Water-driven crop simulation models are commonly employed to evaluate crop yields and irrigation management strategies to improve agricultural water productivity.  Well-tested models can serve as powerful tools for guiding agricultural practices.  The objective of this study was to assess the capability of the AquaCrop model for simulation of cotton transpiration and water use under drip irrigation conditions comparing with field sap flow measurements.  A two-year field experiment (2020-2021) in cotton was conducted in Xinjiang China including two row spacing and two topping methods.  The model adequately estimated canopy cover with a normalized root mean square error (nRMSE) of less than 5% and a model efficiency (EF) close to 1.  The model estimation of transpiration obtained a good agreement with sap flow measurements (nRMSE=22.4%) across all years and treatments.  The model simulated water use efficiency (WUE, 4.42 g m^-2 mm^-1) of cotton were lower than those calculated from actual measurements with WUE of 4.79 g m^-2 mm^-1.  The estimated transpiration was slightly higher than that measured using sap flow meter due to an 11.5% of overestimation for crop coefficient in the model when cotton grew in short and dense canopy structure under drip irrigation and plastic film cover conditions.  Air temperature, vapor pressure difference and radiation had positive effects on cotton transpiration while humidity had negative effects.  The model could capture the trends of transpiration with climate factors, but the climatic effects were stronger than that of sap flow.  In conclusion, AquaCrop model is useful tool in optimizing cotton irrigation strategies.

maize straw return  /  nitrogen application  /  soil physicochemical properties  /  nitrogen use efficiency  /  N₂O emission  /  nitrogen cycle functional microorganisms