A novel method for simulating the dynamics of the single and dual maize crop coefficients in an arid ecosystem

The crop coefficient is a key link between crop evapotranspiration (ETc) and reference evapotranspiration (ET0), which is important for agricultural water management and irrigation strategy. However, how to quantify seasonal variations in the single and dual crop coefficients (Kc and Kcb, respectively) remains a challenge. This study aimed to provide a novel approach with a soil-plant-atmosphere continuum (SPAC) model under various land surface scenarios for reconstructing the dynamics of Kc and Kcb. A numerical SPAC model was validated by comparing with measurements both at hourly and daily mean dataset (e.g., eddy covariance for actual ET). The proposed model was then applied to the Heihe River Basin to calculate the seasonal and annual variations in both Kc and Kcb of maize. Kc and Kcb shown significant seasonality and interannual fluctuations. The Kc and Kcb presented a single‐peak trend, reaching the maximum value in peaking growing season and fluctuating day to day. During growing season, changes in Kc, Kcb and the coefficient of soil evaporation (Ke) varied from 0.19 to 1.57, 0.08–1.50, and 0.01–0.19, with average values of 0.35, 0.39, and 0.04, respectively. It was found that leaf area index (LAI) was the dominant factor regulating Kc, Kcb, and Ke. This study implied that the SPAC model with numerical technique is efficient in reconstructing the dynamics (annual and inter-annual) of the crop coefficient and feasible for diagnosing complex interactions among soil, plants, and the atmosphere under various land surface scenarios.