Micro-Irrigation Systems: Types, Components and Layout
What the exam tests
This domain tests recognition of drip, subsurface drip, micro-sprinkler and mini-sprinkler systems, their components, and how a field layout is assembled from source to emitter.
Core rules and concepts
- A micro-irrigation system has a head control unit, mains, submains, laterals and emitters or micro-sprayers.
- The head control unit normally includes source, pump, filtration, fertigation equipment, pressure gauge, flow meter, valves and backflow prevention.
- Drip emitters may be inline or online, pressure-compensating (PC) or non-PC. PC emitters maintain flow over a wider pressure range and suit uneven fields.
- Layout choices include single-row, paired-row and alternate-row laterals. Spacing must match crop rows, soil wetted width and emitter discharge.
- Micro-sprinklers and mini-sprinklers wet a larger area than drippers but need more pressure and are more affected by wind.
- Filtration must match water quality: screen filters for clean water, media filters for organic or high-solids water.
Worked example
A 1 ha field has rows 1.5 m apart and plants 0.6 m apart, with one 4 L/h dripper per plant. Plants per ha = 10,000 ÷ (1.5 × 0.6) = 11,111. System flow = 11,111 × 4 L/h = 44,444 L/h = 44.4 m³/h. If the field is divided into four operating blocks, each block needs about 11.1 m³/h. The pump, main and filter must be sized for the block flow, not the sum of all blocks running at once, unless the design runs all blocks together.
Traps that cost marks
- Confusing main and submain: the main carries water from the head unit; submains feed laterals.
- Assuming PC emitters remove the need for filtration.
- Ignoring block operation when sizing pump and filter.
- Using sprinkler spacing rules for drip laterals.
- Forgetting air-release and vacuum-relief valves on buried or sloping lines.