Front Cover
 Table of Contents
 Review of literature
 Experimental procedure
 Experimental results
 Literature cited

Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 686
Title: Forage and animal response to different phosphatic fertilizers on pangolagrass pastures
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00027638/00001
 Material Information
Title: Forage and animal response to different phosphatic fertilizers on pangolagrass pastures
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 686
Physical Description: Book
Language: English
Creator: Hodges, E. M
Kirk, W. G.
Peacock, F. M.
Jones, D. W.
Davis, G. K.
Neller, J. R.
Publisher: University of Florida Agricultural Experiment Station,
Publication Date: 1964
 Record Information
Bibliographic ID: UF00027638
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Table of Contents
        Page 2
    Review of literature
        Page 3
    Experimental procedure
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    Experimental results
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
    Literature cited
        Page 27
        Page 28
Full Text

I ru









Review of Literature

Experimental Procedure

Experimental Results


Summary -..

Conclusions ......

Literature Cited -.

Cover: Pangolagrass maintaining a complete cover nine years after planting
on virgin flatwoods soil, with rock phosphate used in a balanced fertilizer


The authors express their appreciation to the Florida Agri-
cultural Research Institute for financial assistance in establish-
ing the pastures used in this experiment.

Forage And Animal Response To Different

Phosphatic Fertilizers On

Pangolagrass Pastures

E. M. Hodges, W. G. Kirk, F. M. Peacock, D. W. Jones,
G. K. Davis, and J. R. Neller'
Phosphorus has long been recognized as an essential element
in plant and animal nutrition. IMost virgin soils of peninsular
Florida are lacking in this element with resultant low forage
yields of inferior nutritional values. It was shown in 1933 that
cattle grazing on areas of acute phosphorus shortage developed
deficiency symptoms (2)'.
Use of phosphatic fertilizers was stressed in the pasture
development programs used in peninsular Florida in the late
1930's, and a definite grazing preference for areas treated with
phosphatic fertilizers was observed on commercial pastures
seeded to carpetgrass (A.xonopus ,if,.' Chase). There were
both growth responses and mineral nutritional improvements.
The value of phosphorus fertilization of pastures was firmly
established by use of raw rock phosphate and superphosphate,
but other phosphatic fertilizers had been less thoroughly evalu-
ated for pasture improvement (4, 5). The acreage of developed
and potential pasture on phosphorus-deficient soils in Florida
is extensive. The choice of an effective and economical source
of this fertilizer element is an important part of every pasture-
cattle management program.


It was shown by Gammon et al. (7) that many virgin soils
in Florida contain less than 0.1 percent total phosphorus, and
some have less than 0.01 percent. Total soil phosphorus data
are variable in value since much of the native soil phosphorus
is present in a form not readily available to plants (1).

'Agronomist, Vice Director in Charge, and Associate Animal Hus-
bandman, Range Cattle Station, Ona; Agronomist, Agricultural Extension
Service, Gainesville; Animal Nutritionist, Animal Science Department; and
Soils Chemist Emeritus, Soils Department, Main Station, Gainesville.
2 Numbers in parentheses refer to literature citations.

Florida Agricultural Experiment Stations

Comparisons of the response of different forage species to
several phosphatic fertilizers have been reported by Jones et al.
(10) on mineral soils and by Neller (14) on organic soils. Becker
et al. (2) showed that the phosphorus content of forage from
native ranges was lower than the 0.13 percent feed requirement
minimum proposed by Black and co-workers (3). It is currently
believed that not less than 0.20 and 0.25 percent of phosphorus
in air-dry forage are the minimum levels necessary for gestating
and lactating cows, respectively, with 0.30 percent needed for
growing animals (Cunha et al. 5).
The work of Blaser and Stokes (4) demonstrated that the
phosphorus content of carpetgrass was increased an average of
78 percent by application of several different phosphatic ferti-
lizers. Unpublished data from the Range Cattle Station showed
that the phosphorus content of pangolagrass (Digitaria decum-
bens Stent.) was increased from 0.08 percent to 0.27 percent
in the air-dry forage by fertilization with 50 pounds of super-
phosphate annually.

Work was started at the Range Cattle Station in November
1946 to study the effect of five different sources of phosphorus
on growth of pangolagrass and on the nutrition of grazing cattle.
The experiment was located on an Immokalee fine sand site
having scattered long-leaf pine (Pinus palustris Mill.) and
covered with wiregrass (Aristida spp.) and saw palmetto (Sere-
noa repeus [Bartr.] Small). Total and dilute acid-soluble soil
phosphorus levels averaged 52 and 5.9 parts per million respec-
tively in the unimproved land, and pH values averaged 4.9.
Clearing of trees and stumps and soil preparation for the first
pastures was initiated during the winter and spring 1946-47.
Pangolagrass was chosen as the forage species because of
its productivity under soil moisture extremes and for the value
of mature herbage when deferred for winter grazing (8, 11).
All experimental pastures were planted by disking and packing
green cuttings into well-prepared soil. Three years were re-
quired for complete establishment of all pastures in the 105-acre
experimental area.
Seven different treatments were established, including super-
phosphate (super) (18), superphosphate plus lime (super +
lime), raw rock phosphate (rock), colloidal phosphate (colloi-

Phosphatic Fertilizers on Pavgolagrass Pastures

dal), triple superphosphate (triple super), basic slag, and no
phosphate (no phos). Each treatment covered 15 acres made up
of two non-adjacent 7.5 acre areas which were in turn divided
equally to permit rotational grazing.
A detailed record of fertilizer applied to each of the seven
treatments is shown in Table 1, with year of planting corre-
sponding to the first fertilization record. Superphosphate and
triple superphosphate were applied annually from 1947 through
1954 at 50 pounds per acre of available PO2.,; basic slag, 500
pounds of material per acre yearly; rock phosphate, 2000 pounds
per acre every third year; and colloidal phosphate, 2400 pounds
per acre at 3-year intervals. Superphosphate and triple super-
phosphate application rates were reduced by one-half during
the 1955-58 period. Basic slag was applied annually at 300
pounds per acre during this time. Colloidal phosphate was spread
at 1000 pounds per acre in 1957, and no rock phosphate was
added after 1953.
Potassium was supplied to all treatments in the form of
muriate of potash at 25 pounds K.O per acre annually from 1947
through 1954 and at 50 pounds thereafter.
The annual rate of nitrogen application was 25 pounds per
acre from 1947 through 1950, 50 pounds per acre during 1951-
54, and 100 pounds thereafter. These fertilization changes yield-
ed a progression of yearly N-P-K fertilization patterns, begin-
ning with 25-50-25 pounds per acre respectively, through 50-
50-25 and, in the final four years, 100-25-50.
Minor elements were applied in sulfate form on all pastures
at time of establishment at per acre rates equivalent to 6.0,
5.0, and 4.0 pounds of CuO, MnO, and ZnO, respectively. Addi-
tional copper sulfate was supplied to all treatments in 1953 at
2.4 pounds CuO equivalent per acre.
Calcic lime was applied only to the superphosphate plus lime
treatment at 1 ton per acre in 1947, 1950, and 1953. All pastures
except those of the superphosphate treatment received dolomitic
lime at 1 ton per acre in 1955.
Phosphorus-carrying fertilizers were applied with drop-type
spreaders to prevent overlapping from one field to another.
All lime and fertilizer materials, including initial treatments,
were surface applied without incorporation.
Soil samples were taken once annually in early spring before
fertilization and consisted of a composite of 20 cores to a depth

Table 1.-Pounds per acre of fertilizer applied 1947-58.

No Super Super Triple Basic
Year Fertilizer Phos Phos + Lime Rock Colloidal Super Slag

1947 N 25 25 25 25 -
P0. -- 50 50 560 -
K,0 25 25 25 25- -

1948 N 25 25 25 25 25
PO, 50 50 50 -
KO1 25 25 25 25 25 -

1949 N 25 25 25 25 25 25 25
P.,0 50 50 480 50 50
K2O 25 25 25 25 25 25 25

1950 N 25 25 25 25 25 25 25
P,05 50 50 560 50 50
K2O 25 25 25 25 25 25 25

1951 N 50 50 50 50 50 50 50
P20, 50 50 50 50
K-0 25 25 25 25 25 25 25

1952 N 50 50 50 50 50 50 50
P2,- 50 50 160 50 50
KO 25 25 25 25 25 25 25

Table 1.-(Continued)

Year Fertilizer

1953 N

1954 N


1955 N

1956 N


1957 N

1958 N














Table 1.--(Continued)









+ Lime































Triple Basic
Super Slag

50 50
50 50
25 25

50 50
50 50
25 25

100 100
25 25
50 50

100 100
25 25
50 50

100 100
25 25
50 50

100 100
25 25
50 50

Florida Agricultural Experiment Stations

of 4 inches in each pasture division. pH values were determined
by use of a glass electrode using a 2:1 water to soil suspension.
Soluble phosphorus was measured by the sodium acetate-acetic
acid method of Morgan (13) and total phosphorus by a method
described by Forbes (6).
One pasture unit of 3.75 acres in each treatment was shallow-
disked for renovation purposes in 1956. Certain pastures in the
no phosphate and superphosphate treatments required cultiva-
tion in 1958.
Forage yields were measured in each 3.75 acre pasture by
harvesting areas protected by 5 by 5 foot wire cages. The cages
were moved to different locations at each harvest, and yields
were determined as total air-dry forage per acre per year. The
grass varied in maturity from early to advanced heading stage
when harvested at three to four dates annually. The sampled
grass was more mature than that grazed by cattle during spring
and summer. Grass for winter grazing was of lower quality
than when sampled in October or November. A composite sample
from three cages in each pasture division was obtained at each
harvest date, making four samples per treatment which were
used for separate chemical analysis.
Two-year-old, bred, grade Brahman heifers were used as the
beginning and replacement animals in this project. All of the
original cattle were sired by one Brahman bull. Each herd
grazed only the four pasture divisions receiving a particular
phosphate treatment. Stocking rates within the experiment
ranged from 1.5 to 3.0 acres per cow unit. The breeding season,
beginning in early April, extended 120 days during the first
six years of the study. This was reduced to 110 days in 1954,
and at the same time, March 20th was adopted as the starting
date. One Brahman bull was used for the four herds in 1948
and 1949, being moved from pasture to pasture on a daily basis.
Two bulls were used with the seven groups of cows in 1950, and
three were used in 1951. A bull was kept with each herd in 1952
and in all subsequent years. Crossbred bulls, 1/- Shorthorn-1/.
Brahman, were used from 1950 and later except that one Brah-
man was used in 1955 and two from 1956 through 1958. The
cows calved in the pastures, and the calves remained with their
dams until weaned at 6 to 8 months of age.
Each group of cows had free access to common salt and to
Range Cattle Station modified "salt sick" mineral (1) consisting

Phosphatic Fertilizers on Pangolagrass Pastures

of 100 pounds common salt, 10 pounds red oxide of iron, 2 pounds
of copper sulfate, and 2 ounces of either cobalt chloride or cobalt
sulfate. The cattle obtained all their calcium and phosphorus
through the forage, since no complete mineral was supplied at
any time. Water was piped from a central well to tanks in all
No supplemental feed was given to any of the seven herds
until 1958, when heavy rains and winterkilling of pangolagrass
severely reduced the forage supply and feeding was required
from March through June. A low-phosphorus ration consisting
of citrus molasses, urea, and cottonseed hulls was provided all
groups on a daily basis, while the cattle of each herd were held
on one pasture division to permit regrowth on the other three.
Recovery of stand and growth was sufficient to provide limited
grazing by June 15, and supplemental feeding was discontinued
in early July.
Cattle were weighed at 28-day intervals from November
1947 through 1952 and at 3-month intervals after that time. The
cattle were sprayed with DDT at the time of weighing or more
often when necessary to control external parasites, particularly
horn flies.
Blood samples were obtained from each cow at 28-day inter-
vals from November 1947 through 1951 and at 3-month inter-
vals after that time. Results of the blood analyses are being
prepared for separate publication.

Air-dry forage yields from all treatments are presented in
Table 2. The annual yields represent a total of three to four
harvests for each year and are summarized for the three ferti-
lizer periods: 1948-50, during which the initial 25-50-25 pounds
per acre of N, P20., and K2O were applied annually; 1951-54,
for which a 50-50-25 pattern was employed; and 1955-58, when
a 100-25-50 relationship of the three major fertilizer compon-
ents was applied.
The forage analyses shown in Table 3 are for two separate
years, each chosen as being typical of the fertilizer management
patterns in which they fell. Each value included is a simple
average of samples from all harvests made during the year on
fertilizer treatment indicated.
Soil analyses of the zero to 4-inch depth are included in Tables

10 Florida Agricultural Experiment Stations

Table 2.-Average annual yield of air-dry pangolagrass per acre.

Average Pounds Per Acre, Annually
Treatment 1948-50 1951-54 1955-58

No phos 3592 6632 8442
Super 5905 8688 11059
Super + lime 6761 10254 13506
Rock 7869 10632 13558
Colloidal 8135* 8224 8021
Triple super 5956* 9018 12726
Basic slag 5514* 9500 13024
Includes 1950 only.

Table 3.-Average protein and phosphorus content of air-dry pangolagrass
herbage for two representative years.

Herbage Analysis, Percent

Protein Phosphorus
Treatment 1951 1958 1951 1958

No phos 4.49 6.91 .12 .10
Super 4.15 6.20 .37 .20
Super + lime 4.50 6.33 .35 .25
Rock 4.30 6.86 .52 .35
Colloidal 3.95 7.90 .32 .28
Triple super 4.03 7.14 .31 .26
Basic slag 3.97 6.87 .26 .24

4, 5, and 6. The yearly value for each treatment is the average
of determinations made on four samples obtained from the sep-
arate fields included in each pasture fertilization practice.
Changes in carrying capacity are indicated in Table 7, and
trends in average weight of cows in December of each year in
Table 8. Addition and removal of cows were planned to main-
tain an intermediate level of forage utilization which provided
enough grass during winter and early spring. Changes in cattle
numbers were kept to a minimum and replacements were of
similar breeding and weight.

Phosphatic Fertilizers on Pangolagrass Pastures

Calving performance of cows and calf weaning data are pre-
sented in Table 9 and 10. All cows present in the herd during
the breeding season were included in the calculation of percent
calf crop the following year.
Gains per acre per year appear in Table 11, with the data
for calf weight and net gain or loss of cows shown separately
and also combined as a total per acre production figure.
Mineral supplement consumption per cow is summarized by
fertilizer treatment periods in Table 12. The mineral used by
the entire herd, including calves and bull, is included in the
consumption figure.

This investigation was designed to study the effect of several
phosphatic fertilizers upon growth of pangolagrass and on the
performance of grazing beef cows. Herd and pasture manage-
ment plans were designed to provide year-round forage. Each
group of cattle depended upon forage for their nutritional in-
take, receiving only water, common salt, iron, copper, and cobalt
in addition. Grass in each treatment received only one phos-
phatic material.
Efficiency of production of the trial herds was placed in sec-
ondary position by the management plan, which called for all
feed to be obtained from pasturage. Stocking rates were ad-
justed at levels which provided a balance between cattle num-
bers and winter and spring forage supplies. Changes in number
of cows per herd were kept at the minimum consistent with this
plan. Supplemental feeding was used only as an emergency
practice because it would have reduced nutritional differences
between treatments. Low temperatures and above-average rain-
fall in January and February 1958 reduced the forage supply
drastically and all cattle required supplemental feeding from
March to July.
Fertilizer.-The fertilization program followed in 1947 when
this trial was begun was similar to established practice. Use of
substantial rates of nitrogen on pasture grasses was still in its
beginning stage, and 25 pounds per acre was considered ade-
quate. Heavy rates of rock phosphate were being used on pasture
under the Agricultural Adjustment Act program. Five years
after an unlimed pasture had been fertilized with finely ground

Florida Agricultural Experimnent Stations

raw rock phosphate at 1800 pounds per acre, the phosphorus
level in the soil had declined to the level found in unfertilized
soil (Forbes, 6). Retreatment with rock phosphate at 3-year
intervals seemed a suitable schedule for the maintenance of soil
phosphorus at an adequate level. Nitrogen rate increases in
1951 and 1955, and phosphorus reductions in 1955 were made
for the purpose of increasing the intensity of use of soil phos-
phorus. The requirement of grass pastures for potash was known
only in a general way, and potash application rates were estab-
lished somewhat arbitrarily (5). Lime was omitted from all
treatments except the superphosphate plus lime until 1955. This
departure from recommended pasture treatment permitted ob-
servation of the various phosphate materials in pastures under
a low-calcium-magnesium regime. Dolomite was applied in 1955
to the five phosphorus sources and to the no phosphate pastures,
thus establishing a complete soil amendment pattern. The ori-
ginal "superphosphate plus lime" treatment received dolomite in
the revised plan, while the original "superphosphate" (unlimed)
pastures continued without lime addition during the 1955-58
test period.

Forage Production.-Moderate stocking rates and a clean,
vigorous stand of pangolagrass helped keep forage production
at an intensive level. The yields obtained (Table 2) were higher
than those measured by Koger et al. (12) grazing pangolagrass
with similar fertilization. Soil and climatic factors and harvest
techniques caused the differences.
A comparison of herbage yields shows that the no phosphate
treatment produced only 54 percent as much forage as the aver-
age of all phosphate treatments during the 1948-50 period when
nitrogen was applied at 25 pounds per acre annually. There was
strong growth response to all five sources of fertilizer phos-
phorus and a substantial degree of variation between the several
materials. The low forage production of the colloidal phosphate
treatment during the 1955-58 period was reflected in the out-
ward appearance of the pastures. This was the primary con-
sideration in the decision to apply additional phosphate to this
treatment in 1957 although soil phosphorus levels (Tables 3 and
4) revealed no shortage of this element.

Forage Analyses.-Protein analyses (Table 3) for 1951 and
1958, which were respectively representative of the 50 and 100

Phosphatic Fertilizers on Pangolagrass Pastures

pounds per acre nitrogen rates, indicate substantial between-
treatment variations in protein content, with the colloidal treated
pasture having the highest value. The relatively low forage
yield obtained on the colloidal treatment and the fact that a
uniform rate of nitrogen was employed may explain the higher
protein content of the forage.
Herbage phosphorus contents were adequate for animal needs
in 1951 in all but the no phosphate treatment (5). These values
had declined by 1958 so that the superphosphate treatment was
at the minimum level, others were slightly higher, and only
forage from the rock phosphate fertilized areas averaged safely
within the desired range. Cattle on the no phosphate treatment
remained vigorous and productive through most of the experi-
ment even though the forage consistently averaged low in phos-
phorus content. Indications of gross phosphorus deficiency are
discussed in a separate section. Grass produced on the phosphate-
treated pastures in 1958 contained at least twice as much phos-
phorus as that from the no phosphate areas. Cows and calves
on these pastures remained in good condition and made satis-
factory growth throughout the experimental period.
Soil Analyses.-Soluble phosphorus tests (Table 4) on all
phosphated pastures were consistently higher than those on the
no phosphate treatment, with the ratio varying widely from
year to year. Total phosphorus analyses (Table 5) on the no
phosphate pastures remained comparatively constant through
the 1947 to 1959 period. The rate of removal of phosphorus by
cattle on this treatment has been calculated to be 1 pound per
acre annually (14). This was approximately 2 percent yearly
of the original amount present in the 0 to 4-inch depth and
would have caused a decline without a source of replenishment.
It must be concluded that pangolagrass absorbed enough phos-
phorus below the 4-inch sampling zone to balance the amount
removed by cattle. Increases in total phosphorus within the
more soluble phosphate treatments developed slowly and were
moderate in extent. Low pH values in effect through 1954
favored a rapid leaching rate (6). Reduced per-acre application
of the readily soluble phosphates in the final four years of the
trial also served to keep phosphorus accumulation in these treat-
ments at a minimum.
pH data (Table 6) reveal small but consistently higher
values for the superphosphate plus lime and the basic slag

Table 4.-Soluble phosphorus (P) as parts per million in surface four inches of soil.


No Phos


Super + lime



Triple super

Basic slag

1947* 1947** 1948 1949 1950 1951 1955 1956 1957 1958

5.6 4.4 4.7 4.9 5.4 6.7 2.9 2.8 3.4 6.0

5.5 6.3 8.2 8.2 10.7 8.2 6.1 8.5 7.0 7.2

5.9 7.9 10.4 8.9 10.9 11.1 7.8 13.1 9.7 8.4

6.6 11.1 11.2 9.9 9.5 11.4 7.2 9.8 11.2 10.7

- 11.6 6.6 5.0 9.9 7.6 7.6

- 9.1 8.5 5.9 7.3 8.5 7.8

- 11.2 10.6 10.2 8.5 21.2 10.9

* Prior to treatment.
* Four months after treatment.




8.8 |

9.9 V

7.1 2




Table 5.-Total phosphorus (P) as parts per million in surface four inches of soil.



1947** 1948

No phos


Super + lime



Triple super

- 131


Basic slag

* Prior to treatment.
** Four months after treatment.



















70 C




96 1

Table 6.-pH of surface four inches of soil.

1947* 1947** 1948 1949 1950 1951 1952 1955 1956 1957 1958 1959

No phos


Super + lime


5.02 4.59 5

4.96 4.52 4

4.95 4.89 4

4.92 4.66 4


Triple super

Basic slag

* Prior to treatment.
** Four months after treatment.

.02 4.44 4.38 4.26 4.54 5.07 5.11 5.42 5.58 4.9

.60 4.46 4.18 4.22 4.58 4.64 4.44 4.77 4.65 4.3

.96 4.79 4.56 4.94 5.20 5.24 5.35 5.71 5.76 5.6

.61 4.56 4.46 4.42 4.80 5.06 5.16 5.56 5.46 5.4

- 4.39 4.34 4.76 5.15 5.32 5.66 5.55 5.6

- 4.19 4.26 4.49 4.90 4.87 5.44 5.18 4.8

- 4.44 4.70 4.99 5.61 5.70 6.19 5.63 5.7


Table 7.-Number of cows per treatment.

Treatment 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958

No phos 2 3 3-5 5 5 5 5 5 5 5 5

Super 4 6 7-9 8 8-9 10 10 10 10 9-10 8-9

Super + lime 7 8 8-9 8 8-9 10 10 10 10 9-10 7-9

Rock 6 9 8-10 8 8-9 10 10 10 10 8-10 7-8

Colloidal 6-9 8 8-9 10 10 10 10 8-9 7-8

Triple super 6-8 8 8-9 10 10 10 10 9-10 7-9 c

Basic slag 6-8 8 8-9 10 10 10 10 9-11 7-9

------------------------------ -- -^ -----------------------------

18 Florida Agricultural Experiment Stations

treatments. Fluctuations in pH readings that cannot be traced
to soil amendment influences are of large magnitude, and ex-
treme caution should be exercised in evaluating them.

Carrying Capacity.-The number of cows per treatment
(Table 7) reached a maximum in 1953, when all pastures were
fully established, management experience had been developed,
and increased nitrogen fertilization was in effect. Only be-
tween the no phosphate and the phosphate treatments was it
possible to determine a consistent, long-term difference in carry-
ing capacity. Growth of grass on the colloidal phosphate treat-
ment was so much reduced by unexplained factors in 1957 that
cattle numbers had to be adjusted downward. Increased forage
supply on the slag treatment during the same year briefly per-
mitted addition of another cow, but the number had to be re-
duced before the end of the year.

Cow Weights.-The consistent increase in average weight
of cows (Table 8) from the early to the later stages of the graz-
ing trial is indicative of adequate forage quality and satisfac-
tory animal condition. It is interesting to note that the basic
slag and rock phosphate treatments had the largest increases
in cow weight, while the former had the highest calving per-
centage, and the latter, one of the lowest. It seems likely that
net cow weight increases observed in the trial were larger than
would be expected with commercial cattle; this weight increase
represents a substantial part of the productive capacity of these
improved pastures.
Table 8.-Average weight of cows, December.
Treatment 1948-50 1951-54 1955-58

pounds pounds pounds
No phos 937 1023 1171
Super 805 981 1181
Super + lime 853 1103 1198
Rock 846 1100 1241
Colloidal 877* 1041 1196
Triple super 825* 959 1169
Basic slag 841* 1084 1260
* For 1950 only.

Phosphatic Fertilizers on Pangolagrass Pastures

Calving and Weaning Records.-Breeding performance of
the cow groups on the different phosphate treatments (Table 9)
was extremely variable from year to year and between fertiliza-
tion periods. Young, bred cows placed on trial at one date went
on an every-other-year calving basis that could not be smoothed
out for several years. Individual cow performance on the no
phosphate treatment resembled the average for all cows on the
experiment and showed no evidence of being hampered by phos-
phorus deficiency. Weaned calf percentage averaged highest on
the basic slag treatment and lowest on superphosphate. Breed-
ing performance was irregular during the 1948-52 period when
bulls were moved from herd to herd; this fact may have reduced
the differences between treatments when results covering the
entire trial were calculated. Culling of non-breeders, use of one
bull for each cow herd, and fertilizer practices which produced
increased supplies of higher quality grass all affected the pro-
duction record during the 1955-58 period. A summary for this
period (Table 10) shows weaned calving percentages averaging
62, 63, and 65 percent respectively for the superphosphate, rock
phosphate, and no phosphate treatments at the low side of the
record; 75, 76, and 76 percent for the intermediate colloidal
phosphate, triple superphosphate, and superphosphate plus lime
treatments; and 87 percent for the top-ranking basic slag.
Calving performance of all groups except cows on the no phos-
phate pastures showed a material improvement in 1955-58 over
the preceding four years of record. Average weaning age and
weight of calves from all treatments show a high degree of
Gain per Acre.-Animal production per acre is a most mean-
ingful overall measure of pasture value. Weight gain per acre
on the basic slag treatment was at or near the top during the
entire trial (Table 11) and averaged 14 percent above the
second-place superphosphate plus lime treatment during the
1951-58 period. The consistent production advantage of basic
slag on pangolagrass is partially offset by the extra cost and
special handling problems connected with its use. Slag is not
mixed and handled in commercial complete fertilizer formulas
and requires separate application. These factors make the choice
between high-producing basic slag and other phosphatic fer-
tilizer materials a matter of local conditions and individual
judgment. Similar limitations may apply to other slag materials

Table 9.-Breeding performance and calf production.

Weaned Calves


No phos*


Super lime*



Triple super**

Basic slag**

























Age Weight

days pounds

211 428

222 454

218 455

207 440

222 462

212 435

218 468

** 1950-58.
*** Birth weight 70 pounds.

Per Cow,









Calf Weight
205 Days***









Phosphatic Fertilizers on Pangolagrass Pastures 21

Table 10.-Average annual weaned calf production
and 203-day calf weight, 1955-58.

Weaned Calves
Production Calf
Treatment Number Percent Weight Per Cow Weight*
pounds pounds pounds
No phos 13 65 512 333 484
Super 23 62 474 294 453
Super + lime 29 76 462 351 430
Rock 24 63 482 304 463
Colloidal 27 75 507 380 472
Triple super 29 76 457 347 457
Basic slag 33 87 506 440 467
* Birth weight 70 pounds.

Table 11.-Cow and calf gains, average per acre per year.

Treatment 1948-50 1951-54 1955-58 1951-58
pounds pounds pounds pounds

No phos Cows 22 7 12 10
Calves 43 96 111 104
Total 65 103 123 114

Super Cows 20 43 50 46
Calves 98 133 180 156
Total 118 176 230 202

Super + lime Cows 20 75 20 48
Calves 133 126 220 173
Total 153 201 240 221

Rock Cows 8 43 28 36
Calves 140 131 185 158
Total 148 174 213 194

Colloidal Cows 25 40 -7 16
Calves 150 148 231 190
Total 175* 188 224 206

Triple super Cows -77 49 22 36
Calves 162 138 211 174
Total 85* 187 233 210

Basic slag Cows 1 59 -8 26
Calves 150 177 276 226
Total 151: 236 268 252

* Includes 1950 data only.

22 Florida Agricultural Experiment Stations

that have not been fully evaluated for pasture production on
sandy soils. Comparison of per acre gains on the two super-
phosphate treatments, one with and one without lime, shows a
consistent difference favoring the lime treatment but with the
margin narrowing as the trial progressed and fertilization
changes were made. Cattle made a higher production record
on rock phosphate than on superphosphate during the 1948-50
period, but were similar in performance during the following
years. This comparison indicates that the high soil and forage
phosphorus analyses and the superior forage tonnage obtained
on the rock phosphate treatment did not provide any outstand-
ing nutritional advantage. All phosphated pastures were much
superior to the no phosphate pastures in beef production, ap-
proaching a 2:1 yield relationship which was similar to that
observed in forage production and stocking rate data.

Mineral Supplement Consumption.-Common salt and modi-
fied "salt sick" mineral were fed in separate feeder compart-
ments, but consumption is recorded as a total in Table 12. The
relationship between the amounts of the two materials con-
sumed varied widely between 2:1 and 1:1 of modified mineral
and common salt, respectively.
Mineral use occurred at comparatively high poundages in
certain periods on some of the pasture treatments which were
considered adequate to supply the phosphorus needs of cattle.

Table 12.-Yearly consumption per cow of common salt and
modified "salt sick" mineral.

Mineral Supplement, Pounds Per Cow Annually
Treatment 1948-50 1951-54 1955-58 1948-58
No phos 69 76 47 63
Super 75 63 33 55
Super + lime 49 28 25 33
Rock 59 59 33 50
Colloidal 78* 66 32 52
Triple super 94* 71 32 56
Basic slag 70* 62 44 54

* Data for 1950 only.

Phosphatic Fertilizers on Pangolagrass Pastures

The luxury consumption of mineral, such as that on triple
superphosphate for 1951-54, probably should not be regarded as
animal response to a nutritional need. A more important factor
was the constant and convenient supply available to cattle con-
fined in small pastures (5). Also calculated to increase mineral
consumption was the low forage quality which occurred during
winter and early spring.
Mineral supplement was eaten at the lowest average rate
per cow on the superphosphate plus lime treatment in all periods
of the trial. Average intake per cow on this treatment for the
entire trial was approximately 40 percent below consumption
on the other phosphate treatments. A relatively higher mineral
intake level was maintained by cattle on the no phosphate treat-
ment although this was not in any given year notably different
than the highest rate of use on the phosphated pastures.
The 1948-50 and 1951-54 records indicate that mineral con-
sumption was reduced by a low per acre rate of lime applica-
tion. The clarity of this trend was much reduced by the 1955-58
mineral use data which showed a sharp decrease on the non-
limed superphosphate treatment as well as on the newly limed
phosphorus sources.
Phosphorus Deficiency.-Although the soil phosphorus level
in the untreated land was relatively low, it is also true that
cattle grazing on this range when it was in the native condition
were thrifty and productive. In the absence of critical deficien-
cies under natural conditions it is not surprising to find cattle
on the no phosphate treatment performing in a near-normal
manner. Gross phosphorus deficiency symptoms were indicated
by bone chewing done by two 3-year-old cows on the no phos-
phate treatment in 1948 and by one of the same cows in 1956.
These lactating cows lost weight, became lame, and were un-
thrifty in appearance. Their condition improved without special
treatment after the calves were weaned. The two cows remained
on trial and produced calves through 18 years of age.

Fertilizer Rate Increase.-Changes in fertilization during the
trial were accompanied by distinct changes in production levels.
Table 13 shows the actual nitrogen rate per acre per year by
periods as well as comparative forage production and animal
gain per acre, using 1948-50 as the base period. Production data
shown in this table include only the three phosphate treatments

Florida Agricultural Experiment Stations

first applied in 1947, which cover the entire trial period. The
fact that fertilization changes other than nitrogen poundage
were effected in 1955 does not detract from this demonstration
of the smaller yield and gain returns obtained. Economic appli-
cations of the fertilizer rate relationships have been discussed
by Reuss et al. (17).

Table 13.-Average relative forage production and animal gain per acre of
super, super plus lime, and rock phosphate treatments during three fertilizer

Period of Trial 1948-50 1951-54 1955-58

Annual N per acre, pounds 25 50 100
Relative forage yield per acre 100 144 186
Relative gain per acre 100 134 165

Pasture Management and Maintenance.-It was observed in
the early phase of this trial (9) that more forage was produced
by spring fertilization than by fall applications of equal rate
and analysis. Pangolagrass planted on newly prepared virgin
land was subject to active carpetgrass invasion after two years
of moderately intensive grazing, using only two pasture divi-
sions in rotation. Fencing and management programs to permit
taller growth of pangolagrass at selected seasons of the year
stabilized the stand so well that some pastures with no mechani-
cal treatment remained covered with a good stand 11 years after
sprigging. The no phosphate pastures proved particularly sus-
ceptible to continuing carpetgrass and broomsedge (Andropogon
spp.) invasion, requiring more renovation than those of any
other treatment. The same problem developed to a lesser extent
on the superphosphate treatment receiving no lime and was
clearly associated with the fertilization and liming program.
The entire forage production-animal nutrition pattern was
thrown into an emergency in the early months of 1958 when
pangolagrass winterkilled severely, having less than 1 percent of
surviving crowns. A low-phosphorus supplement fed to all groups
from March until mid-July 1958, when regrowth was sufficient
to supply cattle needs, kept cows in poor to fair condition. Each
herd was confined to one of the four divisions of their respective

Phosphatic Fertilizers on Pangolagrass Pastures

treatments for the entire March to July feeding period. The
other divisions were fertilized according to the regular schedule
and left to grow without grazing for at least three months.
The most severely winterkilled areas, where surviving plants
were 3 feet or more apart, returned to a full sod and normal
productivity without mechanical treatment or replanting. Re-
establishment was equally vigorous following removal of cattle
from the pasture that was heavily grazed and trampled during
supplemental feeding.
The rather rigid limitations and non-commercial features
of the experiment should be kept in mind when evaluating the
effect of a specific treatment or considering the productivity
of all-grass pastures. Some of these conditions served to improve
production records, while others were a handicap to per-head
or per-acre performance. Maximum use of pasture forage was
promoted by giving careful attention to pasture rotation and
deferred grazing. Time of fertilizer application was methodically
controlled to minimize seasonal extremes of production and to
maintain feeding quality. These advantages were offset by the
exclusion of supplemental feeding in periods of shortage when
additional forage or moderate amounts of protein feed would
have improved animal productivity. The overall lack of flexi-
bility of management was a distinct hindrance to attainment
of higher production efficiency.


Pangolagrass pastures were successfully established and
maintained on Immokalee fine sand uniformly treated with
nitrogen, potash, and minor elements and receiving in addition
either superphosphate, superphosphate plus lime, rock phos-
phate, colloidal phosphate, triple superphosphate, or basic slag.
One fertilizer treatment included no phosphorus.
Addition of phosphorus to the fertilizer treatments increased
forage production by as much as 50 percent and herbage phos-
phorus content by two to four-fold.
Soluble soil phosphorus during the course of the experiment
ranged from 2.9 to 6.7 ppm on the no phosphate treatment and
from 5.3 to 21.2 on the phosphated pastures. Total soil phos-
phorus values remained near 50 ppm on the no phosphate treat-
ment from 1947 through 1959. Large increases in total soil

26 Florida Agricultural Experiment Stations

phosphorus readings were recorded for the rock and colloidal
phosphate applications, while superphosphate, triple superphos-
phate, and basic slag produced small upward changes. Annual
application of basic slag at 500 pounds per acre produced a
rising trend in pH values. A limited effect resulted from apply-
ing J ton per acre of calcic lime at three-year intervals. Addi-
tion of dolomite increased pH to the recommended 5.5 level in
the second year after treatment.
Groups of grade Brahman cows grazing continuously on the
pasture treatments from 1947 to 1958 remained healthy and pro-
ductive without supplemental feed or phosphatic mineral supple-
ment. Rotation and deferred grazing combined with increased
fertilizer application stabilized carrying capacity of the phos-
phated pastures at one cow per 1.5 to 2.0 acres. Omission of
phosphorus resulted in a 40-50 percent reduction in carrying
capacity. Average weight of cows on all treatments increased
gradually, approaching or passing 1200 pounds in 1955-58.
Weaned calf crop percentage, 1948-58, ranged from 79 on
basic slag to 61 on superphosphate without lime, with an average
for all cows in the trial of 68 percent. Weaned calf production
on the no phosphate treatment averaged 69 percent. Annual
application of basic slag produced highest average beef gain
per acre, 252 pounds annually, 1951-58. Superphosphate plus
lime was second with 220 pounds, and the other treatments
averaged downward to 194 pounds per acre for rock phosphate
and 113 pounds for no phosphate.
Mineral consumption was highest on no phosphate and lowest
on superphosphate plus lime. Two cows on no phosphate de-
veloped phosphorus deficiency symptoms while nursing calves,
but recovered without treatment after weaning.


Results obtained in this experiment are applicable to Im-
mokalee and other acid flatwoods soils in central and south
Florida. The phosphorus supply in virgin soils of this type is
inadequate for optimum growth of pangolagrass, and phos-
phorus content of herbage produced is marginal for cattle nutri-
All forms of phosphate tested increased pangolagrass growth
and raised herbage phosphorus content to levels considered ade-

Phosphatic Fertilizers on Pangolagrass Pastures

quate for animal nutrition. Beef cows remained in excellent
flesh and at a moderate production level while obtaining all
energy, protein, calcium, and phosphorus from pangolagrass
Superphosphate and triple superphosphate are the most
widely useful sources of phosphorus for pangolagrass pastures
by virtue of their productivity and favorable cost and handling
factors. Need for a fertilizer source of sulfur frequently en-
hances the value of superphosphate (16). Problems of extra cost
and separate distribution limit the large scale application of
other types of phosphate fertilizer.
Annual application rates of 25 to 50 pounds per acre avail-
able P205 as superphosphate, triple superphosphate, or basic
slag support vigorous pangolagrass growth with no excessive
accumulation of soil phosphorus. High levels of herbage and soil
phosphorus obtained with rock phosphate do not give propor-
tionately higher forage or animal production.
Application of lime produces small increases in pangolagrass
forage and beef production; liming to at least pH 5.5 is recom-
mended for all improved grass pastures. Added increments of
nitrogen increase forage and beef production.


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Kidder. Minerals for dairy and beef cattle. Fla. Agr. Exp. Sta. Bul.
513. 1953.

2. Becker, R. B., W. M. Neal, and A. L. Shealy. Stiffs or sweeny (phospho-
rus deficiency) in cattle. Fla. Agr. Exp. Sta. Bul. 264. 1933.

3. Black, W. H., L. N. Iaab, J. M. Jones, and R. J. Desberg. Effects of
phosphorus supplements on cattle grazing on ranges deficient in this
mineral. USDA Tech. Bul. 856. 1943.

4. Blaser, R. E., and W. E. Stokes. Effect of fertilizer on growth and
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Bul. 390. 1943.

5. Cunha, T. J., R. L. Shirley, H. L. Chapman, C. B. Ammerman, G. K.
Davis, W. G. Kirk, and J. F. Hentges, Jr. Minerals for beef cattle in
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6. Forbes, R. B. The effect of fertilizers and pasture crops on Immokalee
fine sand. Unpub. Masters Thesis. University of Florida. 1948.

7. Gammon, Nathan, Jr., J. R. Henderson, R. A. Carrigan, R. E. Caldwell,
R. G. Leighty, and F. B. Smith, Physical, spectrographic and chemical
analyses of some virgin Florida soils. Fla. Agr. Exp. Sta. Tech. Bul.
524. 1953.

8. Hodges, E. M., D. W. Jones, and W. G. Kirk. Grass pastures in central
Florida. Fla. Agr. Exp. Sta. Bul. 484. 1951.

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sand in relation to pasture yield and animal response. Unpub. Masters
Thesis, University of Florida. 1950.

10. Jones, D. W. E. M. Hodges, and W. G. Kirk. The effect of fertilizer
phosphates on soil phosphorus and pasture production. Proc. Assoc.
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11. Year-round grazing on a combination of native
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J. M. Myers, A. C. Warnick, and N. Gammon, Jr. Beef production,
soil and forage analyses and economic returns from eight pasture pro-
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13. Morgan, M. F. Chemical soil diagnosis by the Universal Soil Testing
System. Conn. Agr. Exp. Sta. Bul. 450. 1941.
14. Morrison, F. B. Feeds and Feeding. 22nd Ed. 1956.

15. Neller, J. R. Availability of the phosphorus of various types of phos-
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16 ....... Comparisons of phosphorus fertilizers for pastures
on flatwoods soils in Florida. Fla. Agr. Exp. Sta. Tech. Bul. 651. 1963.

17. Reuss, L. A., N. K. Roberts, and R. E. L. Greene. Pangolagrass
pastures for beef production in central Florida-a method of determin-
ing the economics of establishing and fertilizing them. Fla. Agr. Exp.
Sta. Bul. 585. 1957.

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