Assessing the effects of agricultural waste returning on soil moisture characteristics

Agricultural waste is an emerging and promising resource due to its abundant organic compounds and high water-holding capacity. It plays a crucial role in improving soil water use efficiency and contributing to sustainable agricultural development. This study aimed to investigate the impact of returning agricultural waste on soil moisture characteristics. Different volume ratios (4:5:1:0, 3:5:1:1, 2:5:1:2, 1:5:1:3, and 0:5:1:4) of agricultural waste blend (AWB) consisting of cattle manure, yellow loam soil, wheat straw, and distiller's grains were examined, and the water-holding performance of the five AWB ratios under various suction forces was compared. The analysis confirmed the suitability of the Van Genuchten-Mualem model for fitting soil moisture characteristic curves at different ratios. The study also examined the influences of AWB ratios on soil-specific water capacity, hydraulic parameters, and equivalent pore size. The results showed that agricultural waste effectively increased soil-specific water capacity, available water content, soil WHC(Water-holding capacity), and soil pore count. Furthermore, reducing cattle manure and increasing distiller's grains enhanced these effects. For instance, when the AWB ratio was 0:5:1:4, soil-specific water capacity increased by 47.7%, while field WHC and available water content increased by 9.9% and 3.8%, respectively. Additionally, the number of extremely small and small pores increased by 1.4% and 0.77%, respectively. These findings provide valuable theoretical guidance for agricultural waste treatment and improving soil WHC. Based on the results, it is recommended to increase the proportion of distiller's grains and reduce organic fertilizer when using agricultural waste for improving soil WHC.