They need up to 140 per cent of evaporation for best production when grown on coastal sands from Myalup to north of Perth. Because of their shallow root depth they need to be watered every day and their watering should be related to daily evaporation. The home-made evaporimeter may not be sensitive enough for daily readings. Check local evaporation figures for these areas to see how they compare with the home-made evaporimeter. If salty water is to be used, the replacement rate should be increased.
Some pasture species are less drought tolerant than others.
Clovers are the most valuable species in the sward but are the least drought tolerant, compared with kikuyu or paspalum, which are the most drought tolerant. By the time a plant is showing visible signs of wilting, its growth has already slowed significantly. By watering less often, the growth of the less desirable species is favoured and clover content drops. Flood irrigation needs to be based on an evaporation rate that ensures their water is applied early enough to maintain best plant growth. Irrigate pastures each time cumulative evaporation from a 'Class A' pan reaches 70 mm.