Soil Bacterial Community Structure and Function under the Substitution of Chemical Fertilizer with Maize Straw

Abstract

The long-term extensive application of chemical fertilizers wreaks havoc on soil bacterial structure and function. To reduce the damage caused by chemical fertilizers, a six-year experiment was performed to study the effects of replacing 0% (CK), 25% (S25), 50% (S50), 75% (S75), and 100% (S100) of 225 kg ha−1 mineral nitrogen fertilizer with an equivalent amount of nitrogen from maize straw on the soil bacterial community structure, diversity, and function. The results showed that Proteobacteria, Acidobacteria, and Gemmatimonadetes were the dominant soil bacterial phyla after the replacement treatments. Replacing mineral nitrogen fertilizer with an equivalent amount of nitrogen from maize straw significantly reduced the number of Photobacterium and bacterial populations involved in genetic information processing in soil, but significantly increased the number of bacterial populations involved in organismal systems, human diseases, and environmental information processing. Compared with other treatments, the relative abundance of TK10 significantly increased by 33.52–76.36% in S25. The number of subgroup 6, Gram-negative, biofilm-forming, potentially pathogenic, and anaerobic bacteria significantly increased, whereas that of Chloroflexi and Blastocatellia subgroup 4 significantly decreased in S50 and S75 compared with CK. The number of TK10 and Blastocatellia subgroup 4 in S50 and S100, respectively, was significantly lower than that in CK. Bacterial species were significantly more present in S25 than in S75. The diversity of bacterial species in S75 was significantly lower than that in CK. S25 and S100 were more favorable to increasing the number of Gram-positive, aerobic, mobile-element containing, and stress-tolerant bacteria. Rhodobacteraceae, Pyrinomonadaceae, Xanthobacteraceae, Nocardioidaceae, and Vulgatibacteraceae with statistical differences in CK, S25, S50, S75, and S100, respectively, could be used as biomarkers. Chloroflexi, Acidobacteria, and Nitrospirae could be used as the main basis for the bacterial classification of soil samples in the equivalent substitution of nitrogen chemical fertilizer with maize straw. S25 is ideal for increasing soil bacterial species richness and abundance.