Hongbao Wu

Introduction: Cadmium (Cd) and arsenic (As) co-contamination in paddy soils poses a persistent challenge for rice safety due to their distinct responses to soil redox conditions. Although organic amendments have been widely used to regulate metal(loid) availability, their effects on Cd/As behavior in soil-rice systems under contrasting water regimes remain unclear. Methods: A pot experiment was conducted under flooding-moisture alternation (FM) and continuous flooding (F) to evaluate the effects of fulvic acid (FA), humic acid (HA), and woody peat (PT) on Cd/As availability, Cd/As in iron plaque (IP), and grain Cd/As accumulation. Results: HA reduced soil available Cd under both water regimes, whereas FA decreased it mainly under F. Available As changed little under FM but increased under F, particularly with FA and PT. Water regime also altered Fe _IP , Cd _IP , and As _IP relationships. Under FM, As _IP was positively associated with Fe _IP , whereas Cd _IP showed no significant relationship with Fe _IP . Under F, both Cd _IP and As _IP were positively associated with Fe _IP . The changes in soil availability and IP-associated retention did not directly translate into grain Cd/As accumulation. PT produced the largest simultaneous decreases in grain Cd and As concentrations under FM, by 47.20% and 23.96%, respectively, and resulted in the lowest screening-level grain risk index (GRI). Under F, all amendments reduced grain Cd, with HA showing the greatest effect, whereas only FA also reduced grain As. The GRI decreased across all amendment treatments under F. Grain Cd under FM and grain As under F were mainly linked to root uptake and shoot-to-grain transfer, whereas grain Cd under F and grain As under FM were more related to soil mobility and IP-mediated retention. Discussion: These findings demonstrate that amendment effects on grain Cd/As concentrations were water-regime dependent: PT simultaneously reduced both elements under FM, whereas under F, HA produced the greatest grain Cd reduction and FA was the only amendment that also reduced grain As. These concentration-based responses require further field validation together with biomass and yield assessment.

This study investigated the effects of foliar selenium (Se) application (either alone or in combination with compound adjuvants or microbial agents) on the yield, Se distribution, translocation, organic Se forms, and mineral composition in black wheat ( Triticum aestivum L. ). Using sodium selenite (Na ₂ SeO ₃ ) as the Se source, five treatments were applied via unmanned aerial vehicle (UAV) spraying under optimal field conditions (30 L per 10 mu; clear, windless afternoons): CK (distilled water control), T1 (Na ₂ SeO ₃ alone), T2 (Na ₂ SeO ₃ + adjuvant), T3 (Na ₂ SeO ₃ + microbial agent), and T4 (Na ₂ SeO ₃ + adjuvant + microbial agent). Key findings revealed that T2 significantly increased the 1000-grain weight by 13.79% compared to CK, while other treatments showed no significant yield improvements. All Se treatments markedly elevated total Se content across plant tissues, with T1 and T2 achieving the highest and statistically similar Se accumulation in grains (grain Se content increased about 9–10 fold versus CK). T1 demonstrated the most efficient Se translocation from spikes to grains and husks. Organic Se speciation analysis identified selenomethionine (SeMet) as the predominant form in grains, with T1 yielding the highest SeMet concentration, while the addition of auxiliaries (T2, T3, T4) significantly reduced SeMet content compared to T1. Additionally, Se application enhanced essential mineral levels (Ca, Mg, Zn, Fe) while reducing toxic heavy metals (As, Cd, Pb). Notably, T2 was particularly effective in reducing Cd concentration to 0.032 mg/kg, meeting food safety thresholds. These results demonstrate a clear trade-off: foliar Se application alone (T1) optimizes nutritional quality via SeMet enrichment, whereas its combination with an adjuvant (T2) provides a balanced strategy, enhancing yield and Cd safety alongside robust Se biofortification. This integrated foliar application approach offers insights for balancing Se enrichment and heavy-metal mitigation in functional agriculture.

Earthworms, as a common soil animal, play an important role in the material cycle and nutrient transformation process of many terrestrial ecosystems (Ngo et al., 2012;Hoeffner et al., 2018). Earthworms can promote the mineralization of nitrogen and phosphorus, and thereby enhance the availability of soil nutrients (Medina-Sauza et al., 2019). Earthworms enhance soil porosity through their burrowing activities, facilitating soil aeration and drainage while improving soil structure, promoting plant root growth, and enhancing root access to water and nutrients (Ganault et al., 2024).Moreover, enhancing earthworm activity may increase microbial diversity and activity in the soil, accelerating litter decomposition and contributing to the carbon (C) sequestration in soil (Liu et al., 2019).Vermicompost is the excrement of earthworms, which provides a more stable habitat for microorganisms by regulating pH and cation exchange capacity (Lim et al., 2015). Vermicomposting takes advantage of earthworms during composting to generate an organic material that may be physically, nutritionally, and biochemically improved compared to compost (Akhila and Entoori, 2022). This process converts nutrients in organic matter (such as nitrogen and phosphorus) into forms that are easily absorbed by plants, thereby increasing soil fertility (Lim et al., 2015;Hoeffner et al., 2018).The role of earthworms in shaping soil microbial communities and regulating C cycling has emerged as a central focus in soil ecological research (Ahmed and Al-Mutairi, 2022;Thomas et al., 2020). However, in recent years, the population of earthworms in the soil has gradually decreased due to intensive agricultural activities.So, how to adopt scientific and reasonable earthworm breeding techniques has become a key issue (Pelosi et al., 2013). Thus, this article aims to provide a theoretical basis and technical guidance for earthworm breeding techniques, and deeply analyze the roles of earthworms in microbial regulation and soil C sequestration.The selection of a suitable earthworm species is important for breeding (Butt, 2008). Currently, there are over 6,000 species of earthworms in the world (Singh et al., 2020). Ecologically, earthworms can be classified into three categories: epigeic, endogeic, and anecic species, based on the living behaviour (Wasunan et al., 2023).Briefly, epigeic earthworms survive on the surface of soil and consume surface organic matter, endogeic earthworms burrow horizontal galleries to feed on soil organic matter, and anecic earthworms burrow vertical galleries to feed on a mixture of surface and deep soil organic matter (Hoeffner et al., 2018). Among them, epigeic earthworms are the most suitable for converting organic matter, while anecic earthworms are more suitable for use as high-protein feed for livestock and poultry (Qiu, 1999;Rong et al., 2020). The Eisenia Fetida belongs to the epigeic earthworm, which has a strong ability to decompose organic wastes such as livestock manure and urban sludge, and is suitable for breeding with manure (Yadav and Garg, 2011). In addition, the Ohira Ⅱ earthworms can withstand low temperatures and can still move at -10 °C , making them suitable for high-density breeding in cold regions like Northeast China (Liu et al., 2021). The Pheretima Guillelmi has a relatively large body size, prefers organic wastes and fertile soil, and is suitable for breeding in vegetable fields and areas with sufficient feed (Lin et al., 2024).Apart from species selection, earthworm breeding techniques involve inoculation density, breeding substrate, breeding environment, etc. (Figure 1). Different densities of earthworms are closely related to their growth and development. The appropriate density of earthworms is 1.5 kg/m 2 (Wang et al., 2023;Xiao et al., 2023). Appropriate temperature, humidity, and sufficient food can reduce the occurrence of earthworm escape (Presley et al., 1996;Chen and Zhong, 2022). To prevent natural enemies, 5% lime can be scattered around the farm to form a defense line (Yi, 2018).Livestock and poultry manure are commonly used as the substrate for earthworm breeding (Bakayoko et al., 2009). The breeding site should be close to livestock and poultry farms or in an open area that is convenient for storing raw materials (Meng, 2018;Xiao et al., 2025), which facilitates breeding substrate acquisition. Cow manure is more beneficial for the growth of earthworms, the production of vermicompost, and the optimal maturation of the substrate compared to pig manure and sheep manure (Vodounnou et al., 2016;Wang et al., 2022). The C/N ratio and pH value in the substrate are important factors affecting the growth and reproduction of earthworms.The optimal C/N ratio is 25:1, and the pH value typically ranges from 6.5 to 7.5 (Sonia et al., 2016;Behera, 2018). During the breeding process, feed is usually added once a week, with a cover depth of 15-20 cm (Liu, 2023).Temperature and humidity are also key factors for the growth and reproduction of earthworms. Earthworms prefer to grow in cool and humid environments (Grant, 1955;Ma et al., 2019). To provide the most suitable environment for the growth and reproduction of earthworms, the moisture content of the substrate should be monitored daily (Perreault and Whalen, 2006;Han et al., 2024). The temperature range most suitable for earthworm growth is typically 15-25 °C , and the humidity is approximately 60%-70% (Baker and Whitby, 2003;Li et al., 2020;Yin et al., 2022).Earthworms constitute the dominant biomass of invertebrates in soil and are known as the "engineers of the soil ecosystem" (Blouin et al., 2013). Earthworm activities create dynamic microenvironments that significantly alter the composition and function of soil microorganisms, ultimately affecting C sequestration processes (Dempsey et al., 2013;Medina-Sauza et al., 2019). A previous study showed that inoculating different ecological types of earthworms...

Fertilizer nitrogen (N) application has been shown to impact methane (CH₄) emissions, yield and quality from rice cropping systems, yet the responses of CH₄ fluxes, yield and quality to N reduction and combined application of organic fertilizer in subtropical rice cropping systems are not well documented. Six experimental treatments were conducted: N90 kg N ha^-1 of urea (N1), organic fertilizer with equal N90 (O1) and 80% urea + 20% organic fertilizer (N1O1), farmer’s common practice with N270 kg N ha^-1 of urea (N2), organic fertilizer with equal N270 (O2) and 80% urea + 20% organic fertilizer (N2O2) were conducted to simultaneously measure the CH₄ flux, yield and quality from a subtropical rice cropping system in south China. Results showed that increased N fertilizer application significantly stimulated soil CH₄ emission, increased rice yield and altered quality in paddy fields. CH₄ emissions were quantified under different N fertilizer management practices in the peak rice growing season during the tillering and heading stages, respectively. Organic fertilizer alone increased CH₄ emission by 442.1% in O1 and by 337.3% in O2 compared with urea. However, relative to organic fertilizer, organic fertilizer combined with urea significantly decreased CH₄ emissions by 48.4% in O1 and by 39.2% in O2. Compared with N1 and N2 treatment, rice yield was significantly decreased by 34.4% and 39.5% under O1 and O2, while significantly enhanced by 49.8% and 22.3%, respectively, under N1O1 and N2O2 (P < 0.05). The protein content significantly increased under N1O1 by 18.8% and 41.5%, the amylose content by 30.3% and 14.8%, and the gel consistency by 32.7% and 15.5% in contrast to N1 and O1 (P < 0.05). Similarly, the protein content, amylose content and gel consistency under N2O2 were consistent with the rice quality under the N1O1 treatments above. In summary, optimizing organic fertilizer combined with urea practices was a win-win strategy to improve grain yield and quality while reducing CH₄ emissions in the rice cropping system. This study provides new insights into the fertilizer types on CH4 emission and rice production of rice cropping systems.

Wheat grain yields, quality, and nitrous oxide (N₂O) emissions were controlled through the type and application rate of nitrogen (N) fertilizer. Here, we investigated the optimal management of N fertilization by examining the combined effects of organic and N fertilizers on wheat yields, quality, and N₂O emissions. Field trials under six treatments were located on campus farms at Anhui Science and Technology University, including farmer’s common practice (270 kg N ha^-1, N270), 2/3 reduction in N270 (90 kg N ha^-1, N90), organic fertilizer with equal N270 (OF270), 2/3 reduction in OF270 (OF90), 4/5 reduction OF270 + 1/5 reduction N270 (20% OF270 + 80% N270), and 4/5 reduction OF90 + 1/5 reduction N90 (20% OF90 + 80% N90) were applied to winter wheat. The plots were arranged in a randomized complete block experimental design. The N₂O emissions were quantified under different fertilization measures in the peak wheat growing season during sowing, jointing, and grain filling stages, respectively. Compared with N270 and N90 treatments, N₂O emissions were significantly decreased by 18.6% and 27.2%, respectively, under 20% OF270 + 80% N270% and 20% OF90 + 80% N90 (p < 0.05). Further, N₂O emissions in N270 were increased by 50.8% relative to N90. Wheat yields increased significantly under 20% OF90 + 80% N90 by 27.6% (N270) and 16.4% (N90), and were considerably enhanced under 20% OF270 + 80% N270 by 40.6% (N270) and 12.7% (N90) in contrast to OF270 and N270 (p < 0.05). Compared with N90, the content of wet gluten, protein and starch under 20% OF90 + 80% N90 treatment significantly increased by 7.7%, 13.8% and 7.9%, and enhanced by 7.6%, 4.8%, 8.0% relative to OF90, respectively (p < 0.05). The starch content increased significantly by 2.0%, whereas the settlement value decreased considerably by 2.9% under 20% OF270 + 80% N270 (p < 0.05), and there was no notable difference in the wet gluten and protein contents (p > 0.05). Our findings indicated that organic fertilizer mixed with N fertilizer can effectively reduce N₂O emissions, increase both the grain yields and quality in wheat field compared with N fertilizer alone.

As one of the dominant species of the alpine grassland on the Qinghai–Tibet Plateau, the activities (e.g., gnawing, burrowing, and grass storage) of plateau pikas (Ochotona curzoniae) directly alter the plant community structure of the grassland ecosystem and affect livestock production and greenhouse gas emission. In order to investigate the effects of rodent isolation (RI) on plant community structure and greenhouse gas emission in the alpine grassland of the Qinghai–Tibet Plateau, we established plots of rodent isolation and rodent activity (i.e., the control sample (CK)) in the 14th village, Seni District, Nagqu City in May 2018. From July 2019 to September, the numbers, sizes, and total damaged area of effective holes; the height, coverage, and aboveground plant biomass; and the methane (CH₄) and nitrous oxide (N₂O) emissions of the alpine grassland were monitored by the quadrat survey method and static closed-chamber method. The results show that the invasion and tunneling of Ochotona curzoniae resulted in the destruction of alpine grassland measuring 0.064 m² per square meter, while the rodent isolation plots showed that 97.9% of the alpine grassland remained unaltered; such unaffected land implies that the economic income of herdsmen could increase by 140 CNY hm⁻². The rodent isolation plots also show that the height and proportion of grasses and sedges in the alpine grassland increased, while the proportion of poisonous weeds decreased. Moreover, the rodent isolation plots also showed a significantly increased coverage of aboveground biomass (p < 0.05), although species richness showed no significant effect based on the Shannon–Weiner, Simpson, and Pielou indices (p > 0.05). The soil uptake of CH₄ and N₂O was 204.99 ± 50.23 μg m⁻² h⁻¹ and 4.48 ± 1.02 μg m⁻² h⁻¹ in the rodent isolation plots, significantly higher by 465.75% and 3001.4% relative to the rodent activity plots, respectively (p < 0.05). Therefore, the establishment of rodent isolation areas can effectively alleviate the degree of damage to alpine grasslands in the short run and slow down the greenhouse gas emission rate to some extent. However, excessive rodent control may also have negative effects on grassland ecosystems, so more attention should be paid in future studies to determining the disturbance threshold of plateau pika in this area. These results provide theoretical guidance for rodent control, grassland protection, and ecological environment management on the Qinghai–Tibet Plateau.

The variations of the stable isotope compositions in water provide critical information on hydroclimatic mechanisms. The climatological and hydrological processes in the Nujiang headwaters in the central Qinghai–Tibetan Plateau are extremely complex and are controlled by alternating continental/local recycled and maritime moisture. However, previous studies have only derived limited data from different types of water in the Nujiang headwaters. Therefore, aiming to understand the sources of stable oxygen (δ¹⁸O) and hydrogen (δ²H) isotopes’ compositional variability and how these are related to hydroclimatic processes, we measured δ¹⁸O and δ²H values from surface waters, snow and precipitation across the Nujiang headwaters from April to September 2018. We found higher δ¹⁸O (−13.7‰), δ²H (−101.8‰) and deuterium excess (d-excess; 7.6‰) values in the non-monsoon season and lower values in the summer monsoon season. Our findings indicated that the δ¹⁸O and δ²H compositions were significantly affected by different moisture sources in this region. The slope (6.66) and intercept (−14.90) of the surface water line (SWL: δ²H = 6.66 δ¹⁸O − 14.90, R² = 0.98) were lower than those of the local meteoric water line (LMWL: δ²H = 9.50 δ¹⁸O + 41.80, R² = 0.99) and global meteoric water line (GMWL), indicating that precipitation was the primary water vapor source for surface water, and evaporation was the dominant hydrological process for the Nujiang headwaters. In general, δ¹⁸O and δ²H tended to be negatively correlated with precipitation and air temperature. In addition, δ¹⁸O and δ²H values in the Nagqu River were inversely correlated with the intensity of discharge, highlighting a precipitation-driven isotope-discharge pattern. Our findings provide a theoretical basis for the hydroclimatic mechanisms occurring in the Nujiang headwaters and further augment our understanding of the southern–middle–northern hydroclimate in the Qinghai–Tibetan Plateau.