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Group Title: Department of Soils mimeographed report
Title: 1955 cooperative fertilizer trials with field crops
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Permanent Link: http://ufdc.ufl.edu/UF00091559/00001
 Material Information
Title: 1955 cooperative fertilizer trials with field crops
Alternate Title: Cooperative fertilizer trials with field crops, 1955
Department of Soils mimeographed report 56-2 ; University of Florida
Physical Description: 19 leaves : ill. ; 28 cm.
Language: English
Creator: Pritchett, William L
Henderson, J. R
Mixon, Aubrey C
Breland, H. L ( Herman Leroy ), 1916-
University of Florida -- Dept. of Soils
University of Florida -- Agricultural Experiment Station
Publisher: Department of Soils, Florida Agricultural Experiment Stations
Place of Publication: Gainesville, Fla.
Publication Date: February 1956
 Subjects
Subject: Fertilizers -- Florida   ( lcsh )
Plants -- Nutrition -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: compiled by W.L. Pritchett ; cooperators, J.R. Henderson, Aubrey Mixon and Herman L. Breland.
General Note: Cover title.
General Note: "February 1956."
 Record Information
Bibliographic ID: UF00091559
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 310114962

Table of Contents
    Title Page
        Title Page
    Part I. Yield results: Fertilizer trials with corn
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Part II. The relationship of yield responses to soil fertility levels
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
Full Text







Department of Soils Mimeographed Report 56-2

February 1956












1955 COOPERATIVE FERTILIZER TRIALS WITH FIELD CROPS


Compiled by

W. L. Pritchett


Cooperators:


J. R. Henderson and Aubrey Mixon,
Extension Agronomists; County Agents;
and Herman L. Breland, Soils Department,


University of Florida
Agricultural Experiment Station
J. R. Beckenbach, Director
Gainesville, Florida







1955 COOPERATIVE FERTILIZER TRIALS WITH FIELD CROPS


The series of fertilizer trials with field crops, initiated in 1954, was
continued in 1955 with certain modifications. In addition to the tests with corn,
peanuts, and flue-cured tobacco, which were used in 1954, a series of trials were
also conducted on cotton and soybeans. These field trials were located on the
principal soil types in the field crops areas of north and west Florida. A total
of 38 tests were established in 12 counties in the area; however, due to poor
stands, drought, or disease and insect damage in certain areas, only 24 of the
tests were deemed valid and consequently worthy of harvest.

The purposes of the tests were (1) to study further the relationship between
the levels of available plant nutrients in the soil, as determined by a chemical
analysis of the soil,, and the crop yield response to rates of fertilization over
a wide range of soils. These values should be useful as an aid in interpreting
soil test results. (2) they also serve to check the present general fertilizer
recommendations, particularly in soil areas not represented by soils at the
Branch Experiment Stations.

The treatments for each type of crop remained the same for all areas, with
certain noted exceptions, so that locations served as replications.

Soil samples (0-6" depth) were taken from each plot area before fertilization.
The samples were analyzed for pH, CaO, MgO, P205 and K20 and the results are
given in part II of this report.

PART I

Yield Results: Fertilizer Trials with Corn

The treatments involved two whole-plots receiving (1) 300 pounds of 5-10-10
and (2) 600 pounds of 5-10-10 fertilizer applied as a base application at plant-
ing time. The whole plots were each split into 10 sub-plots for side-dress
treatments. The ten sidedress treatments were made at the second cultivation of
the corn and involved four rates of nitrogen, 0, 30, 60, and 90 pounds per acre.
There were also three rates of potassium, 0, 30, and 60 pounds of K20 per acre,
in combinations with the nitrogen.

The sources of nitrogen and potash in the sidedressings were ammonium
nitrate and potassium chloride, respectively. The variety of corn used in every
trial, except one, was Dixie 18. The plant population varied from approximately
6,000 plants on the lighter sands to about 900 plants per acre on the sandy
loams.

Yields of corn from 12 areas are given in Table 1. Corn yields were in-
creased in six of the fields from the base application of 600 pounds of 5-10-10
as compared to the 300 pounds application (when the yields were averaged over
the 10 sidedress treatments). However, in five of the fields no such response
was obtained. (The Hunter field was omitted since yields were obtained only at
the 300 pound rate.) When the fields were grouped into light sands of the





2


Suwannee valley and the sandy loams of west Florida, the average yields of corn
on the light sands were 43.3 bushels for the 300 pound base application and 46.2
bushels per acre for the heavier rate. The yields of corn on the sandy loams of
west Florida were somewhat higher than on the light sands (49.0 bushels and 50.7
bushels for the 300 and 600 pound applications, respectively); however, the in-
crease from the extra 300 pounds of base fertilizer was less.

The average corn yields in bushels per acre associated with the use nitrogen
sidedressing for all locations were as follows:
0-0-0 30-0-60 60-0-60 90-0-60
All locations 37.2 45.6 47.1 48.0
Light sands only 35.0 43.4 4.0 46.4
Sandy loams only 41.6 0,0O 53.2 51.1

These yields are averaged over the two base applications, so that even the
"no sidedress" plots had previously received a base application of 15 or 30
pounds of nitrogen and 30 or 60 pounds of phosphorus and potassium. Nevertheless,
a significant yield increase resulted from the application of 30 pounds of
additional nitrogen in 9 of the 12 locations when no additional potash was
applied and in 10 of the locations where a uniform application of potash was
made at the same time as the nitrogen treatments.

The response to additional potash as sidedressing was closely related to
the available potassium in the soil reserve, as will be discussed in section ,J3t
Suffice it to say that in most locations a small additional increase in yields
were obtained from the application of 30 and 60 pounds of K20 as sidedress, over
and above that resulting from the nitrogen applications. In eight of the
locations, low in exchangeable potassium, one to ten bushel increases were
obtained from the extra 30 pounds of K20.

Yields of corn in a trial in Escambia county in which four levels each of
phosphorus and potassium were modes are given below (average of four replications):
Treatments Corn Yields
Bu./Acre
80-0-120 71
80-72-120 77
80-108-120 87
80-144-120 77
80-144-0 83
80-144-30 81
80-144-60 85
80-1U4-120 79
80-0-0 77

In this test a significant response resulted from the use of phosphorus up
to 108 pounds of P205; however, no response was obtained from the addition of
potash. As will be noted later, this test was conducted on a soil that tested
rather low in available P205 and high in exchangeable potassium.





TABLE 1. 1955 Fertilizer Trials* (Yields of shelled corn in bu/acre)
: Base :
:appli- : Topdress Application; pounds plant food/acre
:cation : 1 : 2 3 : : 5 : 6 7 : : 9 : :
:5-10-10:0-0-0:30-0-0:30-0-30:30-0-60:60-0-0:60-0-30:60-0-60:90-0-0:90-0-30:90-0-60:
:lbs/acre Beach Gilchrist Co.
: 300 : 39.0: 45.2 : 40.6 : 46.8 : 51.5 : 51.5 : 57.7 : 62.4 : 49.9 : 56.2 :
:600 : 39.2: 45.2 : 49.9 : 40.6 : 43.7 : 48.4 : 48.4 : 49.9 : 70.2 : 64.0 :
: Ave. : 39.0: 45.2 : 5.3 : 43.7 : 47.6 : 50.0 : 53.0 : 56.2: 60.0 : 60.1
Quency Gilchrist Co. (Lupines)
: 300 : 42.7: 45.2 : 5 .9 : 61.4 : 51.5: 2.3 : 54.0 : 48.1 : 51.5 : 52.3
: 600 : 51.5: 50.2 : 9.8 : 58.9 : 61. : 61.4 : 58.1: 54.8 : 58.9 :58.1
Ave. : 47.1: 47.7 : 54.4 : 60.2 : 56.4 : 56.8 : 56.0 : 51.4 : 55.2 : 55.2
: Morris Jefferson Co.
: 300 : 32.1: 32.1 : 39.3 : 39.3 :32.1 3.7 : 39.3 : 35.7 -
: 600 : 32.1: 39.3 : 39.3 : 42.8 : 50.0 : 42.8 : 46.4 : 46.4 : 39.3 : 35.7
: Ave. : 32.1: 35.7 : 39.3 : 41.5 :: 41.5 : 39.2 : 42.8 : 1.5 : 39.3 : 35.7
: Scruggs Jefferson Co.
: 300 : 42.3: 51.7 : 54.1 : 7.0 : 61.1 : 56.: 56.4 : 61.1 61.1 : 63.5 :
: 600 : 35.3: 4.1 : 42.3 : 51.7 : 47.0 : 56.4 : 51.7: 61.1 58.8 : 58.8 :
SAve. : 38.7: 47.9 : 48.2 : 49. : 54.1 : 56.4 : 54.1: 61.1 : 60.0 : 61.2 :
: Clayton Jefferson Co.
300 : : 32.5 : : 337 : : 30.0 : 26.9 : 21. :
S600 : 44.0: 30.0 : 44.0 : 41.6 : 38.6 : 42.3 : 31.2: 42.9: 34.9 : 39.8 :
: Ave. : 44.0: 31.2 : 44.0 : 37.6 : 38.6 : 36.2 : 31.2 : 34.4 : 34.9 : 30.6
Hunter Columbia Co.
: 300 : 10.2: 22.9 : 2.5 : 27 : 18.5: 23.1 : 26.2 : 17.0: 24.8 : 29.2 :
only: :
Ratliff Hamilton Co.
: 300 : 23.6: 27.8 : 24.9 : 26.3 : 33.5 : 31.4 : 30.4 : 21.6 : 37.1 : 38.8
: 600 : 31.4: 35.2 : 37.3 : 38.4 : 33.8 : 35.5 : 36.8: 28.4 : 35.4 : 36. :
: Ave. : 27.5: 31 : 31.1 : 324 33.6 33. 33.6 25.0 :36.3 : 37,6 :
: Faulkner Taylor Co.
: 300 : 45.6: 46.0 : 59.9 : 54., : 43.7 : 51.3 : 52.1: 43.5: 63.7 : 59.3
: 600 : 38.2: 45.8 : 50.9 : 58.5 : 45.1 : 9.2 : 57.7 : 45.4 : 55.0 : 62.9
: Ave. :T1.9i: 55.4 566 : .5: 0.2 .: 59 :E.4 : 9.3 61.1
Clemmons Okaloosa Co.
: 300 : 46.3: 55.8: 50.0 : 50.1 : 57,4 : 5.8: 56.8 : 51.4 : 53.8 : 57.3
:600 : 51.3: 53.6: 55,6 : 58.2 : 58.2 : 61.3 : 64.2 : 58.3 : 60.3 : 68.8 :
: Ave. :i88: 5:7 52.8 : 5.2 :7.: 60.0 : 60.5 : 57 6 : 7.0 : 63.0 :
Gilley Escambia Co.
300: 57 : 7 74 7 7 : 74 : 86 : 76 : 70* :63
600 6 : 73 : 75 : 87 : 98 80 : 83 7 : 6 82 :
: Ave. :~ 60.~:1: 7U.5 : 81. .0 86,0 : : 84.5 : 75.5 : 67.5 : 72. :
: Barrineau(1) Escambia Co. (Ruston)
300 : 30 : 36 : 38 :1 31 :31 0 35 :33 : 34 : 3 :
:600 : 32 : 3 : 34 : 29 : 31 32 33 3 : 30 :35
:Ave. :31 :3-:36 : 30 : 31 : 36 : 34 :33 : --32 :-34 :
: Barrineau(2)- Escambia Co. (Norfolk)
S300 : 24 : 33 33 : 36 :36 : 37 :31 : 38 :36 :33
600 : 28 : 3 : 3 : 35 : 30 : 30 : 37 : 35 : 3 :37
: Ave : 2"6:33: 33 3 3 33 : 33 : 34 36 :35 :35


* Yields of shelled corn in bu/acre at approximately 13% moisture,








FERTILIZER TRIALS WITH COTTON

Only two test areas with cotton were harvested in 1955. The fields were in
Okaloosa and Escambia Counties on relatively heavy soil and the ten treatments
were the sample at both locations. The treatments were arranged in a split plot
design with basic applications of 20-0O-40 and 40-80-80 as the whole plots.
Each of these were divided into five sub-plots consisting of a check and two
rates each of nitrogen and potash. The yields of cotton in pounds per acre of
seed cotton are given in Table 2 below:
TABLE 2. 1955 Fertilizer Trials with Cotton(Yields of seed cotton in pounds/acre)


: Base
: application
: 5-10-10


S Topdress application, lbs/acre plant food :
: 1 : 2 : 3 : 4 : 5 :
: 0-0-0 : 20-0-0 : 20-0-20 : 40-0-0 : 40-0-40 : Ave. :


Ibs/acre : Crabtree Escambia Co.
: 400# : 2241 : 2677 : 2116 : 215 : 2552 : 2400 :
: 800# : 1992 : 2552 : 1961 : 2366 : 2303 : 2235 :
SAve. : 2116 : 2619 : 2039 :2391 : 2428
Clemmons Okaloosa Co.
: oo00# : 806 : 5 : 1395 : 1612 : 1550 : 1290:
: 800 : 930 : 744 : 105 : 1101 : 1116 :989:
SAve. :868 : 915 : 1225 : 1357 : 1333 :


There was a reduction in yields when the base application was increased from
400 pounds to 800 pounds per acre of 5-10-10, in both locations. On the other
hand the application of nitrogen sidedressing increased yields at both the 20 and
40 pound rate. The increase was more pronounced with the 00 pound base than
with the 800 pounds of 5-10-10 base application.

The addition of 20 pounds of K20 as sidedress increased yields in Okaloosa
County. However, it did not increase yields in Escambia County or a soil high
in exchangeable potassium.
FERTILIZER TRIALS WITH SOYBEANS

Five tests were conducted in Escambia County in 1955 on various soil types.
The treatments, made at planting time, consisted of four rates each of phosphorus
and potassium. The yields, given in Table 3, were relatively high in all loca-
tions and little response was obtained from any of the treatments.

There was a response to phosphorus on the Barrineau and Viedak fields and
an indicated response to potassium on the Hubert and Viedak farms. However, it
should be pointed out that the exchangeable soil potassium levels were high in
all fields.








TABLE 3. 1955 Fertilizer


trials with soybean (yields in
(Escambia Co.)


bushels per acre)


: P20 Applied : Potash Applied, Lbs/acre :
: Lbs/acre : 0 : 30 : 60 90 :
: Hubert (Red Bay f.s.) )
0 : 28.7 : : 33.2 :
S 30 :30.4
60 32.1 :
:90 : 31.6 : 3.8 :33.5 35. :
S Ave.
: Barrineau (Ruston f.s.l)
:0 : 3.7 : : 31.5
: 30 :36.0 :
60 : ,1
:90 : 38.1 :38.1 : 1.6 :38.2 :
: Ave.
Viedak (Tifton f.s.l.)
0 : 20.5 24.5
: 30 25,0 :
60 :25.9
: 90 : 24.6 25.7 : 25. : 29.9
S Ave.
: Godwin (Tifton f,s.l,)
0 37.9 : 0. :
S 30 :: 1.2
S 60 39.8
: 90 : 41.3 :39.9 : 2. : 2.6 :
S Ave.
: Kemper- (Norfolk or Goldsboro:fB.s,1)
0 : 44.4:: : 2.2 :
S 30 0: .2
60 : .0 :
: 90 : S4.1 : 46.2 : 4.7 : 1.5
: Ave,


FERTILIZER TRIALS WITH PEANUTS

Only one of the four fertilizer tests with peanuts established in 1955 was
harvested. The yields of peanuts in this field in Holmes County were low and
no response was obtained from the application of 500 pounds of gypsum and only
a small response from the fertilizer applications. The treatments and yields
of peanuts, in pounds per acre are given in Table 4. A further discussion of
the summary of the two years results will be given in Part X.J.








TABLE 4, 1955 Fertilizer Trials with Peanuts (pounds per acre)


: Gypsum : Base Application
: Top dress : check : 0-40-40 0-40-80 : 0-40-120 : 0-80-80 : Ave :
I Ibs./acre : Carter Holmes Co. :
: 0 :671: 660 : 616 : 583 : 605 : 627
: 500 :59 : 627 : 715 : 704 506 : 629
: Ave. : 555 : : 64 : 665 : 6143 : 32 :



FERTILIZER TRIALS WITH TOBACCO

Fertilizer trials with flue-cured tobacco conducted in 1955 were of the
same design as used in 1954. Seven treatments were made as sidedressings. A
basic application of 1200 pounds per acre of a 3-9-9 tobacco fertilizer was made
in two applications, at planting and two weeks after planting, to all plots. A
second sidedress application was made about four weeks following transplanting.
The treatments made atthis time are given in Table 5, along with the yields and
the order of rank based upon leaf quality or selling price.

TABLE 5. Yields of Flue-Cured Tobacco and Leaf
Quality Rank in Fertilizer Trials, 1955
:Treatments : Carver : Fowler Osteen
: Fertilizer : Total Plant : Gilchrist Co, : Su3wannee Co.: Lafayette Co. :
: Applications : Food :Yield Rank: Y:eld Rank : Yield Rank :

: 1200# 3-9-9 : 36-108-108 : 1767 (6) : 900 (7) : 1236 (2) :
:1600# 3-9-9 : 48-144-144 : 1860 (5) : 10oo (6) : 1413 (1)
:2000# 3-9-9 : 60-180-180 : 2526 (2) : 10O (5) : 1532 (3)
:1200# 3-9-12 : 36-108-144 : 2217 (1) : 1200 (2) : 1171 (6)
:1200# 3-9-15 : 36-108-180 : 1535 (7) : 1200 (3) : 1425 (4)
: 1350# 4-8-12 : 54-108-164 : 1845 (4) : l50 (1) : 1216 (7)
S1350#4-8-16 : 54-108-218 : 1922 (3) : 1200 (4) : 1371 (5)


The yields were generally increased with an increase in the rate of 3-9-9
fertilizer from 1200 to 1600 and 2000 pounds per acre even though none of the
fields were irrigated, he quality of the leaf was also generally improved by
the higher applications. That the increase in yield and quality were largely
due to the extra potash contained in the higher rates of mixed fertilizer can
be seen from the comparable results obtained from the fourth treatment which
contained a low nitrogen and phosphorus level but high potash. This treatment
was equal to a 1200 pound application of 3-9-12, and gave good results in two
of the three tests. (The validity of the Osteen test might be questioned since
each priming was made on all treatments at the same time. disregarding differences
in maturity,)


V _







PART II
7
The Relationshin of Yield Resnonses to Soil Fertility Levels

As an aid in interpreting the results-of chemical soil tests in terms of
amounts and kinds of fertilizer to apply for most economic crop production, soil
samples were collected from all of the test areas before fertilization, The
samples were then analyzed by the methods used in the Soil Testing Laboratory*
and the results related to the yield responses from varying levels of fertiliza-
tion for a number of crops. A summary of these relationships for potassium and
phosphorus is given in the following section.

Potassium: Under conditions where potassium was the only limiting factor,
as far as it was possible to control these factors, there was a significant posi-
tive correlation between the amount of potassium available to the crop and the
yield of same. This was true in both 1954 and 1955 on the light sands as well as
the heavier sandy loams.

In 1954, yields of corn in eight of the ten experiments were significantly
increased by base applications of 15-30-30 over the check treatment. However, in
this dry year, yields in only five of the ten fields were further increased by
raising the base application to 30-60-60 or to 45-90-90. The increase in corn
yields resulting from the sidedress application of 30 pounds per acre of K20 was
closely related to the exchangeable K20 in the soil at planting time, as can be
noted in Figure 1. In general soils containing more than 80 pounds of K20 did
not respond to additional amounts of potash over that applied in the base fertil-
izer. As expected, the increase in corn yields due to potash sidedressing tended
to be greatest on the plots receiving the low base application and decreased as the
amount of potash in the base treatment was increased.

In the twelve 1955 tests with corn, two base applications of 300 and 600
pounds per acre of 5-10-10 were applied at planting and three levels of potash
were made as sidedress treatments. The response to these 3 potash treatments
(0, 30 and 60 pounds per acre of K20) are given in Table 6. The corn yields are
the average of the two base applications and represent 6 replications per location.
In these tests the correlation between corn yield increases to potash sidedressing,
in the presence of a basic fertilizer treatment containing 30 to 60 pounds of K20
per acre, with the exchangeable potassium in the soil was highly significant. This
relationship is shown graphically in Figure 2. Fields containing more than 60 to
70 pounds of exchangeable K20 gave little response to the additional potash in the
sidedressing, while those fields containing less than this amount generally did
respond to this treatment.

The percentage yield of the 0 level of potash sidedress was determined for
each location. This was done by dividing the yield at the low levels by the corn
yield at the high level of potash application and multiplying by 100. These are
shown in Figure 3. Due to the small number of locations with low exchangeable
K20, a desirable growth curve was not obtained as shown by the dots in Figure 3.
Nevertheless, by using the modified mitscherlich equation, as suggested by Bray;

log (A-y) = log A-cl b,

where A = yield with 60 pounds of K20 sidedressing;


*Soils Department Mimeo Report 55-1
































Exchangeable Soil Potassium, Lbs/ac K20
Increases in Corn Yields from 30 Pounds of applied K20 on Soils
with varying levels of ex. Potassium (1954)


60 lbs. K20
applied
0 c

30 lbs. K20
applied

,_,,^ ^ ,_r-_* ,_. ,^*~~^ ^ -- ^ '^ .....JlA ,-* ,,-Se-) >S


75 100 125
Exchange Soil Potassium, Lbs/ac. K20


150


Response of corn to 30 and 60 pounds of applied K20 on Soils
with varying levels of Exchangeable Potassium.


Figure 1.


Figure 2.


i__l_~ ) I_____I__~__ I___ ~ ii_ ~______ X _~ ii___rij_ ~


1io0


100


120









y = yield without K20 sidedressing;
b= exchangeable K20 in soil;
cl= proportionality constant; a cl value

was determined for each field. Using the mean cI value (0.0169) for all fields
the estimated growth curve was constructed (solid line in Figure 3). This curve
indicates the percentage of the top yield (obtained in the presence of potash
sidedressing) that can be expected on fields containing an indicated amount of
exchangeable potassium with a base application of 600 pounds of 5-10-10 per acre
but without the K sidedress application. In other words, a field containing 40
pounds of exchangeable K20 could be expected to yield about 82 percent as much
corn without the potash sidedressing as with the 60 pounds of K20 sidedressing.
(This, of course, assumes that a base application has been made.)

The results of these cooperative trials are also supported by data from other
experiments in the same general area during the 1954 and 1955 period. For example,
experiments conducted in Escambia County on soils containing more than 150 pounds
of exchangeable K20 have failed to respond to applications of 30, 60, 90 or 120
pounds of potash applied at planting. In another trial in western Florida, the
yield response of corn to 30 pounds of K20, applied to plots with soil containing
a residual of approximately 53, 65, 77 and 105 pounds of exchangeable K20, respec-
tively, was significant on plots containing 77 pounds of K 0 or less, but not sig-
nificant on plots containing more than this amount. The 1955 corn yield results
from the 5 x 5 x 5 Fertility Experiment at the West Florida Experiment Station, in
which five levels of potassium were obtained in Red Bay soil, also indicated that
no economic increases could be expected from potash fertilizer on corn on soils
containing more than about 120 130 pounds of exchangeable K20.

In terms of predicting fertilizer needs for corn grown on soils in North and
West Florida, this means that on soils testing 120 pounds or more of exchangeable
K20 per acre no economic response can be expected to potash fertilization. Except
for a starter application of this nutrient, which should probably be made under all
conditions, no potash should be needed during this crop year on soil with this
potash reserve. Assuming an average efficiency of 70 percent for potash fertilizer,
an approximation of the potassium fertilizer needs of soils testing less than
120 130 pounds can be made as follows:

(130 X)/.70 = amount K20 to apply.
(X = exchangeable K20, Ibs./acre, in the soil).

Two cotton fertility trials were conducted in Escambia and Okaloosa counties
last year. An average increase of 310 pounds of seed cotton was obtained from the
use of 20 pounds of K20 as a sidedressing on the cotton grown on Ruston sandy loam,
containing 66 pounds of exchangeable K20. Since a base application, containing
40 pounds of K20, had been made at planting time, this represents an increase in
seed cotton from the use of 60 pounds as compared to 40 pounds of K20. On the
other hand, cotton grown on Tifton fine sandy loam containing 216 pounds of K20,
by the soil test, produced a slightly lower yield when the sidedress was applied
than when it was not made. Although, there were not sufficient soils represented
in the cotton trials to draw any conclusions, it is believed that the values pre-
sented above for corn will also hold for predicting the fertilizer needs for cotton.










Table 6 The Response of Corn to Potash Sidedressing in 1955.


: : Potash Sidedress
S: Exch. : Lbs/Acre K2O


:Farm :County :


Beach

Quency

Morris

Scruggs

Clayton

Hunter

Ratliff

Faulkner

Clemmons

Gilley

Barrineau


Gilchrist

Gilchrist

Jefferson

Jefferson

Jefferson

Columbia

Hamilton

Taylor.

Okaloosa

Escambia

Escambia


Soil Types

Jonesville f.s,

Jonesville f.s.

Norfolk 1.f.s.

Blanton l.f.s.

Ruston l.f.s.

Norfolk 1.f.s.

Lakeland f.s.

Elanton f.s.

Norfolk f.s.1.

Tifton f.s.1.

Ruston f.s.l.


: Soil K90 : 0 : 30 : 60
: Lbs/A : Bu./A


66

28

S129

S 96

S 56

56

S 67

: 57

S 66

S179

S161


49.6

51.8

39.5

54.3

34.7

19.5

30.0

44.9

55.8

78.3

33.0


51.8

55.8

39.3

54.8

38.4

24.1

33.6

54.9

56.6

73.0

34.7


52.3

57.1

40.0

54.9

33.1

27.0

34.5

57.5

59.2

79.3

32.7


: Norfolk f.s.l. : 263


: Barrineau : Escambia


: 34.0 : 33.7 : 34.7 :


- ---








The experiments designed to establish a relationship between the level of
K20 in the soil and the need for potash fertilizer on peanuts have not lead to
any conclusions. Peanuts are a difficult crop to work with and many of the trials
were not harvested. It is also difficult to determine if growth factors, other
than the one under study, are at an optimum level. Nevertheless, in the 6 trials
in 1954 and 1955 that were harvested, the average increase from the application of
0-40-80 over the yield from 0-40-40 was -100 pounds of nuts on soils testing high
in potassium, +46 pounds on soils testing medium, and +162 pounds of nuts on soils
testing low in exchangeable potassium.

Six fertility experiments were conducted with flue-cured tobacco during the
past two years. Five levels of potassium fertilization were included. All plots
received a base application of 36-108-108, made in two equal applications of 600
pounds of 3-9-9 per acre. The check plots received no additional potash; however,
other plots received 36, 54, 72, and 108 pounds of potash at a second sidedressing.
It should be noted that the 54 and 108 pound treatments also received additional
applications of 18 pounds of N so that the average yields listed below for these
two treatments are the results of additional N as well as the additional K20.


Additional Potash as Sidedress Average Yield of Leaf Relative Quality
K20/Acre Lbs./Acre Rating

0 1094 5
36 1269 3
54* 1295 4
72 1180 1
108* 1315 2

Also received 18 pounds of N as sidedress.

The relative quality ratings are based on the average price received for the
cured tobacco. The potash level of all the fields used in these trials were low
to very low in potassium as are most soils used in the production of flue-cured
tobacco. While all fields did not respond the same to all potash treatments, there
was a general response to the additional potassium applied as sidedressing. It
would appear that 108 pounds of potash as applied in 1200 pounds of 3-9-9 fertili-
zer, is not sufficient for flue-cured tobacco on soils testing low to very low in
exchangeable K20.

Five replicated fertility experiments in Escambia on soybeans, which included
'four levels of potassium fertilization (0, 30, 60, and 90 pounds/acre of K20)
failed to show any significant response to this plant food. However, all soils
on which the trials were located tested high to very high in exchangeable potassium.
An attempt will be made this coming year to locate these trials on soils containing
a wide range of potassium levels.

Yield curves constructed with the use of field data have probably been more
widely used than pot or culture data to show the relationship between soil nutrient
supply and plant growth. However, due to the difficulty in controlling many of the
environmental factors in the field, pot studies present many advantages in work of
this type; although, admittedly, work carried out under these artificial conditions
may not have direct field application.







12
In order to compare the results obtained in the field with those secured
under controlled conditions, oats were grown in the greenhouse on the following
three soil types: Arredonda loamy fine sand, Red Bay fine sandy loam, and Klej
fine sand. On the first two soils four rates of potassium were applied and mixed
throughout the soils in 2 gallon pots, The treatments were 0, 30, 60 and 120
pounds per acre of K20. In the third soil, Klej fine sand, only the 0, 30, and
60 pound rates were used. A base application of nitrogen and phosphorus was made
to all pots and dolomitic limestone was also applied to the Klej soil.

Two harvests of the above ground portion of the plants were made. The plant
materials were oven-dried, weighed, and ground for determination of potassium con-
tent. The total yields (two cuttings), percent potassium, total K20 absorbed,
and percent recovery of applied potash is given in Table 7.

Assuming that the oats growing in the pots with two sources of potash, soil
and fertilizer, will absorb this nutrient in proportion to the amounts available,
one should be able to construct curves to indicate the available potash supplied
by the soils.

The estimate of the amount of soil potash is also obtained by extrapolating
a growth response to the intersection with the X axis, as proposed by Mitscherlich,
The distance from the origin to this point of intersection gives the units of soil
nutrient as available as the fertilizer added to obtain the response curve. As
can be seen in Table 3, there is little difference in growth due to treatment and
consequently the "b" value overestimates the amount of potassium available in
these soils.

There is a significant difference in the percent K in the plants and in the
total K20 uptake by the plant. This suggests that the yield-of-potassium curves,
as proposed by Dean, may more nearly measure the available K20 in the soil. Curves
for the three soils are shown in Figure 4. It is interesting that the available
soil potassium as indicated by the curves is approximately 1.5 times as much as
that extracted by ammonium acetate (pH 4,8). These values for the Arredonda, Red
Bay, and Klej soils were about 320, 118 and 84 pounds per acre respectively for
the curve and 228, 84, and 54 pounds of K20 per acre as indicated by soil test,










Table 7 Yield of Oats and Total Potassium
Uptake in Greenhouse Experiment.


:K20 Applied: Total Plant Yield : Percent K Total K20 : Percent
: Lbs/Acre : Grams/Pot/Dry Matter in Plants:Absorbed, Lbs/A:Recovery of Fertilizer

Arredonda loamy fine sand
0 : 19.85 : 3.23 : 205.7 -
30 : 20.92 : 3.33 : 223.5 : 49
60 : 20.65 3.56 : 235.9 s 42
120 : 22.27 : 3.95 : 282.2 : 53

Red Bay fine sancy loam
0 : 13.61 : 0.96 : 83.8 :
30 : 14.03 : 1.13 : 101.7 60
60 : 14.79 : 1.33 : 126.2 71
120 : 16.06 : 1.63 : 167.9 : 70
Klej fine sand
0 : 12.88 0.76 : 62.8 -
30 : 12.20 : 0.99 : 77.5 : 49
60 13.66 :1.23 t 107.8 :75








0 -O--j-Lhf


25 50 75 100
Exchangeable Soil K20, Lbs/acre
Relationship between exchangeable Soil K20 and Corn
Plots receiving no K Sidedressing


125

Yields on


Total K20
Absorbed, Lbs/ac.


290


100


- ,-


Soil K20, Lbs/ac.

Figure 4. Yield of Potassium Curve


+-'j* Fertilizer K20,
S Lbs/acre


IOO
1100




0
75


o
H


S50
0
O
CH
0
U

25


1d


Figure 3.


3LeFI I MOMMM=I-"C* -i IMMMU= I' ~ '








Phosphorus: As noted in the previous discussion, a rather wide variation in
certain soil properties, such as texture, nature of the clay mineral, organic mat-
ter content, and base exchange capacity does not appear .n rr-n+.1y infIlnor- +.h=
relartin hip orf t-ap response wv-th wohngoe~ soil potassium. If this is indeed
the case, it should be possible to establish correlations between response and
available soil potassium over a fairly wide range of soil conditions. On the
other hand, some of these same soil factors, particularly texture and nature of
the soil colloid, have a marked effect upon the availability of the phosphorus ion.
Under these conditions it is necessary to consider the soil type or area, as well
as the crop to be grown, cropping history, etc., when interpreting the test re-
sult in terms of phosphorus fertilizer needs of a soil.

Some of the relationships of yields of crops (reported in Part I) with avail-
able phosphorus from the cooperative fertilizer tests and greenhouse experiments
are discussed in this section.

Average corn yields from ten treatments containing 30 pounds of P20 each
as compared to yields from the ten treatments containing 60 pounds each, are
given in Table 8. The contents of available soil phosphorus, as measured with
an ammonium acetate (pH 4.8) extractant, are also given for the pre-fertilization
samples from each field. Figure 5 illustrates the relationship of the increases
in corn yields from the use of 60 pounds of P205 over the yields resulting from
applications of 30 pounds of P205. In general, the corn yields increased with
the use of the extra 30 poundsof P209 on soils low in available phosphorus but
did not significantly increase on soils containing higher amounts of this plant
food. Since an increase of about two bushels of corn would be necessary to pay
for the extra phosphorus, at present prices, it would appear that the application
of the extra phosphorus would be economical on soils containing less than about
14 to 18 pounds per acre of available P20 On the other hand on soils such as
the predominately sandy soils included in these tests, containing more than 14 to
18 pounds of available phosphorus, it would probably not be economical to apply
more than a starter application of about 30 pounds of P205 per acre.

Table 8. Corn yields from 30 and 60 pounds per acre of applied PO0.


Available Applied Phosphorus
Farm Soil Type pH Soil P205 Lbs/acre P205
30 60
lbs/acre Bu/acre Bu/acre
Beach Jonesville f.s. 5.7 hO 50.1 49.9
Quincy Jonesville f.s. 5.8 35 51.8 56.3
Morris Ruston l.f.s. 5.5 5 35.7 41.4
Scruggs Ruston l.f.s. 5.3 9 55.5 50.7
Clayton Ruston l.f.s. 5.6 1 28.9 39.3
Hunter Norfolk fs. 5.3 33 22.2
Ratliff Lakeland f.s. $.4 7 29.5 34.9
Faulkner Blanton f.s. 5.6 6 52.0 50.9
Clemmons Norfolk l.f.s. 5.2.-. 9 53.8 59.0
Gilley Tifton f.s.l. 5.4 13 74.3 78.2
Barrineau (1) Ruston f.s.l. 5.6 27 34.2 32.4
Barrineau (2) Norfolk f.s.l. 6.0 51 33.7 33.4








Indications are that the level of available soil phosphorus at which no
economic increase in corn yields may be expected -- above that received from a
starter application -- is no more than 6 to 10 pounds of P2P5 on the sandy loams
of West Florida.

The corn yield response to varying'levels of phosphorus fertilizer on Tifton
fine sandy loam in Escambia County, testing 6 pounds of available soil phosphorus
in the pre-fertilization samples, are shown in Figure 6. On this soil in 1955
yields increased with applications up to 108 pounds of P205 but decreased with
heavier applications. These yields are-not unlike the corn yields received on
soil containing varying levels of residual phosphorus, accumulated over a period
of five years, on a Norfolk fine sandy loam at the West Florida Station. On
this 5 x 5 x 5 experiment (Project 544 Progress Report) corn yields increased
with each level of residual phosphorus up to about 15 pounds of P 20 (extracted
with acid ammonium acetate). However, considering the large applications of
fertilizer phosphorus required to increase the available soil phosphorus to this
level, it is probably more economical to maintain the level to the range of 6-10
pounds on soils of this type. In a similar test on Red Bay fine sandy loam, the
yields were only about 60 percent as high as on the Norfolk, but the relationship
between levels of residual phosphorus and corn yields were about the same.

Results from cooperative fertilizer trials with peanuts in 1954 and 1955
and from the West Florida Station indicate that economic responses to fertilizer
phosphorus cannot be expected on soils containing more than 6 to 10 pounds of
phosphorus, in West Florida.

Table 9. Oat yields, plant uptake and percent recovery of applied Phosphorus
(p32) in greenhouse experiment.


P20 Total Content Total Recovery P20 Recovery A
Applied Yields P in Uptake of from of
gms/pot Plants P20, Fertilizer Fertilizer Fertilizer Value
Percent Lbs/a P20 P205
Percent Percent Percent
Arredonda fine sand (2 gal. pots)
1. O 27.2 0.436 80.7 -
2. 25 26.3 0.410 73.5 0.0 3.21 9.43 756
3. 50 27.9 0.428 81.4 1.4 5.82 9.47 812
4.100 28.1 0.475 90.8 10.1 12.03 10.92 733

Red Bay Sandy loam (1 gal. pots)
1. 0 12.5 0.131 22.3 -
2. 50 14.5 0.141 27.9 11.2- 31.84 17.77 107
3.100 15.8 0.149 32.0 9.7 49.99 16.00 100
4.200 17.0 0.162 37.4 7.6 67.84 12.69 95

Klej fine sand (1 gal. pots)
1. 0 16.7 0.155 35.3 -
2. 50 17.3 0.162 38,2 5.8 14.58 11.14 294
3.100 16.6 0.177 39.9 4.6 24,84 9.91 300

Determined with use of P32








In a greenhouse experiment, the response of oats to levels of phosphorus fer-
tilization (applied as radioactive P32) was studied on three soils from Central
and North Florida, which varied widely in their chemical and physical properties.
The soils were (1) Arredonda fine sand, a phosphatic soil from Central Florida,
(2) Red Bay sandy loam, with a heavy subsoil and a large capacity to fix phos-
phorus, (3) Klej fine sand from Central Florida, a soil with a low exchange cap-
acity. The rates of phosphorus were 0, 25, 50 and 100 pounds per acre of P20O
on the Arredonda; 0, 50, 100 and 200 pounds on the Red Bay; and 0, 50, and 100
pounds of P 20 on the Klej soil. Nitrogen and potassium were applied to all pots
at rates calcGlated to be optimum. The treatments were replicated three times and
oat yields were taken twice. The yields of oven-dry plant material for the two
harvests are given in Table 9. A definite yield response was obtained only on
the Red Bay soil. It should be pointed out that the extractable phosphorus (with
acid ammonium acetate) was 7 pounds per acre for the Red Bay, but 41 and 20
pounds per acre for the Arredonda and Klej soils, respectively. With these amounts
of phosphorus in the latter soils, a response would probably not be expected.

The phosphorus content of the plant material was determined by chemical analyses
and the total amount of phosphorus contained in the above-ground portion of the
plant was calculated. The recovery, or efficiency, of the fertilizer phosphorus
was calculated by two methods in Table 9. In the direct method, the difference
between the total uptake of P205 by the plants in the check and the uptake by
plants in a certain treatment is divided by the rate of P205 applied. Since all
the phosphorus taken up by the plants in the check pots comes from the soil, the
additional phosphorus taken up by plants in the fertilized pots can be assumed to
be supplied by the fertilizer. The phosphorus content of oats on the Arredonda
soil is considerably higher than oats grown on the other soils. However, the
recovery of fertilizer is rather low at the low levels of application on this soil,

With the use of p32, the percentage of the phosphorus absorbed by the plant
that was derived from the fertilizer was calculated. The percent recovery of the
fertilizer in the oat plants was also calculated by dividing the pounds of P20g
per acre taken up by the plant, that was derived from the fertilizer, by the rate
of application. It will be noted that the two methods of calculating the percent
recovery of fertilizer phosphorus do not give the same results.

The "A" value (Soil Sci. 73:263-271. 1952) was also determined for the three
soils for the various levels of application. This value is an estimate of the
amount of available phosphorus in the soil. The assumption is made that plants
growing on soils containing fertilizer phosphorus mixed with the soil will remove
phosphorus from the fertilizer and from the soil in amounts relative to the avail-
ability of the phosphorus in each. The "A" values are from 15 to 18 times greater
than the values determined by extracting with acid ammonium acetate; however,
the values for the soils remain in the same relative position.

When the "yield of phosphorus curves" were constructed, as described earlier,
the estimated values of available soil P205 were 250, 750, and 775 pounds for Red
Bay, Klej and Arredonda, respectively. The Mitscherlich "b" value, obtained by
extrapolating the growth response to the intersection with the x axis gave even
higher values for phosphorus for these soils.

If a soil test must measure the total amounts of the available forms of phosphor-
us in the soil, as suggested by Bray, then the ammonium acetate extractant does not
meet that requirement, as measured by the "A" value, the yield of phosphorus curve,











r the Mitscherlich "b" value. It gives a much lower value than any of the latter
methods; however, the proportion of one to the other is relatively constant. In
another study a series of samples varying widely in their phosphorus content,
ere analyzed by the Bray method (0.03N NHhF in 0.1 N HC1) and by the acid
ammonium acetate method. In this study the strong Bray extractant removed approx-
mately 33 times as much phosphorus as the ammonium acetate. It was interesting
o note that this relationship was almost constant within the range of the sands
nd sandy loams included in the study,


100 Copies Soils Department -
























\


S10 20 30 40 50

Soil Phosphorus, Lbs/acre P205

Figure 5. Increase in corn yields from 60 Ibs. of P20O over the
yields received from 30 lbs/acre of applied P205 on
soils containing varying levels of available phosphorus.


90 O


80 b


Figure 6,


36 72 108 144
Fertilizer Phosphorus, lbs/acre P205
Corn yield responses to fertilizer phosphorus on Tifton f,s.l


o





0
e

o


**




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