Crop Response, Protected Cultivation and Scheduling
Crop response and scheduling
This domain tests how crops respond to water, how protected cultivation changes the water balance, and how to schedule irrigation using ET, soil moisture or plant indicators. It expects water productivity, not just water delivery.
Core rules
- ETc = ET0 × Kc; in a polyhouse, ET0 must be adjusted for reduced radiation, wind and humidity, so open-field values overestimate demand.
- Mulch and protected structures reduce evaporation; ventilation and humidity control affect transpiration and disease.
- Schedule with a combination of ET, tensiometers or moisture sensors, and crop stage; check the root zone, not just the surface.
- Deficit irrigation can improve quality in some crops but reduces yield if pushed too far; avoid stress at flowering and fruit set.
- Fertigation in protected cultivation must match EC and pH targets and avoid salt buildup.
Worked example
A 500 m² polyhouse tomato crop has adjusted ETc = 4 mm/day. Daily demand = 500 × 0.004 = 2 m³ = 2,000 L. At 2.5 plants/m², there are 1,250 plants; one 2 L/h emitter per plant gives 2,500 L/h total. Run time = 2,000 ÷ 2,500 = 0.8 h/day. If humidity is high and ventilation is poor, ETc may be lower; using the open-field value would over-irrigate and raise disease risk.
Traps
Do not apply open-field ET inside a polyhouse; do not ignore mulch, humidity or crop stage; do not schedule by calendar alone; do not over-fertilize through drip without checking EC; do not let salts accumulate in the root zone.