Nitrogen is needed at early stages of development to encourage good strong seedling and plant development. Peak requirement is just before flowering. Most phosphorus is required early on in the plant’s development to ensure good root growth and flowering. Potassium is needed in greater quantities than nitrogen. Calcium is also needed in relatively large quantities, mostly from flowering through fruit development and up to harvest. In many situations, it is equally as important as nitrogen. Over 60% of nitrogen, phosphorus and potassium taken up by the plant, is utilized by the fruit.
More potassium, nitrogen and calcium are removed by tomatoes than any other nutrient.
Excessive use of nitrogen can produce a crop that is too vigorous, has poor flowering and excessively large fruit. Around 5 – 5.3 lb of nitrogen is removed for every ton of crop produced. Some nitrogen is normally broadcast preplanting or at transplanting, unless rainfall patterns are likely to lead to leaching. This is followed by side dressing prior to flowering.
Most Phosphorus is required early on in the plant’s development to ensure good root growth and flowering. Crops need 0.4 – 0.8 lb P/t of fruit.
Potassium is needed in greater quantities than nitrogen. Plant uptake is around 5.2 - 7.2 lb K/t of fruit with the highest demand during fruit bulking. Base applications of potassium are usually followed by regular applications throughout the season.
Calcium needs are around 3.4 lb Ca/t of fruit. In many situations, it is equally as important as nitrogen. Peak calcium needs are from flowering, through fruit development and up to harvest. Since only 5% of Ca is found in fruit and 95% in the vegetative parts of the plant, the need for Ca is also high during vegetative growth. Therefore a steady supply of calcium is needed throughout the season.
Magnesium is also important, though it is needed at lower rates than calcium – crops require 0.6 - 1.2 lb Mg/t of fruit – split throughout the season. Peak uptake is around flowering.
Sulfur is needed throughout the growing period with tomato plants taking up around 1.2 lb S/t of fruit produced.
While much lower levels of micronutrients are needed to satisfy yield and quality tomato crop production, the correct balance of these trace elements is essential. Leaf tissue analysis to assess micronutrient need, will enable deficiencies to be correctly diagnosed and treated.
Boron is one of the key micronutrients. It has a significant effect on fruit ripening characteristics. It is essential for the structural integrity of the plant and important for pollen viability, flower and fruit development.
Zin is another key micronutrient. It is important for the development and function of growth regulators (e.g. auxin) that influence internode elongation.