Effects of Different Sod-Seeding Patterns on Soil Properties, Nitrogen Cycle Genes, and N2O Mitigation in Peach Orchards

To clarify the role and mechanism of sod-seeding patterns in improving soil fertility and mitigating nitrous oxide (N2O) emissions in peach orchards, we conducted a study since 2023. Taking clean tillage (CK) as the control, three sod-seeding patterns—Trifolium repens–Lolium perenne mixed sowing (TPr), T. repens single sowing (Tr), and L. perenne single sowing (Pr)—were tested to analyze soil physicochemical properties, nitrogen cycle functional genes, and N2O emission-related genes, and to explore the driving mechanism of N2O mitigation. Results showed that all three sod-seeding patterns significantly reduced soil pH and bulk density, increased soil electrical conductivity and mean aggregate size, and improved soil nutrient status compared with CK; TPr performed best, significantly enhancing soil enzyme activities related to carbon and nitrogen cycles. Sod-seeding patterns had no significant effect on genes involved in assimilatory nitrate reduction, denitrification, or nitrification, but significantly increased dissimilatory nitrate reduction (DNRA) and nitrogen degradation gene abundances, and reduced N2O-producing gene (amoA + amoB, nirS + nirK) abundances. Field monitoring indicated TPr reduced N2O emissions by 34.0%, 35.7%, and 41.0%, relative to CK, Pr, and Tr, respectively. Structural equation modeling revealed that sod-seeding reduced N2O emissions mainly by decreasing soil NH4+-N content and nirS + nirK abundance. In conclusion, sod-seeding patterns improve soil fertility and mitigate N2O emissions in peach orchards, with TPr showing the best comprehensive benefits.