Straw return alleviates the negative effects of saline sodic stress on rice by improving soil chemistry and reducing the accumulation of sodium ions in rice leaves

Straw return is considered as an effective management strategy to improve soil performance. However, few studies have focused on the effects of straw return on soil chemical properties, organic carbon sequestration, and physiological characteristics and yield of rice in saline sodic rice fields. In this study, a 4-year field experiment was conducted in a saline sodic region of northeast China to investigate the effects of different straw return rates (CK, T1, T2, T3, and T4 were 0, 2.8, 4.2, 5.6, and 7 t ha−1 of straw, respectively) on soil properties, ion accumulation in rice leaves, leaf membrane permeability, photosynthetic characteristics and yield. The results showed that: (1) straw return reduced Na+ accumulation, Na+/K+, cell membrane permeability and malondialdehyde content in rice leaves by reducing the soluble salt content, pH, exchangeable sodium and exchangeable sodium percentage of the soil, which in turn alleviated the damage of saline sodic stress on rice; (2) straw return improved photosynthetic efficiency of rice populations by increasing stomatal conductance, net photosynthetic rate, chlorophyll content and leaf area index; (3) straw return significantly increased rice yield and gradually improved with adding years, but the excessive return rate reduced the positive effect of straw return; (4) the optimal straw return rate increased gradually with the increase of straw return years. Therefore, for the sustainability of soil and environment, it is recommend straw return in saline sodic areas, but the return rate should not be too high in the early stage of straw return.