Effect of straw maturing agents on fungal diversity in soil with different textures under returned straw conditions

In order to select a straw maturing agent suited to local conditions, straw return on medium and sandy loam were investigated in a continuous maize crop in the West Liaohe Plain irrigation area. Straw returned to the field was treated with Zhongnonglvkang, Renyuan, or Nongfukang maturing agent, or without maturing agent as a control. The diversity and community structure of soil fungi was studied using a high-throughput sequencing technique in 0-15 cm, 15-30 cm and 30-45 cm soil layers during the maize silking stage. The results showed that the number of OUT (operational taxonomic units) in sandy loam treated with returned straw and maturing agent was higher than that of control. However, in medium loam, the results were opposite. The relative abundance of Mortierellomycota, Ascomycota, and Basidiomycota for all treatments was higher than in the control, the dominant genera being Mortierella and Guehomyces. Different straw maturing agents and soil textures resulted in different fungi responses. The composition and abundance of soil fungi in medium loam were not significantly affected by returning straw with Zhongnong and Nongfukang application, although applying Renyuan led to significant changes. Significant composition changes and an increase in soil fungi abundance were identified in sandy loam when returned straw was treated with Zhongnong and Renyuan. The results of Linear discriminant analysis Effect Size (LEfSe) analysis showed that soil fungi diversity differed among three treatments. For sandy loam with Zhongnong application, medium loam with Renyuan, and medium loam with Nongfukang, the most significant fungal classifications were phyla Basidiomycota and Ascomycota, class Agaricomycetes, orders Pleosporales and Agaricales, and species Mortierella fimbricystis. The difference in treatment response was also reflected in the maturing agent effects on fungi in different layers of medium and sandy loam. With increased depths, the relative abundance of Mortierella spp. first increased and then decreased, while the relative abundance of Guehomyces spp. decreased. The relative abundance of Guehomyces spp. in deep soil was higher than that in surface soil after the application of straw maturing agent (except for Nongfukang in medium loam). The relative abundance of these two dominant genera in the 0-15 cm soil layer was significantly increased in sandy loam by returning straw and applying Zhongnong. In medium loam, returning straw and applying Renyuan increased the relative abundance of Guehomyces spp. in the 0-15 cm soil layer and the relative abundance of Mortierella spp. in the 15-45 cm soil layer. Under returned straw conditions, effects of straw maturing agent varied with soil texture; therefore, the combined application of straw and straw decomposing agents should be adapted according to local conditions.