Long-term fertilization alters soil microbiological properties and then affects the soil organic carbon (SOC) pool. However, the interrelations of SOC with biological drivers and their relative importance are rarely analyzed quantitatively at aggregate scale. We investigated the contribution of soil microbial biomass, diversity, and enzyme activity to C pool in soil aggregate fractions (>5 mm, 2–5 mm, 1–2 mm, 0.25–1 mm, and 0.25 mm aggregates rather than in 0.25 mm aggregates explained 21% and 2% of C, respectively. Overall, organic matter addition could contribute to higher C storage by boosting fungal community and enzyme activity rather than by changing microbial community diversity in macro-aggregates.

Long-term continuous cotton cropping results in a significant decrease in soil quality and soil organic carbon, threatening cotton yield. The application of organic amendments is considered an effective management practice for the sustainability of soil productivity and often increases yield. However, the sustainable improvement in the cotton yield, stability, and soil fertility over time resulting from organic amendments with cotton straw and organic manure still need to be confirmed with research, especially under a continuous cotton cropping system. This study evaluated the effect of 12 years of consecutive application of cotton straw and organic manure on continuous cotton yield, soil quality, and soil organic carbon. Four treatments, i.e., chemical N and P fertilizers (NP, control), NP plus cotton straw (NPS), NP plus manure (NPM), and NP plus cotton straw and manure (NPSM), were carried out. The results indicated that the addition of cotton straw and organic manure improved the temporal stability and sustainability of cotton yield. The combination of cotton straw and organic manure resulted in the greatest improvement, increasing the average annual cotton yield by 32.28% compared with the control (NP). A correlation analysis revealed that cotton yield was closely related to soil quality and soil organic carbon. The application of cotton straw and organic manure increased cotton yield by enhancing soil fertility, especially the quantity and quality of soil organic carbon, which improved the supply and cycling of soil nutrients and benefited the stability and sustainability of the cotton yield. Reusing cotton straw and organic manure could improve the sustainable productivity of cotton soil and provide additional environmental value as well as having great potential for cleaner and sustainable cotton production.

Organic wastes have a positive impact on soil physical and chemical properties in the agroecosystems. However, its main effects on soil organic carbon (SOC) or total organic carbon, TOC (SOC and coal-C) contents as well as their effects on soil physico-chemical properties are still unclear. Two types of organic wastes (maize straw and manure) were utilized in dryland affected by mining activities to quantify their relative effect on soil physico-chemical properties. Regression analysis was used to assess the relationship between the soil physical properties, SOC, and TOC as well as their respective contributions to improving these properties. Treatments included control (CK), straw (S), low manure (LM), medium manure plus straw (S-MM), and high manure plus straw (S-HM). The results showed that SOC, soil bulk density, mean weight diameter (MWD), soil total porosity, soil penetration resistance, saturated hydraulic conductivity, and soil infiltration rate were strongly influenced by the application of organic wastes. A stronger linear relationship between SOC and the MWD, (R² = 0.93, p < 0.05) compared to that between TOC and MWD indicated the important role of SOC in improving soil aggregation relative to the effect of TOC. According to the principal component analysis (PCA), the application of organic wastes had stronger effects on SOC contents and physical properties than TOC (SOC and coal-C). These findings advance our understanding of the actual effect of organic wastes on soil physical properties and SOC in dryland affected by mining activities and could inform fertilizer management decisions to improve soil properties.

Most research on immobilized microorganisms employs biomass charcoal as a carrier, but limited studies explore coal-based resources for microbial immobilization. Herein, lead-resistant functional strains were immobilized using weathered coal as a carrier, resulting in the development of a weathered coal-immobilized microbial material (JK-BW) exhibiting high efficiency in lead removal from solutions. A quadratic polynomial model for the adsorption capacity and adsorption rate of JK-BW on Pb²⁺ was developed using the Box-Behnken method to determine the optimal adsorption conditions. The Pb²⁺ adsorption mechanism of JK-BW was studied through batch adsorption and desorption experiments along with SEM-EDS, BET, FT-IR, and XPS analyses. Findings indicated that optimal conditions were identified at 306 K temperature, 0.36 g/L adsorbent dosage, and 300 mg/L initial solution concentration, achieving a peak adsorption performance of 338.9 mg/g (308 K) for the immobilized material, surpassing free cell adsorption by 3.8 times. Even after four cycles of repeated use, the material maintained its high adsorption capacity. Pb²⁺ adsorption by JK-BW involved monolayer chemisorption with ion exchange, complexation, precipitation, physical adsorption, and microbial intracellular phagocytosis. Ion exchange accounted for 22–42% and complexation accounted for 39–57% of the total adsorption mechanisms, notably involving exchanges with K, Ca, Na, and Mg ions as well as complexation with –OH, –COOH, CO–OH, –COOH, CO–, NH₂, and the β-ring of pyridine for Pb²⁺ adsorption.

Soil salinization is a major threat to agriculture and food security globally. The effectiveness of amendments on soil quality and crop production is management-dependent, and low-cost management practices are essential for developing countries. In this 3-year field study, the effects of cattle manure and gypsum amendments on the physicochemical properties of saline–alkali soil were evaluated. We found that both single gypsum and mixed amendments significantly reduced soil hardness, bulk density, pH, and soil salt content in 20–40 cm in 2015 and 2017. A more significant decrease in soil EC and density was observed with the mixed amendments compared to single gypsum after three years of reclamation. Specifically, applying mixed amendments (M-G15) led to a significant increase in Hordeum yield by 60.94%, whereas the application of single gypsum increased Hordeum yield by 25.20–53.14%. This indicated that co-application of cattle manure can reduce the amount of gypsum needed to achieve similar improvements in soil properties and Hordeum yield, with a long-term cumulative effect. Na⁺/(Ca²⁺ + Mg²⁺) showed the largest negative contribution to Hordeum yield under amendments, while soil bulk density showed the second largest number of negative effects on Hordeum yield under mixed amendments. Single gypsum improved the soil’s physical quality during the early stage of saline–alkali soil remediation, and mixed amendments improved the soil’s physicochemical properties and Hordeum yield during the late stage of remediation. Na⁺/(Ca²⁺ + Mg²⁺) in topsoil was confirmed to be the dominant factor under the mixed amendments affecting Hordeum yield, followed by the soil bulk density. These results confirm that the co-application with cattle manure achieves a similar reclamation effect with a reduced gypsum dosage, thereby lowering the reclamation costs of saline–alkali land in semi-arid areas.