This study aimed to understand how different factors like soil texture, organic matter, and soil biota affect nitrogen levels in grassland soils. Researchers developed a method to measure soil organic matter fractions directly and created models to predict soil organic matter dynamics and nitrogen supply. They found that soil texture influences the amount of organic nitrogen and the decomposition rate of organic matter. Sandy soils protect organic matter by coating it with clay and silt particles, while fine-textured soils also protect it in small pores and aggregates. Bacteria and nematodes in the soil are found in different pore sizes, suggesting they are spatially separated. The differences in carbon-to-nitrogen ratios of microbes in different soils explain variations in carbon and nitrogen mineralization rates.