Straw return with diverse nitrogen fertilizer application rates modulate ecosystem services and microbial traits in a meadow soil

Abstract. Nitrogen (N) fertilization has received worldwide attention due to its benefits to soil fertility and productivity, but excess N application also causes an array of ecosystem dis-services, such as greenhouse gas emissions. Generally, soil microorganisms are considered to be involved in upholding a variety of ecosystem services and dis-services. However, the linkages between soil ecosystem services and microbial traits under different N fertilizer application rates remain uncertain. To address this, a 4-year in situ field experiment was conducted in a meadow soil on the Northeast China Plain after straw return with the following treatments combined with regular phosphorus (P) and potassium (K) fertilization: (i) regular N fertilizer (N+PK); (ii) 25 % N fertilizer reduction (0.75N+PK); (iii) 50 % N fertilizer reduction (0.5N+PK); and (IV) no N fertilizer (PK). Ecosystem services, dis-services and microbial traits responded distinctly to the different N fertilizer rates. Treatment 0.75N+PK had overall positive effects on soil fertility, productivity, straw decomposition, and microbial abundance and function and alleviated greenhouse effects due to N deficiency. Meanwhile, 0.75N+PK upregulated aboveground biomass and soil C:N and thus increased the abundance of genes encoding cellulose-degrading enzymes, which may imply the potential ability of C and N turnover. In addition, most observed changes in ecosystem services and dis-services were strongly associated with microbial modules and keystone taxa. Specifically, the Lasiosphaeriaceae-driven module 1 community promoted straw degradation and C and N release, while the Terrimonas-driven module 3 community contributed to production improvement, which was conducive to soil multifunctionality. Therefore, our results suggest that straw return with 25 % chemical N fertilizer reduction is optimal for achieving ecosystem services. This study highlights the importance of abiotic and biotic factors in soil health and supports green agricultural development by optimizing N fertilizer rates in meadow soil after straw return.