Changes in soil characteristics and rice yield under straw returning in saline sodic soils

ABSTRACT Planting rice is one method to effectively utilize saline sodic land, but the rice yield is not high due to the saline sodic stress that affects rice growth. Straw return can improve soil fertility, but it is unknown whether the physicochemical properties of saline sodic soil can be improved by straw return and whether straw return can improve the productivity of saline sodic land. Therefore, we conducted a 4-year field trial to assess the effects of adding straw at 0, 2800, 4200, 5600, and 7000 kg ha−1 (CK, S1, S2, S3, and S4) on the soil physical properties, soil chemical properties, soil nutrients, and rice yield in saline sodic lands from 2017 to 2020. Our results show that a decrease in soil bulk density (BD) and a decrease in the percentage of < 0.053 mm particle size aggregates after straw incorporation depend on the straw incorporation rate. Soil exchangeable Na+ (ENa+) and exchangeable sodium percentage (ESP) were significantly lower in the straw treatments than in the CK treatment, and straw incorporation also had a positive effect on the reduction of soil pH and EC. Straw incorporation had a positive effect on the accumulation of soil organic matter (SOM) and total nitrogen (TN). SOM and TN gradually increased with the increase of straw incorporation rate. Rice yield showed a trend of increasing and then decreasing with the increasing straw incorporation rate, with the highest yield under the S3 treatment at a four-year average yield of 8.57 t ha−1. There was no significant difference between the S3 and S4 treatments in soil physical structure, chemical properties, or nutrients during the experiment. Therefore, we conclude that a reasonable amount of straw incorporation for improving saline sodic soil properties as well as for increasing rice yield in the first four years is 5600 kg ha−1 (S3 treatment).