Crop Coefficients of Spring Wheat in Windy Dust Area

Crop coefficient is one of the most important parameters needed for crop water requirements using the reference crop method. In this paper, crop coefficients of spring wheat (k_c) were calculated by using the water balance method. The change of k_c during spring wheat growing period in windy dust area was analyzed. The k_c as functions of days after planting (DAP) and cumulative growing degree (CGD) were derived, and the third k_c was derived from the data using the FAO "Straight-Line" Method. The results showed that there were good sixth-order polynomial and forth-order polynomial relations between k_c and DAP and CGD, respectively. The high coefficients of determination (R²>0.94) for the DAP and CGD regressions indicate that the curves fit the data well. The three typical k_c values, derived by using the FAO "Straight-Line" Method at the initial, middle growth stages and at harvest data were 0.57, 1.70, 0.55, respectively.