Effects of Organic Additives and Planting Methods on Fungal Populations in the Rhizosphere of Paddies

In this research, the effects of organic amendments and planting methods on the grain yields, enzyme activity, soil quality, and the structures of fungal populations in the rhizosphere of rice were evaluated. In comparison to the control group with direct seeding, the transplanting method resulted in a 23.5% higher grain yield. Furthermore, rice straw addition significantly improved fungal diversity indices (i.e., Chao1, ACE, Shannon, and Simpson). Dissimilarity distances and principal coordinate analysis revealed substantial variations in the compositions of root-associated fungal communities across the experimental groups with different planting methods. When the transplanting method was used, the Ascomycota, Basidiomycota, Chytridiomycota, Olpidiomycota, Aphelidiomycota, Monoblepharomycota, and Calcarisporiellomycota phyla became dominant. Biochar and rice straw applications caused substantial increases in the abundance of the Ascomycota, Basidiomycota, Chytridiomycota, Rozellomycota, Mucoromycota, Olpidiomycota, Aphelidiomycota, and Gammaproteobacteria phyla. Changes in enzyme activity and the physicochemical properties of the soil were also observed across the treatment groups with different planting methods and organic amendments. Direct seeding enhanced cellulase activity, microbial biomass carbon and nitrogen, available nitrogen, available potassium, nitrate nitrogen, and ammonium nitrogen, whereas transplanting boosted the activity of sucrase and urease enzymes. Rice straw application enhanced cellulase activity and the concentrations of available nitrogen, available phosphorus, nitrate nitrogen, and ammonium nitrogen in the soil. Biochar addition resulted in increased urease activity, microbial biomass carbon and nitrogen, soil pH, and available potassium. The Ascomycota abundance and grain yield exhibited a positive connection, while unclassified_Fungi exhibited negative correlations with the soil pH, organic carbon, available phosphorus, grain yield, and activity of sucrase and urease. Mortierellomycota was positively correlated with microbial biomass nitrogen and nitrate nitrogen. Overall, both the organic additives and planting methods influenced the soil properties, enzyme activity, rhizosphere fungal populations, and grain yield. These results provide new insights and a theoretical basis for studying the changes in soil fungal diversity and richness with different planting methods and organic amendments in Northeastern China.