Keywords: Fertigation, Drip Irrigation, Fertilizer Solutions, Fertigation Equipment.

Fertigation is defined as application of fertilizers through irrigation water. It is considered an integral part of plant nutrient management under pressurised irrigation.

In a fertigated system, timing, amounts, concentrations and ratios of fertilizers applied are easily controlled and thus lead to optimisation of yield and product quality. Co-application of mineral nutrients and water via fertigation avoids excessive leaching of nutrients from the rhizosphere, and minimises groundwater contamination. A short literature review on the effect of fertigation on crop yields is presented. An example of nutrient uptake by greenhouse tomatoes and fertigation recommendations, based on nutrient uptake curves is given.

Fertilizers are injected into pressurised irrigation water through fertilizer tanks and by a variety of fertilizer pumps. The area to be fertigated, availability of electricity and manpower, requirement for automation and costs, determine the selection of specific equipment. Nutrient supply through fertigation may be by continuous and controlled concentration in irrigation water, or in batches by a predetermined nutrient quantity per area and time.

The choice of a fertilizer to be used in fertigation depends on:
- Form - soluble solid and liquid fertilizers are both suitable;
- Solubility: a pre-requisite is complete solubility at field temperature which may change when mixed with other fertilizers;
- Corrosivity: acidic and/or chloride containing fertilizers are usually more corrosive than others;

Fertilizers producing the lowest ionic strength, electrical conductivity and osmotic pressure are preferred.

Interaction of fertilizers with irrigation water compounds may cause precipitates and clogging of the emitters. High concentrations of calcium, magnesium and bicarbonate in irrigation water combined with phosphate or sulfate fertilizers may increase the hazard of clogging. Polyphosphate fertilizers, in specific concentrations, induce sequestering of calcium ions and may prevent clogging.

Prof. Josef Hagin, Technion - Israel Institute of Technology, Water Research Institute, Haifa, Israel
Anat Lowengart-Aycicegi, Israeli Ministry of Agriculture - Extension Service

24 pages, 8 tables, 4 figures, 50 refs.