Vegetable irrigation practices vary between sand, muck, and rockland soils, and affect fertilization practices accordingly. Technological advances, such as drip tape and fertigation, have had a large effect on improving profitability of vegetable crops in Florida, and reducing environmental impacts of excess nutrients, particularly in sand soils vulnerable to nutrient leaching loss.
Sand soils are suitable for fresh market vegetable production in full-bed mulch culture combined with microirrigation, e.g., subsurface drip irrigation, e.g., drip tape and fertigation. Muck or humic soils are often subirrigated by seepage from lateral ditches. Rocklands are irrigated by sprinklers from shallow wells.
It is critical that soil tests be done before planting, because this may affect the recommendation for preplant fertilizers placed in the mulch bed before covering, also because once nutritional deficiency symptoms are noticed, it may be too late to save the situation. It is very important for the interpretation of soil tests that the proper extractant be used depending on soil pH. For many Florida soils, particularly higher pH soils, the Mehlich III extraction is preferable to the commonly used Mehlich I. Mehlich III will show P levels approximately 2 x what are shown by Mehlich I.
The main fertilizer nutrients for most vegetables, depending on soil sufficiency, are N, P, K, and Mg. Soils with high Mg may need additional K; this is expressed as the Hartz ratio = exchangeable K/(sqrt(exchangeable Mg)) in meq/100g units. In coarse soil, when the Hartz ratio is less than 0.6, additional K is needed.