Measurement of Evapotranspiration from Different Pasture Types Using the Rapid Chamber Method

A rapid chamber method (RCM) for evapotranspiration measurement was evaluated in the early stages of a wheat crop by comparison with the Bowen ratio method. Results from the two methods were in good agreement, particularly when slow fan speeds were used in the portable chamber. The rapid chamber method was then used to measure the evapotranspiration from degraded (mainly annual grasses), phalaris (Phalaris aquatica) dominant and phalaris-white clover (Trifolium repens) pastures. ?Evapotranspiration measurements obtained using the RCM compared well with those from a water balance method for the three pasture types over a six day period in July 1997. Daily evapotranspiration rates for the three pasture types were not different during this period as atmospheric demand limited evapotranspiration.