Don't get caught out by rapid increases in crop water use in spring-early summer

Rapid crop growth combined with increases in seasonal water demand (ETo) can increase crop water use by more than 400% in a matter of weeks. Watch your crop and weather conditions and be prepared to increase irrigation amounts to match crop water needs.

  • Crop growth can be very rapidly increasing canopy cover. This can drive big increases in water use. For example, a lettuce crop can grow from established seedlings (crop factor of 0.25) to full canopy (crop factor of 0.8-1.0) very quickly.  
  • Evapotranspiration increases during spring, and typically peaks around mid January.  Get 7 day ETo forecasts from IrriSAT or from apps like The Yield.

Combine crop factors and ETo to get estimates of crop water use (ETc):

ETc = crop factor x ETo

Remember to take into account crop development (crop factors) to get crop water use (ETc), otherwise you are not getting the whole picture. See this corn factsheet for an example.