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Copyright 2005, Board of Trustees, University
Homestead AREC Research Report SB73-4 .....-... September-4;- 1973
Response of Four Tomato Varieties to Rates of N, P, and K
-i -" Paul G. Orth-
The role of fertilizers in the production of tomatoes needs continued 'tudyP'forjat
least two reasons. First, tomato quality and yield vary-as the influence of father
interacts with fertilization and other cultural practices. Many tests are needed to
measure the response to fertilizer under the different types of weather patterns
normally encountered. Second, tomato varieties respond differently to weather.
Therefore, more is learned about these differences in response if more than one
variety is included in a fertilizer test. The following experiment was carried out
to measure the response of four varieties of tomatoes to five rates of fertilization,
Four varieties of tomatoes were grown at the fertility levels shown in Table 1.
Fertilization was uniform until the second side-dressing, 38 days after planting.
Treatment 1 was low fertility and treatment 5 medium fertility. Treatment 2 was low
in nitrogen, 3 was low in phosphorus, and 4 was low in potassium. The first side-
dressing was placed between the rows, the second on the outside. The four varieties
grown, (direct-seeded) Tropi-Red, Walter, MH-l and a "908" line from the breeding
program were planted two rows per bed and replicated seven times. Each plot con-
sisted of ten feet of bed with about 20 plants at harvest. Other cultural practices
were routine and uniform for all treatments.
* Results and Discussion
Two weeks after planting MH-1 seedlings were largest and "908" seedlings were small-
est, but five days later Walter seedlings were smallest, and the other three vari-
eties about equal in size. Most plants increased 25% in weight per day during the
first half of December; this growth rate declined to 12%/day by the end of December.
The plants developed good size. Visually, MH-l plants were the least vigorous with
a tendency toward lighter green color whereas plants of "908" variety were darker
green and the most vigorous at all fertilizer rates. As fruit neared maturity,
plants on treatment 5 appeared the most vigorous and those on treatment 1 the least.
Some fruit was picked between February 15 and 28, but the main pickings were March 6
and 13. Cool weather during February delayed maturity and probably increased fruit
size. Yield data are summarized in Table 2. Fertilizer treatment had no statisti-
cally significant effect on marketable yield or fruit size. Variety did have a
significant effect on yield and fruit size. MH-1 gave the lowest yield and 908 the
highest. Both MH-l and Tropi-Red tended to produce a greater proportion of larger
fruit than the other two varieties. For example about 44% were in the 6 X 6 size
and 21% in the 7 X 7 size for these varieties compared with 30% 6 X 6 size and 26%
7 X 7 size for Walter and "908".
Five fruit of each variety and each fertilizer treatment were rated for three quality
factors by Dr. Bryan four weeks after picking. On a rating scale of 1 to 5 with 5
being firm,fruit from treatment 5 (average rating 4.0) were significantly firmer
than those from treatment 1 (average rating 3.1). MH-l and "908" produced firmer
SAssistant Soils Chemist, Agricultural Research and Education Center, University
of Florida, IFAS, Homestead, Fla. 33030.
Table 1. Fertilization rates applied to four tomato varieties.
At Planting (11/10/72)
Semi-banded with2 eed-
Banded near seed-
At Side-dressing #1 (12/12/72)--
N P205 K20 Mg0
Total Fertilizer Application
1 72 165 114 32 35
2 72 280 234 57 40
3 122 165 234 57 40
4 122 280 114 57 40
5 122 280 234 57 40
SN and K came from slow release fertilizer Osmocote.
/ N and K came from slow release fertilizer Sulfur-coated
urea and KC1.
2 Nutrient sources were ammonium nitrate (33-0-0), concentrated
superphosphate (0-46-0), potassium sulfate (0-0-50), magne-
sium sulfate, and manganous oxide.
Table 2. Marketable tomato yields in response to variety
and fertilizer rate.
Marketable Yields Tons/Acre*
MH-1 Tropi-Red Walter
Yield by Size-
2.92 c 4.00 c
4.26a 6.78 b
6.48 c 4.54ab
10.74a 13.76 b
15.32 c 17.57 d
- Yield by Treatment -
10.74a 13.76 b
15.32 c 17.57 d
Comparing numbers horizontally, numbers followed by the
same letter are not statistically different at the 5%
level, Duncan's Multiple Range Test.
fruit (average rating 4.3) than the other two varieties (average rating 3.0). There
were smaller differences in internal color and green gel. The trend was for poorer
quality for treatment 1 and better quality for treatment 5. Variety had little
effect except for lighter internal color with "908".
A good crop of tomatoes was produced in this experiment with 122 Ibs/A of N, 280 lbs/
A of P205, and 234 Ibs/A of K20. Although yield was not significantly reduced by
using 72 lbs of N, 165 lbs of P205 or 114 lbs of K20, fruit quality was somewhat
reduced. As mentioned previously fertilizer is only one factor affecting fruit
quality and yield, therefore, these rates serve only as guidelines. More important
is the evidence that all four varieties responded similarly and that variety was the
most important factor affecting fruit yield and size.