Molecular Microbiology Research 2024, Vol.14, No.6, 290-297 http://microbescipublisher.com/index.php/mmr 293 effects, however, may lead to more stable changes in microbial community structure and function. For example, a 40-year study found that long-term fertilization significantly altered bacterial community composition, particularly when organic inputs were included (Muhammad et al., 2022). Seasonal variations also play a crucial role in microbial activity. During the maize growing season, the combination of straw incorporation and N fertilization was found to activate nitrifiers and the nitrification process, especially at mid-growing season when soil C and N availability were low (Sui et al., 2022). This suggests that the timing of straw and fertilizer application can significantly influence microbial community dynamics and soil fertility throughout the growing season. 5 Impact on Maize Yield 5.1 Mechanisms linking microbial communities to crop yield Microbial communities play a crucial role in nutrient cycling, which directly impacts crop yield. Nitrogen-fixing bacteria, such as those in the genera Azospirillumand Pseudomonas, convert atmospheric nitrogen into forms that plants can absorb, thereby enhancing nitrogen availability in the soil (Salvo et al., 2018). Similarly, phosphorus-solubilizing bacteria help in converting insoluble phosphorus compounds into soluble forms, making them accessible to plants. This microbial-mediated nutrient availability is essential for the growth and productivity of maize (Geist et al., 2023). Microbial activity also contributes to soil structure improvement. The production of extracellular polysaccharides by soil microbes helps in the formation of soil aggregates, which improve soil aeration and water retention. Enhanced soil structure facilitates better root growth and nutrient uptake, ultimately leading to higher crop yields (Chen et al., 2021; Sui et al., 2022). For instance, the incorporation of straw and nitrogen fertilization has been shown to improve soil enzyme activities and microbial community structure, which are critical for maintaining soil health and fertility (Muhammad et al., 2022). 5.2 Effects of straw and fertilizer management on yield Different straw incorporation and fertilization regimes have varying impacts on maize yield. Studies have shown that straw returning combined with nitrogen fertilization significantly enhances soil fertility, enzyme activities, and microbial diversity compared to traditional planting methods (Yang et al., 2020). For example, a study conducted in Northeast China demonstrated that straw incorporation with moderate nitrogen fertilization improved soil enzyme activities and microbial communities, leading to better soil quality and higher maize yields (Sui et al., 2022). Field studies have provided valuable insights into the effects of straw and fertilizer management on maize yield. In a long-term study on China's Loess Plateau, straw mulching combined with nitrogen fertilization significantly increased soil moisture content, organic carbon, and enzyme activities, resulting in improved soil quality and higher crop yields (Chen et al., 2021). Another study in subtropical China found that low irrigation combined with optimal nitrogen fertilization (N300) enhanced soil enzyme activities and bacterial diversity, which are key indicators of soil health and productivity(Muhammad et al., 2022). 5.3 Yield improvement strategies through microbial manipulation Combining microbial inoculants with straw and fertilizer application can further enhance maize yield. Inoculating maize with plant growth-promoting rhizobacteria (PGPR) such as Azospirillum brasilense and Pseudomonas fluorescens, along with nitrogen fertilization, has been shown to increase grain yield and modify rhizosphere microbial communities (Salvo et al., 2018). This approach leverages the synergistic effects of microbial inoculants and nutrient management to boost crop productivity. The use of biofertilizers and organic amendments is another effective strategy to enhance microbial activity and improve crop yield. Biochar amendments, for instance, have been found to increase soil organic carbon, total
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