Zhenhua Chen

Contemporary mine restoration faces challenges in achieving self-sustaining ecosystems. Accelerating pedogenesis within iron tailings offers a promising strategy by fostering organic carbon (OC) stabilization and soil structure development via organo-mineral complex formation. This study elucidated the microscale mechanisms governing exogenous OC fixation at mineral interfaces in iron tailings during simulated pedogenesis. Controlled microcosm experiments employed iron tailings of sandy and loam textures amended with farmyard manure (F), Mollisols (M), or their combination (FM), alongside original iron tailings as a control. Over 160 days, we tracked OC fractionation, Fe/Al oxide dynamics and mineralogical evolution. Key findings revealed that FM treatment induced the most significant OC accumulation, increasing total OC by 163% (loam) and 108% (sand), with MOC exhibiting the largest relative surge (455% loam, 217% sand). This coincided with pronounced increases in reactive Fe/Al oxides, particularly oxalate-extractable Fe (Fe_ox; +230% loam, +212% sand) and pyrophosphate-extractable Al (Al_p; +122% loam, +54% sand). Mineralogical characterization (XRD) demonstrated distinct phase transformations in amended tailings (e.g., formation of anorthite, grunerite, ankerite), indicative of accelerated weathering. XPS analysis confirmed the presence of surface Fe³⁺/Fe²⁺ species and suggested Al-O-C bonding. These reactive secondary phases, characterized by high specific surface area, facilitated robust OC sequestration primarily through MOC formation. The synergistic input of farmyard manure and Mollisols proved most effective in driving these processes, particularly in loam-textured tailings. Our results provide novel mechanistic insights into Fe/Al-OC association dynamics during tailings pedogenesis. This understanding underpins strategies for enhancing in situ soil formation in iron tailings, ultimately promoting sustainable ecological restoration of mine-degraded landscapes.

In Northeast China’s black soil region, we examined how different straw return strategies—no return (CK), direct straw incorporation (SD), and biochar application (BC)—interact with three nitrogen levels (N0, N60, N100) to affect soil properties, enzyme activities, and the chitin-degrading ChiA functional gene. Both SD and BC significantly increased soil nutrients (total carbon, ammonium nitrogen, available potassium, and soil organic matter) and reduced bulk density. They also enhanced the activities of key carbon—and nitrogen-cycling enzymes, including nitrate reductase and N-acetylglucosaminidase. Straw return method and nitrogen rate both influenced ChiA abundance, but straw management was the primary driver of ChiA community structure according to principal component analysis. Actinobacteria and Proteobacteria dominated the bacterial phyla. Correlation analysis identified bulk density, total nitrogen, C/N ratio, available potassium, soil organic matter, and NAG activity as key factors shaping the ChiA community. Both straw return strategies improved soil fertility and chitin degradation potential. Among them, direct straw return combined with conventional nitrogen application (SD N100) showed the most balanced performance in sustaining soil health and agricultural productivity in the Mollisol region.

Soils with an albic horizon (characterized by a bleached, nutrient-poor eluvial layer), classified primarily as Albic Planosols and associated groups (e.g., Albic Luvisols and Retisols) in the World Reference Base for Soil Resources (WRB), are widespread in Northeast China and suffer from inherent poor nutrient availability and low crop productivity. The present study aimed to evaluate the efficacy of novel microbial–enzyme composite biofertilizers in ameliorating Albic soils. This comprehensive assessment investigated their effects on soil nutrient availability, microbial community structure, and the activities of key enzymes involved in nutrient cycling (e.g., dehydrogenase and phosphatase). Concurrently, the impact on maize crop performance was determined by measuring changes in agronomic traits, including chlorophyll content, stem diameter, and final grain yield. A field experiment was conducted in Heilongjiang Province during the 2023 maize growing season using a randomized block design with six treatments: CF (conventional chemical fertilizer, 330 kg·ha⁻¹ NPK), OF (chemical fertilizer + 1500 kg·ha⁻¹ organic carrier), BF1 (OF + 75 kg·ha⁻¹ marine actinomycetes), BF2 (OF + 75 kg·ha⁻¹ actinomycetes + 45 kg·ha⁻¹ phytase), BF3 (OF + 75 kg·ha⁻¹ actinomycetes + 45 kg·ha⁻¹ mycorrhizal fungi + 45 kg·ha⁻¹ phytase), and BF4 (OF + 75 kg·ha⁻¹ actinomycetes + 45 kg·ha⁻¹ mycorrhizal fungi + 45 kg·ha⁻¹ phytase + 45 kg·ha⁻¹ β–glucosidase). The results showed that biofertilizers significantly increased microbial abundance and enzyme activity. The integrated treatment BF4 notably enhanced topsoil fungal abundance by 188.1% and dehydrogenase activity in the 0–20 cm layer, while also increasing available phosphorus by 92.6% at maturity. Although BF4 improved soil properties the most, BF3 produced the highest maize yield—boosting grain output by 18.3% over CF—and improved stem diameter and chlorophyll content. Strong correlations between microbial parameters and enzyme activities indicated a nutrient-cycling mechanism driven by microorganisms, with topsoil fungal abundance positively linked to alkaline phosphatase activity (r = 0.72) and subsoil bacterial abundance associated with available phosphorus (r = 0.65), demonstrating microbial–mediated carbon–phosphorus coupling. In conclusion, microbial–enzyme biofertilizers, particularly BF4, provide a sustainable strategy for enhancing Albic soil fertility and crop productivity.

China possesses abundant stover resources, and promoting the recycling of stover instead of open burning is a crucial measure for reducing carbon emissions and protecting the atmospheric environment. This study systematically investigated the effects of four stover management strategies—stover removal (CK), direct stover return (SD), stover biochar return (BC), and a combined half-stover half-biochar return (SB)—on soil physicochemical properties, enzyme activities, and microbial communities in the meadow brown soil of Northeast China. The results demonstrated that BC treatment significantly increased the soil total carbon (TC), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), and available potassium (AK) contents. SB treatment showed the most pronounced enhancement in TP. Regarding enzyme activities, Compared with CK, SD significantly increased the activity of N-acetyl -β -D-glucosaminase (NAG). Furthermore, all stover return practices significantly enhanced bacterial community diversity but suppressed fungal diversity. SB treatment resulted in the greatest improvement in bacterial richness and diversity. Beta diversity analysis revealed that SD and SB significantly altered the soil microbial community structure, whereas BC had a minimal impact. In conclusion, the combined application of stover and biochar (SB) exhibited the most consistent and beneficial outcomes across multiple soil health indicators, highlighting its potential as an effective integrated strategy for enhancing soil fertility, promoting carbon sequestration, and sustaining the health of the meadow brown soil ecosystem in Northeast China.

Fuxin County, located in the agro-pastoral ecotone of Northeastern China, has a well-developed stock farming industry. The evaluation of its livestock and poultry farming volume, fecal production, and cropland fecal load will provide a critical foundation for rational production planning, enhancing the efficient utilization of livestock and poultry fecal resources, and promoting the sustainable development of integrated agriculture and animal husbandry at a regional level. An assessment of Fuxin County was conducted using surveys and statistical data in 2022. The results revealed an annual farming volume of 4.75 million pig equivalents, fecal and urine production of 1,041.68 million tons (Mt), and a cropland fecal load of 32.63 t·ha^-1. The livestock and poultry fecal load warning value was calculated at 1.09, corresponding to pre-warning level IV. Therefore, Fuxin County should further formulate an overall development plan of animal husbandry, prioritize technologies for efficient livestock and poultry fecal resource utilization, strengthen cross-regional coordination in fecal management, and accelerate the development of green agricultural practices.