A Study on Variation of Priestley-Taylor Model Parameter in Rain Fed Spring Maize Field

The study of Priestley-Taylor (PT) reference crop evapotranspiration model coefficient (α) in local is of great significance in semi-arid agricultural water resources efficient use and precision irrigation in corn. Here, based on the FAO (1998)-recommended Penman-Monteith (PM) reference crop evapotranspiration as a standard method, water and heat exchange and its estimated parameters were determined by eddy covariance technique and Priestley-Taylor model under local climatic conditions. The results indicated that the estimated values of reference crop evapotranspiration (ET0-PT 1.26) in gained by PT mode-recommended coefficient (α = 1.26) lowed by 21.2% during non-growth stages (from November to April next year), and reached an average of 5.5% above PM model reference crop evapotranspiration (ET0-PM) during May to September. The local PT model coefficient α value was 1.15 ± 0.06. The gained average PT mode coefficient at noon during growth stages showed a peak trend with the highest value 0.67 ± 0.08 at tasseling to flowering stage and with the lowest value 0.26 ± 0.13 at seedling stage. In conclusion, the reference crop evapotranspiration estimated accurately by PT mode in the semi-arid climate area, a local PT parameter is required to gain firstly.