Field and laboratory studies towards better use of saline irrigation water in NW China

The Shiyang River basin is located in the northwest China and suffers from water scarcity, drought and salinity. The objective of this paper is to evaluate the impact of saline water on crop yield and on the soil water retention capacity under different irrigation treatments and climate conditions. A soil water and solute flow model was calibrated at low salinity level (Tds= 0.8 g l-1 identified as C08) and at a moderate salinity level (Tds =5 g l-1 identified as C5). Numerical experiments were carried out on a dry and wet year The water retention capacity (WRC) was larger for the C5 treatment for all depths: 121.09 mm for the C08 and 249.53 mm for the C5 , both for the 0 - 100 cm soil layer. The lower WRC for the C08 treatment can be explained by higher percentage of macropores and by a partial redistribution for the C5 treatment of the porosity in smaller and more retentive micropores. Model calibration gave RMSE = 0.06 cm3 cm-3 for the C08 and 0.045 cm3 cm-3 for the C5 For the C08 treatment available soil water, AW, in the 0 - 60 cm root zone was lower than WRC for 84 days in 2005 (dry year) and 71 in 2002 (wet year). For the C5 treatment, instead, AW < WRC for the entire irrigation season of 93 days in all years. The numerical experiments gave higher WUE on the C08 treatment than the C5 treatment for all years considered.