Organic materials return suppressed soil N2O emissions by changing the composition instead of abundance of denitrifying microbial community

Abstract

Organic materials returned to the field have a significant effect on N₂O emissions from agricultural fields, but the knowledge about the relationship between soil denitrifying microorganisms and N₂O emissions is limited. Hence, we delved deeper into the significance of denitrifying microorganisms in N2O emissions by examining the soil N2O emissions, gene copy numbers, and community structures of denitrifying microorganisms during the wheat harvest season, three years after the partial substitution of chemical nitrogen fertilizers with various organic materials, including straw, pig manure, and biogas residues. The results showed that compared with chemical fertilizer, straw return did not change N₂O emission, and pig manure and biogas residue, especially pig manure return, significantly reduced N₂O emission (62 % and 45 %). Organic materials return did not change the gene copy number of denitrifying microorganisms, but had a significant effect on the community structure. The relative abundance of genera in the three organic materials treatments differed significantly from the chemical fertilizer treatment. The pig manure treatment had marker genera in the nosZ gene. Among the nirK, nirS, and nosZ genes, Sinorhizobium, norank_p_environment_samples, and unclassified_k_norank_d_bacteria, respectively, had the greatest effect on N₂O emissions. The results of the RDA and the minimum depth method indicated that K, pH, and SOC were the key environmental factors influencing the structural changes of nirK, nirS and nosZ communities. Overall, organic materials, especially pig manure, effectively suppressed N₂O emissions by changing the relative abundance and community structure of the dominant genera of denitrifying microorganisms.