Diversified rotation reduced N₂O emissions by shaping N-cycling microbial communities and increasing their network...

Increased crop diversity can alter soil nitrogen (N) levels, soil properties, and functional microbial communities, leading to changes in potential nitrous oxide (N₂O) emissions. However, our understanding on relationships between N₂O emissions and related microbes in diversified rotation systems is still limited. Here, we established a long-term field experiment to investigate the response of N₂O emissions regulated by five N-cycling genes in three rotation systems. Our results showed that N₂O emissions in wheat and maize seasons in diversified rotations (spring maize → winter wheat - summer maize and spring peanut → winter wheat - summer maize) were 15.5 %- 51.1 % and 15.9 %- 53.3 % lower than that in winter wheat - summer maize rotation (P < 0.05), respectively. Diversified rotations decreased abundance of ammonia-oxidizing archaea (AOA) amoA, AOB amoA, nirK and nirS genes in both wheat and maize seasons, while increased abundance of nosZ gene in maize season, leading to lower soil N₂O emissions. Changes in these functional genes correlated significantly with soil moisture, nitrogen availability, and enzyme activity (L-leucine aminopeptidase and Urease). Besides, diversified rotations increased number of nodes, edges and degree of the co-occurring network and sub-network, while reduced average path length and betweeness. These microbial co-occurrence network complexity indicators were significantly correlated with N₂O emissions. This indicates that increase in aboveground crop diversity drives the increase in complexity of belowground N-cycling related microbial interaction networks, which leads to lower N₂O emissions. In summary, diversified rotations show promising potentials to lower N₂O emissions in agricultural soils.