## 4 Discussion
### Effects of Different Treatments on Soil Organic Carbon Components  
Numerous studies have demonstrated that incorporating organic materials into soil promotes the storage of soil organic carbon. The addition of organic materials introduces a substantial amount of carbon sources to the soil, leading to a significant enhancement of the microbial environment. This, in turn, influences the active organic carbon components of the soil [46; 47; 48; 49]. [PERSON] et al. (2024) discovered that combining straw returning to the field with organic fertilizer resulted in a greater increase in soil organic matter content compared to simply returning straw to the field [50]. [PERSON] et al. (2008) emphasized that a specific ratio of corn stalks and organic manure was advantageous for the accumulation of soil organic carbon [51]. The experiment revealed that the organic carbon components in soil after 150 days of each treatment followed this order: T2 \(>\) T3 \(>\) T4 \(>\) T1. Specifically, T2 treatment led to an 18.07% increase in SOC content compared to T1, while T3 treatment resulted in a 15.41% increase. These findings demonstrate that adding straw as organic manure can effectively boost soil organic carbon levels, aligning with prior research [52]. The application of livestock and poultry manure can provide an organic carbon source for soil, increasing the total organic carbon content. Additionally, it supplies nutrients and energy for microorganisms, influencing the decomposition of straw [53]. Correlation analysis indicates a positive relationship between the rate of mass loss in straw and soil organic carbon (SOC). As straw decomposes, the carbon it releases interacts with soil particles, contributing to the formation of soil organic matter and ultimately increasing the soil organic carbon content [54]. Soil humus is a unique type of organic matter that is formed through the humification process, where undecomposed organic matter in soil is converted into humus. This process primarily involves the transformation of humic acid carbon, fulvic acid carbon, and humin carbon. Fulvic acid carbon is converted into humic acid carbon through oxidation condensation, which is crucial for the accumulation of humic acid carbon [55]. [PERSON]'s research demonstrated that carbon from corn can be transferred to and stabilized by humus matter [56]. [PERSON] and colleagues also observed an increase in humic acid content in both surface and subsurface layers after straw was returned to the field, with a subsequent yearly increase in humic acid content correlating with the number of years of deep return [57]. [PERSON] et al. have demonstrated that the fermentation of straw and cow dung in the field significantly enhances the content of humic acid and humic acid carbon, ultimately leading to an improvement in the quality of soil humus [58]. Their experimental findings revealed that incorporating straw and poultry manure into the soil, as opposed to the T1 treatment, led to increased levels of soil water soluble substances, humic acid carbon, fulvic acid carbon, and humin carbon. The application of livestock and poultry manure serves as an energy and carbon source for microorganisms, boosting their abundance and activity, thereby expediting straw decomposition. This approach notably enhances the mineralization and decomposition of corn stalks and the production of soil humus compared to other methods. The decomposition of corn straw involves gradual mineralization of its own components, as well as the condensation of lignin and decomposition intermediates with proteins and amino acids into polymer humic substances like humic acid [59]. [PERSON] et al. (2011) demonstrated that soil humic acid (HA) is easily formed during straw decay by converting reducing functional groups into oxidizing functional groups [60]. The increase in fulvic acid content in soil treated with straw and livestock manure was found to be lower than that of humic acid.