COMBINED FERTILIZATION AND IRRIGATION OF VEGETABLE CROPS IN SANDY SOILS
The main consideration is given to the NO3 - N concentration in the soil volume occupied by the active root system. The optimum NO3 - N concentration for tomatoes and sand dunes was found to by 10± 3 meq/1. This is the same concentration of Hoegland's nutrient solution. The same concentration was also found best on highly calcareous soil.
Phosphate and potassium are being adsorbed to the soil and the adsorption curve can serve as a tool to plan the needed supply. The demand for high phosphate concentration for younger seedlings and the limitation of phosphate amounts in the irrigation system leads to preseeding incorporation of superphosphate and later supply of phosphate through the irrigation system.
The supply of nutrients should be planned according to the pattern of uptake by the irrigated plant. This practice prevents excess concentration in early growth and assures the daily demand for the macronutrients in later growing stages.