Fertigation: What It Is and How It Works

What is fertigation?

Fertigation — from fertilization and irrigation — is the delivery of dissolved plant nutrients through the drip irrigation system directly to the root zone. The core advantage over broadcast or surface fertilizer application is precision: nutrients arrive where the plant can use them, when it needs them, in a form it can absorb.

Efficiency gains are real and measurable: less nutrient is lost to leaching, volatilization or surface runoff; application timing can match the crop’s demand curve rather than the convenience of field operations.

How the system works

A fertigation system adds concentrated fertilizer stock solutions to the irrigation water flow, either through venturi injectors, dosing pumps or proportional systems. The diluted solution reaches the root zone through the drip emitters.

Stock solutions are prepared in advance at high concentration. Calcium-containing fertilizers must be kept in a separate stock from sulphate- or phosphate-containing products — mixing them in concentrated form causes precipitation. Stock A typically holds calcium nitrate; stock B holds the remaining salts. Both are injected separately and mix in the main water line.

EC management

EC is the daily management variable of a fertigation system. The applied EC is set by the stock concentration and dilution ratio; the drain EC reflects what is accumulating in the root zone.

A simple rule of thumb: if drain EC is consistently more than 0.5-1.0 dS/m above applied EC, salt is accumulating and a leaching irrigation is due. If drain EC is below applied EC, the root zone may be drying out between irrigations.

pH management

The target range for most crops is 5.5-6.5 in the applied solution. Outside this range, phosphate, iron, manganese and zinc become increasingly unavailable. Automated pH dosing pumps (typically adding phosphoric or nitric acid) maintain the range without manual intervention in commercial systems.

Drain monitoring

Drain water analysis is the feedback loop of the system. The percentage of drain (drain volume ÷ applied volume × 100) should typically sit between 15% and 30%. Monitoring this figure — along with drain EC — provides an early-warning signal for salt build-up well before the crop shows symptoms.