Water use and crop coefficient determination for irrigated winter wheat in Arizona

Abstract

Estimates of evapotranspiration (ET) were irrigated winter wheat in the spring of 1988 9 made for based on measurements of latent heat flux using Bowen ratio systems at the University of Arizona's Maricopa Agricultural Center (MAC). Data were examined over a 132 day period. For the same time period, reference ET estimates were made in the same region using a modified Penman equation based on data from the Arizona Meteorological Network (AZMET). A comparison of ET estimates for 118 days prior to wheat senescence shows excellent agreement (r^2 = 0.94). This implies that a simple crop coefficient can be used as a basis for irrigation scheduling for winter wheat grown under climatic conditions similar to those at MAC in 1988. In addition, the ET estimates were used to test the validity of a previously determined crop coefficient for winter wheat based on heat units and to assess current groundwater allocations in Arizona.