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Copyright 2005, Board of Trustees, University
Mimeographed Report No. 3 University of Florida September 1937
SUB-TROPICAL EXPERIMENT STATION
Homestead, Florida Subtropical Experiment Station
SOME FERTILIZER EXPERIMENTS WITH TOMATOES ON THE Homestead
LIME-ROCK "PINELAND" SOILS OF SOUTHERN DADE COUNTY
W. M. Fifield and H. S. Wolfe
The purposes of the experiments herein reported were to determine the relative value
fora fall crop of tomatoes of (1) different fertilizer ratios, (2) a high-analysis fertilizer as
compared with a standard low-analysis material, (3) different rates of application of a standard
formula, and (4) to determine if the addition of manganese sulfate to the regular fertilizer was
The experiments were conducted at the Sub-Tropical Experiment Station, near Homestead,
during the seasons 1932 to 1936, inclusive. The soil on which the tests were performed is typical
of that comprising the southern area of the Miami oolite (lime-rock) series. It is commonly re-
ferred to by growers of the Redland District, in which it occurs, as "pineland" or "rockland" soil,
as compared with the larger area of lower-lying calcareous marl nearby on which the spring tomato
crop is grown. Fertilizer tests with tomatoes on the marl (glade) soils will be reported later,
Each year the tests were conducted on land which had not previously been planted with
tomatoes, and which had never before been fertilized heavily.
The L=932 tests
The tests were conducted on a somewhat different basis the first year (1932) than in
succeeding years, In 1932 a 4-7-5 formula (without manganese) was used as a control, with 75% of
the nitrogen derived from the organic sources Peruvian guano, whale tankage, cottonseed meal, and
goat manure. The rest of the control mixture was composed of ammonium sulfate, superphosphate, and
sulfate of potash, Nitrophoska No. 5 (10-20-20) was used as the high-analysis fertilizer. It was
applied at the rate of 500 lbs. per acre. For the manganese treatment, 150 Ibs. of 65% manganese
sulfate was added per ton of control fertilizer.
Three different rates of application were made of the control mixture, 750, 1500, and
3000 lbs. per acre. The remaining treatments consisted of ratios in which the percentages of each
of the three major fertilizer elements (nitrogen, phosphoric acid and potash) were doubled and
halved independently of each other. All treatments except the three control mixture rates, and the
high-analysis material, were applied at the rate of 1500 lbs. per acre. The treatments totaled
eleven, and each was replicated once. 3-':'''
The 1933, 1934, and 1935 tests
The experiments during the next three years differed from the earlier work in several
respects. The control formula, while still a 4-7-5, had a different composition in that only 65%
of the nitrogen was derived from organic sources, and those sources were limited to Peruvian guano
and cottonseed meal. The low nitrogen (2-7-5) treatment was discontinued. The basic rate of ap-
plica ion of the various treatments was raised to 2800~ bs. per vcre. The high-analysis fertili-
D e at 930 Ibs. In addition to the 2800-lb. rate the control mixture
zer/was also applied at 4200-lb. (1i control) and 5600-Ib. (double control) rates. The number of
replications was increased to ten for each treatment each year. In 1935 the high-analysis treat-
ment was dropped and a new treatment substituted. This new treatment consisted of a 4-12-8 formula
with 100 Ibs. of manganese sulfate added per ton. Its composition, though differing in percentage,
was otherwise similar to that of the control mixture.
The 1936 tests
At the end of the fourth year it became advisable to make certain further changes in
the experimental procedure. Due to the fa"t that the cost of Peruvian guano had advanced consider-
ably, many commercial fertilizer manufacturers were by this time using less expensive organic
sources of nitrogen. Therefore in this experimental work, fish tankage was substituted for the
Peruvian guano previously used. The basic rate of application was also changed for the final
season's work. The control and other mixtures were applied at the rate of200QO lbs. per acre. In
addition, the control mixture was also applied at 3000 (1 control) and 4000-lb. (double control)
rates, respectively. In other respects the treatments were similar to those used previously.
Although it is recognized that due to the several changes made during the course of the
experiments, the data of the first and last year are not strictly comparable with those from the
other three, the average yields of marketable fruit for each of the five years have been presented
in the single table below for ease of comparison.
lHSW 9-23-37 100
Average yields of marketable fruit. in bushel crates per acre, of the various treatments compris-
ing the "pineland" tomato fertilizer experiments from 1932 through 1936.
Treatment Formula 1932 1933 1934 1935 1936 Average
Number of pickings 9 7 4 4 5 -
Doublecontrol 4-7-5 270 297 160 179 207 223
High phosphorus 4-14-5 208 280 192 187 228 219
New formula (High PK) 4-12-8 +Mn '186 ,.223 205
Manganese 4-7-5 -Mn 193 .., 244 151 179 182 190 /
High potash 4-7-10 148 253 149 2151 203 181 / f
/r '03 1 1 .
1i control 4-7-5 148 181 203 177 --
/," y- f 3f
Control 4-7-5 170 219 137 169 187 176 ( J 7 "
/ii ") '
High nitrogen 8-7-5 228 223 111 '151 131 169 / t
Low potash 4-7-21 160 194 133 162 161 162 / '
Low phosphorus 4-3j-5 163 204 102 163 148 156 / f(
Synthetic (-/, ) 10-20-20 20, 17' 125 147 -
Low nitrogen 2-7-5 i'20 '- 120 --1--
Half control 4-7-5 '18 -- -- 118
The averages for the five year period, as pointed out above, should not be too closely
interpreted as a summary of the experimental results. They are included merely to indicate general
tendencies, and to provide a convenient basis for listing the various treatments in the order
given in the table. Some are based on but one to three years, data, and others on five.
The treatments in any given year, however, may be compared with each other. The dif-
ferences in yield between treatments the first year are less significant than are those of the
next four, because the 1932 average yields are based upon only two replications, while each of the
others had ten.
Some of the findings were quite consistent throughout the five year period in spite of
the occasional changes made in experimental treatments.
The high phosphate treatment (4-14-5) always significantly outylelded the control, and
in 3 of the 5 years it outylelded the double control application.
The new 4-12-8 plus manganese formula significantly outylelded the control mixture both
years It was tested, and yielded about as well as high phosphate, but no better.
The double control application (3000 lbs. in 1932, 5600 lbs. In 1933-34-35, and 4000 lbs
in 1936) showed a significantly higher yield every year than the regular application (half as much),
but in some seasons the increase in yield did not justify the expense of the extra fertilizer.
The "l1 control" treatment (50% heavier application than the regular control) yielded
practically the same as the double control treatment two years out of three.
The high potash treatment outylelded the regular control in three out cf five years.
Two years (1932 and 1935) it yielded less than the control. These same two years it was even out-
yielded by the low potash treatment.
The high nitrogen treatment outylelded the control treatment considerably the first
year, was practically the same the second year, and the last three years yielded definitely less
than the control. In fact, the last two years it was the lowest yielding treatment of all those
The addition of 150 lbs. of manganese sulfate to the control fertilizer resulted in
definitely higher yields each year it was tried. The fifth year, when only 100 Ibs. was added,
the difference In yield was hardly significant.
The low phosphorus and the.low potash treatments yielded less than the control every
year, but in some seasons the yield from the low potash treatment was not markedly lower than the
The low nitrogen and the half control treatment each gave low yields the only year
they were tested.
The high-analysis fertilizer was significantly outyielded by the control mixture in
each of the three seasons compared.
It should be pointed out while recording the results of the experiments, that during
the first year nine pickings were made, seven were obtained the second year, and four, four, and
five respectively, in the next three. Pickings were made not oftener than once a week whenever
sufficient marketable fruit matured to warrant harvesting, as is customary among commercial growers
The climatic conditions varied considerably from year to year. In 1932 adequate
moisture was available, there were no tropical storms in the area during the growing season, and
temperatures were satisfactory for a good crop. The season of 1933 was also fairly good. In
1934 the plants grew and yielded well through four pickings when they were killed by a freeze. In
1935 the plants were badly whipped about by high winds before the first picking, and largely be-
3ause of the drought conditions which followed, never fully recovered. The season of 1936 was
fair except that soil moisture was below the level necessary for optimum yields, and the vines did
not hold up well.
With respect to the variations In seasonal conditions and the number of pickings ob-
tained from year to year, it might be pointed out that seldom do the growers of fall tomatoes in
this area enjoy more than two very favorable seasons In succession. Although during the course of
these experiments seven or more pickings were obtained In two of the five years, it is usually con-
sidered that four or five pickings are all that can be counted upon from a single "pincland" crop.
Common fertilizer practice has been based on these expectations.
It Is conceivable that a response to certain fertilizer treatments may be more marked
in later pickings than In earlier ones, and hence the results of seasons in which a large number
of pickings were secured might not be strictly comparable, on the basis of total yields, with
those of fewer pickings. However, since the minimum number of pickings obtained in any season
during the course of the experiment was sufficient to compare favorably with ordinary commercial
results, an analysis of the data by pickings is not included In this preliminary report.
The experimental results indicate rather definitely that phosphoric acid Is a more
limiting factor than either potash or nitrogen for tomato yields on these "pineland" soils, at
least when they are first cropped. The data show that doubling the phosphoric acid content (14%)
from the amount usually applied (7%) increased the yields about as effectively as doubling the
entire application of a standard 4-7-6 formula. Doubling the potash percentage of the basic con-
trol mixture increased the yields in a majority of the years, but not to the same extent as phos-
phoric acid, and on the average the extent of increase did not justify the cost.
The fact that the 4-12-8 plus manganese formula did not yield better than the 4-14-5
(high phosphate), but did yield better than the high potash (4-7-10) in the years tried, also in-
dicates that doubling the phosphate alone is more important than partially increasing both phos-
phoric acid and potash.
The data also indicate that the addition of 150 Ibs. of 65% manganese sulfate per ton
of fertilizer can be counted upon to increase the yields of tomatoes on "new" land in a majority
of yeP;s. This is significant since it has not been the general practice to add manganese to the
The data show no advantage to be obtained over a period of years In increasing the
nitrogen content much beyond 4% when 65% of this nitrogen is derived from organic sources. The
first year, In which nine pickings were obtained, increasing the nitrogen to 8% was definitely
profitable. The second year, with 10% less from organic sources and seven pickings of fruit, no
increase was obtained. In each of the last three years of the experiment, with only four or five
pickings, yields from 8% nitrogen were actually less than from 4% nitrogen.
The results of testing various rates of application of a 4-7-5 indicate that while
very heavy applications may be profitable In certain seasons yielding 7 to 9 pickings, n more
ordinary years yielding 4 or 5 pickings, applications of about 3000 Ibs. per acre would be more
With respect to the high-analysis fertilizer tested during the first three years of
the experiment, it should be pointed out that only one particular product was tried--a 10-20-20
"Nitrophoska". It cannot definitely be concluded from this experiment that all high-analysis fertil-
izers are unprofitable for "pineland" tomato crops. The material tested was applied In such a manner
as to obtain as nearly as possible amounts of nitrogen and phosphoric acid equivalent to the amounts
applied in the regular 4-7-5 analysis, which was about one-third as concentrated. The amount of
potash applied in the high-analysis fertilizer was, of course, higher than that of the control
It is recommended on the basis of these experiments that the equivalent of a formula
analyzing 4% nitrogen, 14 to 16% phosphoric acid, 5 or 6% potash, and containing 150 lbs. of man-
ganese sulfate per ton, be applied to "new" land for "pineland" tomatoes at the rate of one ton per
acre. The experiments Indicate that increases in the percentages of potash and nitrogen, or in the
total amount of fertilizer per acre above the amounts recommended are not likely to be profitable In
a majority of seasons.