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

Fertigation is defined as application of fertilisers 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 fertilisers 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.

Fertilisers are injected into pressurised irrigation water through fertiliser tanks and by a variety of fertiliser 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 fertiliser to be used in fertigation depends on:
- Form - soluble solid and liquid fertilisers are both suitable;
- Solubility: a pre-requisite is complete solubility at field temperature which may change when mixed with other fertilisers;
- Corrosivity: acidic and/or chloride containing fertilisers are usually more corrosive than others;

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

Interaction of fertilisers 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 sulphate fertilisers may increase the hazard of clogging. Polyphosphate fertilisers, 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.