Modeling soil water-salt dynamics and crop response under severely saline condition using WAVES: Searching for a target irrigation volume for saline water irrigation

Water shortage and serious soil salinization are two general features in arid regions. Crop models can provide constructive suggestions for scientific soil water-salt regulations. In the study an ecohydrological crop model WAVES (the WAter Vegetation Energy and Solute model) was employed to examine the crop responses to soil water-salt dynamics in a severely dry and saline region of southern Xinjiang, China. Observation data of film-mulched cotton with the initial soil salinity of 7.19–9.80 g kg-1 (EC1:5 of 1.56–2.12 dS m-1) were collected in 2009 and 2010 with five different irrigation water salinity treatments 0–11.05 g L-1 (EC of 0–11.85 dS m-1). Results showed that the relative absolute errors of simulated soil water and salt were less than 4.1% and 12.4% in 2010 (calibration), and 11.1% and 13.2% in 2009 (validation). The coefficient of determination of yield in calibration and validation was 0.93 and 0.74, respectively. Simulated dynamics indicated soil salt accumulation at a depth of 40 cm. Results of scenario analysis showed that crop water productivity was the highest when the total irrigation volume was 275–325 mm in all scenarios. Saline water with a certain degree of salinity can be used for irrigation without causing a severe yield reduction (20% reduction). This study provided a scientific basis for water management in areas with severe drought and salinization.