Optimizing Straw Return Practices to Improve Soil Properties and Crop Yield in Saline-Alkali Soils: A Global Meta-Analysis Coupled With Machine Learning

Abstract

Soil salinization threatens global food production and sustainable arable land use. Although straw return is widely considered a resource-friendly technique for alleviating saline-alkali soils, its overall efficiency, dominant controlling factors, and optimal management levels remain unclear at the global scale. A global meta-analysis of 153 studies, 1092 paired observations, combined with machine learning methods, was conducted to quantify the effect of straw return on crop yield and major soil salinity indicators, to identify dominant controlling factors of the variability, and to optimize straw return management practices in saline-alkali soils. The results showed that straw return increased crop yield by 16.2% and reduced soil exchangeable sodium percentage (ESP) and electrical conductivity of the saturated soil extract (ECe) by 16.5% and 21.3%, respectively. Response magnitudes varied with climate, soil properties, and agricultural management. Random forest analysis further indicated that agricultural management practices were the most important factors to control changes in the crop yield, ESP, and ECe. Recommended straw return practices varied with return method and straw size: under mulching, approximately 5000–6000 kg·ha⁻¹ for straw size ≤ 5 cm and 9000–10,000 kg·ha⁻¹ for straw size > 5 cm; under incorporation, approximately 4000–5000 kg·ha⁻¹ for straw size ≤ 5 cm and 5000–6000 kg·ha⁻¹ for straw size > 5 cm. Overall, these results demonstrate that scientifically managed straw return can simultaneously enhance crop productivity and alleviate soil salinization, providing a scientific basis and practical guidelines for improving soil health and food security in saline-alkali agroecosystems under a changing environment.