Effect of Straw Biochar on Soil Properties and Wheat Production under Saline Water Irrigation

Use of saline water for irrigation is essential to mitigate increasing agricultural water demands in arid and semi-arid regions. The objective of this study is to address the potential of using straw biochar as a soil amendment to promote wheat production under saline water irrigation. A field experiment was conducted in a clay loam soil from eastern China during 2016/2017 and 2017/2018 winter wheat season. There were five treatments: freshwater irrigation (0.3 dS m^−1), saline water irrigation (10 dS m^−1), saline water irrigation (10 dS m^−1) combined with biochar of 10, 20, 30 t ha^−1. Saline water irrigation alone caused soil salinization and decreased wheat growth and yield. The incorporation of biochar decreased soil bulk density by 5.5%−11.6% and increased permeability by 35.4%−49.5%, and improved soil nutrient status. Biochar also reduced soil sodium adsorption ratio by 25.7%−32.6% under saline water irrigation. Furthermore, biochar alleviated salt stress by maintaining higher leaf relative water content and lower Na⁺/K⁺ ratio, and further enhanced photosynthesis and relieved leaf senescence during reproductive stages, leading to better grain formation. Compared to saline water irrigation alone, biochar application of 10 and 20 t ha^−1 significantly increased wheat grain yield by 8.6 and 8.4%, respectively. High dose of biochar might increase soil salinity and limit N availability. In the study, biochar amendment at 10 t ha^−1 would be a proper practice at least over two years to facilitate saline water irrigation for wheat production. Long-term studies are recommended to advance the understanding of the sustainable use of straw biochar.