Rice Genomics and Genetics 2024, Vol.15, No.4, 203-211 http://cropscipublisher.com/index.php/rgg 208 (Figure 3). Considering that the contents of MOC and POC in large-sized aggregates are much higher than those in small-sized aggregates, it can be speculated that the complex structure of macroaggregates may be a hotbed for the accumulation of physical components of organic carbon. However, the relationship between aggregate structural characteristics and the accumulation of organic carbon components needs to be further clarified in future studies (Zhao et al., 2023). In addition, according to Liu et al. (2021), the use of biochar in rice cultivation can improve soil quality by reducing soil bulk density, increasing soil organic carbon content, and improving nutrient availability. These improvements in soil properties can improve rice productivity and nitrogen use efficiency. Figure 3 Scanning electron micrograph of water-able aggregates in different treatments (Adopted from Zhao et al., 2023) 4.3 Driving factors of dynamic changes of organic nitrogen Climatic factors play a crucial role in the dynamic changes of organic nitrogen in rice cultivation. Temperature, precipitation, and humidity can influence soil microbial activity, nitrogen mineralization rates, and overall soil nitrogen dynamics. For instance, the study on paddy soils in China highlighted that soil microbial carbon and nitrogen showed similar patterns with total nitrogen, suggesting that climatic conditions, along with paddy management practices, significantly impact SON composition and mineralization (Wang et al., 2017). Agricultural management practices, such as fertilization, flooding, plowing, and organic material incorporation, are key drivers of changes in soil organic nitrogen. The continuous application of organic materials, such as milk vetch, rice straw, and poultry manure, has been shown to improve soil nitrogen fractions and enhance soil fertility (Yu et al., 2020b). Additionally, the incorporation of rice straw and the use of biochar have been found to reduce nitrogen leaching and improve nitrogen use efficiency, contributing to better soil health and crop productivity. The findings from the provided research papers align with existing literature on the effects of long-term rice cultivation on soil organic nitrogen dynamics. Previous studies have consistently shown that organic material
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