Effects of Spent Mushroom Substrate on Physicochemical Properties of Seedling Substrate and Quality of Rice Seedlings

This study investigated the effects of substituting spent mushroom substrate (SMS) for traditional topsoil on rice seedling quality, soil physicochemical properties, and microbial communities during rice seedling stage. Compared with traditional rice soil-grown seedlings (CK), adding SMS promoted root growth, increased soluble protein content, and superoxide dismutase (SOD) activity in rice seedlings, Adding 50% proportion of SMS has the best effect. Relative to CK, SMS increased organic matter (SOC), total nitrogen (TN), and total phosphorus (TP) by 21.26-118.48%, 50.44-71.68%, and 23.08-80.17%, respectively. Soil total porosity and aerated porosity also increased to different degrees.Moreover, enzyme activities were enhanced with SMS incorporation. Additionally, SMS significantly increased the relative abundance of Bacillus, Bacteroidetes, and other bacteria compared to CK, especially adding 50% of SMS can increase the abundance of pseudomonas by 8.42 times compared with CK. Effect of adding SMS on fungi compared with CK, the abundance of Ascomycota was markedly elevated. Partial substitution of paddy soil with SMS can ameliorate soil properties, improve seedling quality, and increase microbial diversity. This study provides a basis for SMS to replace traditional rice soil seedling cultivation.