Abstract:Aiming to explore the effects of different straw returning methods on soil salinity content and summer maize yield under the alternate irrigation of canal-well, field experiments with different tillage modes were carried out in Hetao Irrigation District in 2018 and 2019. The experiment consisted of four different treatments. It included conventional tillage without straw returning (CK treatment), straw surface covering (BF treatment), straw deep buried (SM treatment) and straw mixing (HB treatment) to the field under the irrigation mode of brackish and fresh water. The results showed that salt accumulated in soil at 1m after harvest under all treatments, and the treatments of straw returning reduced the salt accumulation rate significantly. Compared with CK treatment, the BF, SM and HB treatments decreased the salt accumulation rate by 8.7 percentage points, 12.4 percentage points and 6.9 percentagepoints, respectively. SM treatment had the minimum salt accumulation rate, with an average salt accumulation rate of 3.2% in two years, and the desalination zone was formed in the soil depth of 20~40cm. After harvest, the sodium adsorption ratio (SAR) of saturated extracts of different soil layers treated with CK treatment was increased by 10.2%~53.3% compared with the initial value, with a high risk of soil sodification. The SAR was effectively reduced by straw returning measure. SM treatment had the minimum SAR of different soil layers after harvest, which was decreased by 0.4%~73.0% compared with the initial value. and could alleviate soil salinization. Path analysis showed that the main decision factor of summer maize yield was ear length and the limiting factor was bald pointed. Compared with CK, the BF, SM and HB treatments increased production by 11.2%, 19.8% and 11.6%, respectively, and increased WUE by 18.4%, 36.1% and 21.2%, respectively. The comprehensive effect of SM treatment was better. The research could provide theoretical basis for safe utilization of brackish water and straw resource utilization in Hetao Irrigation District.
