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Tomato Trials: Fertilize and Graft for Success

By Adam Russell
Texas A&M AgriLife Extension Service

Statewide tomato trials revealed a fertilization program can help plants reach their production potential, in some locations over 30 pounds of fruit per plant, said a Texas A&M AgriLife Extension Service specialist. Dr. Joe Masabni, an AgriLife Extension small-acreage horticulturist in Overton, has concluded his 2017 tomato trial investigating grafted versus non-grafted plants and fertilization programs pertaining to yields. Comparable trials were conducted by specialists in College Station, Lubbock, Uvalde and Weslaco.

Masabni said the research indicates that commercial producers and home gardeners can improve yields by implementing fertilization programs as well as by grafting plants. The trial included two tomato varieties — ‘TAMU Hot,’ which was developed as a heat-tolerant summer variety, and ‘Tycoon,’ a 2014 Texas Superstar variety. Varieties were grafted with Estamino and Multifort rootstock for their disease-resistance characteristics. Masabni said grafting is usually done to prevent soil diseases from stunting or killing susceptible tomato varieties. “Grafting certainly helped the tomatoes’ performance,” he reported. “I was pleasantly surprised to see that grafting improved yields in those two varieties.”

‘Tycoon’ without grafts produced 13 pounds of tomatoes per plant during the growing season. Grafted ‘Tycoons’ produced 18 pounds per plant on Multifort rootstock and 20 pounds per plant on Estamino. Similar yield trends were tracked at the other trial locations.

However, according to Masabni, tomatoes can require twice as much fertilization as squash or cucumbers each season. So the most important aspect of tomato production is fertilization. “Tomato production can be tricky because they are heavy feeders,” he said. “They require a lot of fertilizer to reach their potential.”

By providing the correct amounts of nitrogen, potassium and phosphorous at the right development stage for the plant, Masabni estimated that producers should expect 20 pounds of tomatoes per plant at minimum. For optimal production, he recommends 150 pounds of nitrogen, 80 pounds of potassium and 100 pounds of phosphorous per acre per season. He also recommends fertilizing every 10 days and basing fertilizer selection on the plant’s production stage. “Using different fertilizers at different stages of growth can help the plant reach its maximum potential.”

For example, pre-plant starter fertilizer is high in phosphorus, which encourages root development for seedlings. Triple 10 or Triple 13 fertilizers are good for vegetative growth. Flowering plants need additional calcium nitrate, which prevent blossom-end rot, and potassium, which helps with fruit development, taste, firmness and ripening. A good source of calcium nitrate is eggshells, Masabni advised. Grind one eggshell per plant to a powder and add vinegar to the powder overnight. The vinegar-eggshell solution promotes faster absorption of calcium by the plant. “Just remember that N is for leaves, P is for roots and K is for fruit.”

Producers can complete the fertilization regimen two to three weeks before the growing season ends if the plants appear to have one more harvest left. Another important production practice is tracking yields and making notes of how the plants perform under the fertilization program. Masabni suspected that many gardeners do not track yields and are content with whatever the plants produce. “Some gardeners are happy with 10 pounds of tomatoes per plant,” he said. “But they shouldn’t be content. I was happy with 20 pounds per plant, but other researchers at other locations were getting double that amount, so I know I can do better.”

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