Analysis on Coupling Degree among Crop Evapotranspiration, Effective Precipitation and Water Requirement of Corn on Southern Kerqin Sandy Land in China

Historical characteristics of crop evapotranspiration and irrigation requirement were the bases for determining the irrigation quota in local areas. Based on the trials of two years, crop evapotranspiration and crop coefficient of corn at monthly growth stages were determined and tested by soil water balance method in Fuxin of the southern kerqin sandy land. Using the weather data in Fuxin and Chaoyang from 1953 to 2009, estimated the coupling degree between crop water requirement of λ and apply irrigation water (ETaw) in growing season under three hydrologic years (P=25%,50%and75%).Under the humid year (25%),λ (0.756) in Fuxin was more suitable than Chaoyang (0.694),ETaw(95.5mm) in Fuxin was lower than Chaoyang (148.7mm);under the normal year (50%),λ(0.622) in Fuxin was close to Chaoyang (0.647),ETaw(180.4mm) in Fuxin was higher than Chaoyang (154mm); under droughty year (75%), λ (0.574) in Fuxin was also more suitable than Chaoyang (0.523),ETaw (204.8mm) in Fuxin was also lower than Chaoyang (245mm). The monthly change of λ and ETaw were sharping and influenced irrigation frequency in the growing season of humid and droughty year. The method and results can be further applied to agricultural water management study and guide irrigation in other same regions.