Drip irrigation

Source and pump

A borehole, a river or a reservoir, with a pump sized to the flow and the pressure the system needs.

Filtration

Emitters have narrow passages, so the water is filtered at the head of the system before it reaches them.

Fertigation

Fertiliser dosed into the water, so the crop is fed each time it is irrigated.

Mainline and valves

A buried mainline carries the water to the field, and valves divide the field into blocks watered in turn.

Laterals and emitters

Drip lines along the rows, with emitters spaced to the crop, each releasing a set flow.

Root zone

The water spreads through the soil around the roots, and the ground between the rows stays dry.

• Vegetables and row crops
• Orchards and tree crops
• Plantations
• Crops under cover
• Farms where water is scarce

What the design looks at

• The crop, its row spacing and its root depth.
• The soil, which sets how far the water spreads from each emitter.
• The water source: how much it gives, and how clean it is.
• Emitter flow and spacing, and how far each lateral can run with even pressure.
• Block sizes, so the pump always runs at the flow it was chosen for.
• Filtration matched to the water and to the emitters.

Indicative field application efficiency, with good design and management: 80–90% or more. Source: FAO (1989) Irrigation Water Management Training Manual No. 4, Annex I; USDA-NRCS (1997) National Engineering Handbook Part 652, Ch. 6. These are indicative ranges, not guarantees.