Sestava talne mikrobne združbe in emisije didušikovega oksida v odvisnosti od obdelave tal in gnojenja

Reduced tillage intensity is known to increase soil organic carbon (SOC) in the topsoil, but can also lead to increased microbially derived nitrous oxide (N2O) emissions. In this study, we evaluated the effects of two tillage systems [no-till (NT) vs. conventional plough tillage (CT)] in combination with different fertilisation treatments [mineral (MIN), compost (ORG), and unfertilised control (CON)] on soil physical, chemical and biological properties, as well as N2O emissions, after more than two decades. First soil sampling was conducted down to 60 cm, followed by seasonal gas and topsoil (0–10 cm) sampling. In the top 10 cm, higher SOC content was observed in NT than CT, while fertilization affected SOC down to 20 cm, with higher values in ORG fertilization than the other treatments. This pattern correlated with the gradient of microbial biomass and N-functional gene abundances (qPCR). Ratio between the two N2O-reducing communities (nosZI/nosZII) increased significantly with soil depth and was higher in NT than CT, indicating niche differentiation caused by gradients in environmental conditions. The highest seasonal cumulative N2O emissions were in MIN fertilization, followed by ORG and CON, coinciding with AOB/16S ratio as one of the main explanatory variables of multiple regression. A higher genetic potential for N2O emissions was observed under NT than CT, as indicated by an increased (nirK+nirS)/(nosZI+nosZII) ratio, although this potential was not realized in the form of increased emissions. Lower than expected cumulative emissions in NT-ORG were explained by an increased N2O sink potential (PDA), which positively correlated with proportion of nosZII in the metagenome (WGS). Our results suggest combining organic fertilisation with NT as a promising approach for mitigating N2O emissions; however, addressing the yield gap is necessary before incorporating those practices into recommendations for farmers.