Irrigation and Farm Machinery
Domain 11 connects water application and mechanisation: how much to apply, when to apply it, and which machine does which job.
Irrigation
- Water requirement is driven by crop evapotranspiration; schedule by IW/CPE ratio, tensiometers or soil moisture.
- Surface, sprinkler and drip methods; drip saves water and permits fertigation.
- 1 hectare-millimetre = 10,000 litres; 1 cm depth over 1 ha = 100,000 litres.
Machinery
- Tractors and power tillers for primary tillage; rotavator for seedbed preparation.
- Sprayers: knapsack, boom, air-assisted; calibrate before use.
- Dusters, seed drills, transplanters, harvesters, chaff cutters, pumps.
Worked example
A drip system has 2,000 emitters of 4 L/h. One hour delivers 8,000 L. If the crop needs 6 mm/day over 0.2 ha, volume = 6 mm x 2,000 m2 = 12,000 L. Run time = 12,000 / 8,000 = 1.5 hours. Reasoning: 1 mm over 1 m2 equals 1 litre, so depth converts directly to volume; divide by system discharge and allow for efficiency losses.
Marks-losing traps
- Confusing 1 mm with 1 cm of irrigation depth.
- Sizing a pump by area rather than by discharge and head.
- Spraying without calibration, causing overdose.
- Irrigating on a fixed schedule without checking soil moisture.