Trichoderma Rhizosphere Soil Improvement: Regulation of Nitrogen Fertilizer in Saline–Alkali Soil in Semi-Arid Region and Its Effect on the Microbial Community Structure of Maize Roots

In order to reduce the actual impact of a saline–alkali environment on maize production in semi-arid areas, it is particularly important to use the combined fertilization strategy of Trichoderma microbial fertilizer and nitrogen fertilizer. The purpose of this study was to investigate the effects of different concentrations of nitrogen fertilizer combined with Trichoderma on improving the structural characteristics and ecological functions of maize rhizosphere microbial community in semi-arid saline–alkali soil. Through the microbiome analysis of maize rhizosphere soil samples with 60 kg N·ha−1 (N1) and 300 kg N·ha−1 (N2) nitrogen fertilizer combined with Trichoderma (T1) and without Trichoderma (T0), we found that the combination of Trichoderma and different concentrations of nitrogen fertilizer significantly affected the structure of bacterial and fungal communities. The results of this study showed that the combination of Trichoderma and low-concentration nitrogen fertilizer (N1T1) could improve soil nutritional status and enhance its productivity potential, revealing the relationship between beneficial and harmful fungal genera, microbial diversity and abundance, and crop biomass, which is of great significance for improving agricultural production efficiency and sustainable development.