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ABSTRACT

TRANSFORMATION OF PHOSPHORUS IN SOILS AFTER
FLOODING AS MEASURED BY CHEMICAL EXTRACTION
AND UPTAKE BY RICE
BY

Manoowetaya Srisen

Eight Michigan soils, including sandy loam, loam, clay loam and
clay textures with poorly and well-drained soils of each texture, were
selected to study in the greenhouse. Both A and B horizons of each
soil were placed in one-gallon cans with plastic liners. Rice seed-
lings were planted in NR and NPR treatments (100 ppm of each element).
Also, a control pot (NK, 100 ppm of each) with no rice was maintained.
Micronutrients were added after the soils were submerged. Soil samples
before flooding were analyzed to determine pH, Eh, saturated CaSOa

extractable Mn, 0.1 NH OAcl extractable Fe, organic matter and Bray's

4
P-l, Olsen's sodium bicarbonate P, and Truog's dilute sulfuric acid P.
Soil and water samples after flooding were taken at 3-week intervals
and analyzed for pH, Eh, extractable Mn and Fe, Bray's P-l, Olsen's P
and Truog's P. Yield of rice was determined at the end of the study.
The following conclusions were drawn:
1) The yield of rice responded remarkably to P application in B

horizons whereas little response to P fertilization was found in A

horizons.

Manoowetaya Srisen

2) Relative yield of rice was related to either Bray's P-l or
Olsen's sodium bicarbonate extractable P where soils containing less
than 10 ppm P before flooding responded to P fertilization. P
extracted by Truog's weak sulfuric acid was not related to relative
yield of rice.

3) After flooding there was a large chemical change:

a) pH of the soil increased about 1 pH unit, except in soil
in which initial pH was lower than 5.30. In the latter, pH changed
slightly due to flooding.

b) Eh decreased considerably due to submergence of the soils,
except soils with high acidity (pH about 4.6-5.3).

c) Extractable Fe and Mn increased greatly after flooding,
reached the maxima at 3-6 weeks, after which they declined slightly
with time. Fe remained more constant after reaching the maxima.

d) The amount of extractable P by Bray 1, Olsen's and Truog's
increased remarkably due to flooding. The quantity of Truog's P
increase was much more than Bray's P-1 and Olsen's P. Olsen's P and
Truog's P showed good relationship between initial P and P after

flooding.

TRANSFORMATION OF PHOSPHORUS IN SOILS AFTER
FLOODING AS MEASURED BY CHEMICAL EXTRACTION

AND UPTAKE BY RICE

BY

Manoowetaya Srisen

A THESIS

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

MASTER OF SCIENCE

Department of Crop and Soil Sciences

1971

This work is dedicated to the
Thai farmers who have devoted
themselves to my country for
centuries, and to my parents

to which my debt is beyond thanks.

ACKNO‘JLE DGEMENTS

The author wishes to express his Sincere gratitude to his major
professor, Dr. B. G. Ellis, for his patient guidance and helpful
suggestions throughout the course of this study and preparation in
the manuscript. Sincere thanks is also expressed to the members of
the Department of Crop and Soil Sciences for the many opportunities
for intellectual growth.

I am indebted and grateful to the Thai Government for financial
support which has enabled me to complete the study.

Special thanks is expressed to my friend, Usana Navanugraka, for

her encouragement and support in this undertaking.

ii

TABLE OF CONTENTS

INTRODUCTION 0 O O O O O O O O O O O O O O O O O 0
LITERATURE REVIEL-J O O O O O O O O O O O O O O O 0

Rice I O C O I O O O O O O O C C O O O O O O
Flooding Soils . . . . . . . . . . . . . . .

Oxidation-Reduction Potential and Soil Acidity

Mn and Fe . O O O O O O O O O O O O O O O O O
P and Reducing Conditions . . . . . . . . . .

MATERIALSANDMETHODS . . . . . . . . . . . . .'.

mterials O O O O O I O O O O O O O O O O I 0

Greenhouse Work . . . . . . . . . . . . . . -,

Flooding the Soil . . . . . . . . . . . . . .
Preparation of Rice Seedlings . . . . . . . .
Sampling . . . . . . . . . . . .
Exchangeable Fe+2 Analysis . . . . . . . . .
Extractable Mn . . . . . . . . . . . . . . .
Redox potential and pH analysis . . . . . . .
Available P Analysis . . . . . . . . . . . .
Color Development . . . . . . . . . . . . .
l, 2 ,4-Aminonaphtholsu1fonic Acid Reductant in
Perchloric System Method . . . . . . . . .

RESULTS AND DISCUSSION . . . . . . . . . . . . . .
Yield of Rice . . . . . . . . . . . . . .
Chemical Changes in Soil Water After Flooding
Chemical Change in the Soil After Flooding .
Transformation of Soil P After Flooding . . .

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . .

BIBLImRAPHY O O 0 O O C O O O O I O O O O O O O O

API)ENDIX O O O O O O O O O O O O O O O O O O O 0 0

iii

Page

26
26
31
33
35
41
43

46

TABLE

la.

2a.
3a.
4a.
5a.
6a.
7a.
8a.

9a.

10a.

11a.

12a.

13a.

LIST OF TABLES

Soil series and location of soils studied . . . . .

Yield of greenhouse rice as influenced by soil type,

horizon and P level . . . . . . . . . . . . . . .

Soil type, chemical and physical properties of the
eight Michigan soils used in the greenhouse study

Soil-water pH with time after flooding . . . . . .
Soil-water Eh with time after flooding . . . .
Soil-water P content with time after flooding . .
Soil-water Mn content with time after flooding . .
Soil-water Fe content with time after flooding . .
Soil pH with time after flooding . . . . . . . . .
Soil Eh with time after flooding . . . . . . . . .

Soil P extractable by Bray Pl as influenced by
time after flooding . . . . . . . . . . . . , ...

Soil P extractable by Olsen's sodium bicarbonate
method as influenced by time after flooding . . .

Soil P extractable by Truog's weak H2804 method as
influenced by time after flooding . . . . . . . . .

Soil Mn++ content with time after flooding . . . .

Soil Fe++ content with time after flooding . . . .

iv

Page

19

27

46
47
48
49
50
51
52

53

54

56
57

58

LIST OF FIGURES

FIGURE Page
1. The relationship between Bray P-l phosphorus and
relative yield of rice . . . . . . . . . . . . . . . . . . 28

2. The relationship between Olsen's sodium bicarbonate
extractable phosphorus and relative yield of rice . . . . 29

3. The relationship between Truog's weak sulfuric acid
extractable phosphorus and relative yield of rice . . . . 3O

4. Bray P-l extractable phosphorus initially and after
three weeks' flooding . . . . . . . . . . . . . . . . . . 38

5. Olsen's sodium bicarbonate extractable phosphorus
initially and after three weeks' flooding . . . . . . . . 39

6. Truog's weak sulfuric acid extractable phosphorus
initially and after three weeks' flooding . . . . . . . . 4O

INTRODUCTION

Rice (Oryza sativa L.) is one of the most important grain crops in

 

the world. It is the staple food of the populous Far East and has also
become an important crop in some countries of America, Europe, Africa
and West Asia (Guidry, 1964). The total world production of rice in
1968 was 181 million metric tons and the area devoted to rice production
was 238 million acres (U.S.D.A., 1969).

Rice is usually grown under paddy or flooded conditions. Where
soils are submerged, the flow of oxygen from the atmosphere to the soil
is curtailed and the oxygen entrapped between soil particles is readily
consumed by aerobic soil microorganisms for their respiration.
Consequently, a flooded soil will be devoid of oxygen, for all practical
purposes, within a day of flooding causing the aerobic soil micro-
organisms to become inactive or die. The facultative and obligate
anaerobic organisms then take over decomposition of plant residue and
soil organic matter using oxidized soil components (e.g., ferric and
inorganic compounds). This will produce a deficiency of oxygen in
flooded soils except in a very thin soil surface layer (a few milli-
meters thick).

The environmental conditions prevailing in submerged soils are
entirely different from those of well-drained soils. It has been shown
by many experiments (Ponnamperuma, Tianco and Loy, 1967) that dramatic

chemical changes occur after a soil is flooded.

Many workers (Mandel and Das, 1970) have reported no response of
paddy rice to P fertilization even though upland rice does respond.
This has been chiefly due to the increase in availability of native P
in submerged soils. Most workers in this field (Mandel and Das, 1970)
have the opinion that the increase is largely due to the reduction of
FePO4 to more soluble P compounds under anaerobic conditions.

Considerable work has been done on the transformation of water
soluble P applied to upland soils. But similar studies in submerged or
lowland soil are very limited and the effect of flooding on P trans-
formation in Michigan soils has received no prior attention. The
objectives of this study were: 1) to determine the nature, magnitude,
and dynamics of both native and applied P after flooding soils; 2) to
study the response of rice to P fertilization; and 3) to study the
relationship between the solubility of P and Fe, Mn, pH, and Eh

changes due to flooding.

LITERATURE REVIEW
Rice

Rice is grown over a very wide range of climatic, soil and water
conditions, ranging from moist tropical to semi-arid regions in warm
temperature climates; in heavy clay or infertile sandy soils; on dry
land or in swamp land with water that may be 20 feet deep, and in fresh
or brackish water. Innumerable varieties of rice that exist account for
this cosmopolitan nature, for a variety may be found to suit almost any
condition, provided that the plant is subjected to abundant sunshine,
sufficient for the requirements of the particular variety (Grist, 1965).

The highest yields of rice are obtained in countries in a sub-
tropical or warm temperature climate especially between 30 to 450 north
of the equator. These are not, however, the extreme limits at which
successful cultivation is possible. For instance, in Europe cultivation
has moved northward to 490 north latitude in Czechoslovakia, and in the
Soviet Union it extends to 470 north latitude and may be extended to
50-53° north latitude.

Paddy rice production is adapted to regions of high temperature and
prolonged sunshine. The average temperature required throughout the
life of the plant ranges from 68 to 100 F. The total temperature
required (sum of daily mean temperatures during the growing period) is
between 3,000 and 4,000 F. This is probably the lower range of require-
ment for in many countries this figure is greatly exceeded. In Hungary,

one of the most northerly situated rice-producing countries, a total

3

temperature of 5,500 F and 1,200 hours of sunshine are considered the
lowest limits for successful production in paddies.

The altitude at which paddy rice may be grown depends on latitude.
It has been grown at 10,000 feet in the Himalayas, 6,000 feet in the
Philippines, and over 4,000 feet in South America, while in many
countries it is grown at altitudes exceeding 2,000 feet. But the area
cultivated at considerable elevations is small compared to flat land
because in such regions it is difficult to supply and control water.

The length of day is one factor affecting rice production. Paddy
rice varieties can be grouped, based on photoperiodism, as sensitive
and nonsensitive varieties. Sensitive varieties flower when the day
length decreases and reaches a critical value for induction of the
flowering phase. Such varieties are frequently of medium to long
maturation periods. The inducement of flowering by shortening the day
length influences their ripening period so that they are "date fixed”
with regard to maturation date though their growing period can be
extended by earlier planting. Nonsensitive varieties do not respond to
the differences in photoperiod; their length of life is independent of
day length so they can be grown at any season. They are "period fixed”
with regard to length of maturation and the date of planting has little
influence on the length of life. They may be influenced by factors
other than photoperiod such as temperature. Among sensitive varieties
there are variations in the degree of response to photoperiod.

The types of soil suitable for paddy cultivation depend more on
the condition under which the plant is grown than on the nature of the
soil. Chemical analyses of a soil do not appear to provide a very sure

guide as to its suitability for paddy cultivation. The fact that a

soil can produce satisfactory paddy crops annually for centuries has no
parallel in agriculture. Thus, paddy soils which are dissimilar in
chemical composition will yield equally good crops. The apparent
paradox may be partially explained by the nutrient-carrying role of

irrigation water.

Flooding_Soils

Flooding produces drastic changes in a soil. Ponnamperuma (1964)
stated that water-logging caused a decrease in redox potential, an
increase in pH in acid soils, an increase in specific conductance,
the disappearance of nitrate accompanied by accumulation of ammonia,
the generation of a variety of organic substances, an increase in
solubility of Fe, Mn, P and Si, and the displacement of cations into

the soil solution.

Oxidation-Reduction Potential and Soil Acidity

Reduction of the soil is the most important chemical change brought
about by flooding. Oxidation-reduction potential or redox potential
(Eh) is a quantitative measure of the intensity of this change.

Because of their diagnostic and interpretative value in the study of
water—logged and submerged soils, marsh soils, lake muds, and marine
sediments, redox potentials have been extensively measured and their
ecological significance indicated. Ponnamperuma and Castro (1964)
stated that the single electrical property that served to differentiate
a submerged soil from an upland soil was its redox potential. The high
promise this property has for diagnostic and interpretative purposes in

rice production cannot be fully exploited without a clear understanding

of the redox system in submerged soils.

Application of the concept of oxidation-reduction potentials to a
soil system has been tried by numerous researchers, but they have, at
best, had only limited success. As will be seen later, different
conclusions have been reached by various workers as to the usefulness
of redox potential measurements as a valid analytical tool.

Yamane and Sato (1968) conducted a series of experiments to
determine the best way to obtain reproducible redox potentials of
submerged soils. They found that the area of the electrode was related
to the measured Eh values. The smaller the area of the electrode, the
slower the soil Eh value was reached. Therefore, they felt that
platinum electrodes should be at least 100 mm2 in area. Even with such
large electrodes, it was necessary for the electrode to be in contact
with the soil for longer than 6 hours and, in most cases, at least
24 hours to obtain reproducible results.

Ponnamperuma, Tianco and Loy (1967) in a 17-week study found that
the quantitative treatment of redox equilibria in such a complex system
as a flooded soil was difficult because: 1) the highly dynamic nature
of the flooded soil prevents the attainment of a stable, true equilibria;
2) of uncertainty about which of a large number of possible redox systems
is operating at a given time; 3) the lack of thermodynamic data on the
transition elements present in the soils that undergo reversible oxida-
tion reduction; 4) complex formations which may alter redox equilibria
between inorganic ions; and 5) the uncertainty about the true potential
of a reduced soil--the soil potential or the potential of the soil
solution. However, they were able to determine that the equation

Eh a 1.058 - 0.059 log Fe+2 - 0.177 pH (1)

where Fe++ = activity of ferrous ion of soil solution

7
holds for most of the 17 weeks of submergence. They proposed that the
precipitation of the metastable compounds Fe(OH)3 and Fe3(OH)8 in the
equilibria was confirmed by their findings, indicating that the soil
solution was the thermodynamically meaningful phase.

In another paper, Ponnamperuma, Loy and Tianco (1969) also
attempted to study the quantitative change of redox potential, pH and
activity of Mn++ in solutions of flooded soils. They found that the
data supported the hypothesis that the manganese dioxides involved in
redox equilibria in soils that undergo seasonal oxidation-reduction are
complex, non-stoichiometric oxides of variable composition where
apparent standard-free energies of formation are considerably less than
those of their theoretical counterpart.

Jeffery (1961) found that he could differentiate between oxidized
and reduced soils with Eh measurements, but the error was too great to
yield precise information about the state of reduction of the water-
logged soils. He also felt that the large experiment error made it
of little value to correct for pH change. He suggested that a more
accurate estimation of the state of reduction of a soil could be
obtained by determining the concentrations of the two oxidation states
of Fe in the soil. He developed the equation

Eh = 1.033 - 0.0601 CFe+2 - 0.180 pH (at 30 C) (2)

where C +2 = ferrous iron concentration fine/l) in soil solution
Fe

as being applicable to water-logged soils.

In another paper, Jeffery (1961) expanded this equation and made
experiments in an effort to define oxidizing conditions, healthy
reducing conditions, and extreme reducing conditions in quantitative

terms. Using the above equation, he developed the term rh =

8

Eh + 0.180 pH and calculated the value rh >1.34 volts for oxidizing
conditions, rh equal to 1.12-1.27 volts for healthy reducing conditions
and rh < 1.15 volts for extreme reducing conditions.

Mukhopadhyaya, Fisher and Smith (1967) studied the effect of
submergence and lime treatment on changes in Eh, pH, plant uptake of
Mn, yield of rice grain and straw. They found that the Eh values in
all treatments declined sharply during the first two to three weeks of
submergence, after which relative stability was attained. The pH of
both limed and unlimed soils stabilized near 7.0 after 64 days of
flooding.

Ponnamperuma and Castro (1964) studied 31 soils of known chemical
compositions by submerging them in pOLs. The redox potentials in the
soils and the leachates were measured at regular intervals with black
platinum electrodes. Parallel chemical and physico-chemical determina-
tions were made on the soil and the soil solution.

Eh, dE/de and chemical analyses were the criteria used for
identification of the redox systems. The Eh of soil immediately after
moistening ranged from +350 to +620 m.v. The potentials were highly
correlated with pH and defined by the equation

Eh = 851.2 - 56.47 pH.

This suggested that the potential of aerobic soils was governed
by the irreversible oxygen system.

During the first three days after flooding, Eh of all soils
dropped a few hundred m.v. The subsequent changes of Eh varied from
soil to soil but five patterns were noted. Soils low in organic matter
showed a small decrease in potential and maintained positive potential

even after 180 days of submergence. Soils rich in N03- maintained an

Eh of about +200 m.v. for two weeks and then showed a drop in potential.
In soils with a high content of MnOZ, Eh decreased gradually to 0 m.v.
after 180 days of flooding. Soils rich in active iron decreased the Eh
to approximately 50-200 m.v. and appeared to be strongly buffered. The
greatest decrease in Eh and the lowest Eh were shown by soils low in
N03-, MnOz and Fe203 but high in organic matter. The result showed that
the poising systems operate in flooded soils in the sequence predicted
by thermodynamics.

The potential of the soil could not be interpreted quantitatively
in terms of the concentration of Fe++ or Mn++. Also dE/de for the
soils diverged markedly from dE/de for the inorganic systems likely to
be operating in reducing soils; dE/de varied with the soils, stage of
reduction and the kind and amount of organic matter. Further, Eh of the
soil was considerably lower than Eh of the leachate which could be due
to filtering out or adsorption of bacteria and enzymes by the soil as
the soil solution was removed.

This observation and the fact that a high proportion of the reduced
products in the soil solution were organic substances suggest that the
redox systems in reduced soils are organic systems mediated by enzymes.
In other words, the potential of reduced soils is Probably bacterial

potential.
Mn and Fe

Robinson (1930) found that submerged soil solutions were different
from aerated soil solutions in that they contained high concentrations
of Fe and Mn. The Fe and Mn were present as protobicarbonates.

Submerged soil solutions were also high in Ca and Mg and contained H28

and other sulfides.

10

He stated that the high concentration of Fe, Mn, Ca and Mg was
caused indirectly by the microbiological action on the organic matter
which produced C02 along with other gases. It was the C02 that was
mainly responsible for holding the Fe, Mn, Ca and Mg in the solution.

In the absence of organic matter the solubility of Fe, Mn, Ca and Mg
was not increased under submerged soil conditions. He also found that
toxic concentrations of Fe++ and sulfides developed in a few days after
submergence. Toxic concentrations of Mg developed somewhat more slowly.

The International Rice Research Institute (1963) reported that
flooding the soil caused a reduction of Fe and increased its solubility.
Only a small amount of the reduced Fe in a flooded soil is in the soil
solution. The bulk of it is in the solid phase as the hydroxide,
carbonate, sulfide or exchangeable Fe++1

The reddish brown latosolic soils (pH values of 4.6-6.2, active Fe
content of 2.8-7.6%, and organic matter content of 2.3-4.3%) showed steep
increases in the concentration of reduced Fe during the first 30 days of
submergence. The concentration reached a maximum value of about
10,000-15,000 ppm and remained more or less constant. Soils with lower
organic matter or active Fe content, regardless of pH and texture,
attained lower maxima (6,000-9,000 ppm) and at a slower rate than the
first group. Soils low in active Fe, irrespective of pH and organic mat-
ter content, attained still lower maxima (SOC-4,000 ppm) at an even
slower rate. This result suggests that the maximum amount of reduced
Fe in a soil is determined by the active Fe content and availability of
organic matter with pH being relatively unimportant. They also reported
that Mn compounds, such as ferric iron, function as electron acceptors

in biological oxidations in flooded soils and undergo reduction, forming

11

the more soluble manganous compounds. Mn was more easily reduced than
Fe, but the kinetics of Mn reduction was similar to that of Fe.

There were marked differences among the soils in the pattern of Mn
reduction. Soils with a high content of active Mn, regardless of pH
and organic matter content, showed steep increases in Mn++ during the
first 30 days of submergence and declined slowly thereafter. Soils low
in active Mn increased slowly in Mn++ concentration and reached
maximum values which were very much lower than in the higher manganese
soils. The overriding factor that determined the kinetics of Mn
reduction was the active Mn content of the soil.

Takkar (1969) conducted a laboratory experiment to observe the
effects of different levels of organic matter and different incubation
times on extractable Fe and active Mn. Acidic, neutral, calcareous
and saline-alkali soils were studied at 60% water-holding capacity
(WHC) and under water-logged conditions. He found that the availability
of Fe and Mn was influenced by the temperature in these soils. On
incubations at 60% WHO, a marked increase in Fe was observed after
85 days and a decrease in Mn was observed after 7 days with increased
organic matter content and with the time lag in most soils. An
exception was the acidic soils where increases in Mn were found after
69 days.

Similarly, under water-logged conditions, marked increases in Fe
and decreases in Mn were noticed after 7 days. The lowest amount of Fe
and the time lag in its release in calcareous soils were due to the
presence of iron oxides in highly crystalline forms in these soils.
High content of free Fe and low pH resulted in higher amounts of

extractable Fe in acidic soils. Under water-logged and high organic

12

matter content conditions, a decrease in Eh and a high concentration of
ferrous iron were observed. This was accompanied by a decrease in pH

except in acidic soils where pH increased.

P and Reducing Conditions

 

Considerable work has been done showing that submergence of a soil
causes the availability of P to increase. Gasser (1965) noted that
flooding soils caused an increase in acid-soluble P. This increase
could be attributed to the reduction of ferric phosphate to ferrous
phosphate. He proposed that in assessing the P status of rice soils
the ferric phosphate should be considered as an ”available” form.

Hayes and Phillips (1958) reported that the redox potential had
little or no effect upon the level of P in soil solution. They felt
that the biological system was the controlling factor and that the
inorganic chemical system was secondary in importance. After water-
logging a series of soil samples and administering antibiotics to
quench the biological system, 10 out of 12 of the soil samples showed
an increase in P under reducing conditions; but in 4 out of 10 the
difference was less than 5%. They concluded that these results
indicated the minor influence of the inorganic reducing system upon P
levels in solution.

Shapiro (1958) showed that flooding caused an increase in P
availability. He noted that applied P was utilized more efficiently
under flooded conditions. These results held for soils high, moderate
and low in native P. His data show that the increased P availability
came from both the Fe-P and Al-P fractions but that the Fe-P fraction

was affected to a much greater degree. He proposed that the small

13

increase in Al-P availability was probably due to a chelation reaction.
The large increase in Fe-P availability was due to the reducing
conditions brought on by the addition of organic matter and flooding
the soil.

Mandal (1964) tested the effects of starch and lime on the avail-
ability of P in water-logged soil and found that water-logging a soil
only slightly increased acetic-acid soluble P with a slight decrease in
Fe-P and no change in the Al-P or Ca-P. When starch was added, however,
a considerable increase in acetic-acid soluble P and a decrease in the
Ca-P fraction occurred. He stated that the release of large quantities
of C02 formed during starch decomposition may have caused tricalcium
phosphate to convert to more soluble di- and mono-calcium phosphates.
The addition of lime caused a decrease in Fe- and Al-P, especially
Fe-P. Ca-P was increased appreciably, the effect seeming to be a
conversion from Fe-P to Ca-P upon flooding. He suggested that in acid
soils having most of their inorganic P in the ferric form liming
followed by the addition of organic matter in a few days will result in
an increase in P under water-logged conditions.

Mandal further found that after 105 days of water-logging the Al-P
fraction remained unchanged. The Ca-P fraction showed results similar
to the Al, except in very high organic matter soils where C02 evolution
was sufficiently high to be important. His data did not support the
view that the increased availability of soil P upon water-logging is
largely due to the reduction of ferric phosphate. The data on P
availability suggested that the reduction of ferric phosphates did not
occur to any great extent or that, if it did proceed, a reversion

reaction with Fe+3 in the soil occurred at almost an equal rate.

14

Patrick (1964) found that extractable ferric and ferrous forms of
Fe were very sensitive to changes in redox potential of the soil.

Ferric iron predominated at potentials above +200 m.v. and extractable
Fe was mostly ferrous below +200 m.v. At the same time, he found that
extractable P increased over threefold between redox potentials +200 and
~200 m.v. The sharp break in the phosphate release curve at +200 m.v.,
the same point at which ferric Fe began to be reduced, indicated that
the conversion of P to an extractable form is dependent upon the reduc-
tion of ferric compounds in the soil.

Broeshart, Haunold and Fried (1965) noted that flooding significantly
increased the availability of soil P in rice soils in which free CaCO3
is absent. The reduced availability of phosphates under upland conditions
was not enough to account for the reduced growth of rice under upland
conditions in their opinion. They also found that the availability of
fertilizer P was similar under reduced or oxidized conditions but that
the efficiency of use was greater under flooded conditions.

Williams and Simpson (1965), in conducting experiments on cultiva-
tion and water-logging, found that flooding for 1-2 days produced
anaerobic conditions that caused a decrease in P availability and an
increase in sorption capacity. This reduced P availability applied both
to soil P and applied P. They concluded that the decrease in P avail-
ability upon water-logging was due to the effects of certain reactions
during the water-logging treatment. Reducible metals such as Mn could
have interfered; the nature of the sorption sites may have been altered
due to Fe reduction causing P to be more tightly bound; or some of the
P sorbed could have been occluded by reprecipitation of Fe upon

restoration of aerobic conditions. They felt that the increase in $011

15

P availability upon water-logging must be due to the presence of
easily reducible ferric phosphates. Soils low in ferric phosphates
would not be expected to increase in P availability upon water-logging.

Ehiang (1968) noted that soils rich in organic matter showed rapid
lowering of Eh and increased formation of organic acids and gases upon
water-logging. Disintegration of soil aggregates and lowered Eh values
caused an increase in P solubility. These effects were more significant
in Fe-rich soils. H2, H28 and the organic acids, especially HOAc,
increased P solubility in Fe- and Al-rich soils whereas C02 increased
Ca-P solubility.

Patrick and Mahapatra (1968) and Mahapatra and Patrick (1969) showed
that the greatest change in a P fraction between a soil under flooded
conditions and under aerobic conditions occurs in the reductant-soluble
fraction. When placed under water-logged conditions, the reductant-
soluble fraction was greatly decreased indicating that the ferric oxide
coating on the P had been reduced to a soluble ferrous oxide and the P
released to the solution. The mechanism of P release in a flooded soil
may be explained by 1) reduction of ferric phosphate to soluble ferrous
phosphate; 2) release of occluded P by reduction of ferric oxide coat-
ing; 3) displacement of P from Fe- and Al-P by organic anions;

4) hydrolysis of Fe- and Al-P; and 5) anion (phosphate) exchange between
clay and organic anions. They warn, however, that resorption processes
can occur and water-logging will not always increase available P.

Furukawa and Kawaguchi (1969) submerged paddy soil samples for
2 weeks at 40 C and obtained up to a 21% decrease in organic P. This
decrease correlated well with the increase of Bray No. 2 extractable P

and was attributed to the mineralization of organic P. This increased

16
mineralization was thought to be due to the enhanced solubility of Fe
or A1 salts of inositol hexaphosphoric acid, the prominent organic P
constituent, by reducing conditions or pH increase and rapid hydrolysis
accompanying submergence.

Chakravarti and Ghoshal (1968) mixed two acid soils with 50% dried
grass and each of the following treatments: 1) Fe-P; 2) Al-P; or 3) Fe
and Al-P. Then they water-logged and incubated the samples at room
temperature for 53 days. The amount of P released was found to be
greatest in the Fe phosphate treatment followed by Fe and A1 phosphate
treatment, Al phosphate and the control in decreasing order.

Terman, Allen and Engelstad (1970) conducted a greenhouse pot
experiment with flooded rice on a soil which was low in available P for
upland crops. Marked yield responses by rice to applied P were obtained,
but maximum yields were obtained at much lower rates of applied P than
was true for most upland crops. Response to applied P decreased with
liming of the soil and with increasing levels of acid-soluble soil P.
Granular, water-soluble sources of P were most effective. The P in
Fe-P was more available than that in Al-P in the flooded soil. Both
forms were more available in fine particles than as granules and in
colloidal form rather than fine crystals.

Mandal and Das (1970) studied the transformation of applied water-
soluble phosphate in three acidic lowland rice soils and stated that
the amount of added P remaining in solution in equilibrium with the
soil declined sharply in all three soils but the rate at which it
declined was found to be influenced more by the Fe203 and active iron
content of the soils than by the pH of the soils. The solid-bound P

fraction in the treated soils showed practically no increase over the

17
untreated ones. The aluminum phosphate fraction in the treated soil,
however, showed a marked increase over the untreated one in all three
soils. The magnitude of increase appeared to be influenced by Fe203
and active iron content, rather than by the pH of the soils. The
calcium phosphate fraction showed little increase in all the soils with
application of phosphate. Reductant-soluble iron phosphate showed
significant increase only on one soil which was comparatively rich in

Fe203 and active iron.

MATERIALS AND METHODS

This study was conducted in a greenhouse by growing rice on eight
Michigan soil series.
I. Materials

a. Rice: Oryza Sativa Linn. Japonica type, Nato variety.

 

b. Fertilizer:

 

l) N as (NH4)ZSO4 (1.414 gm (100 ppm N) per pot)
2) K as KCl (0.5727 gm (100 ppm K) per pot)

3) P as Ca (HZPO (1.052 gm (100 ppm P) per pot)

4’2
4) Micronutrients:

Cu804'5H20 0.0240 gm/l (6.4 ppm Cu)

Zn 804'7H20 0.0296 gm/l (6.5 ppm Zn)

H3803 0.1860 gm/l (37.0 ppm B)
(NH4)6M0702'4H20 0.0035 gm/l (1.9 ppm Mo)
CoClz 0.0028 gm/l (0.6 ppm Co)

The micronutrients were made up to a 1000 ml solution with dis-
tilled water and 6 ml of this solution added to each pot after flooding.
c. Type and location of soil samples
Michigan soils (Table l) were selected to give a
variation in chemical properties such as pH, organic matter content,
amount of Fe and Mn and physical characteristics including drainage

and texture which ranges from sandy loam to clay soil.

18

19

Table 1. Soil series and location of soils studied.

 

 

Soil series Drainage Texture Location

1. St. Clair well drained clay T23,RTE SE%ofSE%ofNE%ofSZ

2. Hoytville poorly drained clay T9N,R1W NE%ofNE%ofNE%ofSl8
3. Morley well drained clay loam Tls,R5E swgofswkofNWkofSZB
4. Sims poorly drained clay loam T9N,R3E NW%ofNWkofNEkofS33
5. Miami well drained loam T4N,R1W SE%ofSE%ofSW%ofS30
6. Conover poorly drained loam T4N,R1W SE%ofSE%ofSE%ofSl9
7. Hillsdale well drained sandy loam T4N,R1W NE%ofNE%ofSE%ofSl9
8. Locke poorly drained sandy loam T4N,R1W NE%0fSE%ofSE%ofSl9

 

Both surface soil (Horizon A) and subsoil (Horizon B) were collected
from eight soil series. The detailed soil characteristics are given in

the soil profile description in Table 1a of the Appendix.

II. Methods

1. Greenhouse work

 

a. Soil preparation:

 

Soil samples were air dried in the greenhouse for
1-3 days until their moisture content became satisfactory for screening.
Each sample was passed through a 2 mm sieve and air dried. Three
thousand grams of each prepared soil sample was weighed out and placed
in a l-gallon can with a plastic liner.
The treatments were as follows:

Can No. 1 mixed with NR and did not grow rice.

Cans No. 2, 3, 4 mixed with NR and rice grown.

Cans No. 5, 6, 7 mixed with NPR and rice grown.

There was a total of 112 cans for the 16 soil samples.

20

2. Flooding the soil

 

After the fertilizer treatments were added to each soil,
each pot was flooded with distilled water. Six m1 of micronutrient
solution was added to each pot about 2 weeks before transplanting rice
seedlings. The level of water was maintained at about 6 cm above the

soil surface.

3. Preparation of rice seedlings

 

RiCe seeds were germinated in a flat of water-saturated
sand and kept in a greenhouse for 2 weeks until they became 10-15 cm
high. Then 3 rice seedlings were transplanted to the previously flooded
soil in each can.

masses

At 3-week intervals, both soil and water samples were
collected for laboratory analysis. The soil samples were taken with a
1 in diameter tube and kept in covered polyethylene cups. Water samples
were taken by pipet and kept in sealed glass bottles.

b. Analytical Methods

The moisture content of the soil samples of each can was
determined for calculation of the oven-dried soil used in each chemical
analysis.

Before flooding the soil pH, redox potential and content of
organic matter, Mn, Fe, and P were determined.

Redox potential, pH, Mn, Fe and P content were determined for
all samples (both soil and water) collected after flooding.

l. Exchangeable Fe+2 analysis

Exchangeable Fe+2 is not completely extracted from a

soil by neutral NH40Ac in the usual procedure for exchangeable cations

21

+3 during the extraction and much of it

because Fe+2 is oxidized to Fe
then precipitated.

From a freshly collected soil sample, field moisture conditions
unchanged, an equivalent to 5 gm of oven-dried soil sample was quickly
weighed out, placed in a 150 ml Erlenmeyer flask and 50 m1 neutral

IN NH OAc solution added. The suspension was shaken vigorously for

4
30 seconds and quickly filtered through a previously prepared Buchner
funnel fitted with filter paper. Three successive 10 ml portions of

neutral lN NH4OAc solution were employed for further extraction of the
soil. The entire extraction was completed in 5 minutes or less. The
quantity of Fe in the filtrate was determined by use of a Perkin-Elmer

Model 303 atomic absorption spectrophotometer.

2. Extractable Mn

 

Saturated CaSO4 solution was used to extract Mn from the
soil. An equivalent of 5 gm of oven-dried soil sample was shaken in
25 m1 of saturated CaSO4 for 15 minutes. The solution was filtered and
Mn content of the clear filtrate determined on a Perkin-Elmer Model 303
atomic absorption spectrophotometer.

3. Redox potential andng analysis

The redox potential and pH of the samples were measured
by using a Sargent Model DR pH meter. A glass electrode and a saturated
calomel electrode were used to obtain pH measurements. A 1 cm2 bright
Pt electrode was used along with a saturated calomel electrode to
measure redox potential. The ratio of soil and distilled water was
1:1 (10 gm of oven-dried sample to 10 m1 of distilled water) and pH was
measured after stirring for 30 minutes.

4. Available P analysis

Three extracting solutions were utilized in this study

for soil samples both before and after flooding.

22

(a) Dilute acid-soluble P of soils (Truog’s solution)
An equivalent of 1 gm of oven-dried soil was
weighed and placed in 100 ml of the buffered 0.0023 H2804 extracting
solution. The suspension was shaken for 30 minutes and immediately
filtered through a retentive P-free filter paper. Then the clear
filtrate was analyzed for P content by the molybdenum blue color
reduction method.

(b) Dilute fluoride--Dilute acid-soluble P (Bray's

 

extraction solution)

 

An equivalent to 2.85 gm oven-dried soil sample
was weighed out into a 125 ml Erlenmeyer flask. Then 10 ml of 0.03M
NH4F in 0.25M HCl extracting solution was added and the suspension was
shaken for 60 seconds. The suspension was immediately filtered and the
clear filtrate retained for P determination.

(c) Hydroxyl and carbonate extractable phosphorous of
soils (Olsen's extracting solution)
An equivalent to 2.5 gm of oven-dried soil sample
and 1 teaspoon of P-free carbon black (Davco activated carbon G-60,
washed with -IH.HC1) was suspended in 50 ml of 0.5M NaHC03 extracting
solution with pH 8.5. The suspension was shaken for 30 minutes,
filtered and the clear filtrate retained for P analysis.

d. Color Development

 

2.1 Chlorostannous Reductant in a Sulfuric System Method
Chlorostannous-reduced phosphomolybdic blue in a
sulfuric system and 1,2,4-amino naphthal sulfonic-reduced phosphomolybdic
blue color method, in a perchloric acid system were utilized in this

study (Jackson, 1965). The heteropoly complexes are thought to be

formed by coordination of molybdate ions with P as the central

23

coordinating atom. These heteropoly complexes are slightly yellow but
appear colorless in lower concentration. The addition of a reducing
agent will bring about a reduction in the phosphomolybdic complex
yielding a blue color that can be measured colormetrically at 660 mph
The concentration of P, molybdate ion, pH and reductant must be care-
fully controlled to take advantage of a narrow region where only the
heteropoly complex is reduced and not the excess or an appreciable
amount of interfering ions such as arsenic.

The chlorostannous-reductant molybdophosphoric blue color method
in a sulfuric acid system has the highest sensitivity per unit of P
present, providing a working range from 0.02 to 0.6 ppm of P. It pro-
vides for noninterference of Si in solution up to 200 ppm, Fe++ up to
100 ppm, Fe+H up to 2 ppm, Ti up to 20 ppm, Ca and Mg up to 500 or
more ppm, N03- up to 100 ppm, F up to 5 ppm, C1 up to 250 ppm, 804-
up to 1000 ppm--but it includes arsenate in chemical equivalence to P.
This method was used to determine P in water samples and in the fil-
trate of soil before flooding.

Twenty-five ml of centrifuged water sample or the filtrate of
soil sample is placed in a 50 m1 volumetric flask and 2-4 drops of
2,4-dinitrophenol indicator added and pH adjusted with 2N H2804 or
2N Na2C03 until 1 drop of 2N Na2C03 produces a yellow color (pH about
3). Two ml of 2.5% sulfomolybdic acid solution is added and the sample
diluted nearly to volume with distilled water and thoroughly mixed.
Then 0.2 m1 of 0.1g SnClz is added to develop the color. The sample
is diluted to 50 ml with distilled water. After 5 minutes, but not

later than 10 minutes, the color is read photometrically on an Evelyn

photoelectric colorimeter at 660 ml/(filter).

24

2.2 1,2,4-Aminonaphtholsulfonic Acid Reductant in

 

Perchloric System Method

 

The l,2,4-aminonaphtholsulfonic acid-reduced molybdo-
phosphoric blue color method in perchloric acid system is about
one-sixth as sensitive as the above method with the standard curve
ranging from 0.4 to 2.4 ppm of P. The chief advantage of this method
is that 200 ppm of ferric iron will not interfere with the development
of the blue color. Thus, it is well suited to the determination of
total P of soils following perchloric acid digestion of the sample.

The iron gives the solution a greenish cast, but that effect is
eliminated by the light filter. Ti and V do not interfere nor does Mg
from the magnesium nitrate ashing procedure. Silica and nitrate are
eliminated by HC104 predigestion. This method was utilized for P
determination on flooded soils.

An aliquot of 5-25 m1 of filtrate is pipeted into a 50-volumetric
flask. The pH is adjusted to 3 with 2N HClO4 or 2N NaZCO3, 2,4 dinitro-
phenol being used as an indicator. Then 5 ml of 60% HClO4 is added and
the solution volume is adjusted approximately to 40 ml. The solution
is thoroughly mixed after each successive reagent is added. (The
temperature is maintained at 25 C I 4 C throughout the color develop-
ment.) Next 1.6 m1 of 1,2,4-aminonaphtholsulfonic acid reagent is
added. (Reductant reagent is recrystallized l,2,4-aminonaphtholsulfonic
acid, Eastman Kodak Co.). Exactly 15 minutes before the colorimetry
reading 4.0 m1 of the ammonium molybdate solution is added. The volume
is quickly adjusted to 50 ml with distilled water. At the end of
15 minutes, optical density is read with a 660-mfllight maximum on an

Evelyn photoelectric colorimeter. For F extractable P of soil, H3B03

25
is added in the ammonium molybdate solution to remove F interference in

the molybdenum blue color reaction.

- +—) -
4F + H3303 + 3H (— (BF4) + 31120 (1)

RESULTS AND DISCUSSION

Yield of Rice

 

Soil type had relatively little influence upon the oven-dry
weight of rice plants except that the A horizon of the Sims and the
B horizon of the Locke were exceptionally high yielding (Table 2).
Both soils are poorly drained with high quantities of available P.

In general, the yield of rice per pot from A horizons was greater
than that of B horizons. But the locke soil was an exception.

There was no response to P application on rice yield for A
horizons except in the Locke soil. Without P application the A
horizons yielded much more than the B horizons except for the Locke
soil. A significant response to P fertilization of B horizons was
obtained. Indeed, this response was often dramatic; for example, in
the St. Clair B, NK yield was 1.33 g as compared to 18.67 for NPK.

There was little difference between yield of rice from A and
B horizons after P fertilization. The greater P response with B
horizons is associated with lower native contents of available P
(Table la, Appendix).

The relationship between the amount of extractable P of the soil
samples before flooding determined by Bray's No. 1, Olsen's and
Truog's methods and the yield of rice was examined by plotting the

relative yield against the amount of extractable P (Figures 1, 2 and

3).

26

27

The relative rice yield was defined as:

yield of rice of NK treatment .
yield of rice of NPK treatment

 

The relationship between P extracted by Truog's method and rice
yield (Figure 3) is very poor. But the Bray No° l-P and Olsen P were
related to the yield of rice. The soils with Bray No. l-P and Olsen P

at the level of 10 ppm or lower responded to P fertilization (Figures 1

 

 

 

 

 

and 2).
Table 2. Yield of greenhouse rice as influenced by soil type, horizon
and P level.
Yield of rice (gm/pot)
Soil Type Horizon NK1 NPK1 Averages
A B (A and B)

St. Clair A 20.67 18.67 19.7 14.8
B 1.33 18.67 10.0

Hoytville A 18.17 19.50 18.8 14.5
B 2.00 18.33 10.2

Morley A 15.50 16.17 14.2 13.8
B 8.67 17.83 13.2

Sims A 23.17 24.00 23.6 19.0
B 10.33 18.50 14.4

Miami A 16.00 16.17 16.1 14.5
B 9.50 16.17 12.8

Conover A 16.33 19.33 17.8 14.4
B 4.33 17.66 11.0

Hillsdale A 14.66 14.50 14.6 13.6
B 9.33 16.17 12.8

Locke A 11.83 19.50 15.7 17.4
B 19.00 19.33 19.2

Average A 17.00 18.48 17.56 15.25
B 8.06 17.83 12.95

Averagg, A & B 12.53 18.16 15.25

 

Soil Type (A&B)
3.363 gm
4.391 gm

Treatment (NK, NPK)
L.S.D. 0.05 3.330 gm
0.01 4.474ygm

Average (A, B)
2.945 gm
4.058ygm

1Each value is an average of 3 replications.

Relative yield of rice

llOr" 0A

100 t‘

 

0w
9
TD

90 '

 

50 '

GB
40 '-
30 '

20 ~-

 

 

Bray P-l before flooding (ppm)

Figure 1. Relationship between Bray P-l phosphorus and relative yield
of rice.

—28-

Relative yield of rice

100

90

80

70

60

50

40

30

20

10

 

 

 

 

0A
B
~
.013
l l l l f
10 20 30 40 50
Olsen's sodium bicarbonate P before flooding (ppm)
Figure 2. The relationship between Olsen's sodium bicarbonate extract-

able phosphorus and relative yield of rice.

-29-

Relative yield of rice

110

100

90

80

70

60

50

40

30

20

10

F (3A

(3A

In OB

 

I l l l l J
20 40 6O 80 100

Truog's weak sulfuric acid P before flooding (ppm)

Figure 3. The relationship between Truog's weak sulfuric acid extract—
able phosphorus and relative yield of rice.

-30-

31
Chemical Chapges in Soil Water After Flooding

The pH of soil samples before flooding ranged from 4.60-6.76.
After flooding, the pH of the soil water generally increased during the
first 3 weeks and then stabilized (Table 2a, Appendix). The increase
in pH was of the order of 1 pH unit or a lO-fold decrease in hydrogen
ion concentration. The control pots without plants were not greatly
different from those containing rice plants with or without P fertiliza-
tion indicating that the growing plant had relatively little influence
upon the soil water pH.

Soils with lower initial pH values showed much more buffering
capacity than soils with higher initial pH values. For example, in the
B horizon of the Morley soil (pH 4.6), the pH value was rather constant
throughout the experiment. This may be due to the fact that in acid
soil an equilibrium exists between H and Al. In soils with low pH's,
as in Sims B with soil (pH 4.6), much of the Al may be present as
hexahydrated A1+3 ions (Seatz and Peterson, 1967). This complex ion
would 3Ct as strong buffering components in the acid soils.

The Eh of the soil samples before flooding ranged from 525-696 m.v.
Generally the Eh of the soil water samples dropped markedly from the
original Eh values after 3 weeks of flooding (Table 3a, Appendix).
After that the redox potentials of the soil water decreased slightly
with time. The Eh of soil water from the A horizons was lower than
that of the B horizons. This may be due to the greater activity of
microorganisms associated with the higher organic matter content in the
A horizons than that in the B horizons. In some soils the redox
potential showed some fluctuation. This may be due to many factors.

It has been suggested that the redox system in flooded soils would be

32

generated by the bacterial metabolism and/or activated by enzymes
giving rise to the name ”bacterial potentials” (The International Rice
Research Institute, Annual Report, 1965). This bacterial potential may
fluctuate due to the condition of the system. The P application did not
appear to affect Eh when compared to the control (Table 3a, Appendix).
The amount of P in water samples was very small when compared to
the amount of P in the soil samples before flooding (Table 4a, Appendix).
Even in the soils with high P contents such as Sims A, Hillsdale A and
Locke A and in P application treatments, the amount of P in the water
samples was less than 1 ppm. This shows that the rate of P fixation or
precipitation with active cations in the soils is much greater than the
rate of P liberation from the soil into the water sample. This occurs
because the available forms of P (HPOA-Z, H2P04-1) are easily fixed in
the soil with active cations of Fe, Al, Mn and Ca. In acid soils, there
is an enhancement in the activity of Fe, A1 and Mn. Under such condi-
tions soluble P is markedly fixed as very complex and insoluble compounds
of these elements. At pH's above seven, the complex and insoluble

calcium phosphates are formed. It was noted that the amount of P in

water samples decreased with time after flooding. This may be due to
plant uptake and recrystallization of P in the soil.

Only a small fraction of the exchangeable Mn was found to be water
soluble (Table 5a, Appendix). Generally the amount of water-soluble Mn
in soil water samples decreased with time after flooding. But in
Morley A and Miami A soils the amount of water-soluble Mn was increased
after 3 weeks of flooding and maintained a high level until 6 weeks,
after which the amount of water-soluble Mn in water samples decreased

with time. P application showed little effect on the amount of Mn in

the water samples.

33

The amount of water-soluble Fe in the soil water of all soils was
very small (Table 6a, Appendix). In some soils the amount of water-
soluble Fe increased after 3 weeks of submergence, for example, Morley A,
Sims A, Miami A and Locke A. But after that it decreased with time. In
Hoytville B, Morley A and Sims B, the amount of water-soluble Fe could
not be detected after 15 weeks of flooding. This shows that the rate of
Fe released into the soils is very slow. The decrease of water-soluble

Fe with time may be due to reprecipitation of Fe and/or plant uptake.
Chemical Change in the Soil After Flooding

The pH of most soils increased about 1 pH unit after 3 weeks of
flooding and reached a maximum value about 6 weeks of submergence, after
which it stabilized throughout the experiment. Soils with lower initial
pH values, for example in Morley B (pH 4.60), St. Clair B (pH 5.30) and
Hillsdale B (pH 5.20), had higher buffering capacities and pH values
were relatively stable after flooding. The reason for this was given in
the prior section.

Generally the amount of hydrogen ion concentration decrease in the
A horizons after flooding was greater than that of B horizons, for
example, the Locke A soil increased from pH 6.00 to about pH 6.80 when
compared to Locke B soil which increased from pH 6.29 to about pH 6.53
after 3 weeks of flooding (Table 7a, Appendix).

The P application showed no effects on pH change when compared to
control (no rice plants) and no P application treatment.

The redox potential of A horizons of the soils before flooding was
slightly lower than that of B horizon.

After flooding, the Eh of all soils decreased remarkably. The

redox potential of A horizons of all soils decreased more than that of

34

B horizons, for example, in the Hoytville A the Eh dropped approximately
400 m.v. whereas the Eh of the B horizon dropped only about 150 m.v.

In general Eh of A horizons decreased about 200-500 m.v., and the Eh of
B horizons dropped approximately 150-300 m.v. This may be due to more
reduction reactions in A horizons associated with higher organic matter
content. This is called bacterial potential of the soil system. In
some soils the Eh decreased until the redox potential reached the
maximum about 36 weeks after submergence, and then they increased
slightly afterwards, e.g., Miami A and Morley A soils. But in most
soils the Eh decreased rapidly within 3 weeks and remained rather con-
stant afterwards. P fertilization has no effect on Eh changes after
flooding when compared to the controls. It was noted that the Eh of
soils with lower pH values and higher buffering capacity, such as

St. Clair B, Morley B and Hillsdale B, did not decrease much after
flooding.

Generally, the amount of Mn increased more in the A horizons than
in the B horizons, e.g., in St. Clair A the amount of extractable Mn
increased about 30-fold, whereas in St. Clair B the amount of extract-
able Mn increased only about 4-fold from the original extractable Mn.
Even in Morley soil the original extractable Mn of the B horizon was
greater than that of A horizon (16 ppm compared to 1.6 ppm), but the
amount of extractable Mn increased only 6-fold whereas in A horizon the
amount of extractable Mn increased approximately 80-fold. The result
showed that there were stronger reducing conditions in the A horizons
than in the B horizons associated with higher inorganic matter content
and also higher microbial activities in A horizon.

The amount of extractable Mn increases generally reached their

maxima within 3 weeks and after that they decreased slightly with time

35

or held constant in some soils, e.g., in Hoytville A the amount of
extractable Mn in the soil stabilized at 3.5-5.5 ppm throughout the
experiment. P fertilization showed no effect on the increases in the
amount of Mn due to flooding.

The amount of 1N NH4OAc extractable Fe in the soils before flooding
was very small and ranged from less than 1 ppm to about 1.5 ppm. The
amount of extractable Fe in B horizons was slightly greater than that
of A horizon (Table la, Appendix).

The amount of extractable Fe in some soils increased greatly after
flooding, e.g., in Hoytville A the amount of extractable Fe before
flooding was 0.29 ppm and at 6 weeks of submergence the amount of
extractable Fe was about 60 ppm. The amount of extractable Fe increase
reached the maxima about 6 weeks of flooding and held rather constant
afterwards. In general the amount of extractable Fe in A horizons
increased more than that of B horizons, e.g., in St. Clair A the amount
of extractable Fe increased from the original of 0.29 ppm to about
12-14 ppm, whereas in the B horizon it increased from the original of
1.48 ppm to about 4-9 ppm after 6 weeks of flooding. This may be due
to more anaerobic metabolism in A horizons than in B horizons associated
with higher inorganic matter content. It was noted that in the Sims A
and Hillsdale A the amount of extractable Fe in control pots without
rice plants was greater than that in no P and P application treatments.
This showed that growing rice plants were able to reduce the quantity of

available Fe in the soils.

Transformations of Soil P After Flooding

 

During submergence the soil studies all increased in available P as

measured by plant growth and 3 chemical extractants. The soils before

36

flooding can be divided into 2 groups based on the amount of P
extracted by Bray P-l: those containing l.3-7.9 ppm P and those con-
taining 37-58 ppm P. The amount of native P extracted by Bray P-l from
A horizons was generally greater than that extracted from B horizons
except for the Locke soils.

After flooding the amount of Bray P-l in the soils increased
considerably due to the reducing conditions, e.g., the Morley A in-
creased from 6.5 ppm to about 90 ppm and the Marley B increased from
3 ppm to about 77 ppm. The amount of Bray 1 extractable P of A
horizons increased more than that of B horizons, for example, in
Miami A the amount of extractable P increased from 4.8 ppm to 95.6 ppm
in the control (no rice plants). This may be due to the higher amount
of native P and organic matter in A horizons. The amount of extract-
able P increased due to flooding, reached a maxima in 3-6 weeks, after
which it decreased orderly and dropped to about one half of the maximum
value at 15 weeks of submergence. This may be due to recrystallization
of P, assimulation by microorganisms and/or plant uptake. P application
increased the amount of P extracted by Bray P-l in the soils. For
example, in Hillsdale A with a high level of native P initially
(57.9 ppm) the amount of Bray P-l increased to a maximum of 109, 99 and
135 after flooding in control (no P and no rice plants), NR and NPR
treatments, respectively. In the Hillsdale B with lower native P
(5.2 ppm), the amount of Bray P-l increased due to flooding to 56 ppm
in control, 55 ppm in NK treatment and 203 in the application treatment
at the maxima.

Soils high in extractable Fe showed relatively little increase in

P due to flooding compared to the soils lower in extractable Fe. For

37

example, in Hoytville A where extractable Fe at the maxima was about
50-55 ppm, the amount of P extracted by Bray P-l increased from

7.47-17 ppm in control, 59 ppm in NR and 61 ppm in NPK treatments; in

the Hoytville B, with 6 ppm of extractable Fe at maxima after flooding,
the amount of P extractable by Bray P-l increased from 2.94 ppm to

89 ppm, 77 ppm and 86 ppm in control, NR and NPR treatments, respectively.

There appeared to be little relationship between extractable Mn,
pH or Eh and extractable P.

There was no relationship between the amount of native P by Bray's
method before flooding and the amount of Bray P-l after flooding
(Figure 4), even though a large increase in extractable P occurred upon
flooding.

Extractable P by both Olsen's and Truog's methods showed a good
relationship between initial P and P after 3 weeks of flooding. In
Olsen's the increase was about 40%, whereas Truog's P increased more
than 100% after flooding.

The pattern of P release by flooding as measured by Truog's
extraction was similar to that measured by Bray's P-l in that it
increased sharply, reached a maximum in 3-6 weeks and then steadily
declined at 15 weeks. The quantity of P released, however, was much
larger than in the case of Bray's P-l. It was large enough to suggest
release of organic P. P extracted by sodium bicarbonate (Olsen's)
increased to a maxima in about 3 weeks and remained constant throughout

the study.

80

60

40

20

 

 

O
O
O
b
0.—
00 00°
0
109.0419110111.
0 20 40 60 80 100
P after 3 weeks flooding (ppm P)
Figure 4. Bray P-l extractable phosphorus initially and after three weeks'

flooding.

-38—

P before flooding (ppm)

100

90

80

70

60

50

40

30

20

10

r
(y. 0

C)
C)
5'0/c>°o|.111.1.a

 

0 10 20 30 40 50 60 70 80 90 100

P after 3 weeks flooding (ppm)

Figure 5. Olsen's sodium bicarbonate extractable phosphorus
initially and after three weeks' flooding.

-39-

P before flooding (ppm)

Hoo

mo

00

no

No

 

 

 

.
t
I O
O

n — n — b — u — . bu - Lt

o No no 00 mo woo Hmo who woo Hmo moo mmo who
w mmnmu u amme mHooawsm Acvav

mwmcwm m. chom.m 2mm? mchcuwn moan mxnumnnmcpm wromeOHCm HownmeH% man mmnmu nrumm

Smmwm. mHoomHDN.

SUMMARY AND CONCLUSIONS

Eight Michigan soils ranging from loamy sand to clay with both
poorly and well-drained soils of each texture and with high and low
nature P were selected to study in the greenhouse. Rice seedlings were
planted in NR and NPR pots of 3 replications. Also, a control pot (NK)
with no rice was maintained. Soil samples before flooding and soil and
water samples after flooding were taken at 3-week intervals and analyzed
in the laboratory. Yield of rice was determined at the end of the study.

The following conclusions were drawn:

1. Rice did not respond to P application in A horizons.

2. There was a marked response of yield of rice to P fertilization
in B horizons.

3. Relative yield of rice was related to either Bray's P-l or
Olsen's sodium bicarbonate extractable P where soils containing less
than 10 ppm P before flooding responded to P fertilization. P extracted
by Truog's weak sulfuric acid was not related to relative yield of rice.

4. There were large chemical changes due to flooding.

a. pH of the soil increased about 1 pH unit except in
soils whose initial pH was lower than 5.30. In the latter, pH changed
slightly due to flooding.

b. Eh decreased remarkably due to flooding except in soils
with high acidity (pH about 4.2-5.3).

c. The amount of exchangeable Fe and Mn increased consider-
ably after flooding, reached the maxima at 3-6 weeks, after which they

41

42

decreased slightly with time. Fe remained more constant after reaching
the maxima than Mn.

d. The amount of extractable P by Bray l, Olsen's and
Truog's methods increased considerably due to flooding. The quantity
of Truog's increase was much more than Bray's P and Olsen's P. Olsen's

P and Truog's P showed good relationship between initial P and P after

flooding.

BIBLIOGRAPHY

BIBLIOGRAPHY

Broeshart, H., Haunold, E. and M. Fried. 1965. The effect of water
conditions and oxidation-reduction status of rice 80118 on the
availability of soil and fertilizer phosphate. Plant and Soil
23:305-313.

Chakravarti, S. and T. K. Ghoshal. 1968. Anaerobic reduction
phosphate solubility. J. Indian Soc. Soil Sci. 16:409-413°

Chiang, Ching-Tsun. 1968. Availability and forms of phosphorus in
paddy soils: V. factors affecting the solubility of soil
phosphorus. Taiwan Fertilizer Co., Ltd., Res. Bull. No. 30.
pp. 11-37.

Furukawa, H. and K. Kawaguchi. 1969. Contribution of organic
phosphorus to the increase of easily soluble phosphorus in
water-logged soils, especially related to phytic phosphorus
(inositol hexaphosphate). Nippon Dojo-Hiryogaku Zasshi 40:141-148.

Gasser, J. X. R. 1956. The effects of anaerobically fermenting rice
straw on the mobilization of aluminum, calcium and iron phosphate.
6th International Cong. of Soil Sci., Vol. C, pp. 479-491.

Grist, D. H. 1965. Rice. Longmans, Green and Co., Ltd. London.

Guidry, N. P. 1964c A graphic summary of world agriculture. Misc.
Pub. No. 705, U.S.D.A., U.S. Govt. Printing Office, Washington,
DOC. pp. 21-25.

Hayes, F. R. and J. E. Phillips. 1958. Lake water and sediment: IV.
radiophosphorous equilibrium with mud, plants and bacteria under
oxidized and reduced conditions. Limnology and Oceanography 3:
459-475 0

Jackson, M. L. 1965. Soil chemical analysis. Prentice-Hall, Inc.,
Englewood Cliffs, N.J. U.S.A.

Jeffery, J. W. O. 1961. Defining the state of reduction of a paddy
soil. J. of Soil Sci. 12:172-179.

. 1961. Measuring the state of reduction of a paddy soil.
J. of Soil Sci. 12:317-325.

Mahapatra, J. C. and W. H. Patrick, Jr. 1969. Inorganic phosphate
transformation in water-logged soils. Soil Sci. 107:281-288.

43

44

Mandel, L. N. 1964. Effect of time, starch and lime on the
transformation of inorganic P in a water-logged rice soil. Soil
Sci. 97:127-132

Mandal, L. N. and R. K. Das. 1970. Transformation of applied water
soluble phosphate in acidic lowland rice soils. Soil Sci. 10:
263-267.

Mukhopadhyay, A., Fisher, T. R. and G. E. Smith. 1967. Submergence
and liming effects on soil: 1. changes in pH, Eh and manganese
uptake by rice plants. Soil Sci. 104:107-112.

Patrick, W. H., Jr. 1964. Extractable iron and phosphorus in a
submerged soil at controlled redox potentials. 8th International
Cong. of Soil Sci. Bucharest, Rumania. pp. 605-609.

Patrick, W. H., Jr. and I. C. Mahapatra. 1968. Transformation and
availability to rice of nitrogen and phosphorus in water-logged soils.
Advances in Agron. 20:323-359.

Ponnamperuma, F. N. 1964. Dynamic aspects of flooded soils. The
mineral nutrition of rice plants. The International Rice Res.
Institute. The John Hopkins Press, Baltimore, Maryland. U.S.A.
pp. 295-328. .

Ponnamperuma, F. N. and R. U. Castro. 1964. Redox systems in sub-
merged soils. 8th International Cong. of Soil Sci. Bucharest,
Rumania. pp. 107-109.

Ponnamperuma, F. N., Tianco, E. M. and T. Loy. 1967. Redox equilibria
in flooded soils: I. The iron hydroxide systems. Soil Sci. 103:
374-382.

. 1969. Redox equilibria in flooded soils: II. The
manganese oxide system. Soil Sci. 108:48-57.

Robinson, 0. W. 1930. Chemical phase of submerged soils. Soil Sci.
30:197-217.

Seatz, L. F. and H. B. Peterson. 1970. Acid, alkaline, saline and
sodic soils. Soil Chemistry. Amer. Chem. Soc. Monograph Series,
New York. pp. 293-295.

Shapiro, R. E. 1958. Effect of flooding on availability of phosphorus
and nitrogen. Soil Sci. 85:190-197.

Takkar, P. N. 1969. Effect of organic matter on soil and manganese.
Soil Sci. 108:108-112.

Terman, G. L., Allen, S. E., and 0. P. Engelstad. 1970. Response by
paddy rice to rate and sources of applied phosphorus. Agron. J.
62:390-394.

45

The International Rice Research Institute. 1963. Soil Chemistry.
IRRI Annual Report. Los Baunos, Laguna, The Philippines.
pp. 61-86.

U.S.D.A. 1969. Agricultural Statistics. 1969. U. S. Govt.
Printing Office. Washington, D.C. U.S.A. pp. 21-35.

Williams, C. H. and J. R. Simpson. 1965. Cultivation and water-
logging on soil phosphorus availability. Aust. J. of Agric. Res.
16:413-427.

Yamane, I. and K. Sato. 1968. Measurement of redox potentials of
submerged soils. Nippon Dejo-Hiryogaku Zasshi 39:535-542.

APPENDIX

46

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Odmsmwo m
moww Hwbm onmwowmm Hoxncum monwmo: (w: m: zmnnmn :5 mm wnfiw.m opmms_m Hucom.m
a.<. x u:uunuu-uuauaauuu wee uuuuuuunuuuuuuunu-
mn. onwH amHH anmwoma on< b m.om mom u.~o u.oo o.~o u.oo HH.m~ HH.~
w m.vo moo .mo N.bu H.om N.oo H.oH Hw.N
mo<n<HHHm booupw aflmwsma onw > o.mo moo b.oo o.mo o.~o u.bu b.bm mw.o
w o.um mwm .Nm o.uo o.ob H.uo u.~H bo.u
zonwmw amHH anmwoma owmw Home > o.um woo u.oo H.mo 0.9» o.bo ~.mm Ho.o
w b.mo moo .mm Ho.m H.Hu N.ob b.9u NN.H
mHBm voonww anmwoma nwow Homa > m.Nw moo o.uu o.mo o.No wo.m bN.w www.w
w o.wb mum .ou o.m~ o.mo ~.mo H.uo mo.m
zwwsw amHH anmwsma Home > o.bm mob N.mb H.9m o.mo b.um u.m~ Hu.m
w m.mm mow .bm H.~o o.mo N.mu b.Hm m.o~
nooo<mn boouww aHmHSma Homa > o.mo mmo u.~m N.mo o.mo u.oo Ho.Nm No.H
w 0.0» mum .oo H.bo 0.9a N.NH N.oo uo.o
mHHHmamHm amHH anmwnma mmsow Home > m.mN mom p.00 u.~b o.ub mu.o No.0 uw.o
w w.~o moo .bH o.om o.ab m.~o o.m~ oo.m
roman ooouww anemone manna Home > o.oo woo N.VN H.wo o.Hm bw.u no.» ob.u
w o.~o wow .bo o.m~ o.~o w.bu m.bu uu.o

 

47

 

 

 

 

Table 2a. Soil-waterng with time after flooding.
Initial Time after flooding (weeks)
Soil Type Treatment Soil pH 3 6 9 12 15
---------------- p 27------—---------
St. Clair C 5.95 6.92 7.69 7.35 8.26 8.01
A NK 6.84 7.74 7.10 8.12 7.73
NPK 6.88 7.83 7.36 7.56 8.10
St. Clair C 5.30 6.00 4.37 4.48 4.84 4.77
B NK 5.71 4.36 4.52 4.91 5.22
NPK 5.68 4.19 5.14 6.43 6.34
Hoytville C 6.50 6.95 8.38 7.50 8.11 8.08
A NK 7.24 8.39 7.69 8.30 8.23
NPK 7.42 8.57 7.77 8.39 8.55
Hoytville C 6.76 7.04 8.17 7.94 8.14 8.08
B NK 6.96 8.11 8.00 8.06 8.23
NPK 7.11 7.60 7.67 7.99 8.06
Morley C 6.38 7.16 7.99 7.58 7.84 8.15
A NK 6.83 7.33 7.69 7.98 7.60
NPK 7.03 8.14 7.36 7.64 7.65
Morley C 4.60 4.70 4.90 4.18 4.18 4.75
B NK 4.78 4.92 4.04 4.74 5.05
NPK 5.63 5.38 5.33 6.11 6.45
Sims C 6.23 7.10 8.41 7.05 8.15 8.30
A NK 7.05 8.31 7.18 7.68 7.83
NPK 7.58 8.19 7.14 7.43 7.83
Sims C 6.54 6.60 7.97 8.17 8.12 8.11
B NK 6.80 8.30 7.91 8.01 7.95
NPK 6.64 8.13 7.68 8.15 8.09
Miami C 6.48 7.65 7.73 8.08 8.26 7.31
A NK 7.49 7.81 7.81 8.10 7.64
NPK 7.89 8.37 7.81 8.05 7.65
Miami C 6.52 6.85 7.33 6.68 7.15 6.65
B NK 7.56 7.16 7.16 7.63 7.53
NPK 7.84 7.62 7.31 7.73 7.74
Conover C 6.50 7.60 7.40 8.08 8.31 8.42
A NK 7.36 8.20 7.81 8.10 7.90
NPK 7.16 8.17 7.54 7.95 8.18
Conover C 6.64 6.20 7.41 8.23 8.09 8.42
B NK 6.38 7.82 8.06 8.41 7.76
NPK 6.59 7.53 7.73 7.81 8.02
Hillsdale C 5.82 5.65 7.35 8.24 7.86 7.86
A NK 5.59 7.49 7.15 7.43 7.52
NPK 6.19 7.44 7.10 7.18 7.11
Hillsdale C 5.20 6.77 6.67 4.61 4.07 3.97
B NK 6.25 5.63 4.99 5.89 5.30
NPK 5.26 4.82 6.24 6.45 6.23
Locke C 6.00 7.20 7.73 8.07 7.53 6.86
A NK 7.02 7.93 7.21 7.30 7.57
NPK 7.20 7.79 7.18 7.31 7.33
Locke C 6.29 7.30 7.91 5.59 6.09 5.91
B NK 7.39 7.62 6.98 7.17 7.36
NPK 7.20 7.56 7.32 7.07 7.77
1

NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NR and NPK are averages of 3 replications; the

value for Control (C) is a single determination.

C = Control (NK) with no plants, NR = 100 ppm N, 100 ppm K,

48

 

 

 

Table 3a. Soil-water Eh with time after flooding.
Initial Time after flooding (weeks)
Soil Type Treatment Soil Eh 3 6 9 12 15
--------------- m.v.2 ----------------
St. Clair C 545 491 443 440 427 418
A NK 497 443.3 460.3 433.6 405.3
NPK 422.7 438.6 455.7 429 401.3
St. Clair C 695 555 586 555 497 468
B NK 601.3 583 558.3 473.3 487.3
NPK 576 565 531.3 456.7 449
Hoytville C 559 500 376 435 382 378
A NK 473 386.3 444.7 394.7 393
NPK 480 376.7 440.7 406.7 406.7
Hoytville C 525 515 452 432 401 431
B NK 501.3 440 437 402 411.3
NPK 545 449 454.3 409.7 403.7
Morley C 569 535 379 449 377 414
A NK 450 416.3 457 401 410.7
NPK 395 378 471 417 417
Morley C 685 650 534 586 477 468
B NK 647.3 549 606.7 499 495.7
NPK 663 555.7 551.3 468 469
Sims C 599 491 363 478 368 402
A NK 485.7 385.7 488.3 410.3 426.7
NPK 432.7 394.7 483.3 427 420
Sims C 570 439 360 442 413 392
B NK 481 391.7 459.3 416.7 421.3
NPK 497 401.3 470 410 417.3
Miami C 544 445 394 387 417 403
A NK 430.7 405 416.3 436.3 469.7
NPK 426.3 380.7 423.3 425.7 452
Miami C 561 515 450 472 442 466
B NK 530.3 477 446 434.8 451
NPK 531.3 482 444.3 434.7 441.3
Conover C 555 395 392 383 383 379
A NK 417.3 427 418.3 406.7 426.7
NPK 454 389 432 417.3 426
Conover C 535 495 521 392 409 419
B NK 474 465 404.7 397 418
NPK 503 456 424.3 403 423
Hillsdale C 595 561 437 403 397 412
A NK 527 499 493 428 442.3
NPK 542 465 484 440 435.3
Hillsdale C 660 641 468 597 525 550
B NK 642 510 552 478 493
NPK 660 535.7 505.7 470 461
Locke C 536 519 439 421 419 454
A NK 496.7 447 462 433 430
NPK 510 449.7 464 436 432.7
Locke C 587 545 499 494 459 460
B NK 546 473 476.7 436 434
NPK 567 507.7 487.3 447.7 435

 

1C = Control (NK) with no plants, NR = 100 ppm N, 100 ppm K,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NR and NPK are averages of 3 replications; the
value for Control (C) is a single determination.

Table 4a.

49

 

 

 

Soil-water P content with time after flooding.

Initial P Time after flooding (weeksy

Soil Type Treatment Soil Content 3 6 9 12 15
------------ ppm3 -n-a-a-Q-n—u—a-u-n-

St. Clair C 7.06 .24 .20 .06 .09 .01

A NK .14 .13 .04 .12 .02

NPK .25 .14 .09 1.44 .04

St. Clair C 2.09 .08 .13 .05 .04 .01

B < .16 .10 .07 .09 .01

NPK .19 .15 .07 .13 .10

Hoytville C 7.47 .18 .14 .13 .11 .02

A NK .19 .11 .08 .09 .02

NPK .22 .17 .12 .10 .05

Hoytville C 1.30 .14 .11 .10 .09 .01

B NK .06 .12 .09 .09 .04

NPK .12 .22 .09 .10 .05

Morley C 6.49 .19 .15 .08 .06 .08

A NK .17 .15 .09 .08 .08

NPK .42 .22 .10 .09 .09

Morley C 2.94 .12 .18 .08 .03 .02

B NK .14 .19 .08 .08 .06

NPK .16 .22 .10 .08 .10

Sims C 39.48 .73 .53 .13 .21 .13

A NK .38 .33 .16 .26 .07

NPK .68 .57 .20 .10 .16

Sims C 2.69 .10 .10 .08 .03 .01

B NK .14 .11 .10 .03 .03

NPK .16 .15 .10 .06 .05

Miami C 4.78 .22 .15 .10 .04 .12

A NK .29 .08 .07 .04 .07

NPK .36 .16 .10 .05 .12

Miami C 2.57 .16 .11 .09 .06 .07

B NK .11 .13 .07 .04 .11

NPK .29 .20 .10 .08 .05

Conover C 7.90 .46 .15 .13 .10 .11

A NK .30 .08 .12 .08 .05

NPK .35 .21 .19 .08 .03

Conover C 2.21 .18 .11 .08 .05 .12

B NK .09 .06 .12 .06 .06

NPK .30 .16 .12 .08 .07

Hillsdale C 57.91 .32 .14 .15 .08 .07

A NK .32 .19 .10 .07 .07

NPK .37 .29 .22 .07 .10

Hillsdale C 5.26 .15 .09 .06 .07 .07

B NK .21 .09 .06 .06 .10

NPK .21 .10 .09 .07 .11

Locke C 41.71 .41 .12 .12 .13 .14

A NK .38 .11 .20 .07 .11

NPK .81 .14 .13 .08 .14

Locke C 3.47 .15 .08 .12 .02 .02

B NK .21 .09 .10 .04 .04

NPK .25 .22 .12 .06 .07

 

1C = Control (NK) with no plants, NK = 100 ppm N, 100 ppm K,

NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Determined by Bray's Pl method.
3Values reported for NK and NPK are averages of 3 replications; the value

for Control (C) is a single determination.

50

 

 

 

Table 5a. Soil-water Mn content with time after flooding.
Initial Time after flooding (weeks)

Soil Type Treatment Extractable Mn 3 6 . 9 12 15
--------------- ppm2 --—----------

St. Clair C 3.09 .40 .21 .02 .02 07

A NK .18 .28 .02 .01 13

NPK 1.09 .09 01 .01 .16

St. Clair C 2.43 .22 .48 1.10 1.00 .83

B NK .31 .46 .69 .59 41

NPK .30 .65 .02 .02 06

Hoytville C 0.50 .17 03 .16 .02 02
A NK .15 06 01 .02 .004

NPK .15 .08 01 02 .05

Hoytville C 0.76 .17 .07 .02 -- .01
B NK .14 .25 .01 -- .02

NPK .12 11 .01 -- .03

Morley C 1.59 5.40 4.92 .01 .01 .12
A NK 5.11 4.93 .18 .07 .10

NPK 7.69 6.82 .02 .01 .60

Morley C 16.8 1.57 7.81 15.4 11.2 .80

B i 1.99 9.53 8.50 2.88 1.42

NPK 3.57 11.1 .25 .04 .45

Sims C .50 .08 .74 .11 .008 .10

A NK .06 .13 .04 .003 .05

NPK .20 .48 .02 -- .02

Sims C .82 .06 .08 .01 -- .02

B NK .07 .06 .02 -- .03

NPK .07 .05 .01 -- --

Miami C 1.45 2.81 6.07 3.95 .32 3.10

A NK 3.32 4.50 .04 -- .27

NPK 3.31 .75 .02 -- .06

Miami c 1.20 .17 .18 .01 -- .06

B NK .11 .08 .04 -- .06

NPK .09 .14 .01 -- .05

Conover C 2.50 .37 3.96 .46 .10 .77

A NK .68 2.25 .02 -- .05

NPK .46 1.18 .03 -- .03

Conover C 1.40 .15 .05 .02 -- .07

B NK .15 .05 .03 -- .01

NPK .12 .04 .03 -- .11

Hillsdale C 7.24 .08 3.42 .19 .01 .52
A NK .18 3.95 .06 -- .40

NPK .45 3.08 .05 -- .15

Hillsdale C 6.05 .41 1.66 6.17 5.34 5.11

B NK .42 1.29 .92 .40 .51

NPK .49 2.81 .06 -- .08

Locke C 1.59 .05 .07 .05 -- .03
A NK .09 .08 .03 .02 .004
NPK .11 .07 .03 -- --

Locke C 0.82 .04 .01 .18 .08 .01
B NK .04 .06 .04 -- --

NPK .14 .11 .05 -- .01

 

1C = Control (NK) with no plants, NK = 100 ppm N,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

100 ppm K,

2Values reported for NK and NPK are averages of 3 replications; the value
for Control (C) is a single determination.

51

Table 6a. Soil-water Fe content with time after flooding.

 

 

 

1 Initial Time after flooding (weeks)
Soil Type Treatment Extractable Fe 3 6 9 12 15
------------ ppmz -----—-------
St- Clair C .29 .18 .07 .36 .24 --
A NK .30 .07 .01 .18 .10
NPK .70 .05 .01 .15 .04
St. Clair C 1.47 .33 .09 .20 .21 .04
B NK .49 .20 .24 .18 .04
NPK .38 .29 .16 .22 .72
Hoytville C .29 .19 1.15 .05 1.09 .96
A NK .22 .63 .01 .15 .11
NPK .27 .50 .01 .19 .01
HOthille C .44 .22 .04 -- .16 --
B NK .34 .04 -- .17 --
NPK .90 .17 .01 .22 --
Morley C .44 .97 1.46 .04 .19 --
A NK .72 .50 .03 .14 --
NPK 1.06 1.55 .01 .04 --
Morley C 1.17 .28 .09 -- .19 .22
B NK .61 .08 -- .13 --
NPK .17 .13 .01 .13 .03
Sims C .29 .43 7.09 .09 2.28 2.51
A NK .34 2.00 .04 .22 .13
NPK 2.27 6.08 -- .22 .08
Sims C .59 .46 .02 .09 .14 --
B NK .81 .08 .01 .12 --
NPK .25 .12 .06 .09 --
Miami C .59 .69 3.28 4.75 .69 .32
A NK 1.22 4.28 .05 .14 .01
NPK 1.69 .55 .02 .11 .05
Miami C .59 .10 .07 -- .12 --
B NK .41 .05 .04 .15 .07
NPK .66 .86 .02 .17 .01
Conover C .5884 .45 3.03 .13 .21 .32
A NK .43 .39 .01 .10 .04
NPK .31 1.00 .01 .12 .07
Conover C .4411 .55 .05 .02 .17 --
B NK .41 .06 .01 .08 .12
NPK .37 .04 .01 .10 .26
Hillsdale C .7359 .18 .60 .07 .12 .54
A NK .35 .54 .01 .06 .07
NPK .33 1.14 -- .08 .01
Hillsdale C .4411 .27 .09 .05 .16 --
B NK .34 .06 .02 .12 --
NPK .50 .10 .03 .11 .07
Locke C .1468 .97 .19 .05 .07 .02
A NK 1.18 .28 .01 .08 .23
NPK 1.12 .72 -- .11 .28
Locke C .2939 .25 .05 .04 .09 °l3
B NK .35 .14 -- .10 .22
NPK .27 .18 .03 .14 .24

 

1C = Control (NK) with no plants, NR = 100 ppm N, 100 ppm K,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NK and NPK are averages of 3 replications; the
value for Control (C) is a single determination.

52

 

 

 

 

Table 7a. Soil_pH with time after flooding.
Initial Time after flooding (weeks)
SoilyType Treatment Soil pH 3 6 9 12 15
------------- sz ---------------
St. Clair C 5.95 6.76 7.35 7.40 7.46 7.33
A NK 6.98 7.32 7.35 7.19 7.20
NPK 7.10 7.37 7.42 7.30 7.28
St. Clair C 5.30 5.43 5.16 5.21 5.24 4.73
B NK 5.08 5.04 5.08 5.27 4.93
NPK 4.98 4.92 5.39 5.80 5.73
Hoytville C 6.50 7.20 7.40 7.39 7.36 7.42
A NK 7.32 7.42 7.40 7.33 7.43
NPK 7.42 7.48 7.44 7.35 7.59
Hoytville C 6.76 7.29 7.43 7.44 7.42 7.48
B NK 7.39 7.32 7.33 7.34 7.43
NPK 7.40 7.25 7.30 7.25 7.34
Morley C 6.38 7.55 7.47 7.40 7.28 7.46
A NK 7.38 7.45 7.38 7.09 7.03
NPK 7.38 7.44 7.40 7.19 7.10
Morley C 4.60 5.46 4.81 4.96 5.02 5.09
B NK 5.13 4.78 4.89 4.96 5.09
NPK 5.20 4.70 4.26 5.52 6.11
Sims C 6.23 6.76 7.41 7.57 7.38 7.34
A NK 7.02 7.39 7.30 7.04 7.05
NPK 7.13 7.37 7.31 7.01 7.18
Sims C 6.54 7.05 7.32 7.36 7.52 7.46
B NK 7.02 7.08 7.20 7.31 7.22
NPK 7.03 7.09 7.24 7.40 7.38
Miami C 6.48 6.85 7.02 7.38 7.51 7.37
A NK 7.11 7.20 7.19 7.01 7.05
NPK 7.11 7.38 7.27 7.17 7.14
Miami C 6.52 6.80 6.40 6.71 6.92 6.66
B NK 6.66 6.49 6.77 6.91 6.85
NPK 6.59 6.54 6.77 6.80 7.14
Conover C 6.50 6.94 7.67 7.61 7.56 7.43
A NK 6.99 7.55 7.40 7.32 7.20
NPK 7.00 7.62 7.50 7.26 7.24
Conover C 6.64 6.74 7.31 7.42 7.64 7.32
B NK 6.66 7.21 7.29 7.38 7.21
NPK 6.84 7.21 7.24 7.27 7.15
Hillsdale C 5.82 6.80 6.73 7.06 7.32 7.30
A NK 6.93 6.92 6.94 6.88 6.98
NPK 6.88 6.83 6.90 6.76 6.96
Hillsdale C 5.20 5.50 5.07 5.03 4.87 4.95
B NK 5.40 4.99 5.06 5.21 5.91
NPK 5.25 4.99 5.60 6.00 5.96
Locke C 6.00 6.70 6.96 7.11 7.27 6.94
A NK 6.94 6.76 6.92 6.98 6.80
NPK 6.89 6.85 6.97 7.02 6.76
Locke C 6.29 6.50 5.84 6.45 6.65 6.42
B NK 6.52 5.91 6.37 6.94 6.87
NPK 6.66 6.22 6.68 7.02 6.80
1C = Control (NK) with no plants, KN = 100 ppm N, 100 ppm K,
NPK a 107 ppm N, 100 ppm P, 100 ppm K.
2Values reported for NK and NPK are averages of 3 replications; the

value for Control (C) is a single determination.

53
Table 8a. Soil Eh with time after flooding.

 

 

Initial Time after flooding (ygeks)
301133.. Treatment1 3011 Eh 3 6 9 12 15
----------- m.v.2 -----------
St. Clair C 545 214 158 167 201 150
A NK 259 164 166 171 136
NPK 213 136 128 125 121
St. Clair C 690 419 495 447 429 408
B NK 516 511 486 442 438
NPK 537 528 488 310 363
Hoytville C 599 74 59 61 71 73
A NK 78 81 83 113 87
NPK 79 67 66 83 60
Hoytville C 525 345 428 345 311 262
B NK 380 430 378 347 250
NPK 386 433 263 176 98
Morley C 569 251 117 101 168 160
A NK 82 85 163 274 118
NPK 58 106 146 273 106
Morley C 689 500 514 483 461 429
B NK 529 537 507 485 376
NPK 541 561 487 410 240
Sims C 599 83 55 58 60 47
A NK 70 76 90 91 106
NPK 60 68 75 82 52
Sims C 575 224 188 186 168 81
B NK 236 228 211 208 120
NPK 194 225 190 150 88
Miami C 544 95 288 117 127 159
A NK 119 272 216 216 178
NPK 82 218 184 169 123
Miami C 561 385 371 335 368 271
B NK 405 408 365 348 234
NPK 407 422 369 304 139
Conover C 550 135 175 109 119 130
A NK 76 174 154 154 160
NPK 81 120 125 132 166
Conover C 535 385 335 322 343 218
B NK 386 360 357 356 211
NPK 393 384 299 221 127
Hillsdale C 595 240 314 161 150 182
A NK 164 282 226 206 127
NPK 174 259 200 182 116
Hillsdale C 660 450 462 447 473 408
B NK 476 496 460 463 290
NPK 504 451 432 352 283
Locke C 536 181 261 280 156 184
A NK 122 286 233 204 182
NPK 111 235 190 172 173
Locke C 587 376 460 406 321 196
B NK 395 482 419 240 212
NPK 399 475 395 186 99

 

1C = Control (NK) with no plants, NK = 100 ppm N, 100 ppm K,
NPK a 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NK and NPK are averages of 3 replications; the
value for Control (C) is a single determination.

54

 

 

 

 

Table 9a. Soil P extractable by Bray P1 as influenced by time after
flooding.
Initial P Time after flooding_(weeks)
Soil Type Treatment Soil Content 3 6 9 12 15
------------- ppmz --------------
St. Clair C 7.06 22.2 30.3 19.7 12.8 9.3
A NK 25.9 35.0 25.7 22.8 8.8
NPK 34.4 34.0 33.2 23.1 12.7
St. Clair C 2.08 14.3 45.9 43.4 26.6 24.8
B NK 19.2 34.7 38.7 27.4 16.5
NPK 36.5 49.5 47.0 29.5 28.0
Hoytville C 7.47 17.3 13.5 12.1 10.0 8.0
A NK 14.8 59.4 20.4 11.4 3.1
NPK 20.0 61.8 30.8 12.1 5.2
HOthille C 1.30 49.9 89.8 39.9 39.9 20.5
B NK 22.1 77.3 31.7 24.3 6.9
NPK 22.5 86.9 45.1 31.6 10.1
Morley C 6.48 47.2 87.1 45.9 48.5 28.4
A NK 57.1 94.2 48.2 44.8 31.6
NPK 77.4 100.5 61.7 61.7 34.6
Morley C 2.94 75.3 62.1 55.7 51.3 41.0
B NK 73.3 70.1 61.4 35.9 45.5
NPK 80.6 101.2 79.4 47.5 44.8
Sims C 37.4 65.6 42.2 39.9 23.0 25.7
A NK 67.2 46.1 27.7 26.6 21.7
NPK 81.8 50.6 33.0 20.6 23.7
Sims C 2.69 49.9 49.9 39.9 35.4 13.5
B NK 43.3 46.6 39.6 35.7 16.9
NPK 46.4 48.8 42.7 45.1 19.0
Miami C 4.78 51.3 95.6 54.2 44.7 14.3
A NK 57.0 96.6 63.3 38.0 18.7
NPK 59.4 102.0 73.3 52.0 23.1
Miami C 2.56 26.6 19.7 23.0 23.9 21.3
B NK 57.3 22.9 22.2 24.2 18.6
NPK 84.9 25.5 27.9 28.6 18.6
Conover C 7.8964 42.2 30.3 21.3 19.7 19.7
A NK 33.3 36.6 20.2 15.3 15.9
NPK 68.7 44.7 29.2 28.7 22.5
Conover C 2.2055 18.1 26.6 29.4 21.3 12.1
B NK 51.1 31.4 26.6 21.1 12.9
NPK 29.4 32.0 30.1 28.4 13.8
Hillsdale C 57.9099 109.2 92.6 77.5 71.2 49.9
A NK 63.6 99.9 74.7 65.1 50.9
NPK 111.1 135.5 92.7 76.5 65.8
Hillsdale C 5.2593 41.0 56.9 35.4 41.0 39.9
B NK 39.9 55.8 34.0 30.5 36.1
NPK 203.0 99.3 44.2 41.6 52.1
Locke C 3.4718 89.7 114.4 52.7 48.6 54.2
A NK 196.4 100.1 41.8 37.3 43.1
NPK 240.7 125.3 51.5 59.2 50.5
Locke C 41.7105 52.7 89.4 32.3 34.4 29.4
B NK 74.0 79.4 29.1 27.8 18.4
NPK 94.4 84.2 31.0 28.8 32.1
1

C = Control (NK) with no plants, NR = 100 ppm N, 100 ppm K,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NK and NPK are averages of 3 replications; the
value for Control (C) is a single determination.

55

Table 10a. Soil P extractable by Olsen's sodium bicarbonate method as
influenced by time after flooding.

 

 

Initial P Time after flooding (weeks)
Soil Type Treatment1 Soil Content 3 6 9 12 15
------------- ppm2 ---------------
St. Clair C 11.52 19.6 20.6 20.6 19.6 17.8
A NK 20.0 21.6 19.3 20 5 16.0
NPK 32.4 32.7 29.1 28.5 25.6
St. Clair C 1.01 2.92 10 8 9.98 9.16 3.67
B NK 6.55 12.2 11.9 10.8 6.24
NPK 33.9 31.2 23.5 18.4 11.3
Hoytville C 4.47 20.6 16.9 12.5 17 8 15 1
A NK 18.5 18 1 17.5 16 6 15 1
NPK 19.3 29 7 25.6 22 2 19 0
Hoytville C 3.20 13.3 14.2 12.5 11.6 6.76
B NK 13.4 13.6 13.2 11.3 6.50
NPK 19.7 18.7 16 3 13.3 7.03
Morley C 7.58 20.6 14.2 13.3 13.3 14.2
A NK 17.0 18.1 14.8 11.9 9.98
NPK 38.3 28.0 26.2 22.9 16.0
Morley C 4.47 6.78 9.16 7.55 5.20 7.55
B NK 16.4 9.98 8.36 4.95 6.76
NPK 39.8 31.1 22.9 16.7 19.0
Sims C 42.6 55.6 49.7 41.5 46.8 46.8
A NK 55.1 42.4 44.6 51.0 46.9
NPK 62.8 55.1 55.7 60.0 47.3
Sims C 1.70 16.0 9.98 11.6 12.5 12.5
B NK 10.5 11.9 10.5 7.60 11.3
NPK 30.2 19.4 16.0 15.7 13.9
Miami C 3.51 5.97 12.5 13.3 12.5 11.6
A NK 13.6 13.6 11.1 9.22 9.46
NPK 27.6 21.2 19.0 15.7 12.3
Miami C 4.15 4.43 9.16 7.55 5.97 6.46
B NK 9.10 9.33 8.89 6.01 8.44
NPK 30.6 15.4 14.2 9.71 8.99
Conover C 10.2 16.9 15.1 13.3 11.6 12.5
A NK 21.0 13.9 11.9 11.1 11.1
NPK 35.6 30.8 23 7 19 7 16.9
Conover C 2.00 9.98 7.55 6.76 7.55 5.97
B NK 6.78 10.7 7.30 5.53 5.48
NPK 22.5 16.0 17 8 9 18 9.18
Hillsdale C 25.8 41.57 31.8 29.7 32.0 30.8
A NK 41.5 27.6 33.5 32.8 30.7
NPK 47.3 33.1 45.1 39.9 38 6
Hillsdale C 6.50 12.5 12.5 10.8 9.16 9.98
B NK 12.8 6.50 9.19 8.92 7.58
NPK 49.8 25.5 25.3 26.6 20.3
Locke C 23.7 32.0 27.6 29.7 29.7 24.5
A NK 39.4 22.2 20.6 19.4 19.3
NPK 51.6 38.8 32.4 29.6 27.1
Locke C 5.47 7.55 6.76 3.65 4.43 5.97
B NK 11.1 3.43 4.67 3.96 5.72
NPK 25.5 16.9 11.8 11.6 14.9

 

1C = Control (NK) with no plants, NK = 100 ppm N, 100 ppm K,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NK and NPK are averages of 3 replications; the
value for Control (C) is a single determination.

Table 11a. Soil P extractable by Truog's weak H280

56

by time after flooding.

4 method as influenced

 

 

 

Initial P Time after flooding (weeks)
8011 Type Treatment Soil Content 3 6 9 12 15
nnnnnnnnnnnnnn ppmz ---------------
St. Clair C 11.2 114. 86.3 60.5 28.9 10.7
A NK 71.8 75.0 53.7 28.0 11.7
NPK 116. 102. 66.1 42.8 21.5
St. Clair C 13.2 32.7 21.4 28.9 10.5 17.8
B NK 47.2 17.9 26.6 11.8 14.1
NPK 67.6 52.4 43.1 25.3 31.6
Hoytville C 51.6 149. 177. 133. 118 73.2
A NK 65.0 157. 120. 70.3 64.8
NPK 118. 174. 129. 87.0 70.1
Hoytville C 40.3 77.5 90.8 64.7 48.3 36.6
B NK 55.1 76.1 69.0 27.7 31.6
NPK 75.0 92.4 82.0 69.4 45.8
Morley C 16.0 64.7 81.8 48.3 44.4 25.2
A NK 60.8 103. 48.4 25.2 32.7
NPK 95.4 125. 49.7 47.1 49.7
Morley C 22.1 56.4 48.3 36.6 25.2 21.4
B NK 41.8 47.0 32.9 24.0 21.1
NPK 57.8 49.2 43.2 39.0 22.8
Sims C 113.1 214. 255. 195. 144. 123.
A NK 193. 289. 189. 121. 101.
NPK 232. 339. 291. 143. 117.
Sims C 80.8 118. 149. 123. 109. 44.4
B NR 158. 160. 103. 96.8 69.4
NPK 180. 206. 170. 116. 77.7
Miami C 17.5 73.2 77.5 48.3 36.6 28.6
A NK 96.3 40.5 45.8 36.7 26.4
NPK 128. 87.8 74.7 69.0 52.7
Miami C 5.62 68.9 56.4 32.7 36.6 32.7
B NK 70.4 60.0 34.1 40.6 25.2
NPK 106. 67.7 45.9 23.8 48.5
Conover C 29.0797 73.2 86.3 77.5 64.7 64.7
A NK 71.7 65.5 67.6 64.8 69.0
NPK 136. 134. 102. 85.0 71.8
Conover C 30.0082 139. 90.8 114. 109. 95.3
B NK 124. 107. 101. 96.8 92.3
NPK 141. 135. 146. 118. 115.
Hillsdale C 71.9123 133. 109. 109. 86.2 104.
A NK 146. 111. 110. 85.1 92.4
NPK 199. 115. 133. 111. 108.
Hillsdale C 60.8 40.4 44.4 36.6 32.7 36.6
B NK 37.9 45.9 34.0 31.5 22.8
NPK 63.3 48.5 47.5 51.2 39.2
Locke C 64.2730 160. 149. 139. 118. 104.
A NK 127. 139. 132. 120. 103.
NPK 153. 162. 164. 139. 104.
Locke C 37.0073 68.9 86.3 77.5 64.7 56.4
B NK 43.1 79.0 77.5 63.3 36.6
NPK 72.0 83.7 79.0 71.9 59.2

 

1C = Control (NK) with no plants, NK = 100 ppm N, 100 ppm K,

NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NR and NPK are averages of 3 replications; the

value for Control (C) is a single determination.

57

 

 

 

Table 12a. Soil Mn++ content with time after flooding.
Initial Time after flooding_jgeeks)
Soil Type Treatment1 Mn Content 3 6 9 12 15
----- -------- ppmz -----------—---
St. Clair C 3.08 98.1 107. 75.0 42.1 41.2
A NK 96.3 86.2 70.3 61.8 51.3
NPK 96.0 79.8 72.7 60.4 68.4
St. Clair C 2.43 9.03 11.7 13.3 14.7 14.8
B NK 9.94 11.3 13.8 13.5 12.9
NPK 10.5 12.2 19.6 19.3 21.2
Hoytville C .50 4.05 4.04 5.06 5.06 3.86
A NK 3.66 3.31 4.43 3.78 5.57
NPK 3.49 3.41 4.85 5.17 4.98
Hoytville C .75 1.61 1.46 2.08 2.71 2.76
B NK 1.76 1.10 3.32 2.87 6.39
NPK 2.18 2.15 5.27 7.50 12.5
Morley C 1.58 142. 128. 83.3 69.8 51.2
A NK 126. 107. 77.7 76.2 44.7
NPK 130. 118. 88.1 83.0 64.2
Morley C 16.8 92.7 131. 75.0 67.4 49.6
B NK 90.8 99.9 71.0 61.4 43.8
NPK 102. 106. 73.9 72.9 56.1
Sims C 5.03 7.35 5.24 6.85 7.33 5.28
A NK 6.30 4.02 4.08 3.05 1.32
NPK 6.07 4.97 5.29 4.70 3.49
Sims C .82 9.74 3.82 6.59 6.56 11.5
B NK 7.46 8.50 8.10 6.77 11.1
NPK 9.41 5.91 10.2 13.6 13.9
Miami C 1.45 81.7 77.3 64.7 44.4 49.5
A NK 78.4 74.4 49.6 41.6 52.5
NPK 76.7 76.8 68.5 47.7 53.2
Miami C 1.20 12.6 6.47 12.7 15.4 16.5
B NK 17.0 11.7 14.3 18.7 29.8
NPK 17.3 10.9 15.5 24.1 33.8
Conover C 2.4952 82.5 80.0 66.5 44.6 56.9
A NK 78.6 68.9 48.4 45.0 51.5
NPK 79.4 73.5 69.4 56.5 54.9
Conover C 1.3953 26.2 9.80 22.8 25.5 28.2
B NK 25.4 15.9 17.4 18.6 34.6
NPK 33.3 16.4 31.8 49.3 52.5
Hillsdale C 7.2392 123. 107. 75.0 60.0 61.4
A NK 126. 121. 77.9 61.6 60.4
NPK 122. 112. 78.0 59.2 65.4
Hillsdale C 6.0537 8.96 17.6 22.7 20.9 23.8
B NK 10.3 13.7 22.8 31.4 38.5
NPK 11.9 20.8 30.5 54.7 47.1
Locke C 1.5880 8.75 4.53 6.20 5.31 3.19
A NK 7.76 4.84 5.95 5.50 4.38
NPK 7.93 4.93 6.83 6.28 4.43
Locke C .8207 3.40 .95 .87 .73 .67
B NK 3.42 .88 .81 1.35 1.27
NPK 3.57 .93 1.38 1.60 1.47

 

1C = Control (NK) with no plants, NK = 100 ppm N, 100 ppm K,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NK and NPK are averages of 3 replications; the value
for Control (C) is a single determination.

58

 

 

 

Table 13a. Soil Fe++ content with time after flooding.
Initial Time after flooding (weeks)
Soil Type Treatment Fe Content 3 6 9 12 15
--------------- ppmz ---------------
St. Clair C .29 1.04 15.7 18.2 16.2 17.4
A NK 1.61 17.4 18.3 12.0 14.2
NPK 1.89 17.5 20.5 14.2 14.7
St. Clair C 1.48 1.25 9.40 10.2 7.29 8.97
B NK 1.61 5.61 6.34 5.46 6.38
NPK 3.03 4.53 9.94 6.66 8.54
Hoytville C .29 2.73 55.8 49.1 52.2 60.1
A NK 4.68 77.0 41.7 56.4 73.5
NPK 3.74 49.0 48.9 53.0 64.6
Hoytville C .44 1.68 5.85 10.8 5.91 6.58
B NK 1.46 7.88 5.68 4.03 5.15
NPK 1.32 4.06 5.75 5.34 6.23
Morley C .44 2.73 22.0 22.3 18.6 23.6
A NK 2.88 26.7 22.8 22.2 23.8
NPK 4.95 28.5 27.0 25.3 26.9
Morley C 1.17 1.68 0.87 1.33 .99 1.04
B NK 1.11 1.10 .38 .41 1.11
NPK 1.11 1.45 1.05 .94 1.46
Sims C .29 38.7 45.1 65.2 54.7 62.1
A NK 9.45 48.0 34.7 44.5 55.1
NPK 7.16 50.3 41.0 42.2 53.7
Sims C .59 4.43 7.47 5.91 4.88 6.37
B NK .48 5.02 2.73 3.24 3.94
NPK .69 3.64 3.52 3.92 4.48
Miami C .59 12.0 9.86 8.51 8.34 10.0
A NK 10.7 15.6 10.3 10.2 12.9
NPK 8.09 11.1 9.60 8.67 11.6
Miami C .59 .20 5.13 2.50 3.35 4.01
B NK 1.82 1.10 2.28 1.61 1.68
NPK 2.56 7.97 3.29 2.34 2.73
Conover C .59 1.68 9.68 9.56 7.64 7.88
A NK 1.39 16.3 5.63 12.74 10.6
NPK 1.74 16.3 14.6 12.3 11.3
Conover C .44 1.25 3.16 2.00 1.66 1.89
B NK 1.32 2.10 .83 1.61 1.11
NPK 2.02 4.14 .49 1.56 1.04
Hillsdale C .74 19.7 15.3 10.9 9.56 11.8
A NK 7.76 13.1 8.18 9.64 10.8
NPK 9.93 11.4 7.61 11.0 13.3
Hillsdale C .44 1.04 2.45 2.67 1.83 2.73
B NK 1.60 1.45 0.72 1.44 1.53
NPK 2.16 2.25 1.61 2.39 2.38
Locke C .15 1.04 13.7 6.91 10.8 10.0
A NK 1.04 11.9 5.40 6.61 8.18
NPK .83 10.4 6.32 9.11 11.1
Locke C .29 .20 1.22 .66 .83 .83
B NK .76 2.10 1.01 .99 .90
NPK 1.11 1.81 1.55 1.52 1.61

 

1C = Control (NK) with no plants, NK = 100 ppm N, 100 ppm K,
NPK = 107 ppm N, 100 ppm P, 100 ppm K.

2Values reported for NK and NPK are averages of 3 replications; the value
for Control (C) is a single determination.