Impact of saline water irrigation on water use efficiency and soil salt accumulation for spring maize in arid regions of China

• Yield, WUE, and soil salt change were analyze based on a field saline irrigation experiment.
• SWAP model was calibrated and verified using field experiment data.
• Crop water use and soil salt with longer term saline water irrigation were simulated with the SWAP model.
• Irrigation with saline water at concentrations below 3 g/L will reduce the yield by no more than 10%.

Saline water irrigation represents the future of agriculture in the arid regions of northwestern China. Therefore, saline water irrigation experiments for spring maize were performed for 3 years from 2009 to 2011 in arid regions of northwestern China, and the impact of irrigation with saline water at different concentrations on the water use efficiency and soil salt accumulation was investigated. A SWAP model was calibrated and verified using field experiment data. The relationships of the salt concentration of the irrigation water with the yield and water use efficiency of spring maize were simulated using the SWAP model. Furthermore, the salt transport across the soil layers was quantitatively analyzed. The results showed the following: (1) irrigation with water containing low concentrations of saline (<3 g/L) for 3 consecutive years combined with a single application of fresh spring water before sowing every year did not cause significant changes in the yield of spring maize. (2) Saline water irrigation for 3 consecutive years resulted in an increase in the salt accumulation at a soil depth of 0–100 cm in 2011. This finding indicated that spring irrigation did not completely leach the salt introduced by saline water irrigation. (3) The SWAP simulation indicated that the yield of spring maize declined by 622 kg/ha for every 1 g/L increase in the salt concentration. When the salt concentration of the irrigation water was less than 3 g/L, the yield of the spring maize was reduced by less than 10%, whereas salt concentrations above 3 g/L decreased the yield much more significantly. A simulation over 10 consecutive years of saline water irrigation showed that the spring maize yields of T3, T6 and T9 will reduce by 8%, 33% and 52%, respectively, compared with the yield in 2009. (4) Despite the differences in the salt concentration of irrigation water, the salt residue in the 0–100 cm soil layer due to irrigation with 3 g/L, 6 g/L and 9 g/L saline water accounted for approximately 60% of the total salt in the irrigation water in 2011. The remaining 40% of the salt leached to the soil layer below 100 cm. In conclusion, irrigation with saline water at concentrations below 3 g/L will reduce the yield by no more than 10% compared with fresh water irrigation, but long-term saline water irrigation will result in significant yield losses, even for low concentrations of salt. Thus, the accumulation of salt in the soil after many years of saline water irrigation needs to be addressed by using a proper irrigation schedule in order to ensure the sustainability of saline water irrigation.