An atmospheric and soil thermal-based wheat crop coefficient method using additive crop growth models

Abstract

Accurate crop evapotranspiration simulation is vital for reasonable irrigation planning. The two-step method for crop evapotranspiration estimation has been widely used for irrigation water demand management. However, in the two-step method, the crop coefficient (Kc) is typically taken as a constant in crop growth stages, which may result in a certain error in evapotranspiration estimation. It is of significance to estimate Kc accurately for effective water resources management. Based on three-year lysimeter experimental data collected from the Wudaogou Station for Hydrology and Water Resources, this study proposes a thermal-based Kc method for actual crop evapotranspiration estimation. The proposed thermal-based Kc method uses air temperature and soil heat flux as input variables, which could mainly characterise the thermal effect on crop growth from the atmosphere and soil. Results showed that the proposed method is effective in estimating Kc. The estimated Kc highly correlates with actual Kc values, which are derived from lysimeter observation, with correlation coefficient above 0.87 and Nash-Sutcliffe efficiency above 0.70. The proposed method could estimate Kc daily, which can be used to estimate crop evapotranspiration accurately.