Significance of Mineral Nitrogen Transformation and Microbial Community Stabilization Affected by Organic and Biological Amendment in Intensive Cropping System

Due to intensified use of fertilizers and inconsiderable organic matter return, the intensive cropping system is evidently changing soil properties. Even though the changes are hardly predictable spontaneously, it could appear with imbalanced soil mineral nitrogen transformation and decreased biological nitrogen immobilization. To address this uncertainty, we investigated the linkage of soil nitrogen transformation and soil microbial community distribution with the mineral nitrogen fertilization in long-term intensive cropping system during 2019-2022. In this study a three-factor (Factor A: rate of nitrogen (100, 150, 180 and 230 kg N ha−1); Factor B: organic fertilizers (0 and 300 kg ha−1); Factor C: liquid biological activator (0 and 0.1 L ha−1)) experiment carried out on a loam soil (Calcaric Luvisol) in intensive cropping system (in rotation: winter wheat, winter wheat, winter rape and winter wheat). At the study site, soil organic carbon was significantly higher at higher rates of nitrogen application combined jointly with application of organic matter and biological activator. Although the rate of nitrogen fertilization was increasing, either in combination with organic matter or biological activator, induced no significant changes in the accumulation of total nitrogen. Thus, with higher rates of nitrogen fertilization, the content of biologically transformed nitrogen significantly increased. As nitrogen is released from organic matter, it was evident that organic matter inputs affected the biological nitrogen transformation. Organic matter inputs also affected the increase soil fungal community, however, with higher nitrogen inputs soil fungal and bacteria ratio was decreasing. This study highlights the significance of sustainably maintaining of nitrogen and organic matter inputs in intensive cropping systems.