Response of soil physicochemical properties, soil nutrients, enzyme activity and rice yield to rice straw returning in highly saline-alkali paddy soils

Introduction

Soil salinization and alkalization is a major ecological threat to soil productivity and plant growth. The Songnen Plain in Northeast China occupies a total area of 17.0 million ha, of which 20.12% (approximately 3.42 million ha) area consists of saline-alkali lands (Wang et al. 2009). This area is considered one of the world’s three largest areas of saline-alkali soils (Gong et al. 2021). In addition, the area of saline-alkali soil in the Songnen Plain is increasing at a rate of 20, 000 ha per year due to overgrazing by livestock, population growth, and improper soil management over the years (Wang et al. 2009). The saline-alkali soils of the Songnen Plain primarily contain Na₂CO₃ and NaHCO₃ as the main salt components. Li et al. (2006) and Qadir and Schubert (2002) reported that the features of saline-alkali soils are the high levels of Na⁺, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), and pH in the topsoil. This results in the deterioration of the structure and hydraulic characteristics of the soil, imbalance of available nutrients in plants, and low water permeability, which severely restricts agricultural activities in this type of soil (Gong et al. 2021; Morsy et al. 2022). Rice cultivation can effectively decrease the adverse effects of poor soil structure, and gradually leach saline/sodic from the topsoil via irrigation. Therefore, rice cropping with low-salinity water is the most accepted method for restoring saline-alkali lands and ensuring food security (Huang et al. 2022). However, with the change in global climate, rice production on saline-alkali soils is seriously threatened because of freshwater scarcity, increased soil salinization, and soil nutrient depletion (Jin et al. 2018). Therefore, the improvement in the properties of saline-alkali soils will definitely improve overall soil quality and promote crop growth and development.

Straw returning is considered an effective method of comprehensive utilization of straw (Zhang et al. 2014). It plays an important role in improving soil fertility, optimizing soil structure, regulating the growth and function of the root system, and decreasing environmental pollution caused by burning straw (Qin et al. 2015; Chen et al. 2022). Numerous studies have reported that straw returning can significantly improve soil aeration status and facilitate root penetration into deep soil by enhancing total...