Fertilizer Management for Greenhouse Vegetables
Plants require 16 elements for normal growth and reproduction. The objective of a sound fertilizer management program is to supply these required nutrients in ample, but not excessive amounts for optimum crop production. This chapter will present general information on plant nutrition that will be useful irrespective of the particular cultural system e.g., perlite, rockwool, bag, or NFT hydroponics used by a grower.
The 16 elements required by all plants are carbon (C), hydrogen (H), oxygen (O), phosphorus (P), potassium (K), nitrogen (N), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), boron (B), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo), and chlorine (Cl).
The elements C, H, and O are supplied largely from air (carbon dioxide (CO2) and oxygen), and water (H2O). The remaining 13 elements, usually referred to as mineral nutrients, are supplied from several sources. Small amounts of these nutrients can be derived from the growing media e.g., peat in a bag or trough culture or the water in hydroponics. Well water in Florida contains substantial amounts of Ca and S, and smaller amounts of Mg, and Fe. Most of the needed amounts of the 13 mineral elements, however, are supplied by the grower from fertilizers.
The nutrients N, P, K, S, Ca, and Mg are referred to as the macronutrients because they are required in larger quantities by the plant compared to the remaining elements. The other seven elements are referred to as micronutrients because they are required in small amounts, usually a few parts per million (ppm) in the plant tissue.