Bacteria under fertilization regimes and crops rotation. Bacteria

Soil microbes play key roles in soil nutrients cycling and absorption by crops. Thus, shifts in soil microbial community structure affect the function and productivity of agricultural ecosystems. However, the complex impacts of agricultural management methods, such as fertilization regime, crop rotation, and growth stage, on soil microbial communities remain limited. Here, we used a 33-year field experiment to examine soil bacterial and fungal communities at seedling, flowering, and mature stages for winter wheat and soybean in a wheat-soybean rotation system under four fertilization regimes: no fertilization (NF), mineral fertilizer only (NPK), mineral fertilization with 7500 kg ha-1 of wheat straw (WS), and mineral fertilization with 30,000 kg ha-1 composted cow manure (CM). We used 16S rRNA and ITS amplicon sequencings to determine the taxonomical structure of the bacterial and fungal community. Fertilization not only significantly improved crop productivity but also had a greater effect on soil bacterial and fungal community structure than crop rotation and growth stages. Moreover, more phyla of bacteria than fungi were significantly affected by fertilization regime. In the bacterial community, CM had a positive effect on the abundances of Deltaproteobacteria and Bacteroidetes, while the fungi Glomeromycota and Chytridiomycota were significantly impacted by crop rotation. RDA analysis further showed that manure application combined with chemical fertilizers could reduce the impacts of environmental factors on bacterial community variation when compared to no fertilization, chemical fertilization alone, or wheat straw incorporation combined with chemical fertilization. Our results suggest that fertilization regime is more important than crop rotation or growth stage to soil microbe properties and that different responses of soil bacterial and fungal communities to agricultural practices might influence overall ecosystem function.