Tomato plants require four key elements ensuring healthy growth and a maximum crop yield. Nitrogen, calcium, potassium and phosphorus all affect tomato plants' growth but in different ways. The delivery of these four elements makes a difference. Nitrogen is most effectively delivered as calcium nitrate. Too much nitrogen decreases the plants' health. Know how much is enough and how much is too much.
Tomato plants usually often get much nitrogen and too little calcium and phosphorus, required for strong, thick tomato stalks, strong plant cell walls and disease-resistance. Nitrogen produces early, lush foliage, but impedes fruit set and reduces leaves and fruit production later in the season. Potassium also promotes growth, blossom and fruit set.
Soil for tomato plants should be well drained but holds moisture. The best time to prepare the ground is the previous autumn. Plough and then test the soil. The two nitrogen levels your test will report. AN and NN should be 40 phosphorus and potassium readings 240, calcium 3,000 and magnesium 400. Correct low or high levels.
Fertiliser alone won't produce healthy plants. The availability of calcium and phosphorus depends chiefly upon soil moisture. Too much or too little moisture impedes plant uptake of nutrients. High-calcium soils may produce calcium deficient plants if improperly watered. Microorganisms and organic acids in the soil also affect phosphorus and calcium absorption by the plants. Waterlogged or arid soils inhibit microorganisms and organic acids from doing their jobs.
Nutrient Depletion Issues
Horticulture scientists in Iran demonstrated that attention to calcium and potassium in fertilisation produces the best quality tomatoes. During fruit development, tomatoes deplete potassium and weaken plants. Applying potassium, phosphorus and calcium restores minerals absorbed for fruit growth.
Space tomato plants 2 to 3 feet apart in rows 4 to 5 feet apart. Apply fertiliser on transplanting and again when the first fruits are one third grown. Apply 1.59kg. of calcium nitrate per 100 feet of row or 312 to 340gr/ per plant, mixed into the top inch of soil. Avoid dusting the foliage with the fertiliser. Wash it off if you do. Calcium nitrate is found in many tomato specific fertilisers that also contain potassium, phosphorus and magnesium. An 8-32-16 or 6-24-24 tomato-specific fertiliser is most widely recommended by horticulturists. Fertilisers with calcium nitrate not only provide nitrogen, but calcium as well
Calcium Nitrate Effects
If your tomatoes show distress during the run up to harvest, calcium nitrate boosts plant growth, strong stems and branches. Calcium nitrate delays flowering and seed set. Some gardeners use it for that purpose, applying 1 to 3 gallons of calcium nitrate per acre per week during plant growth. Discontinue calcium nitrate before fruiting begins.
- Journal of Horticulture and Forestry; Uptake of Calcium Nitrate by Tomatoes; G. Peyvast et al; 2009
- University of Missouri Extension; Growing Home Garden Tomatoes; rev. David H. Trinklein; 2010
- International Ag-Labs Newsletter; Tomatoes- Farm and Garden; Daniel L. Skow; June 1991
- NCSU Extension; Garden Note 4 -- Tomatoes; Pam Reading et al; April 1998
- UCANR; Fresh Market Tomato Production in California; Michelle Le Strange et al; 2000