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© 1979

MOHAMED ALI HADIA EL-MEZOGHI

ALLRIG'ITS RESERVED

THE EFFECT OF APPLIED AND RESIDUAL PHOSPHORUS ON
GROWTH OF CORN (Zgg_maxs L.) AND POTATOES

 

(Solaneum tuberosum L.)

By

Mohamed Ali Hadia El-Mezoghi

A THESIS

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

MASTER OF SCIENCE

Department of Crop and Soii Science

1979

ABSTRACT

THE EFFECT OF APPLIED AND RESIDUAL PHOSPHORUS ON
GROWTH OF CORN (ZEE,mays L.) AND POTATOES

(Solaneum tuberosum L.)

 

By
Mohamed Ali Hadia El-Mezoghi

The effect of applied and residual P on growth of corn and
potatoes was measured on a Charity clay soil. Four levels of P
(0, 12.5, 37.5 and 62.5 ppm) were added as Ca(H2P04)2-H20 prior to
growth of corn. After corn, potatoes were grown on the same soils
without any additional P fertilizer.

Yield,percent P and P uptake by corn were almost equally
affected by applied and residual P, except percent P was only af-
fected by residual P. However, the same parameters for potatoes
were affected more by residual P than by previously applied P.

High correlation (r = 0.98) was obtained between the extract-
able P using Bray P1 and Olsen methods. Bray P1 and Olsen tests
were essentially equal in relating P availability for both crops.

After corn or potatoes, apparent P fixation tended to in-
crease with increasing levels of applied and residual P.

A modified Mitscherlich equation was used to evaluate corn
responses to P. Baule units and fertilizer guides for 90, 95 and
97 percent sufficiency of corn yield were calculated for each soil

test method.

This thesis is dedicated to
My Father and Memory of
My Mother

ii

ACKNOWLEDGMENTS

The author expresses special recognition and appreciation to
Dr. Donald R. Christenson his major professor and Committee Chair-
man for his valuable guidance, active assistance, patience and un-
derstanding during this study. Gratitude is expressed also to the
committee members Dr. Boyd G. Ellis, for his keen judgment and
assistance to solve some difficulties of this study, Dr. John C.
Shickluna and Dr. Robert F. Ruppel.

Special gratitude and recognition is expressed to Libyan
People who financially supported this study.

Special recognition and thanks are expressed to my father
and other members of my family for their support, encouragement
and sacrifice.

Appreciation is expressed to Calvin Bricker for his assis-
tance in some lab technical work, to his wife Betsy, for drawing
the response surface graphs and to Mohamed M. Daghel for his help
in using the graphic machine to draw most of the curves of this
study. To my wife, Tunis and our daughter Aml, I am especially
grateful for without their patience and adaptation this study would
never have been finished.

Appreciation is also extended to other members of the Crop
and Soil Science Department for the many opportunities for intellec-
tual growth.

Last, but not least, the author wishes to express his special
gratitude to all of his relatives and friends for their encourage-

ment and help to continue searching.

iii

TABLE OF CONTENTS

LIST OF TABLES ........................
LIST OF FIGURES .......................
CHAPTER

I INTRODUCTION .....................
II REVIEW OF LITERATURE .................

A. Residual P Studies ...............
B. Availability of Various Forms of Soil P . . . . .
C. Methods of Estimating Soil P to Plants .....

III MATERIALS AND METHODS .................
A. Soil Samples ..................

B. Greenhouse Studies ...............

1. Corn Experiment ...............
2. Potato Experiment ..............

C. Methods of Soil Analyses ............

I . Bray P] ..................
2. Olsen's NaHC03 ...............
3. Phosphorus Analysis (Murphy & Riley Method)

D. Plant Tissue Analysis ..............
E. Statistical Analyses ..............
IV RESULTS AND DISCUSSION ................

A Corn Experiment .................
B. Potato Experiment ................
C. Soil Tests ...................
D. The Changes in Soil Tests ............
E Application of a Modified Form of Mitscherlish
Equation ...................

V GENERAL DISCUSSION ...................
VI CONCLUSIONS ......................

iv

15

27
31
37
51
59
71

75

Page
VII APPENDIX ........................ 77
VIII LITERATURE CITED .................... 85

Table

10.

ll.

12.

LIST OF TABLES

Some chemical properties and initial residual P of a
Charity clay soil used in the greenhouse studies .....

The effect of applied and residual P on yield of corn tops
grown in the greenhouse on a Charity Clay soil ......

The effect of applied and residual P on P concentrations
of corn tops grown in the greenhouse on a Charity clay
soil ...........................

The effect of applied and residual P on P uptake by corn
tops grown in the greenhouse on a Charity clay soil

The effect of applied and residual P on yield of potato
tops grown in the greenhouse on a Charity clay soil

The effect of applied and residual P on P concentration
of potato tops grown in the greenhouse on a Charity clay
soil ...........................

The effect of applied and residual P on P uptake by potato
tops grown in the greenhouse on a Charity clay soil

The simple Correlation Coefficients of yield, percent P
in plant tissues and P uptake by potatoes and by corn
grown in the greenhouse on a Charity clay soil as related
to both applied and residual P ..............

The effect of applied and residual P on P extracted by
Bray In (1:8) after harvesting potato crop grown in the
greenhouse on a Charity clay soil ............

The effect of applied and residual P on P extracted by
Bray Th (l:50) after harvesting potato crop grown in the
greenhouse on a Charity clay soil ............

The effect of applied and residual P on P extracted by
Olsen's NaHC03 after harvesting potato crop grown in the
greenhouse on a Charity clay soil ............

Comparisons between the best fitting of quatratic and

stepwise regression relationship for corn yield vs. soil
test and applied P ....................

vi

Page

16

28

29

3O

32

33

34

36

39

40

41

46

Table
l3.

T4.

)5.

l6.

l7.

)8.

T9.

20.

2).

22.

23.

Multiple (non-linear) Coefficients of determination
for yield, percent P, and P uptake as a function of
three soil tests for corn and potatoes grown in the
greenhouse and Charity clay soil ............

Changes in the residual levels of soil P extracted by
Bray P (1:8) soil/solution ratio as affected by
applieé P and production of two crops (corn and pota-
toes) grown in the greenhouse on a Charity clay soil . .

Bray P1 (1:8) soil test values and response of corn
crop grown in the greenhouse on a Charity clay soil to
applied phosphorus ...................

Bray P] (l:50) soil test values and response of corn
crop grown in the greenhouse on a Charity clay soil to
applied phosphorus ...................

Olsen's NaHCO3 soil test values and response of corn
crop grown in the greenhouse on a Charity clay soil to
applied phosphorus ...................

Comparisons of observed and calculated percent suf-
ficiency for corn crop grown in the greenhouse on a
Charity clay soil based on the equation for Bray P1

(l:8) soil test ....................

Comparison of observed and calculated percent suf-
ficiency for corn crop grown in the greenhouse on a
Charity clay soil based on the equation for Bray P1

(l:50) soil test ....................

Comparison of observed and calculated percent suf-
ficiency for corn crop grown in the greenhouse on a
Charity clay soil based on the equation for Olsen's

NaHC03 soil test ....................

Calculated quantities of P required to attain various
percent sufficiency for corn grown in the greenhouse on

a Charity clay soil based on Bray P1 (1:8) equations . .

Calculated quantities of P required to attain various
percent sufficiency for corn grown in the greenhouse on

a Charity clay soil based on Bray P] (l:50) equation . .

Calculated quantities of P required to attain various
percent sufficiency for corn grown in the greenhouse on

a Charity clay soil based on Olsen's NaHCO3 equation . .

vii

Page

50

58

6O

6]

62

65

66

68

69

70

Table Page

Al. The effect of applied and residual P on P extracted by
Bray P1 (l:8) after harvesting corn crop grown in the
greenhouse on a Charity clay soil ............ 77

A2. The effect of applied and residual P on P extracted
by Bray P] (1:50) after harvesting corn crop grown in
the greenhouse on a Charity clay soil .......... 78

A3. The effect of applied and residual P on P extracted by
Olsen's NaHC03 after harvesting corn crop grown in the
greenhouse in a Charity clay soil ............ 79

A4. Changes in the residual levels of soil P extracted by
Bray P1 (l:50) soil to solution ratio as affected by
applied P and production of two crop (corn and potatoes)
grown in the greenhouse on a Charity clay soil ..... 80

A5. Changes in the residual levels of soil P extracted by
Bray P] (l:8) soil/solution ratio as affected by
applied P and production of one corn crop grown in the
greenhouse on a Charity clay soil ............ 8l

viii

Figure

10.

LIST OF FIGURES

The linear relationship between P extracted by Bray P]
(1:50) and by Bray P] (l:8) from a Charity clay soil
after potato crop was harvested in the greenhouse . . . .

The linear relationship between P extracted by Bray P]
(1:8) and P extracted by Olsen's NaHCO3 from a Charity
clay soil after potato crop was harvested in the green-
house ..........................

The linear relationship between P extracted by Bray P]
(l:50) and P extracted by Olsen's NaHC03 from a Charity
clay soil after potato crop was harvested in the green-
house ..........................

Corn yield in relation to applied and Bray P] (l :8) ex-
tracted P from a Charity clay soil after harvesting corn
crop in the greenhouse .................

Corn yield in relation to applied and Bray P1 (l:50)
extracted P from a Charity clay soil after harvesting
corn crop in the greenhouse ...............

Corn yield in relation to applied and Olsen's NaHC03
extracted P from a Charity clay soil after harvesting
corn crop in the greenhouse ...............

The multiple non-linear relationship between extracted
P by Bray P1 (l:8) and the yield of corn tops grown
in the greenhouse on a Charity Clay soil ........

The multiple non-linear relationship between the ex-
tracted P by Bray P] (l:50) and the yield of corn tops
grown in the greenhouse on a Charity clay soil .....

The multiple non-linear relationship between extracted
P by Olsen's NaHC03 and yield of corn tops grown in the
greenhouse on a Charity clay soil ............

The multiple relationship between extracted P by Bray

P1 (1:8) and total P uptake by potato tops grown in the
greenhouse on a Charity Clay soil ............

ix

Page

42

43

44

48

49

54

55

Figure Page

11. The multiple relationship between P extracted by Bray
P] (1:50) and total P uptake by potato tops grown in
the greenhouse on a Charity clay soil .......... 55

12. The multiple non-linear relationship between extracted
P by Olsen's NaHCO3 and total P uptake by potato tops
grown in the greenhouse on a Charity clay soil ..... 57

Al. The linear relationship between P extracted by Bray P]
(1:50) and P extracted by Bray Th (1:8) from a Charity
clay soil after corn crop was harvested in the green-
house .......................... 82

A2. The linear relationship between P extracted by Olsen's
NaHC03 and P extracted by Bray' P1 (l:8) from a Charity
clay soil after corn crop was harvested in the green-
house .......................... 83

A3. The linear relationship between P extracted by Bray P]
(1:50) and P extracted by Olsen's NaHC03 from a Charity
clay soil after corn crop was harvested in the green-
house .......................... 84

CHAPTER I

INTRODUCTION

Phosphorus is one of the elements known to be essential and
a limiting factor for plant and animal growth. Phosphorus plays an
important role in energy conservation and biosynthetic reactions in
plants.

Many agronomists have considered P to be one of the most limit-
ing elements in food production throughout the world. When soluble
P fertilizers are added to the soils most of the P is rapidly con-
verted into relatively insoluble forms. The amount of added P util-
ized by a crop is about 10% of that applied P, due to fixation and
adsorption reaction in the soil (Larsen, 1967). As P is removed
from the soil solution by the crop, it may be replaced by P fixed
from the previously applied P. The rate of release of fixed P may
not be sufficient to supply the crop requirements and so the P
content of soil solution must be replenished during the growing
season.

There are many factors involved in the rate of fixation, rate
of release and availability of various forms of P resulting from P
fertilizer applications to soils.

It is the task of soil scientists or agronomists to evaluate

the availability of this fixed P for subsequent plant growth. A

large amount of effort has been spent in studying soil fertility in
order to develop the suitable extractants to determine the levels of
plant-available nutrients in the soil.

Several soil extractants have been developed in an attempt to
measure the availability of soil P to the growing crops. Generally,
different or modified soil tests are required for different soils.

It is still doubtful that a single extracting reagent will be de-
veloped for all soils in different places.
The available P, as measured by Bray Ffi soil test is used as
the basis for P fertilizer recommendations in Michigan (Warnke gt_al,,
1976). Both Bray Ffi and Olsen's NaHCO3 soil tests (NCR-13, Bulletin
no. 499, 1975) are used as the basis for P fertilizer recommendations
in North Central Region of the USA. High correlations have been ob-
tained between available P extracted by these methods and plant par-
ameters under different conditions.
This study was undertaken on a Charity clay soil in the green-
house with the following objectives:
1) To investigate the effect of both applied and residual P
on the growth of corn and potatoes.

2) To find the relationship between plant parameters and the
amount of extracted P by Bray' P] (1:8 and 1:50) and Olsen's
NaHCO3.

3) To investigate the changes in soil test levels as a result
of applied and residual P.

4) To evaluate soil tests correlations by using a modified

form of Mitscherlich equation.

CHAPTER II

REVIEW OF LITERATURE

One of the most important aspects of the crop fertilization re-
search is evaluation of the residual effects of applied fertilizer.

Only a small portion of the applied P is removed in the har-
vested part of the crop. The rest of the applied P is accumulated

in the soil.

A. Residual P Studies

 

Doll gt_al, (1967) indicated that P applied to the soil may be
fixed in the soil in a form not immediately available to the plant
and that fixed P does have a residual effect serving to replenish the
level of immediately available P as it is removed by cropping. Chris-
tenson and Doll (1968) found that some of the applied P was fixed by
the soil. Davis gt_al, (1959) concluded that there is a buildup in
residual P as a result of certain amounts of P application. Kamprath
and Miller (1958) studied soybean yields as affected by P level of
the soil. They noted that the yield response of soybean was depend-
ent upon the soil P level. Singh gt_gl, (1966) investigated P up-
take by corn under no-tillage and conventional practices. They re-
ported that both the P uptake and total P content of the corn leaves

were larger where the phosphate was surface applied than where it was

incorporated into the soil. Webb gt_al, (1961) reported that drilling

the P fertilizer with seeds was significantly superior to broadcast-
ing. Ham and Caldwell (1978) studied the effect of fertilizer place-

33F uptake on a Waukegan

ment on soybean seed yield, N2 fixation and
silt loam soil. They found that soybean yield and total P uptake
were significantly increased by adding P fertilizer with no differ-
ences among the fertilizer placements. However, Olsen gt_al, (1954)
reported the efficiency of use of added P was more strongly influ-
enced by the initial level of available P than by soil type, soil
texture or CaCO3 content. Shickluna and Lucas (1963) found that P
fixation reduces the availability of both native and applied P to
plants on organic soils with pH above or below 5.5. The availability
of P decreased when soil pH decreased or increased from this level
due to formation of less soluble Fe, Al-, and Ca-P's. Shickluna
(1962), White and Doll (1971) and Doll et_al_(l972) reported that
available soil P tends to increase faster in coarse textured soils
than in fine textured soils for a given level of applied P.

Sanchez (1965) found that of total P uptake by corn plants only
a small fraction came from that P applied for the crop, the rest of
the applied P was accumulated in the soil in different P phosphate
fractions.

The evidence would suggest that the extent of the accumulation
depends on several factors, such as the amount of P being applied,
method of application, soil type, erosion losses and kind of the
crop grown.

The availability of the accumulated P for succeeding crops is
of real practical importance. Several workers have investigated the

residual effect of the applied P. Campbell (1965) studied the

5

residual effect of the applied P for eight years from 0, 29, 58, 118,
and 235 kg P/ha, applied for barley and measured in a six-year rota-
tion of barley, alfalfa (three years), corn and sugar beets grown on
Thurlow clay loam. He found from the applied rates of P that the
amount of P removed by crops in nine years totaled 108, 122, 139,
152 and 200.5 kg P/ha, respectively. The corresponding recoveries
of P from the applied rates were 49, 54, 38 and 40 percent. Most
of the 29 kg P/ha was used in four years. The residual response over
the entire period increased with higher rates. McGeorge (1939) in-
dicated that soluble P fertilizers showed residual responses for
several years. In Idaho, Mannering §t_§l, (1959) reported the P
fertilizer applied in 1951 on soils testing fairly low in available
P, increased yields of barley straw and alfalfa in 1951, of field
beans in 1955, and of sugar beets in 1956. Only rates of 118 kg
P/ha or more significantly increased yields in 1955 and 1956. Al-
falfa showed no yield responses to previously applied P during 1952
and 1954. The P application increased P content of the alfalfa in
all four years. They found that the high rates of P application
(235 kg P/ha or higher) were sufficient to cover a large part of
the crop requirements of available P for plant use six years after
application. MacLean (1964) concluded that under conditions of in-
tensive cropping (12 crops) in the greenhouses, residual P was
highly effective In supplying crop requirements.

Kamprath (1967) found that large initial applications of P to
high P fixing sails had a marked residual effect on the yield of
corn seven to nine years later. McAuliffe g§_al, (1951) studied the

effect of residual P at different pH levels. They concluded that the

6

residual F’may still be effective after eight to thirteen years.
Prince (1953) studied the effects of superphosphate applications

on soil P level and growth of crimson clover. The residual effect
of annual applications of P over a 36-year period was determined in
part by the yields and P content of two clippings of crimson clover
grown in the greenhouse. From application of superphosphate contain-
ing 32P, he concluded that as the available soil P increased, the
percentage of total plant P derived from the fertilizer decreased,
and no significant yield response was obtained from additional appli-
cations of P. He found that the residual P from these superphos-
phate applications had an effective value in supplying crop require-
ments of P particularly at high rates of applications.

Thomas (1964) studied the effect of continuous cropping on the
availability of native and applied P fertilizer. He found that the
residual P significantly increased the P content and hay yields of
alfalfa over several cropping seasons. The residual effect from
application of 117.4 and 234.8 kg/ha of P significantly increased
the P content of alfalfa for four cropping seasons. Hunter 3; 21,
(1961) studied the residual effects of P fertilizer on eastern Oregon
soils. They established a six-year rotation with different crops on
a Owyhee silt loam with a uniform rate of nitrogen. In the sixth
year, they employed different methods to evaluate levels of avail-
able residual P in that soil. They concluded from all methods of
evaluation that the 235.2 kg P/ha rate was adequate for all crops in
the sixth year of rotation and seemed to be effective for three to

four years beyond the sixth year of rotation. The residual P from

117.6 kg P/ha was inadequate for maximum yield of beets. Essentially

no residual P remained in the sixth year from the 29 and 59.4 kg of

P applications. Singh gt_al, (1966) reported that residual P from
annual application of 23.5 kg P/ha was adequate to supply the P re-
quirements of three successive crops of alfalfa and that the applica-
tion of 11.8 kg was inadequate.

In Utah, Haddock and Linton (1957) found pea yields were in-
creased by P fertilization. Yield responses were in the order of
current applied P > one-year residual P > two-year residual P.

Ensminger and Pearson (1957) compared the residual effects of

various phosphates on the basis of yields, 32

P uptake and extractable
P. They concluded that all applied sources had a considerable re-
sidual effect and for any particular source the residual availabil-
ity was in proportion to the amount applied. Moshler §t_al. (1957)
found that the availability of residual P from long-term, superphos-
phate application to Grosclose silt loam exceeded that of rock phos-
phate. 0n the 'A' value bases, they concluded that residual P from
superphosphate was almost four times as available as that from rock
phosphate. However, they reported that crop yields on plots receiv-
ing the two sources were equal except for the first few years when
superphDSphates produced higher yields. They found also that about
75% of the applied P from both sources over 40 years was present in
the soil as residual P. Eik gt_al, (1961) found increased soybean
yields in a greenhouse study to be related to increasing rates of P
applied in the field three to four years previously. Leamer (1963)
found that residual P levels increased plant yields up to the point

at which total P removed by plants was equivalent to that originally

applied. Peck gt_al, (1965) determined that the P from previously

8

applied fertilizer accumulated to a greater extent and had a longer
residual effect than K as measured by soil tests. However, they re-
ported that both P and K accumulated from previously applied fertil-
izers were as important as banded fertilizer of P and K in producing

high yields of table beets.

8. Availability of Various Forms of Soil P

 

Robertson et_al, (1966) investigated the availability and frac-
tions of residual P in soils high in aluminum (A1) and iron (Fe) using
corn as an indicator crop. Grain yields during the first six years
did not differ due to initial application of O to 196 kg P/ha on
Norfolk soil. However, annual applications of P did cause significant
yield increases after the second year. After the sixth year, grain
yields increased significantly due to increasing rates of P applied
six years previously.

Spencer (1957) investigated the distribution and availability
of P added to a Lakeland fine sand soil. He concluded that the great-
est accumulation of added P was within the 29.4 to 40.5 cm subsoil
zone. However, P had leached to a depth of at least 213 cm in some
cases. In evaluating 'A' values, he found P accumulated in the sub-
soil was as available as that P retained in the surface 15 cm of
soil. The major portion of added P was retained in an absorbed or
NH4F extractable form.

Since the development of the chemical fractionation of P pro-
cedure by Chang and Jackson (1957), several workers have attempted to
correlate P uptake by plant with the quantities of various forms of I

P in soil.

9

Susuki gt_gl, (1963) noted that Ca-P and Al-P were important
in supplying P to the plants in 17 Michigan soils ranging in pH from
4.8 to 7.8. However, Ca-P tended to be higher than Al-P on soils of
pH 6.0 or higher, while Al-P was higher than Ca-P on soils of pH 5.6
or lower. Al-Abbas and Barber (1964a) concluded Fe-P to be more im-
portant to supply P to plants than Al-P. 0n the other hand, Smith
(1965), Martens §t_al, (1969) and Halstead (1967) concluded that Al-P
fraction was the main source of plant available P.

Singh et_al, (1966) compared the inorganic fractions of P in
Davidson clay loam soil before and after growth of three crops of
alfalfa. They concluded that Al-phosphate, Fe-phosphate and Ca-
phosphate were sources of P to the first crop and that Fe-phosphate
was the main source of P to the second and third crops. They concluded
that native and residual P present in the soil was predominantly Fe-
phosphate.

Hawkins and Kunze (1965) reported a good correlation between
available P extracted by Olsen's method and Al-P in some Texas Grumo-
sols.

Manning and Solomon (1965) investigated the forms of P formed
in the soil as a result of long-term (more than 65 years) of phosphate
fertilizer application. They found that superphosphate treatments
increased the Al-P and Fe-P fractions while rock phosphate treatments
increased Ca-P fractions. They reported even in a short period of
time P applied as CaHPO4 was converted to Al-P and Fe-P, and concluded
that lime treatments have decreased the amount of Al-P formation. In
Arizona, McGeorge (1939) found that Ca treatments apparently control

the availability of P to wheat plants in some soils.

10

In Virginia, Martens gt a1, (1969) found that P from Al-P
fraction was the main source of P to oat plants grown in greenhouses
in four different soils. They reported that Al-P fraction closely
correlated with Bray P1 extractable P and that Bray P1 extracted P
was closely related to P uptake by the plant from the soil. Hal-
stead (1967) studied the chemical availability of native and applied
P in several Canadian soils, and he found that Al-P fraction was cor-
related with the percentage yields of oats grown in greenhouses and

with available P soluble in NaHCO3.

C. Methods of Estimating Soil P to Plants

 

Due to differences in soil properties from one place to an-
other, Cho and Caldwell (1959) and Walsh §t_al, (1973) reported that
it is impossible to use a single extracting reagent for different
soils. Oko gt_gl, (1974) compared different P extractants on differ-
ent soils of western Nigeria. They concluded that different ecologi-
cal zones may require different extractants. In Nebraska, Olson et
91: (1954) found that a good series classification of soil can be a
valuable indicator of probably P fertility status of the soil. In
comparing Bray P1 and Olsen (NaHCO3) with other extracting methods,
they found that both methods (Bray P1 and Olsen) to be superior and
better adapted to routine analysis over a wide range of pH and tex-
tural conditions than Nebraska buffer and Truog method. Mater and
Sammon (1975) in Syria found that Olsen (NaHCO3) method is adequate
if the soil is grouped according to its genetic origin.

In western Kansas, Smith gt_al, (1957) compared Bray P1 at a

soil-to-solution ratio of 1:50 with NaHCO at 1:20. They found the

3

ll

correlation between plant reSponse and extractable P to be greater
fro Bray P1 (r = 0.88) than for Olsen NaHCO3 (r = 0.51). They found
Bray P1 was more useful than Olsen in relating the available P to
plant response. However, Al-Abbas and Barber (1964b) in Indiana
soils found Bray P1 and Olsen about equal in relating P availability
to plant response.

Pratt and Garber (1964) found Bray P1 and Olsen extractable P
was correlated with NH4F extractable P for 29 California soils rang-
ing in pH from 3.6 to 7.0. Welch et_gl, (1957) used Bray P], Olsen

and 0.03 N_NH + 0.1 N_HCl extractants and found that all these

4
methods have a similar correlation between soil tests and plant
(Ladino Clover) growth. In Michigan, Susuki gt_al, (1963) found that
'A' values which are more indicative of seasonal availability of P
were highly correlated with Olsen, Resin and Bray P1 methods. However,
in Arkansas, McLean and Hoelscher (1954) found that NaHC03- extractable
phosphate from untreated soil was a fair indicator of P205 uptake by
buckwheat on untreated soil, but NaHCO3 test did not show a close re-
lationship with 'A' values obtained with various crops. The acid-
extractable phosphate by both Truog and Bray was poor indicator of
'A' values obtained. Eik et_gl, (1961) studied the residual values
of applied phosphate fertilizer. They found that the residual values
were best correlated with Bray P1 with r = 0.98, while that values
with Olsen test gave a r = 0.51.

MacLean (1964) used NaHCO3 method for evaluating the residual
effect of long-term application of P fertilizer and concluded that
NaHCO3 is a good method in estimating P availability in the soil

being used. In Syria, Matar and Sammon (1975) found that NaHCO3

12

gave the best correlation when soils being grouped according to its
genetic origin. Haas et_al, (1961) found a good correlation between

NaHCO and total P in some virgin soils, but the significant correla-

3
tion did not exist in some other soils in the study. Under Turkish
soil conditions, Yurtsever gt_al, (1965) concluded that NaHCO3 method
is capable of measuring the available forms of P in calcareous soils.
Their results were correlated with P field responses for wheat. They
recommended that any Middle East calcareous soils having an Olsen
(NaHCO3) soil test value of 24 kg PZOS/ha or more will probably be
unresponsive to P fertilizers.

The relationship between the chemically available P and plant
growth responses in several Michigan soils have been investigated by
Smith (1949) and Smith and Cook (1953). They compared several meth-
ods of extraction of the available P and concluded that using Bray P1
extractant is the best and giving clearer picture of P availability
to the crop. However, using 1:50 extraction ratio is more desirable
for measuring absorbed P than the narrow ratio 1:10. The total avail-
able P was found to be more reasonably assessed by the 1:10 ratio
than by wider the ratio. In Minnesota soils, Randall and Grava
(1971) compared the effect of using three ratios of soil to Bray
P1 extracting solution (1:10, 1:50 and 1:100) in order to explain
the variation in P measurements in calcareous soils which had re-
ceived heavy P applications. They found that the variability of
the extractable P was greatly reduced when wider ratios of soil to
extractant solutions were used on calcareous soils.

In Iowa, Charles et_gl, (1962) found significant correlations

with various measurements of field and greenhouse by using Bray P1

13

for prediction of the biological responses to residual P.

Peck gt_al, (1971) studied the changes in Bray P1 soil P test
values resulting from application of P fertilizer. They found that
the increase in soil test values (Bray P1) resulting from annual
application of P fertilizer were about 1 pp2m for each 4 pp2m of P
added in fertilizer during a three-year period on six field experi-
ments. Even over a five-year period following a single fertilizer
application, they obtained the same results.

White (1969) found that water-soluble P and Bray P1 appeared
to measure the same relative amounts of available P except that water
extracted only l/20 as much as the Bray P1 solution. The availabil-
ity of P was studied by Larsen gt_al, (1958). They compared seven
different extracting methods including water. They found that dis-
tilled water extracts gave the most accurate estimates of plant
available P in 1:20 ratio for organic soils and 1:10 for mineral
soils. Webb gt al.(196l)found that a different increase in yield
with increasing water solubility of P from phosphorus source. It can

be seen that Bray P1 method (1945) in which 0.03 N NH F plus 0.025

4

N HCl and Olsen method (1954) in which 0.5 M_NaHCO buffered at pH

3
8.5 are now widely used in different places for prediction P avail-
ability to plants.

NCR-13, Soil Testing Committee has recommended in the Bulletin
499 (1975) the use of both Olsen and Bray P1 methods for the soils
of North Central Region of the U.S.A. Warnke 92.21: (1976) recommended
the use of Bray P1 as a basis for P fertilizer recommendation in Mich-

igan. Christenson and Dudley (1976) found that maximum yield of bar-

ley can be obtained when P fertilizers applied according to soil test

14

recommendation. However, Tesar (1976) studied the alfalfa stands in

Michigan, and he advised that even if the soil test indicates P is

not necessary, the use of a starter fertilizer containing 28 kg of

phosphate is required to get strong seedling developments of alfalfa.
Shickluna and Cook (1959) classified the P status of Michigan

soils and found that most of Michigan soils are low in P and respond

to P fertilization. They recommend that if the soil pH is 7 or higher,

112 kg P/ha are required to be considered as high in P.

CHAPTER III

MATERIALS AND METHODS

A. Soil Samples

 

Soil from the plow layer was collected from plots which had
previously received a total of 0, 448, 895 and 1792 kg P205/ha. After
collection, the four bulk samples were air-dried, individually
crushed to pass a 4-mesh screen, the large roots were removed, thor-
oughly mixed and stored for greenhouse studies.

The soil is mapped as a Charity clay soil (Aeric haploquept)
and is characterized as a fine, illitic, frigid calcareous soil.

Some chemical properties and soil residual levels of P as extracted

by Bray P1 and Olsen (NaHC03) soil tests are given in Table 1.

8. Greenhouse Studies

 

From the bulk soil samples, 3,000 g of soil was weighed into

one gallon polyethylene-lined cans (culture). Four levels of P

equivalent to O, 12.5, 37.5 and 62.5 ppm of soil weight were added as
Ca(H2PO4)2-H20. All treatments were set up as randomized complete

block with four replications.

1. Corn Experiment

 

Uniform applications of 75 ppm of N as NH4N03 and 2 ppm of Zn

as ZnSO4°7H20 were applied to each culture. All P and Zn fertilizer

15

16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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m.ep m.mm e.o_ N.ommp o.eoom m.mo¢ wee o.m m.m HH
m.o_ _.m¢ m.- m.Pmep o.¢mow m.om¢ o o.m m.¢ H
Egg m;\mx N
m om”? wup
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mcmmpo o a
—a xmcm umw~aa< In ucmpm>wzcm Longs:
upmwm Fwom moumu Fwom
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l7

materials required for each culture were mixed thoroughly with the
soil. However, the required amount of N fertilizer for each culture
was divided into two increments. The first increment (50 ppmN),

the equivalent weight of NH4N03 was dissolved in the initial amount
of irrigation water. The second increment was applied with irriga-
tion water after thinning.

After the experimental pots were prepared, about 2.5 cm depth
of dry soil was removed from each culture. The initial irrigation
water (450 ml of distilled water) containing the first increment of
N fertilizer (50 ppmN) was added to each culture. Six corn seeds
[(Zea mays L.)(Michigan 396-3x)] were planted in each culture at the
surface of irrigated soil and covered by the dry soil previously re-
moved. The number of plants was reduced to four plants per culture
seven days after emergence and the second increment of N fertilizer
(25 ppmN) was added with irrigation water.

The soils in the pots were maintained at a moisture equivalent
to 15% of soil weight (about field capacity) during the experiment
period. After 40 days, the corn plants were harvested at the soil
surface, dried at 60°C, weighed, ground to pass a ZO-mesh screen
(using Wiley mill) and stored in zip-lock plastic bags for chemical

analysis.

2. Potato Experiment

 

The soil from the corn experiment was air-dried, crushed to
pass a 4-mesh screen, thoroughly mixed and the large roots were
removed. A 100 9 sample of soil was taken from each culture, and

stored for chemical analysis.

18

On the rest of the soil in each culture and at a depth of
2.5 cm (using the same procedure used for planting corn seeds) six
pregreminated potato (Solaneum tubersum L., Russet Burbank variety)
buds were planted without any additional P fertilizer. The treat-
ments were arranged in a randomized complete block. After two weeks,
the number of plants was reduced to four per culture. The soil in
the pots was maintained at a moisture equivalent to 15% of soil weight
as in corn experiment above. After thinning, 50 ppm of N fertilizer
as NH4NO3 was applied to each culture with irrigation water.

After 35 days, the potato plants were harvested at the soil
surface, dried at 60°C, weighed, ground to pass a 20-mesh screen and
stored in zip-lock plastic bags for chemical analysis.

The soil in the pots was air-dried, individually crushed to
pass a 4-mesh screen, thoroughly mixed, and the large roots were re-
moved. A 100 g of soil sample was removed from each pot and stored

for chemical analysis.

C. Methods of Soil Analysis

 

The soil samples collected from both greenhouse experiments

(corn and potato) were air-dried and ground to pass a 10-mesh sieve.

1. Braygfll

 

Bray and Kurtz (1945) proposed an extracting reagent of 0.03

N_NH F plus 0.025 N_HC1. The exact procedure was discribed in Hand-

4
book on Reference Methods for Soil Testing (1974) and NCR-l3 Soil

Testing Committee Bulletin 499 (1975) as follows:

 

a. Reagent A(l N Nqu) 37.0 grams of NH4F was dissolved in

400 m1 of distilled water and diluted to ggg_liter with

19

distilled water. It was stored in a polyethylene container.
Reagent B(O.5 N_HC1),20.4 ml of conc. HCl was diluted to
500 ml with distilled water.

Extracting_Reagentg(0.03 N NH4F + 0.025 N HCl) 30 m1 of
Reagent A was mixed with 50 m1 of Reagent B and diluted
to gag liter with distilled water. This solution is 0.03
N_in NH4
more than one year.

F and 0.025 N_in HCl and is stable in glass for

Bray PlgExtracting Procedure: The soil to extracting re-

 

agent ratios used were gng_to ejght_and one to fifty,

Duplicate soil samples were shaken with the extracting re-
agent for five minutes on a reciprocating shaker adjusted
to 180 oscillations per minute (0PM) and filtered through
Whatman No. 2 filter paper. The filtration time was lim-
ited to about ten minutes for all samples. The filtrates

were collected and stored in refrigerated compartment.

2. Olsen NaHCO3

 

Olsen gt_gl, (1954) have proposed using 0.5 M_NaHC03 adjusted

to pH 8.5 as an extracting reagent for available P. This method

was modified by Watanabe and Olsen (1965) to eliminate the use of

carbon black from the procedure.

a.

The Extracting_Solution (0.5 M NaHCO3 at pH 8.5), Prepared

 

by dissolving 42.0 grams commercial grade of sodium bicar-
bonate (NaHCO3) in distilled water and diluted to 933_
liter. The pH of the final volume of this solution was

adjusted to pH 8.5 with 50% NaOH. Mineral oil was added

20
to the surface of the solution to avoid exposure of the
solution to air. The solution was stored in polyethylene
container and the pH of the solution was readjusted monthly.

b. Olsen's NaHCO3tExtracting Procedure: The soil to extracting

 

reagent ratio used was Qߤ_t0 tgggty. The soil samples
(duplicate samples) were shaken with the extractant reagent
for 30 minutes on a reciprocating shaker adjusted at 180
0PM and filtered through Whatman No. 40 filter paper. The
filtration time was limited to about 20 minutes for all
samples. The filtrates were collected and stored in a

refrigerated compartment.

3. Phgsphous Analysis (Murphy and Riley Method)

The collected filtrates were then analyzed for P content by
using the ascorbic acid procedure developed by Murphy and Riley (1962)
and later modified by Watanabe and Olsen (1965) to use a single re-
agent for P determination in soil extracts. The modified procedure
was reported in NCR-13 Bulletin No. 499 (1975) and Handbook on Refer—
ence Methods for Soil Testing (1974) as follows:

a. The Procedure for Bray P1:

 

i) Reagent A (molybdate stock solution)
60.0 grams of ammonium molybdate [(NH4)6M07024-4H20]
was dissolved in 200 ml of distilled water (if neces-
sary, heating to 60°C until the solution becomes clear
and then cooled). 1.455 grams of antimony potassium
tartrate was dissolved in the molybdate solution. 700
ml of concentrated H2304 acid was added slowly. After
cooling, the solution was diluted with distilled water

to a final volume of 1000 m1 (this solution may be blue

ii)

iii)

iv)

21

in color, but will clear when diluted for use). The
solution was stored in a dark refrigerated compartment.

Reagent 8(ascorbic acid stock solution)

 

132.0 grams of ascorbic acid was dissolved in 200 ml

of distilled water and then diluted to a final volume
of 1000 ml with distilled water and stored in a dark

refrigerated compartment.

WOrking,Solution

 

It was prepared fresh daily by adding 25 ml of acid
molybdate stock solution (Reagent A) to about 800 ml

of distilled water, mixing and adding 10 ml of ascorbic
acid stock solution (Reagent B). After the contents
were well mixed, the solution was made up to a final
volume of 1000 ml with distilled water.

Phosphorus Standard_(100 ppm) Stock Solution

 

It was prepared by dissolving a weight of 0.4394 grams
of monbasic potassium phosphate (KH2P04) which had been
oven-dried at 100°C into ggg_liter of extracting re-
agent (0.03 N_NH4F + 0.025 N_HC1). Six working phos—
phorus standards were prepared from the above standard
stock solution of P containing from O to 1 ppm P in

the final volume of color test. All dilution of stand-
ards were made with the extracting reagent.

The Color Test for Bray P]

 

The color test was made by transfering exactly 2.0 m1
of soil extract or standard P to a beaker or plastic

cup, 8 ml of working solution (iii) was added,(an

The

22

automatic dilutor was used). The contents were
thoroughly mixed. After 10 to 15 minutes, the color
intensity was measured using colorimeter set at 882

nm. 0n semi-log graph paper, the percent transmittance
(Measured at 882 nm) was ploted on logarithmic scale
against ppm P in the standard on the linear scale.
Phosphorus concentration in soil extract was determined
by comparing the color intensity of the soil extracts
with the standard curve.

Procedure for Olsen's NaHC03

 

1)

ii)

iii)

Reagent A¥(acid molybdate stodk solution)

 

It was prepared by dissolving 12.0 grams of ammonium

molybdate [(NH4)6M07O o4H20] in 250 ml of distilled

24
water. 1000 m1 of 5N__HZSO4 (148 ml conc. H2504 per
liter of distilled water) (ADD THE ACID TO THE WATER)
was prepared. The above two solutions were thoroughly
mixed, brought to a final volume of 2000 ml distilled

water and was stored in a dark refrigerated compartment.

Reagent 8 (Working Solution)

 

It was prepared by dissolving 0.739 grams of ascorbic
acid in 140 ml of reagent A. The reagent must be pre-
pared each day as required since it will not keep for
more than 24 hours.

Phosphorus Standard (lOOppm)Stock Solution

 

It was prepared by the same procedure used for prepar-
ing the standard stock solution for Bray P1 above ex-

cept that all dilutions were made using 0.5 M NaHC03.

23

From this stock solution, six working P standards were
prepared containing from 0 to 1 ppm P in the final
volume of the color test.

iv) The Color Test for Olsen's NaHCO3

 

The color test was made by transfering exactly 5.0 ml

of soil extract or standard P to a beaker, then adding
15 m1 of distilled water and 5 ml of working solution
(Reagent 8) above (an automatic dilutor was used).

The contents were thoroughly mixed and allowed to stand
for 10 to 15 minutes for color development. The color
intensity was measured by using Colorimeter set at 882
nm. 0n semi-log graph paper, the percent transmittance
(color intensity) was plated on logarithmic scale against
ppm in the standard solution on the linear scale. Phos-
phorus concentration in soil extract was determined by
comparing the color intensity of the soil extractes with

the standard curve.

0. Plant Tissue Analysis

 

The corn and potato plant tissues earlier prepared were chem-
ically analyzed by applying Parkinson and Allen's method (1975). The

procedure is as follows:

1. The Digestion Solution

 

The digestion solution was prepared by mixing 350 m1 of H202
(hydrogen peroxide), 0.42 grams of Se powder, and 14 grams of LiSO4°H20
in a flat-bottomed boiling flask of 9gg_liter capacity. 420 m1 of

concentrated HZSO4 (sulfuric acid S.G. 1.84) was added carefully with

24

swirling and cooling. The mixture was stored in a refrigerated compart-

ment.

2. Digestion Procedure

 

One-half gram samples of the ground plant tissue samples were
weighed into 50 ml long-necked reflux flask (duplicate samples were
taken from each tissue sample). Five m1 of the digestion mixture
was added to the flask and heated gently on an electric heater until
the initial reaction subsided. The flask was cooled and the neck of
the flask washed with 10% H202 and the heating continued. When the
peroxide was driven off, the heat was adjusted so the H2504 would con-
dense in the neck of the flask and reflux. Heating was continued
until all traces of yellow color due to residual of organic matter
had disappeared. After cooling, the contents were transferred to a
50 ml volumetric flask, diluted to volume and mixed. These solutions

were stored in a refrigerated compartment for analysis.

3. Standard Curve Preparation

 

A stock standard solution of 500 ppm of P was prepared as fol-
lows: 2.197 grams of KH2P04 (monobasic potassium phosphate) which
had been oven-dried at 100°C was dissolved in 250 ml of distilled
water, and diluted to a final volume of 1,000 ml with distilled
water.

From the stock solution, six standard working solutions were
prepared by transferring 0, l, 2, 3, 4 and 5 ml from the stock solu-
tion of P into a 50 ml long-necked reflux flask. Five ml of the di-
gestion solution was added to each flask and digested by the same

procedure used for plant tissue digestion. At the end of digestion,

25

the flasks were cooled and the contents were transferred to a 50 ml

volumetric flask, diluted to volume and mixed. These standards were

used in color tests and contained 0, 10, 20, 40 and 50 ppm of P, re-

spectively.

4. The Procedure of Ascorbic Acid for Evaluation

 

of P in Plant Tissues

 

a.

b.

Reagent A

0.593 g of antimony potassium tartrate was dissolved in
200 m1 of distilled water 24.5 g of ammonium molybdate
[(NH4)6M07024°4H20] was dissolved in 200 m1 of distilled
water, heating if necessary. After solution was completed
the nixture was cooled. The two solutions were mixed and
256 ml of concentrated sulfuric acid (H2504 with S.G. 1.84)
was slowly added. The mixture was cooled and diluted to
1000 ml with distilled water and stored in a refrigerated
compartment.

Reagent B

It was prepared by dissolving 43.06 grams of ascorbic acid
in 200 ml of distilled water, diluted to a final volume of
1000 ml with distilled water and stored in a dark refriger-
ated compartment.

Working Solution

 

To 500 ml of distilled water, 40 ml of Reagent A was added
and thoroughly mixed. 20 ml of Reagent B was added and
the contents were well mixed and diluted to 1000 ml with
distilled water. This reagent was prepared daily since

it will not keep for more than 24 hours.

26

d. The Color Test for Plant Tissues

 

The color test was made by transfering exactly 0.5 ml

of plant digest or standard solution into 100 ml beaker or
plastic cup, 24.5 ml of working solution above was added
(an automatic dilutor was used). The contents were well
mixed and then 10 to 15 minutes were allowed for color de-
velopment. The color intensity was measured by using
Colorimeter set at 882 nm. 0n semi-log graph paper, the
percent transmittance was plotted on the logarithmic scale
against ppm P in the standard solution on the linear scale.
Phosphorus concentration in plant tissues was determined
by comparing the color intensity of the plant digests with

the standard curve.

E. Statistical Analysis

 

The analysis of variance of data from the corn and potato experiments
were made using factorial analysis with 4 levels of residual P and
4 rates of applied P. A 1% level of significane was chosen and a
least significant difference (LSD) statistical test (Steel and Torrie,
1960) was used to compare previously chosen treatment means. Simple
and multiple regression procedures were used to obtain correlation
coefficients, coefficients of determination and regression coeffic-
ients. All statistical procedures were compiled using a Control

Data Corporation Model 6500 computer.

CHAPTER IV

RESULTS AND DISCUSSION

A. Corn Experiment

 

The interaction between applied and residual P on yields and
P uptake by corn plants was insignificant (Tables 2 and 4), while the
interaction was highly significant for P concentration in corn plant
tissues (Table 3).

Corn yield (Table 2) was increased over the check by applied
P up to 62.5 ppm P and residual P up to 70.5 ppm. However, the in-
crease in corn yield between 37.5 and 62.5 ppm of applied P was not
significant at one percent level.

Phosphorus concentration (Table 3) was increased by applied P
at all residual levels except at 41.5 ppm P. Maximum P concentration
was obtained with 12.5 ppm applied P at 16.4 and 41.5 ppm residual
levels, no significant increase was obtained at 41.5 ppm P, and
37.5 ppm P was required at 70.5 ppm residual level. The
pattern of response is different from what would be ex-
pected. The reason for this irregular pattern of response is not
clear.

Phosphorus uptake by corn plants (Table 4) was obtained by
multiplying the percent P in plant tissues by the yield and is ex-

pressed as milligrams of P per culture. In general, P uptake by

27

28

Table 2. The effect of applied and residual P on yield of corn
tops grown in the greenhouse on a Charity clay soil

 

 

 

 

 

 

 

Residual Applied P (ppm) Average of
P Residual

Bray P1 (1:8) 0 12.5 37.5 62.5 p

ppm P g/culture

11.5 1.91 2.84 4.14 4.02 3.23

16.4 2.47 3.70 4.10 4.91 3.80

41.5 3.89 3.88 4.31 4.73 4.20

70.5 4.03 4.18 4.84 4.93 4.42
average of 3.08 3.65 4.25 4.66
applied P

LSD (1%) comparison of residual or applied P means = 0.50
LSD (1%) for interaction between residual and applied P = NS

Coefficient of variation (CV) = 13.4%

 

Data means of four replications.

29

Table 3. The effect of applied and residual P on P concentration of
corn tops grown in the greenhouse on a Charity clay soil

 

Applied P (ppm)

 

 

 

 

 

 

Residual Average of
P Residual
Bray PT("8) o 12.5 37.5 62.5 P
ppm P % P
11.5 0.10 0.17 0.15 0.15 0.14
16.4 0.17 0.20 0.16 0.17 0.18
41.5 0.19 0.20 0.18 0.18 0.19
70.5 0.16 0.17 0.19 0.20 0.18
average of 0.16 0.19 0.17 0.18
applied P

LSD (1%) comparison of the residual or applied P means

0.02

LSD (1%) for interaction between residual and applied P = 0.03

Coefficient of variation (CV) = 10.7%

 

Data means of four replications

30

Table 4. The effect of applied and residual P onl’uptake by corn
tops grown in the greenhouse on a Charity clay soil

 

 

 

 

 

 

 

Residual Applied P (ppm) Average of
P Residual
BT°Y Pl (1'8) 0 12.5 37.5 62.5 P
PPm P mg/culture A‘—
11.5 1.96 5.07 6.10 6.08 4.80
16.4 4.35 7.06 6.51 8.37 6.57
41.5 7.56 7.66 7.77 8.55 7.88
70.5 6.57 7.02 8.74 10.04 8.09
average of 5.11 6.70 7.28 8.26
applied P

LSD (1%) comparison of residual and applied means = 1.19
LSD (1%) for interaction between residual and applied P = NS

Coefficient of variation (CV) = 18.2%

 

- Total P uptake obtained by multiplying % P in plant tissue
by yield (dry weight) of the crop.

- Data means of four replications.

31

corn plants was significantly increased by applied and residual
levels of P. However, there was an insignificant increase between
12.5 and 37.5 ppm and between 37.5 and 62.5 ppm of applied P. Sim-
ilarly, there was an insignificant increase between 41.5 and 70.5

ppm of residual P.

8. Potato Experiment

 

The interaction between applied and residual P on potato yields
and P concentration in the plant tissues was insignificant (Tables
5 and 6). However, the interaction was highly significant for P up-
take (Table 7).

Potato yields (Table 5) tended to be increased over the check
by increasing rates of applied P up to 37.5 ppm P, however, the in-
crease was not significant. Potato yields were increased over the
residual level of 11.5 ppm P by 70.5 ppm of residual P.

Phosphorus concentration (Table 6) was significantly increased
over the control with rates of 37.5 and 62.5 ppm P, and also over that
of 12.5 ppm P by 62.5 ppm applied P. However, there was an insignifi-
cant increase over the check by 12.5 ppm P or between 12.5 and 37.5 ppm
and between 37.5 and 62.5 ppm applied P. Although there was a signifi-
cant increase in P concentratino over the level of 11.5 ppm residual P
by increasing levels of residual P, there was an insignificant increase
between residual levels of 16.4 and 41.5 ppm P.

Phosphorus uptake (mg P/culture) was obtained by multiplying
the P concentration in the plant tissues by the yield obtained per
culture and is given in Table 7.

The magnitude of response to applied P was different from

32

Table 5. The effect of applied and residual P on yield of potato
tops grown in the greenhouse on a Charity clay soil

 

Applied P (ppm)1

 

 

 

 

 

 

Residual Average of
P Residual
Bray P1 (1'8) 0 12.5 37.5 62.5 P
PPm P g/culture
11.5 4.61 5.42 5.87 5.38 5.32
16.4 5.29 5.38 5.23 4.94 5.21
41.5 5.31 5.75 5.76 5.27 5.52
70.5 5.95 5.83 5.76 5.77 5.83
average of 5.29 5.60 5.66 5.34
applied P

LSD (1%) comparison of the residual or applied P means

0.39

LSD (1%) for interaction between applied and residual P = NS

Coefficient of variation (CV) = 7.5%

 

Data means of four replications.

1Previously applied to corn.

33

Table 6. The effect of applied and residual P on P concentrations
of potato tops grown in the greenhouse on a Charity clay

 

 

 

 

 

 

 

soil
Applied P (ppm)1
Residual Average of
P Residual
Bray PT (1‘8) 0 12.5 37.5 62.5 P
PPm P % P .__
11.5 0.22 0.22 0.26 0.25 0.24
16.4 0.24 0.27 0.28 0.28 0.27
41.5 0.26 0.26 0.27 0.28 0.27
70.5 0.27 0.28 0.29 0.32 0.29
average of 0.25 0.26 0.27 0.28
applied P

LSD (1%) comparison of the residual or applied P means = 0.02

LSD (1%) for interaction between residual and applied P = NS

Coefficient of variation (CV) = 6.4%

 

Data means of four replications.

1Previously applied to corn.

34

Table 7. The effect of applied and residual P on P uptake by
potato tops grown in the greenhouse on a Charity clay

 

 

 

 

 

 

 

soil
- 1
Residual APP11ed P (ppm) Average of
P Residual

BPay PI (1‘8) 0 12.5 37.5 62.5 P

PPm P mg/culture

11.5 9.97 11.90 15.12 13.47 12.61

16.4 12.82 14.70 14.43 13.64 13.90

41.5 13.92 14.85 15.41 14.88 14.76

70.5 16.27 16.01 16.72 18.38 16.85
average of 13.24 14.37 15.42 15.09
applied P

LSD (1%) comparison of residual or applied P means = 0.88
L50 (1%) for interaction between residual and applied P = 1.77

Coefficient of variation (CV) = 6.4%

 

- Total P uptake obtained by multiplying % P in plant tissue
by yield (dry weight) of the crop.

- Data means of four replications.

1Previously applied to corn.

35

one residual level to another. For example, there was a significant
response from applied P at residual levels of 11.5, 16.4 and 70.5 ppm
Bray P1 P, but there was no significant response at 41.5 ppm of resid-
ual P. It took 37.5, 12.5 and 62.5 ppm applied P to give maximum P
uptake for residual levels of 11.5, 16.4 and 70.5 ppm P, respectively.
The reason for this variation in response is not clear.

The linear relationships between plant response parameters, ap-
plied and residual P are shown in Table 8. All correlation coeffici-
ents obtained for corn or potatoes were highly significant with the
exception of relationships between P concentration in corn and applied
P, potato yield and applied P and percent P in potatoes and potato yield.

Yield of corn was slightly more affected by applied P (r = 0.64)
than by residual P (r = 0.47). On the other hand, P concentration in
corn was affected to a greater degree by residual P (r = 0.49) than
by applied P (r = 0.16). Phosphorus uptake by corn was almost equally
affected by applied P (r = 0.52) and by residual P (r = 0.58). Al-
though the relationships between corn parameters were all highly sig-

nificant, P uptake had a better relationship with yield (r = 0.91)

than with percent P (r 0.75).
In comparing the coefficients of variation (CV) in Tables 2,
3 and 4, the corn yield appeared more precisely measured than P con-
centration in corn plant tissue.
The data for potatoes (Table 8), indicate that yield, P concen-
tration and P uptake by potatoes were more affected by residual P
(r = 0.39, 0.60, and 0.69, respectively) than by previously applied
P (r = 0.04, 0.44 and 0.33, respectively). Although both potato

yield and P concentration were highly correlated with P uptake by

36

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37

potatoes, P concentration had a slightly higher coefficient (r = 0.75)
with P uptake than yield with P uptake (r = 0.69). Both coefficients
were lower than what would be expected. The reason for that varia-
tion was not clear. Relatively small coefficients of variation were
shown with the analysis of variance for both parameters.

In comparing simple correlation coefficients (Table 8) between
corn and potatoes, two opposing points are apparent. First, yield
of corn was affected more by applied P than was yield of potatoes
while the opposite was true for percent P in the plant tissue. Again
an explanation for this is not apparent.

Even though, most of the coefficients obtained for corn or po-
tatoes were significant, they do not account for a large variation

in the data.

C. Soil Tests

 

Three extractants, namely Bray FM, using 1:8 and 1:50 soil
to solution ratios and Olsen's NaHCO3 buffered at pH 8.5, using 1:20
soil to solution ratio, were used to extract the available P from
a Charity clay soil before P application in the greenhouse and after
each crop was harvested. The available P extracted from the soil
before P application was defined as the initial or residual soil P.
The available P extracted from the soil after harvesting each crop
was defined as the extracted P.

The amount of P extracted after corn or after potatoes was very
similar. Therefore, only data comparing methods on soil P extracted
after potatoes will be discussed. Data for after corn are presented

in Appendix Tables 1, 2, and 3.

38

The initial residual P and the extracted P by Bray TH (1:8
and 1:50) and by Olsen's NaHCO3 after potatoes were harvested are
given in Tables 9, 10 and 11, respectively.

There was a significant interaction between the applied and re-
sidual P on extracted P by Bray TH (1:8) and Olsen's NaHCO3 (Table
9 and 11). The interaction was insignificant for Bray lfi (1:50)
(Table 10).

Extracted P (Table 9) was insignificantly increased over the
control by 12.5 ppm of applied P on the residual levels of 11.5, 16.4
and 70.5 ppm P. Similarly extractable P was not significantly in-
creased over the level of 11.5 at 16.4 ppm P when no P, 12.5 and 62.5
ppm P were applied.

Bicarbonate extractable P (Table 11) was not significantly in-
creased over the control by 12.5 ppm applied P on both residual lev-
els of 10.3 and 49.5 ppm P.

There was a significant increase in the extracted P (Table 10)
by the increase in applied and residual P, except that the extracted
P was insignificantly increased over 43.1 by 56.9 ppm of residual P.

The linear relationship between the extracted P after potatoes
by any two of the three soil tests is schematically given in Figures
1, 2 and 3. Although all correlation coefficients obtained are highly
significant, Bray 1:50 and Olsen's NaHCO3 had a slightly higher coef-
ficient (r = 0.98) with Bray 1:8 than Olsen's NaHCO3 with Bray 1:50
(r = 0.97).

Similarly, almost the same correlations were obtained between
these soil tests on samples taken after corn crop was harvested

(Appendix Figures 1, 2 and 3).

39

Table 9. The effect of applied and residual P on P extracted by
Bray P1 (l:8) after harvesting potato crop grown in the

greenhouse on a Charity clay soil

 

Applied P (ppm)1

 

 

 

 

 

 

Residual Average of
P Residual
BPay Pl (1‘8) 0 12.5 37.5 62.5 P
PM P

11.5 7.0 10.6 20.1 32.6 17.6

16.4 11.5 15.5 28.7 36.5 23.1

41.5 33.2 42.1 52.1 67.0 48.6

70.5 60.0 59.3 78.4 92.8 72.6
average of 27.9 31.9 44.8 57.2

applied P

LSD (1%) comparison of the residual or applied P means

= 3.0

LSD (1%) for interaction between residual and applied P = 6.0

Coefficient of variation (CV) = 7.8%

 

Data means of four replications.

1Previously applied to corn.

40

Table 10. The effect of applied and residual P on P extracted by
Bray P] (1:50) after harvesting potato crop grown in the
greenhouse on a Charity clay soil

 

 

 

 

 

 

 

Residual Applied P (ppm)] Average of
P Residual
3”” P1 ("50) 0 12.5 37.5 62.5 P
PPm P

43.1 32.8 40.3 60.5 84.6 54.6

56.9 38.2 48.7 67.0 81.0 58.7

114.4 85.3 94.5 123.0 141.4 111.1

166.1 149.7 151.5 179.0 200.3 170.10
average of 76.5 83.8 107.5 126.8

applied P
LSD (1%) comparison of the residual or applied P means = 6.0
LSD (1%) for interaction between residual and applied P = NS

Coefficient of variation (CV) = 6.4%

 

Data means of four replications.

1Previously applied to corn.

41

Table 11. The effect of applied and residual P on P extracted by
Olsen's NaHC03 after harvesting potato crop grown in the
greenhouse on a Charity clay soil

 

 

 

 

 

 

Residual Applied P (PPm)] Average of
P Residual
Olsen's NaHCO3 0 12.5 37.5 62.5 P
ppm P

10.3 5.6 7.1 16.6 24.4 13.4

14.5 10.4 13.6 19.9 34.3 19.7

30.8 24.1 30.8 38.5 49.0 35.6

49.5 43.5 41.5 52.6 63.6 50.3
average of 21.0 23.3 31.9 42.8

applied P
LSD (1%) comparison of the applied or residual P means = 1.7
LSD (1%) for interaction between applied and residual P = 2.3

Coefficient of variation (CV) = 5.8%

 

Data means of four replications.

1Previously applied to corn.

42

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45

From the regression equations obtained between any two of the
used extractants, the amount of P extracted by Bray P1 (l:50) was
over twice the amount of P extracted by Bray P1 (1:8) and over three
times the amount of P extracted by Olsen's NaHCO3.

In addition to linear regression analysis previously discussed,
logarithmic, quadratic and stepwise regression equations were calculated
to determine the best relationship between plant and soil parameters.
Logarithmic equations between plant parameters and soil test levels were
inferior to all other equations. Quadratic equations between plant
parameters and extracted P were superior to stepwise fits taking into
account applied P in all cases, except corn yield. Quadratic and step-
wise regression equations obtained for corn yield and extracted or ap-
plied P are given in Table 12. Response surfaces for corn yield,
applied and extracted P by Bray P1 (1:8) and (1:50) and by Olsen's
NaHCO3 are shown in Figure 4, 5 and 6, respectively.

The multiple (non-linear) relationships obtained by using quad—
ratic regression analysis between extracted P, yield, P concentration
and P uptake by corn or by potatoes are shown in Table 13.

Similar significant coefficients of determination were obtained
between soil test levels and some plant parameters. Specifically,
corn yield, P uptake by corn, percent P in potatoes and P uptake by
potatoes were essentially equally correlated with the soil tests.
0n the other hand, higher coefficients of determination were ob-
tained between percent P in potatoes and soil test levels. However,
the only significant relationship between any soil test and potato
yields was with Bray 1:50. Even still, this accounted for a very

small portion of the variability in the data.

46

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47

 

(5013) PDT).

 

 

 

Corn yield in relation to applied and Bray P] (1:8) extracted P
from a Charity clay soil after harvesting corn crop in the green-

house, as described by the equation

Fig. 4.

Y= 2.13 + 0.06(Bray l:8)-+0.016(Applied P) - 0.0005 (Bray 1:8)2
R2 = 0.63**

48

 

51%
05

 

 

 

18
T
£321}? 150 '
0‘66 ’L 5
Jg‘p ~{a9 b
/
8t .9 5 “P
e 0 P
(7 6 4"l $9
0 5
6000)) 30
0 0
Fig. 5. Corn yield in relation to applied and Bray P (1:50) extracted P

from a Charity clay soil after harvesting corn crop in the green-
house, as described by the equation

Y= 1.65 + 0.03(Bray 1:50) +0.016(Applied P) - 0.00012(Bray 1:50)2
R2 = 0.63**

(8m3) PIBIA

I I
7

 

 

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Fig. 6. Corn yield in relation to applied P and Olsen's NaHCO
extracted P from a Charity clay soil after harvesting
corn crop in the greenhouse, as described by the equation

Y=2.04+0.08 (Olsen's P)+0.016(Applied P)-0.0007 (Olsen's P)2.
R2 = O.63**

50

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51

The non-linear relationship between soil test levels and corn
yileds are schematically given in Figures 7, 8 and 9. As can be
seen, the maximum corn yield can be obtained by 73 ppm P Bray 1:8,
154 ppm P Bray 1:50 or by 56 ppm P Olsen's NaHCO3. Similarly the
non-linear relationship between P extracted after potatoes and P
uptake by potatoes are given in Figures 10, 11 and 12.

In this study, the three soil tests were essentially equal in
their capability to predict P availability. However, the amount of
variability accounted for in anyone of the relationships is not suf-

ficient for very precise predication of response.

0. The Changes in the Soil Test Levels

 

In order to evaluate whether P fixation or release occurred, the
following equation was used:

x = (initial P level + applied P) - (P uptake + extracted P)

If x is positive, fixation apparently occurred and if x is neg-
ative, release apparently occurred. Initial P, is the soil P level
initially extracted from the soil before applying P in the greenhouse.
P uptake, is the total P uptake by both crops (corn plus potatoes).
The extracted P is the amount of P extracted by Bray 1:8 after potato
crop was harvested.

The data (mg P/culture) of applied P, Bray 1:8 residual and ex-
tracted P after potatoes, total P uptake by corn plus P uptake by
potatoes and the amount of change in soil test levels after potatoes
according to the above equation is given in Table 14 and that after

corn crop was harvested is given in Appendix Table 5.

52

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59

The data in Table l4, indicate that some P was apparently
fixed as a result of an addition of different rates of applied P.
The amount of P fixed tended to increase with increasing rates of
applied P on all four soils. Similarly, the same effect was seen
for Bray P1 (l:50) after potatoes and for Bray P1 (l:8) after corn
(Appendix Tables 4 and 5).

In most cases, apparent P fixation also tended to increase
with increasing residual levels at all rates of applied P.

On the other hand, soil test levels were changed when differ-
ent rates of P were applied. For example, Bray P1 (l:8) test level
after potatoes was increased by about 67 mg P/culture when 187.5 mg
P/culture was applied.

E. Application of a Modified Form of
Mitscherlich Equation

 

 

A modified form of Mitscherlich equation was proposed by Bray
(l958). The modified equation takes the form: Log (A-y) = Log A -
Clb - Cx; where A is the maximum yield obtained by any P treatment
pots, y is the yield for any given P rate, b is the soil test value,
x is a given fertilizer rate and C1 and C are constants for b and x,
respectively.

The modified form of this equation was applied in this study
in order to evaluate the responses of corn crop to applied P. The
responses of corn grown in the greenhouse on a Charity clay soil to
applied P and to available soil P as extracted by Bray P1 (l:8 and
l:50) and Olsen's NaHCO3 soil tests are given in Tables 15, l6 and
l7, respectively.

The values of the contants C1 and C were calculated for each

Table 15. Bray P] (l:

crop grown
to applied

60

8) soil test values and reSponses of corn

in the greenhouse on a Charity clay soil

phosphorus

 

Bray P] (1:8)

Applied P ppm

Mitscherlich

 

 

 

 

 

 

 

Soil Test
Initial After C for c for
P Level Corn 0 12.5 37.5 62'5 1b x
-———-— ppm P ———— yield in grams
11.5 8.2 1.75 2.17 4.23 4.17 0.028 0.006
5.8 2.23 4.46 4.54 3.90 0.050 0.117
7.5 1.63 1.86 3.38 4.57 0.026 0.003
5.9 2.04 2.87 4.39 3.45 0.046 0.015
16.4 14.6 2.56 2.71 3.12 4.86 0.022 0.003
16.1 2.90 3.23 4.71 4.91 0.024 0.006
14.2 1.84 4.30 3.79 4.98 0.015 0.052
14.3 2.60 4.59 4.77 4.89 0.023 0.071
41.5 30.2 3.77 4.40 4.88 4.85 0.021 0.030
22.3 4.16 3.39 4.01 4.67 0.043 -
27.8 4.06 3.93 4.48 4.60 0.034 -
24.3 3.58 3.83 3.86 4.80 0.025 0.007
70.5 44.4 3.90 4.02 4.65 4.45 0.018 0.006
50.3 3.73 4.37 4.35 4.80 0.013 0.032
46.5 4.98 4.12 4.07 5.13 0.015 0.001
53.8 4.44 4.22 4.84 5.52 0.013 -
Average of Constants: 0.026 0.027
Standard Error of the Mean: 0.003 0.009

 

61

Table 16. Bray P] (1:50) soil test va1ues and responses of corn
crop grown in the greenhouse on a Charity clay soil to
applied phosphorus

 

Bray P] (1:50)

501] Test App11ed P ppm Mitscherlich

 

 

 

 

 

 

 

P Level Corn 6 x
-———ppm P-———— —————————- yield in grams
43.1 34.7 1.75 2.17 4.23 4.17 0.007 0.006
32.1 2.23 4.46 4.54 3.90 0.009 0.117
30.4 1.63 1.86 3.38 4.57 0.006 0.004
29.9 2.04 2.87 4.39 3.45 0.009 0.015
56.9 41.0 2.56 2.71 3.12 4.86 0.008 0.002
44.3 2.90 3.23 4.71 4.91 0.009 0.006
44.7 1.84 4.30 3.79 4.98 0.005 0.051
35.6 2.60 4.59 4.77 4.89 0.009 0.071
114.4 81.8 3.77 4.40 4.88 4.85 0.008 0.071
85.5 4.16 3.39 4.01 4.67 0.011 -
78.7 4.06 3.93 4.48 4.60 0.012 -
89.3 3.58 3.83 3.86 4.80 0.007 0.004
166.1 135.5 3.90 4.02 4.65 4.45 0.006 0.004
134.6 3.73 4.37 4.35 4.80 0.005 0.030
136.4 4.08 4.12 4.07 5.13 0.005 0.002
135.5 4.44 4.22 4.84 5.52 0.005 -
Average of Constants: 0.008 0.030
Standard Error of the Mean: 0.001 0.010

 

62

Table 17. Olsen's NaHC03 soil test values and responses of Corn
Crop grown in the greenhouse on a Charity clay soil to
applied phosphorus

 

 

 

 

 

 

Olsen Soil . . .
Test App11ed P ppm M1tscher11ch
Initia] After 0 12.5 37.5 62.5 C] for C for
P Level Corn b x
____.ppm p __—— —-yield in grams
10.3 6.9 1.75 2.17 4.23 4.17 0.033 0.007
8.1 2.23 4.46 4.54 3.90 0.036 0.117
7.7 1.63 1.86 3.38 4.57 0.025 0.003
8.1 2.04 2.87 4.39 3.45 0.033 0.015
14.5 10.0 2.56 2.71 3.12 4.86 0.033 0.002
12.4 2.90 3.23 4.71 4.91 0.031 0.006
10.2 1.84 4.30 3.79 4.98 0.026 0.048
11.1 2.60 4.59 4 77 4.89 0.030 0.070
30.8 22.0 3.77 4.40 4.88 4.85 0.029 0.030
22.4 4.16 3.39 4.01 4.67 0.043 -
24.2 4.06 3.93 4.48 4.60 0.038 -
25.3 3.85 3.83 3.86 4.80 0.024 0.007
49.5 44.2 3.90 4.02 4.65 4.45 0.018 0.019
45.4 3.73 4.37 4.35 4.80 0.014 0.033
45.7 4.08 4.12 4.07 5.13 0.015 0.001
44.1 4.44 4.22 4.85 5.52 0.016 -
Average of Constants: 0.028 0.027
Standard Error of the Mean: 0.001 0.009

 

63

soil test as follows: The constant C1 for b was calculated by using
the maximum corn yield obtained at 37.5 or 62.5 ppm applied P as the
value for A yield of the control for y and the indicated soil test
value in each case as b. The constant C for x was calculated by
using the maximum yield of corn obtained at rate of 37.5 or 62.5 ppm
applied P as the value for A, the yield from rate of 12.5 ppm of ap-
plied P as y, the previously calculated 01 value for the soil and
the indicated soil test for b.

In some cases, the yield obtained from the control was higher
than the yield at 12.5 ppm of applied P. This result was not expected
and the reason for that was not very evident. In these cases a nega-
tive value for C was obtained, hence these values were not included
when calculating the average.

Since the constants in Mitscherlich equation are known for
each one of the P extration methods, it is possible to calculate
the percent response of corn crop to P for any given soil test value
obtained by any one of applied soil tests.

Using C1 and C values calculated for soil by any one of the
soil tests, the observed and calculated responses of corn plants to
P are shown in Tables 18, 19 and 20. The data results are given in
"percent sufficiency," that is the percent of corn yield obtained
with a given rate of applied P.

In comparing the values of observed and calculated percent
sufficiency for corn plants, there was essentially not much differ-
ence between the three soil test methods. Although there was no com-
plete agreement between calculated and observed values, the agree-

ment was fairly good in the cases where it would be critical to

64

Table 18. Comparison of abserved and calculated percent sufficiency
for Corn Crop grown in the greenhouse on a Charity clay
soil based on the equation for Bray P1 (1:8) soil test.
Log(A-y) = log A - 0.026b - 0.027x

 

 

 

 

 

 

 

 

 

 

Bray P] (1:8) Applied ppm P
Soil Test
0 12.5 37.5 62.5
Initial After
P Level Corn obs. cal. obs. cal. obs. cal. obs. cal.
—— ppm P % sufficiency
11.5 8.2 41.4 38.9 51.3 71.8 100 94.0 98.6 98.7
5.8 49.1 29.5 98.2 67.4 100 93.0 85.9 98.5
7.5 35.7 36.0 40.7 70.4 74.0 93.7 100 98.7
5.9 46.5 29.8 65.4 67.5 100 93.1 78.6 98.5
16.4 14.6 52.7 58.3 55.8 80.7 64.2 95.9 100 99.1
16.1 59.1 61.7 65.8 82.3 96.0 96.2 100 99.2
14.2 37.0 57.1 86.4 80.2 76.1 95.8 100 99.1
14.3 53.2 57.6 93.9 80.4 97.6 95.8 100 99.1
41.5 30.2 77.3 83.6 90.2 92.4 100 98.4 99.4 99.7
22.3 89.1 73.6 72.6 87.8 85.9 97.4 100 99.4
27.8 88.3 81.0 85.4 91.2 97.4 98.1 100 99.6
24.3 79.2 76.7 78.8 89.2 79.4 97.7 100 99.5
70.5 44.4 83.9 93.0 86.5 96.8 100 99.3 95.7 99.9
50.3 77.7 95.1 91.0 97.7 90.6 99.5 100 99.9
46.5 79.7 93.8 80.3 97.1 79.3 99.4 100 99.9
53.8 80.4 96.0 76.5 98.2 87.7 99.6 100 99.9

 

Table 19.

65

Comparison of observed and calculated percent sufficiency

for Corn Crop grown in the greenhouse on a Charity clay
soil based on the equation for Bray (1:50) soil test.

Log(A - y) = log A - 0.008b - 0.03x

 

Bray P] (1:50)

Applied ppm P

 

 

 

 

 

 

 

Soil Test
12.5 37.5 62.5
Initial After
P Level Corn obs. cal. obs. cal. obs. cal. obs. cal.
—— PPm P % sufficiency
43.1 34.7 41.4 47.2 51.3 77.5 100 96.0 98.6 99.3
32.1 49.1 44.6 98.2 76.4 100 95.7 85.9 99.2
30.4 35.7 42.9 40.7 75.9 74 95.6 100 99.2
30.0 46.5 42.4 65.4 75.4 100 95.5 78.6 99.2
56.9 41.0 52.7 53.0 55.8 78.0 64.2 96.4 100 99.3
44.3 59.1 55.7 65.8 81.1 96.0 96.6 100 99.4
44.7 37.0 56.1 86.4 81.3 76.1 96.6 100 99.4
36.6 53.2 48.1 93.9 77.9 97.6 96.0 100 99.3
114.4 81.8 77.3 77.8 90.2 90.5 100 98.3 99.4 99.7
85.5 89.1 79.3 72.6 91.2 85.9 98.4 100 99.7
78.7 88.3 76.5 85.4 90.0 97.4 98.2 100 99.7
89.3 79.2 80.7 78.8 91.8 79.4 98.5 100 99.7
166.1 135.5 83.9 91.8 86.5 96.5 100 99.4 95.7 99.9
134.6 77.7 91.6 91.0 96.4 90.6 99.4 100 99.9
136.4 79.5 91.9 80.3 96.5 79.3 99.4 100 99.9
135.5 80.4 91.8 76.5 96.5 87.7 99.4 100 99.9

 

66

 

 

 

 

 

 

 

 

 

Table 20. Comparison of observed and calculated percent sufficiency
for Corn Crop grown in the greenhouse on a Charity clay
soil based on the equation for Olsen's NaHC03 soil test.
Log(A - y) = log A - 0.028b - 0.027x

Olsen's Applied ppm P
Soil Test
0 12.5 37.5 62.5

Initial After

P Level Corn obs cal. obs. cal. obs. cal. obs. cal.

—— ppm P-————— % sufficiency

10.3 6.9 41.4 36.1 51.3 71.1 100 94.1 98.6 98.8
8.1 49.1 40.8 98.2 73.3 100 94.5 85.9 98.9

7.7 35.7 39.1 40.7 72.5 74.0 94.4 100 98.9

8.1 46.5 40.8 65.4 73.3 100 94.5 78.6 98.9

14.5 10.0 52.7 47.5 55.8 76.3 64.2 95.2 100 99.0
12.4 59.1 55.1 65.8 79.7 96.0 95.9 100 99.2

10.2 37.0 48.0 86.4 76.5 76.1 95.2 100 99.0

11.1 53.2 51.1 93.9 77.9 97.6 95.5 100 99.1

30.8 22.0 77.3 75.8 90.2 89.1 100 97.8 99.4 99.5
22.4 89.1 76.4 72.6 89.3 85.9 97.8 100 99.6

24.2 88.3 79.0 85.4 90.5 97.4 98.1 100 99.1

25.3 78.2 80.4 78.8 91.1 79.4 98.2 100 99.6

49.5 44.2 83.9 94.2 86.5 97.4 100 99.5 95.7 99.9
45.4 77.1 94.6 91.0 97.6 90.6 99.5 100 99.9

45.7 79.5 94.7 80.3 97.6 79.3 99.5 100 99.9

44.1 80.4 94.2 76.5 97.4 87.7 99.5 100 99.9

 

67

determine whether fertilizer should be applied or not.

Baule units for soil test (b) and for fertilizer (x) were cal-
culated for each extractant. From this, fertilizer guides for 90,
95 and 97 percent sufficiencies were calculated (Table 21, 22 and 23).
This data shows that on a Charity clay soil having a soil test of 60
ppm of Bray P1 (l:8) P, 200 ppm of Bray P1 (1:50) P or 55 ppm of
Olsen's NaHC03 P or more probably will not be responsive to applied P
fertilizer in order to attain up to 97% of sufficiency of yield in
the greenhouse. However, that may not be the case in the field due
to the fact that in the greenhouse the crop stands are not variable
as that in the field, water stress is not prolonged and there are
more plants per unit of soil. This situation probably will result in
more competition due to greater density of roots per culture in the
greenhouse and therefore, a better chance for roots to contact with

the soil or fertilizer P fertilizer particles.

68

Table 21. Calculated quantities of P required to attain various
percent sufficiency for Corn grown in the greenhouse on
a Charity clay soil based on the equation:
Log(A - y) = log A - 0.026b - 0.02 X

 

 

 

Bray P] (1:8) Relative Yield
Soil Test Sufficiency
Leve‘ 90% 95% 97%
PPm P % -———————- ppm P
2.0 11.3 35.1 46.3 54.5
5.0 25.9 32.2 43.4 51.6
10.0 45.1 27.4 38.6 46.8
20.0 69.8 17.8 28.9 37.1
25.0 77.6 13.0 24.1 32.3
30.0 83.4 8.1 19.3 27.5
35.0 87.7 3.3 14.5 22.7
40.0 90.9 0 9.7 17.9
45.0 93.2 - 4-9 13-1
50.0 95.0 - 0.04 8 3
55.0 96.3 - 0 4 3
60.0 97.3 - - 0

 

Baule unit of b = 11.58 ppm P.

Baule unit of x = 11.15 ppm P.

69

Table 22. Calculated quantities of P required to attain various
percent sufficiency for Corn grown in the greenhouse on
a Charity clay soil based on the equation:
Log(A - y) = logA - 0.008b - 0.03x

 

 

 

Bray P] (1:50) Relative Yield
Soil Test Sufficiency
Level 90% 95% 97%
ppm P % ——-————- ppm P
10.0 16.8 30.1 40.7 48.1
20.0 30.8 28.0 38.0 45.4
30.0 42.5 25.3 35.4 42.8
40.0 52.1 22.7 32.7 40.1
50.0 60.2 20.0 30.0 37.4
60.0 66.9 17.3 27.4 34.8
70.0 72.9 14.7 24.7 32.1
80.0 77.1 12.0 22.0 29.4
90.0 81.0 9.3 19.4 26.8
100.0 84.2 6.7 16.7 24.1
110.0 86.8 4.0 14.0 21.4
120.0 89.0 1.3 11.4 18.8
130.0 90.9 0 8.7 16.1
140.0 92.4 - 6.0 13.4
150.0 93.7 - 3.4 10.8
160.0 94.8 - 0.7 8.1
170.0 95.6 - 0 5.4
180.0 96.4 - - 2.8
190.0 97.0 - - 1.0
200.0 97.5 - - 0

 

Baule unit of b = 37.63 ppm P.

Baule unit of x = 10.0 ppm P.

70

 

 

 

 

Table 23. Calculated quantities of P required to attain various
percent sufficiency for corn grown in the greenhouse
on a Charity clay soil based on the equation:

Log(A - y) = log A - 0.028b - 0.027x
Olsen's NaHCO3 Relative Yield
Soil Test Sufficiency
Level 90% 95% 97%

ppm P % -———————- ppm P
5.0 27.6 31.9 43.0 51.2
10.0 47.5 26.6 37.8 46.0
15.0 62.0 21.5 32.6 40.8
20.0 72.5 16.3 27.4 35.7
25.0 80.1 11.1 22.3 30.5
30.0 85.6 5.9 17.1 25.3
35.0 89.5 0.7 11.9 20.1
40.0 92.4 0 6.7 14.9
45.0 94.5 - 1.5 9.7
50.0 96.0 - 0 4.6
55.0 97.1 - — 0
60.0 97.9 - - _

Baule Unit of b = 10.75 ppm P.

Baule Unit of x = 11.15 ppm P.

CHAPTER V

GENERAL DISCUSSION

In fall 1975, soil samples were collected from Saginaw Valley
Beet and Bean Research Farm. The samples were collected from the
plow layer from plots which had received a total of 0, 448, 895
and 1792 kg P205/ha.

Greenhouse and laboratory studies were conducted to evaluate
the effect of applied and residual P on crop growth and soil test
levels. Corn and potatoes were used as a test crop.

In a corn experiment, four levels of fertilizer P equivalent to
0, 12.5, 37.5 and 62.5 ppm P by soil weight was applied. After 40 days
the above ground portion was harvested and soil samples were col-
lected. After the corn crop was harvested, potatoes were grown on
the same soil without any additional P fertilizer. After 35 days
potato tops were harvested and soil samples were collected.

The soil samples collected after harvesting corn and potatoes
were extracted using Bray PH (1:8 and 1:50 soilzsolution ratios)
and Olsen's NaHCO3 extractants. Plant tissue samples were analyzed
for P content using the method described by Parkinson and Allen
(1967).

The data obtained for corn and potatoes indicated that both

crops responding differently to applied and residual P. Yield of

71

72

corn, although significantly affected by applied and residual P,
was more affected by applied P than by residual P. On the other
hand, the percent P in corn tissue was affected by residual P more
than by applied P. Phosphorus uptake by corn plants was almost
equally affected by both applied and residual P.

It was noted in the prior discussion, that some apparent P
fixation occurred in the soil after corn crop was harvested. As
a result of that P fixation, potato yields were affected more by
residual P than by previously applied P. Although the applied P
had a significant effect on percent P in potatoes and P uptake by
potatoes, that effect was relatively small compared to the effect
of residual P on both measurements.

Comparing the linear relationship obtained between any two
of the three soil tests, there was a good agreement obtained be-
tween the three soil tests (r = 0.98). However, the amount of P
extracted by any method was different from the amount of P ex-
tracted by other methods. Bray P1 (1:50) extracted over twice
the amount of P extracted by Bray P1 (1:8), and over three times
the amount of P extracted by Olsen's NaHC03. It is quite clear
from the above discussion some superiority of dilute acid—fluroide
(0.025 fl_HCl + 0.03 M_NHF) extraction of avialable P (especially
1:50 ratio) was obtained over extraction made with 0.5 MNaHCO3
buffered at pH 8.5.

Comparing the amount of extracted P by Bray P1 using 1:8 and
1:50 soil to solution ratios, it is clear, using the wider soil to

solution ratio (l:50) more P was extracted than using 1:8 ratio. The

73

reason for that probably is related to the presence of free CaCO3
content. The CaCO3 content of these soils is about 5%. Using of an
extraction ratio 1:8, provided only sufficient H+ to react with only
20% of the CaCO3 present in the soil. Under such conditions the

acid was completely expended in dissolving CaC03. 0n the other hand,
with an extraction ratio of 1:50 there was sufficient H+ to react
with a soil having 6.25% CaC03. It seems logical that this factor
alone had a significant importance. However, soils very high in

CaCO content might need the use of even wider extraction ratios.

3
In this particular study, although the amount of extracted P
by any method was different from the amount extracted by any of the

other two methods, the three tests were almost equally correlated
with plant parameters. The same conclusion was obtained by A1-
Abbas and Barber (1964b). This may indicate that these methods are
reasonably well adapted to routine analysis to evaluate the avail-
able P on a Charity clay soil. However, Olson gt al. (1954) listed
some difficulties inherent with using Olsen's NaHC03, such as liquid
lose due to C02 evolution as the aliquot for color develOpment is
neutralized, greater time is required for filering than for Bray P]
due to dispersions of clay particles and the increase in pH of the
extractant solution with time giving variations in the amount of P
extracted from the soil. Very recently it has been found that some
microbial activity may take place in stored soil extracts which may

1

affect the amount of P measured. Due to the above difficulties in-

herent with Olsen's NaHC03, the author prefers the use of Bray P1

 

1Personal communication, Dr. B. G. Ellis, Crop and Soil Science
Department, Michigan State University.

74

(especially 1:50) over the use of Olsen's NaHC03.

Extracted P levels before P was added and after the crops were
harvested indicate that soil test levels were increased by applied P.
For example, Bray P1 (1:8) test level after potatoes were increased
by approximately 67 mg P/culture as a result of an application of
187.5 mg P/culture. The soil tests after harvesting corn or pota-
toes, showed some P was apparently fixed on all four soils. The
amount of P fixed tended to increase with increasing levels of both
applied and residual P.

A modified fOrm of Mitscherlich equation was applied. The ob-
served and calculated values of percent sufficiency for corn plants
indicated that there was essentially not much difference between the
three soil tests. The agreement between the observed and calculated
values of percent sufficiency was fairly good in the cases where it
would be critical to determine whether fertilizer should be applied
or not. Baule units for soil test (b) and for fertilizer (x) were
calculated for each soil test. Fertilizer guides for 90, 95 and 97
percent sufficiency were calculated for the three soil tests. Those
guides indicate that a Charity clay soil having a soil test of 60
ppm P Bray P1 (1:8), 200 ppm P Bray P1 (1:50) or 55 ppm Olsen's
NaHCO3 P or more probably will not be responsive to applied P fer-

tilizer in order to obtain up to 97 percent of sufficiency of corn

yield in the greenhouse.

CHAPTER VI

CONCLUSIONS

The conclusions can be summarized as follows:

1)

2)

There was a significant response to applied and residual

P by corn and potatoes.

Yield of corn and P uptake by corn plants were signifi-
cantly affected by applied and residual P, while percent

P in corn plants was only affected by residual P.

Although both P concentration and P uptake by potatoes
were significantly affected by applied and residual P, the
effect of residual P was greater than the applied P. How-
ever, potato yields were only affected by residual P.

The levels of the three soil tests were increased with in-
creasing rates of applied P. Bray P1 (l:8) soil test after
potatoes has been increased by about 67 percent P/culture
when 187.5 mg P was applied.

A significant linear relationship was obtained between the
extracted P by any two of the three soil tests.

The amount of extracted P by Bray P1 (l:50) was over twice
the amount of P extracted by Bray P1 (1:8) and over three
times the amount of P extracted by Olsen's NaHCOB.

The three soil test levels were almost equally correlated

75

8)

10)

11)

12)

76

with corn and potato parameters. This indicates that these
three methods are reasonably well adapted to routine anal-
ysis to evaluate the available P on a Charity clay soil.
The best fits between plant parameters and the extracted P
were obtained by using quadratic regression equations. One
exception was for corn yield where a stepwise regression
fit with extracted P and applied P gave the best fit.

After harvesting corn or potatoes some P was apparently
fixed at all rates of applied P on all four soils.

The amount of P fixed tended to increase with increasing
levels of applied and residual P on all four soils.

Baule units for soil (b) and for fertilizer (x) were calcu-
lated for each extractant. These were 11.6, 37.6 and 10.8
ppm P for soil test values and 11.15, 10.0 and 11.15 ppm

P for fertilizer values as evaluated by Bray P1 (1:8 and
1:50) and Olsen's NaHC03, respectively.

On a Charity clay soil having a soil test of 60 ppm P Bray
1:8, 200 ppm P Bray 1:50 or 55 ppm of Olsen's NaHCO3 P or
more probably will not be responsive to applied P fertilizer

in order to produce 97 percent sufficiency of corn yield.

APPENDIX

Table A1. The effect of applied and residual P on P extracted by
Bray P1 (l:8) after harvesting corn crop grown in the
greenhouse on a Charity clay soil.

 

 

 

 

 

 

 

Initial Applied P ppm
5:221:61. ..
Bray P] (1:8) 0 12.5 37.5 62.5 R851dual
ppm P

11.5 6.8 9.5 17.9 33.6 17.0

16.4 14.7 18.2 22.0 35.5 22.6

41.5 26.1 34.0 45.4 63.2 42.2

70.5 48.7 54.0 66.4 92.1 65.3
average of 24.1 28.9 37.9 56.1

applied P
LSD (1%) comparison of the applied or residual P means = 5.3
L50 (1%) for interaction between applied and residual P = NS

Coefficient of variation (CV) = 15.2%

 

- Data means of four replications.

77

78

Table A2. The effect of applied and residual P on P extracted by“
Bray P] (1:50) after harvesting corn crop grown in the
greenhouse on a Charity clay soil.

 

 

 

 

 

 

 

Initial Applied P ppm
Residual Average of
Levels by Residual
Bray P] (1:50) 0 12.5 37.5 62.5
ppm P
43.1 31.7 34.1 49.0 85.0 50.0
56.9 41.3 46.6 67.1 99.4 63.6
114.4 83.8 95.8 129.8 155.2 116.1
166.1 135.4 156.3 162.8 181.1 158.9
average of 73.1 83.2 102.2 130.2
applied P

LSD (1%) comparison of the applied or residual P means = 12.5
LSD (1%) for interaction between applied and residual P = NS

Coefficient of variation (CV) = 13.5%

 

Data means of four replications.

79

Table A3. The effect of applied and residual P on P extracted by
Olsen's NaHCO3 after harvesting Corn Crop grown in the
greenhouse on a Charity clay soil

 

 

 

 

 

 

 

Initial Applied P ppm
Residual Average of
Levels by Residual
Olsen's NaHC03 O 12.5 37.5 62.5
PPm P
10.3 7.7 10.2 16.5 32.0 16.6
14.5 10.9 13.6 19.9 34.3 19.7
30.8 23.4 31.7 40.1 45.9 35.3
49.5 44.8 50.7 56.6 71.8 56.0
average of 21.7 26.6 33.3 46.0
applied P

LSD (1%) comparison of applied or residual P means = 2.2
LSD (1%) for interaction between applied and residual P = 4.3

Coefficient of variation (CV) = 7.1%

 

Data means of four replications.

80

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LITERATURE CITED

LITERATURE CITED

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87

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88

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