Key Points
- Responses to water stress differ widely across crops.
- The degree and timing of water stress primarily determines the yield effect.
- The time between sowing and harvest may be shortened depending on the intensity and timing of the water stress.
- Potential soil moisture deficit (PSMD) is an index of drought and is the difference between crop demand and the supply of water via rainfall/irrigation.
- The refill point is where all available water has been used up and occurs when water holding capacity reaches 50% (refill point differs for crop and soil type).
- Yield losses for most arable crops may be 1 to 3% for each mm of PSMD over the refill point.
- Water use efficiency (WUE) is the ratio of yield (kg/ha) to crop water use.