Wheat Yield, N Use Efficiency, Soil Properties, and Soil Bacterial Community as Affected by Long-Term Straw Incorporation and Manure Under Wheat–Summer Maize Cropping System in Southern Shanxi Province, China

Straw incorporation and manure are recognized as a sustainable farming practice to enhance soil fertility and improve crop yields. However, the effects of straw incorporation in combination with manure on productivity, soil nutrient status, N use efficiency (NUE), and the bacterial community are not well understood in wheat-summer maize rotation systems in the southern Shanxi Province. The five treatments were (1) CK, no fertilization; (2) NP, inorganic N and P fertilizers; (3) NPM, mineral N and P fertilizers plus chicken manure; (4) SNP, mineral N and P fertilizers plus maize straw; and (5) SNPM, mineral N and P fertilizers plus maize straw and chicken manure. The results showed that NP, NPM, SNP, and SNPM significantly increased wheat yields by 56.19%, 76.89%, 111.08%, and 114.30%, compared with CK, respectively. Nitrogen agronomic efficiency (AE_N), partial factor productivity (PEP_N), apparent recovery efficiency (Apparent RE_N), and accumulated recovery efficiency (Accumulated RE_N) increased by 103.36%, 37.19%, 76.39%, and 30.90% in the SNPM treatment, compared with NP. Straw incorporation and manure significantly improved soil fertility. <i>Proteobacteria</i>, <i>Acidobacteriota</i>, <i>Actinobacteriota</i>, <i>Chloroflex</i>, <i>Bacteroidota</i>, <i>Planctomycetota</i>, <i>Gemmatimonadota</i>, <i>Armatimonadota</i>, <i>Firmicutes</i>, <i>Methylomirabilota</i>, and <i>Myxococcota</i> were the predominant bacterial phyla. Compared with NP, straw incorporation and manure (NPM, SNP, and SNPM) decreased diversities (richness index, Chao1 index, and Shannon index). Principal coordinates (PCoA) and cluster analyses demonstrated that manure treatments (NPM and SNPM) significantly optimized bacterial community structure. Pearson's correlation analysis demonstrated that organic matter, total phosphorus, available nitrogen, available phosphorus, and available potassium had significant positive correlations with <i>Halanaerobiaeota</i> but significant negative positive correlations with <i>Chloroflexi, Entotheonellaeota,</i> and <i>Myxococcota</i>. Wheat yields, AE_N, PEP_N, Apparent RE_N, and Accumulated RE_N were primarily and significantly negatively associated with <i>Cyanobacteria.</i> Straw incorporation in combination with manure significantly optimized bacterial community structure, wheat yields, and N use efficiency through improving soil fertility. Collectively, straw incorporation in combination with manure is a promising practice for sustainable development.