Light, Fertilizer and Cultivar Selection Affect Growth and Yield of Containerized Patio Tomatoes

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University of Florida, IFAS,
Central Florida Research and Education Center,
2807 Binion Road, Apopka, FL 32703-8504.

Research Report RH-96-1

C.A. Conover and Rex Flohr*

Tomatoes are usually grown in the sunniest location possible in order to maximize production. However, some of those who desire to grow their own tomatoes, have space for containers of patio type tomatoes only in locations getting less than the presumed optimum amount of light. Plants grow slower in less than optimum light and use less fertilizer compared to plants grown under optimum conditions. Excess fertilizer may accumulate in the growing medium, further stunting growth and reducing yields.

We wanted to find out if decreasing the normal amounts of fertilizer applied to containerized patio-type tomatoes could prevent the decline in yields expected when plants are grown in less than optimum light. The following experiment was conducted to determine the performance that home gardeners could expect from three cultivars of patio-type tomatoes grown in various shade levels using different fertilizer rates.

The three cultivars selected were 'Micro Tom', 'Patio' and Pixie Hybrid II. 'Micro Tom' is a very short compact plant that produces many small fruits per plant. While 'Patio' and Pixie Hybrid II plants grow somewhat larger and tomatoes are much larger, less tomatoes are produced per plant when compared to the amount produced by 'Micro Tom'.

Seeds of the three cultivars were sown into seed flats September 26, 1994, using Bacto Professional Mix (Michigan Peat Co., P.O. Box 980129, Houston, TX 77098). Flats were maintained on a greenhouse bench where light intensity was 3000 to 4000 ft-c and air temperatures ranged between 65 and 90°F. Tomato seedlings were transplanted into 6-inch pots, again using Bacto Professional Mix, October 11, 1994. Containers were top-dressed October 12, 1994, with 3.30, 5.35 or 7.40 g/6-inch pot of a 17-6-12 (N-P₂0₅-K₂0) slow release fertilizer (17-6-12 Sierra, The Scotts Company, 6656 Grantway, Allentown, PA 18106).

Containerized tomato plants were moved outdoors October 21, 1994, and placed on black ground pack in full sun conditions or on black ground pack inside shadecloth cages that provided 30% shade or 50% shade. All containers were watered using the same overhead sprinkler system that was automatically set to operate for one hour daily. Plants were staked and tied as needed for support using green garden stakes and paper-covered wire twist-ties.

When tomatoes were ripe, they were picked off, counted and weighed. Green fruit still on the plants when research was terminated was also picked off, counted and weighed. Final data was collected and research was terminated December 21, 1994. Final data included plant height (cm), number of tomatoes produced per plant and total weight of tomatoes produced per plant.

Results

Interaction of shade level and fertilizer rate influenced weight of tomatoes harvested (yield) from 'Micro Tom' plants (Table 1). Yield increased when fertilizer rate increased for plants growing in full sun or 30% shade, but decreased when fertilizer rates were increased for plants growing in 50% shade. Plants in full sun fertilized at the highest rate produced the highest yields, but 'Micro Tom' plants in full sun, fertilized at any rate tested, had higher yields compared to plants getting less light and/or fertilizer.

Growth of all three cultivars was compact and sturdy when plants were grown in full sun (Tables 2, 3 and 4). Effects of shade level on height were greater for the two larger cultivars. As shade level increased, the two larger cultivars produced more leggy, elongated growth.

Shade level significantly influenced number and weight of tomatoes produced on 'Micro Tom' (Table 2). Both fruit production and tomato weight increased as shade level decreased. Weight of tomatoes produced in full sun was significantly greater compared to weight of tomatoes produced on plants growing in 50% shade. Shade level did not affect number or weight of fruit produced on 'Patio', but Pixie Hybrid II plants grown in full sun produced heavier tomatoes compared to weight of tomatoes produced on plants grown in 50% shade (Tables 3 and 4).

Fertilizer rate influenced number and weight of tomatoes harvested from the two larger cultivars (Tables 3 and 4). For 'Patio', number and weight of tomatoes increased steadily as fertilizer rate increased. Increases in both number and weight of tomatoes produced on Pixie Hybrid II were greater when fertilizer rate was increased from 3.3 to 5.35 g/6-inch pot compared to the increases seen when comparing weight and number of tomatoes harvested from plants getting 5.35 to plants getting 7.4 g/6-inch pot. At every fertilizer rate tested, Pixie Hybrid II produced more tomatoes than 'Patio'.

Conclusions

For 'Micro Tom', the cultivar most affected by shade level, increasing fertilizer rate increased yields when plants were grown in full sun or 30% shade, but decreased yields for plants in 50% shade. For best tomato production, 'Micro Tom' needs to be grown in no more than 30% shade, so try to place containers where they will get the most light. Since the high fertilizer rate was no better than the medium level, 5.35 g/6-inch pot slow release fertilizer would meet nutritional requirements.

Yields from the two larger size cultivars were much less influenced by shade level, being more affected by fertilizer rate. For 'Patio' and Pixie Hybrid II, the highest fertilizer rate was best for tomato production. Legginess increased with increasing shade levels, but the home gardener could spend a little more time staking plants to give them the additional support needed. Results of this experiment show the three varieties we tested will tolerate less than full sun conditions. Home gardeners need not worry too much about light to moderate shade in areas where the two larger varieties of patio-type tomatoes are grown, as long as 50% shade is not exceeded.

Table 1. Effects of interaction of light level and fertilizer rate on total weight (g) of tomatoes harvested from 'Micro Tom' patio-type tomatoes on December 21, 1994.

Interaction significant at P = 0.0435.

Table 2. Effects of light intensity on 'Micro Tom' patio-type tomatoes grown in 6-inch containers from September 26 until December 21, 1994. Experiment 94-30.

^zheight of tomato plants was measured December 21, 1994, when research was terminated.
^yTotal number of tomatoes produced per plant was counted December 21, 1994.
^xTotal weight of tomatoes produced per plant was determined December 21, 1994. Weight of tomatoes harvested was determined by the formula: total weight of tomatoes produced per plant . number of tomatoes produced per plant.
^wTomato size was determined by adding sizes of tomatoes produced per plant then dividing by number of tomatoes produced per plant.
^v Mean separation in columns by Duncan's multiple range test, 5% level. Means in same columns with same letters are not significantly different.

Table 3. Effects of light level or fertilizer rate on 'Patio' patio-type tomatoes grown in 6-inch containers from September 26 until December 21, 1994. Experiment 94-30.

^zheight of tomato plants was measured at termination of research on December 21, 1904.
^yTotal number of tomatoes produced per plant was counted on December 21, 1994.
^xTotal weight of tomatoes produced per plant was determined on December 21, 1994. Weight of tomatoes harvested was determined by the formula: total weight of tomatoes produced per plant number of tomatoes produced per plant.
^wAverage tomato weight was determined by adding weights of tomatoes produced per plant then dividing by number of tomatoes produced per plant.
^vMean separation in columns by Duncan's multiple range test, 5% level. Means in same columns with same letters are not significantly different.
^uns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

Table 4. Effects of light level or fertilizer rate on Pixie Hybrid II patio-type tomatoes grown in 6-inch container from September 26 until December 21, 1994. Experiment 94-30.

^zHeight of tomato plants was measured December 21, 1994, when research was terminated.
^yTotal number of tomatoes produced per plant was counted December 21, 1994.
^xTotal weight of tomatoes produced per plant was determined December 21, 1994. Weight of tomatoes harvested was determined by the formula: total weight of tomatoes produced per plant. number of tomatoes produced per plant.
^wAverage tomato weight size was determined by adding weights of tomatoes produced per plant then dividing by number of tomatoes produced per plant.
^vMean separation in columns by Duncan's multiple range test, 5% level. Means in same columns with same letters are not significantly different.
^uns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

*Center Director and Professor of Environmental Horticulture (retired 7/96), and Research Gardener, respectively.