A field experiment was designed to assess the impacts of various maize straw (stover) returning methods on the basic soil physicochemical properties and soil quality index in Jilin (NE China). The five treatments were no return of straw residues (CK), straw incorporated evenly into the soil using the crashing-ridging technique (EIS), straw mulching (SM), straw plowed into the soil (SP), and straw returned in granulated form (SG). Relative to the no straw return, EIS effectively reduced soil bulk density and penetration resistance, increased soil total organic carbon (TOC), macroaggregate-associated carbon content, and the accumulation of soil humus. Furthermore, EIS improved soil structure and soil aggregate stability and significantly increased the soil quality index. Among the various straw returning treatments, SM and SG significantly promoted soil macroaggregation and increased macroaggregate-associated carbon content by 23.69% and 21.70% at the soil surface, respectively (as compared with the control). Compared to SM, SP, and SG, EIS significantly enhanced the aliphaticity and hydrophobicity of soil organic carbon. These results suggested that EIS was the most efficient straw return mode to increase TOC and improve soil structure and fertility.

We conducted a 2.5-year field experiment to test the effects of straw incorporated evenly into the soil (EIS) on soil fungal community, SOC chemical composition, and particulate organic matter fractions via comparing with no straw returning (CK), straw mulching (SM), straw plowed into the soil (SP), and identified the linkages between soil fungal community as well as organic C accumulation and POM formation. Our results showed that EIS treatment significantly increased the concentrations of SOC and the proportion of carbohydrate C, di-O-alkyl C, and O-alkyl C in SOC structure, increased the mass proportion and OC contents of MA(c)POM and mM-POM in the upper 40 cm of soil. Meanwhile, EIS treatment increased the relative abundance of Ascomycota, Zygomycota, Chytridiomycota , and Dothideomycetes in 0–20 cm depths, and also had the highest relative abundance of Glomeromycetes and Dothideomycetes in the 20–40 cm soil. Also, our study suggests that straw return enhanced the relative abundances of fungi involved in the carbon cycle and sequestration, including Zygomycota, Chytridiomycota, and Glomeromycota, and Ascomycota. The shifts in fungal community structure can accelerate organic C accumulation and the formation of soil particulate organic matter, especially in EIS treatment.

The application of organic materials contributes to the sustainable development of agriculture. Increased manure inputs have a fundamental effect on the composition and dynamics of soil organic carbon (SOC). In this study, we conducted a 10-year field experiment in Changchun, Jilin, Northeast China, to investigate the effects of manure addition on soil organic carbon components and soil microorganisms. Specifically, we established four treatments: (i) chemical fertilizer or no addition of manure (CK), (ii) pig manure with chemical fertilizer (ZF), (iii) cow manure with chemical fertilizer (NF), and (iv) chicken manure with chemical fertilizer (JF). The results showed that the JF treatment significantly increased the soil organic carbon (SOC), dissolved organic carbon (DOC), and readily oxidized organic carbon (ROC) content by 20.36%, 105.9%, and 61.32%, respectively, relative to CK. The microbial biomass carbon (MBC) content in JF, ZF, and NF treatments were significantly higher than that of CK, which increased by 107.24%, 116.45%, and 96.71%, respectively. The particulate organic carbon (POC) content in NF and JF treatments differed significantly, increasing by 25.61% and 19.01%, respectively, relative to CK. Redundancy analysis showed that continuous manure application had a positive effect on soil microbial community diversity and abundance, which was favorable for the accumulation of soil carbon. We also found that soil fungi were more sensitive than bacteria to changes in soil carbon composition following manure application. In conclusion, adding different organic materials can better support biodiversity conservation and realize ecosystem services of surface carbon storage and soil conservation. Our results reveal the importance of microbial fixation in soil carbon dynamics according to the different distribution of active organic carbon pools, which will help enhance our understanding of the carbon cycle.

In order to test the short-term effects of straw amendment on soil organic C (SOC) stabilization, SOC protection mechanisms, and soil bacterial community, we examined which bacterial taxonomic groups were associated with protected C fractions via different soil depths. We conducted a 5-year field experiment including a total of four treatments: S0 (no straw amendment), S1 (0–20 cm straw-amended soil), S2 (0–40 cm straw-amended soil) and S3 (0–60 cm straw-amended soil). The core method was used for soil sampling, and 180 soil samples was collected. Our results showed that straw amendment significantly increased bulk soil C content, enhanced the constituents of physically separated fractions and their OC contents, and changed the soil bacterial community composition at different soil depths. SOC was more accelerated in macroaggregate-derived unprotected and microaggregate-derived physically protected fractions at soil depths of 0–20 cm. Physically protected and physico-biochemically protected fractions were the major C protection mechanisms at soil depths of 20–40 cm and 40–60 cm soil depths. Our study also provides evidence that straw amendment significantly increases the bacterial phyla abundance of Proteobacteria and Bacteroidetes at each soil depth. Moreover, straw amendment enhanced the relative abundances of Gemmatimonadetes and Nitrospirae at soil depths of 40–60 cm and have a positive correlation with physically and physico-biochemically protected C pools. These results indicate that straw amendment can regulate C sequestration processes by enhancing SOC physical protection and modulating bacterial community, especially in the deep soil. In addition, straw amendment in subsoil (0–40 cm or 0–60 cm) is more beneficial for C storage and stabilization.

Plastic pollution in farmland soil has become a significant concern for scientists studying farmland ecosystems. However, the current research focus on the environmental impacts of plastics in soil overlooks crucial factors such as sources, distribution, and persistence. In this study, we examined the distribution of residual film after eight years of film mulching in mid-April 2018. We also assessed changes in spatial distribution from 2018 to 2020. Our findings reveal that eight years of film mulching significantly increased the quantity of agricultural mulch film residues in the soil. The size of residual film fragments varied from 0.25 cm² to 109 cm², and the average size, number, and quantity of residues were influenced by soil depth. There was a noticeable downward trend in the quantity of agricultural mulch film residues, decreasing annually by 0.525 kg·ha⁻¹. In contrast, the number of residual films showed an average annual growth rate of 2.13 × 10⁵ p·ha⁻¹. Importantly, we observed a substantial accumulation of residual film fragments below the 10 cm soil layer over time. Fragments ranging from 1–5 cm² were the most abundant and gradually accumulated in deeper soil layers, enhancing mulching film recovery efficiency. This study provides valuable insights into the influence of mulch cycles on farmland soil profiles, identifying the key locations and size-to-shape ratios of residual films. These findings serve as a theoretical foundation for implementing effective measures to control mulch film pollution in agricultural practices.