of solubility pro-
ducts as used in the preceding sections of this study.

It should be emphasized here, however, that the fraction-
ation procedure used accounted for only about half of the

total P in this soil after 500 ppm P had been applied.

Jungle Soils

 

In the San Ramon and Satipo soils, AlP and FeP appeared
to be the dominant forms of P removed by the extraction pro-
cedure, while most of the P extracted from the Tingo Maria
soil was CaP (Table 6). However, it should be noted that
the recovery of total P from these soils was very low, rang-
ing from about 8 to 20 percent. This is indicative of the
more severe weathering in the jungle soils than in the

:mountain or coastal soils.

120

When 500 ppm P was applied, most of the applied P was
recovered in the fractionation procedure (Table 7). The
lowest recovery was from the Tingo Maria soil, as would be
expected from the adsorption data showing the low solubility
and the strong bonding energy for P in this soil. Most of
the applied P in all three soils was removed as AlP,
although appreciable amounts of FeP were noted in all
three soils, and a considerable amount of bound P was
extracted from the Satipo soil.

The data obtained from the P fractionation of the
jungle soils to which no P was applied give very little
information relative to the forms of P since the fraction-
ation procedure extracted very little of the total P in
these soils. The non-extractable P is of paramount impor-
tance for a more complete understanding of the P reactions
in the jungle soils. Probably, the greater part of the
native P in these soils exists as Fe and Al compounds,
possibly in occluded or reductant—soluble form, which have
a very low solubility (Syers et al., 1969). The high
recovery of added P on these soils would indicate that the
formation of these compounds probably takes place very
slowly, and is a result of the severe weathering conditions
under which these soils were deveIOped. Similar results
have been reported by Yuan et'al. (1960) on severely

weathered acid soils.

SUMMARY AND CONCLUSIONS

PHOSPHORUS FORMS AND EQUILIBRIA
IN SELECTED PERUVIAN SOILS

PhOSphorus in the coastal soils was primarily CaP,
and the adsorption maxima on these soils was directly
related to the amount of free CaCO3 present. Studies of
the Ca potential indicated that the solubility of P in
these soils is governed mainly by octocalcium phosphate;
when 200 or 500 ppm P was applied, P solubility was
dependent upon dicalcium phOSphate. Not only was the P
adsorbing capacity higher on soils with free CaCO3
(Lambayeque and Casagrande) than on that which did not
contain free CaCO3 (La Molina), but the P was held more
tightly when free CaCO3 was present.

In the mountain soils, the lowest P adsorption maximum
was on the neutral Huancayo soil, in which CaP predominated,
but which contained no free CaCOB. The P solubility in
this soil appeared to be governed by hydroxyapatite, even
at the highest rates of applied P. The P adsorption data
also indicated that the energy of P adsorption was about
twice as high on the Huancayo soil as on the coastal soils.
It seems apparent, then, that the CaP in the Huancayo soil
is present as a more difficultly—soluble form than that in
the coastal soils.

121

122

In the acid Casablanca and Cajabamba soils of the
mountains, FeP predominated, accompanied by relatively
large proportions of AlP; a considerable amount of CaP was
extracted from the Cajabamba soil. These soils were under-
saturated with respect to strengite except when 500 ppm P
was applied, when P solubility appeared to be controlled
by varascite and/or strengite. Adsorption maxima on these
two soils were higher than those of any of the other soils
except for the Lambayeque soil from the coast and the 2
Tingo Maria soil from the jungle, and P was adsorbed more 3
tightly than on any of the other soils except the Tingo 3
Maria soil. 3

The fractionation of P from the jungle soils indicated
that P in the strongly acid San Ramon soil and the slightly
acid Satipo soil was mostly AlP and FeP, while that of the
strongly acid Tingo Maria soil was mostly CaP. However,
only from 8 to 20 percent of the total P in these soils was
removed by the fractionation procedure; so these data are
not adequate to completely characterize the soil P. The
slightly acid Satipo soil was undersaturated with respect
to hydroxyapatite except when 200 and 500 ppm P were applied.
The San Ramon and Tingo Maria soils were undersaturated with
respect to strengite except when 500 ppm P was applied, when
variscite seemed to be controlling P solubility. Highest
absorbing capacity and highest bonding energy for P were

noted for the strongly acid Tingo Maria soil.

123

Extraction of soil P by the fractionation procedure
indicated that the jungle soils are the most severely
weathered and the coastal soils the least weathered of the
nine soils studied. In general, P was absorbed more strongly
on the acid soils than on the calcareous soils.

The forms of P extracted from the soils was related
more closely to pH than to any other soil factor measured.
Forms of P extracted after P was "fixed" generally were in
the same proportions as that extracted prior to P applica—

tions.

BIBLIOGRAPHY
PART II

Alban, L. A., Vacharotayan, S., and Jackson, T. L. 196A.
PhOSphorus availability in reddish brown lateritic
sogls. I. Laboratory studies. Agron. J. 56:555-
55 .

Aslyng, H. C. 1954. The lime and phOSphate potentials
of soils; the solubility and availability of phos—
phates. Roy. Vet. and Agric. Coll. Copenhagen.
Den. Yearbook reprint, pp. 1-50.

Black, C. A. l9h2. The penetration of phOSphate into the
kaolinite crystal. Soil Sci. Soc. Amer. Proc. 6:

Bradfield, R., Scarseth, G., and Steele, J. G. 1935.
Factors affecting the retention of phOSphates by
clays. Third Int. Congress of Soil Science, Vol.

Iz7h.

Bray, R. H., and Kurtz, L. T. 1945. Determination of
total organic and available phOSphorus in soils.
Soil Sci. 59:39-h5.

Chai-Moo-Cho, and Caldwell, A. C. 1959. Forms of phOSphorus
and fixation in soils. Soil Sci. Soc. Amer. Proc.

23:458-460.

Chang, S. C., and Chu, W. K. 1961. Fate of soluble phOSphate
applied to soils. J. Soil Sci. 12:286-293.

Chang, S. C., and Jackson, M. L. 1957. Fractionation of
soil phOSphorus. Soil Sci. 84:133-lhh.

Chang, S. C., and Jackson, M. L. 1958. Soil phOSphorus
fractionation in some representative soils. J. Soil
Sci. 9:109-119.

Chang, S. C., and Juo, S. R. 1963. Available phOSphorus in
relation to forms of phOSphorus in soils. Soil Sci.

95:91-96.

Chu, W. K., and Chang, S. C. 1960. Forms of phOSphorus in
the soils of Taiwan. J. Agric. Assoc., China. 30:
1-12.

124

125

Clark, J. S., and Peech, M. 1955. Solubility criteria
for the existence of calcium and aluminum phOSphates
in soils. Soil Sci. Soc. Amer. Proc. 19:171-17h.

Cole, C. V., and Jackson, M. L. 1950. Colloidal dihydroxy
dehydrogen phOSphates of aluminum and iron with
crystalline character established by electron and
X-ray diffraction. J. Phys. and Colloid Chem. 54:
128—142.

Cole, C. V., Olsen, S. R., and Scott, C. O. 1953. The
nature of phOSphate sorption by calcium carbonate.

Coleman, R. 1945. The mechanism of phOSphate fixation by
montmorillonitic and kaolinitic clays. Soil Sci.
Soc. Amer. Proc. 9:72-78.

Coleman, R., Throup, J. T., and Jackson, W. A. 1960.
PhOSphate sorption reactions that involve exchange—
able aluminum. Soil Sci. 90:1-7.

Dahnke, W. C., and Malcolm, J. L. 196A. Phosphorus frac-
tions in selected soil profiles of El Salvador as
related to their deve10pment. Soil Sci. 98:33-38.

Davis, L. E. 1935. Sorption of phOSphates by non-calcareous
Hawaiian soils. Soil Sci. A0:129—lh8.

Dean, L. A. 1938. An attempted fractionation of soil phos-
phorus. J. Agric. Sci. 28:234-2h6.

Dean, L. A. l9h9. Fixation of soil phosphorus. Advances
in Agronomy. 1:39l-hll.

Drossdoff, M., Quevedo, F., and Zamora, C. 1960. Soils of
Peru. 7th Intern. Congress of Soil 801., Madison,
Wisc.

Ellis, R., and Troug, E. 1955. PhOSphate fixation by mont—
morillonite. Soil Sci. Soc. Amer. Proc. l9:h51-h54.

Fassbender, H. W. 1966. La adsorcton de fosfatos en suelos
fuertemente acidos y su evolucion usando la isoterma
de Langmuir. Fitotecnia Latinoamericana. 3(1-2)
203-21 .

Fassbender, H. W., Muller, L., and Balerdi, F. 1968.
Estudio del fosforo en suelos de Centroamerica.
II. Formas y su relacion con la planta. Turrialba

18(h):333-347.

126

Fife, C. V. 1959a, 1959b, 1962, 1963. An evaluation of
ammonium fluoride as a selective extractant for
aluminum bound soil phOSphate: I-IV. Soil Sci.
87:13-21, 83-88; 93:113-123; 96:112-120.

Fraps, G. S. 1906. Availability of phosphoric acid of the
soil. J. Amer. Soc. Agron. 28:823-83A.

Fried, M., and Shapiro, R. E. 1960. Soil-Plant relations
in phOSphorus uptake. Soil Sci. 90:69—76.

Glenn, R. C., Hsu, P. H., Jackson, M. L., and Corey, R. B.
1959. Flow sheet for soil phOSphate fractionation.
Agr. Abst. pp. 9.

Hanley, K. 1962. Soil phOSphorus forms and their avail-
ability to plants. Irish J. Agric. Res. 1:192-193.

Hawkins, R. H., and Kunze, G. W. 1965. PhOSphate fractions
in some Texas grumosols and their relation to soil
weathering and available phOSphorus. Soil Sci. Soc.
Amer. Proc. 29:650-656.

Henwall, J. B. 1957. The fixation of phOSphorus by soils.
Advances in Agronomy. 9:95-112.

Hsu, P. H., and Jackson, M. L. 1950. Inorganic phOSphate
transformations by chemical weathering in soils as
influenced by pH. Soil Sci. 90:16-24.

Hsu, P. H., and Rennie, D. A. 1962. Reactions of phos—
phate in aluminum systems: II. Precipitation of
phOSphate by exchangeable aluminum on a cation
exchange resin. Can. J. Soil Sci. A2:2lO—221.

Huffman, E. O. 1968. The reactions of fertilizer phos-
phate with soils. Outlook on Agriculture. 5:(5)
202-207.

Jackson, M. L. 1958. Soil Chemical Analysis. Prentice
Hall, Inc., New Jersey.

Juo, A. S., and Ellis, B. G. 1968. Particle size distri-
bution of aluminum, iron and calcium phosphates in
soil profiles. Soil Sci. 106:37h—380.

Juo, A. S. 1966. Chemical and physical factors affecting
the relative availability of inorganic phOSphorus
in soils. Ph.D. Thesis, Michigan State University.

Kelley, J. B., and Midgley, A. R. l9h3. PhOSphate fixa-
tion and exchan e of phOSphate and hydroxyl ions.

127

Khin, A., and Leeper, G. W. 1960. Modification in Chang
and Jackson's procedure for fractionating soil
phOSphorus. Agrochimica. 4:2h6-25h.

Kittrick, J. A., and Jackson, M. L. 1956. Electron micro-
SCOpe observations of the reaction of phoSphate with
minerals leading to a unified theory of phOSphate
fixation in soils. J. Soil Sci. 7:81-89.

Kurtz, L. T. 1953. Inorganic phOSphorus in acid and neu—
tral soils. "Soils and Fertilizer PhOSphorus,"
Chap. III.

Kurtz, L. T., DeTurk, E. E., and Bray, R. H. 1946. Phos-
phate adsorption by Illinois soils. Soil Sci. 61:
111-12h.

Langmuir, I. 1918. The adsorption of gases on plane sur-
faces of glass, mica and platinum. J. Amer. Chem.
SOC. h0:l361-lh02.

Larsen, S. 1967. Soil phOSphorus. Advances in Agronomy.
19:151-206.

Larsen, 8., and Court, M. N. 1960. Chemical potentials
of phOSphate ions in soil solutions. 7th Intern.
Cong. Soil Sci., Madison, Wisc.

Larsen, 8., and Court, M. N. 1961. Soil phOSphate solu—
bility. Nature. 189:16h-165.

Lindsay, W. L., Frazier, A. W., and Stephenson, H. F. 1962.
Identification of reaction products from phOSphate
fertilizers in soils. Soil Sci. Soc. Amer. Proc.

26:446-452.

Lindsay, W. L., and Moreno, E. C. 1960. PhOSphate phase
equilibria in soils. Soil Sci. Soc. Amer. Proc.
24:177—182.

Low, P. F., and Black, C. A. 1950. Reactions of phOSphate
with kaolinite. Soil Sci. 70:273-290.

Melton, J. R. 1964. Availability of aluminum, iron and
calcium phOSphate in soils. M.S. Thesis, Michigan
State University.

Midgley, A. R. l9hO. PhOSphate fixation in soils. A crit-
ical review. Soil Sci. Soc. Amer. Proc. 5:2h-30.

Murphy, H. F. 1939. The role of kaolinite in phOSphate
fixation. Hilgardia. 12:3h3-382.

128

Olsen, S. R. 1953. Inorganic phOSphorus in alkaline and
calcareous soils. "Soils and Fertilizer PhOSphorus"
Chap. IV. Agron. Monographs, Vol. IV. Academ. Press.

Olsen, S. R., and Watanabe, F. S. 1957. A method to deter-
mine a phOSphorus adsorption maximum of soils as
measured by the Langmuir isotherm. Soil Sci. Soc.
Amer. Proc. 21:1hh—1h9.

Ravikovitch, S. 1934. Anion exchange. II. Liberation of
the phOSphoric acid ion adsorbed by soils. Soil

Sci. 38: 279- 290

Russell, E. J., Prescott, J. A. 1916. The reaction between
dilute acids and the phosphorus compounds of the
soil. J. Agric. Sci. 5 110.

Sanchez, C. 1965. Evaluation of certain chemical trans-
formations of soluble fertilizer phOSphorus applied
to three Michigan soils. Ph.D. Thesis, Michigan
State University.

Saunders, W. M. H. 1959. Aluminum extracted by neutral
citrate-dithionite reagent. Nature. 184: 2037.

Scarseth, G. D. 1935. The mechanism of phOSphate reten-
tion by natural alumino silicate colloids. J. Amer.
Soc. Agron. 27. 596- 616.

Schofield, R. K. 1955. Can a precise meaning be given to
"available" soil phOSphorus. Soils Fert. 18: 373-
375.

Sen Gupta, M. B., and Cornfield, A. H. 1962. PhOSphorus
in calcareous soils. IV. The inorganic phOSphate
fractions and their relation to the amount of
calcium carbonate present. J. Sci. Food Agric.

13: 652—655

Sen Gupta, M. B., and Cornfield, A. H. 1963. PhoSphorus
in calcareous soil. IV. Nature of and factors
influencing the fixation of added phOSphate. J.
Sci. Food Agric. IA: 873- 877.

Smith, A. N. 1965. Distinction between iron and aluminum
phOSphate in Chang and Jackson's procedure for
fractionating inorganic soil phOSphorus. Agrochimica.

9: 162-168.

Smith, A. N. 1965. The supply of solublephOSphorus to
the wheat plant from inorganic soil phosphorus.
Plant and Soil. 22: 314-316.

129

Smith, F. W., Ellis, B. G., and Grava, J. 1957. Use of
acid-fluoride solutions for the extraction of
available phOSphorus in calcareous soils and in
soil to which rock phOSphate has been added. Soil
Sci. Soc. Am. Proc. 21:400-A04.

Stout, P. R. 1939. Alteration in the crystal structure
of clay minerals as result of phosphate fixation.
Soil Sci. Soc. Amer. Proc. #:177-182.

Susuki, A., Lawton, K., and Doll, E. C. 1963. PhOSphorus
uptake and soil tests as related to forms of phos-
phorus in some Michigan soils. Soil Sci. Soc. Amer.
Proc. 27:401—h03.

Syers, J. K., Williams, J. D. H., Tyner, E. H., and Walker,
T. W. 1969. Primary and secondary origin of the
"non extractable'soil inorganic phosphorus. Soil
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Tosi, J. A. 1960. Natural Climatic Life-Zones of Peru.
Technical bulletin 5. Inst. Interam. de Ciencias
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Turner, R. C., and Rice, H. M. 195A. Role of fluoride
ion in release of phOSphate adsorbed by Al and Fe
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Weir, C. C., and Soper, R. J. 1963. Solubility studies
of phOSphorus in some calcareous Manitoba soils.
J. Soil Sci. lA:256—26l.

Wild, A. 1953. The effects of exchangeable cations on
the rgtention of phOSphate by clay. J. Soil Sci.
4:72- 5.

Williams, C. H. 1950. Studies in soil phOSphorus: I.
A method for the partial fractionation of soil
phOSphorus. J. Agric. Sci. A0:233—242.

Withee, L. V. and Ellis, R., Jr. 1965. Change of phOSphate
potentials of calcareous soils on adding phosphorus.
SOil SCio SOC. Amer. PTOC. 29:511-514.

Woodruff, J. R., Kamprath, E. J. 1965. PhOSphorus adsorp-
tion maximum as measured by the Langmuir isotherm
and its relationship to phOSphorus availability.
Soil Sci. Soc. Amer. Proc. 29:1A8-150.

Yuan, T. L., Robertson, W. K., and Neller, J. R. 1960.
Forms of newly fixed phOSphorus in three acid sandy
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APPENDIX

APPENDIX I

Location and crop history of the Hodunk sandy loam soil.

The M.S.U. Experimental Farm is located in East
Lansing on the SW % of NE % of SE %, Section 19, TAN,
RlW Meridian Township, Ingham County.

The experimental area used in 1967 was in fallow
in the crOp year of 1965 and 1966. An experiment on
irrigation was set up, using soybeans as a crop. Ferti-
lizers were applied at the rate of 200 pounds per acre
of a 6-24—24 fertilizer grade.

The experimental area used in 1968 was cropped with
potatoes in the 1966 growing season. The area was
fertilized with 166 pounds N per acre, 100 pounds P205
per acre, and 180 pounds K20 per acre. In the year
1967, an experiment in corn was carried out where 100
pounds per acre of a fertilizer mixture of 6-2A-2A grade
was applied, plus additional applications of nitrogen to

get a total of 150 pounds N per acre.

Location and crOp history of the Mo Bride sandy loam soil.
The Montcalm Experimental Farm is located on the SW
% of SW i of Section 8, TllN, R7W Douglas Township,
Montcalm County.
The experimental area used in 1968 was in fallow in
1967, and in 1968 was cropped with kidney beans.
130

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