Enhancing crop yield and microbial diversity in saline-affected paddy soil through biochar amendment under aquaculture wastewater irrigation

Biochar is frequently employed to ameliorate saline-affected paddy soil. However, there are controversial research findings regarding the applicability of biochar for the enhancement of soil physicochemical properties and agricultural (crop) yield, particularly under conditions of wastewater irrigation in agricultural production. This study investigates the effects of controlled soil salinity levels (1 ‰ and 3 ‰), induced using sodium chloride, and the targeted application of biochar in a pot experiment. The study examines the impact on physicochemical characteristics of different soil layers, physicochemical properties, and physiological responses of rice plants irrigated with aquaculture wastewater. It also delves into soil microbial diversity and the predominant bacterial species. The research findings reveal that biochar exerts a significant influence on soil properties and nitrogen content in saline environments. The addition of biochar enhanced soil electrical conductivity (EC), modulated the distribution of organic carbon, and altered nitrogen transformation processes within the soil. Consequently, biochar application resulted in a 14.2 % and 6.81 % increase in rice yield at 1 ‰ and 3 ‰ salinity levels, respectively. Furthermore, biochar increased leaf area by 25.3 % and 45.9 % in 1 ‰ and 3 ‰ salinity stress separately and enhanced the nitrogen content (TN) in leaves by 28.6 % when the soil salinity is 1 g/kg, demonstrating a positive impact on nitrogen uptake. Additionally, biochar has shown potential in mitigating nitrous oxide (N₂O) emissions. Its addition led to a reduction in the relative abundance of Actinobacteria while increasing the relative abundance of Firmicutes. These findings provide novel insights into the transformative potential of biochar in improving the characteristics of saline paddy soil and augmenting rice yield when used in conjunction with aquaculture wastewater irrigation.