Changes in Soil Organic C Fractions and C Pool Stability Are Mediated by C-Degrading Enzymes in Litter Decomposition of Robinia pseudoacacia Plantations.

Litter decomposition is the main source of soil organic carbon (SOC) pool, regarding as an important part of terrestrial ecosystem C dynamics. The turnover of SOC is mainly regulated by extracellular enzymes secreted by microorganisms. However, the response mechanism of soil C-degrading enzymes and SOC in litter decomposition remains unclear. To clarify how SOC fraction dynamics respond to C-degrading enzymes in litter decomposition, we used field experiments to collect leaf litter and SOC fractions from the underlying layer in Robinia pseudoacacia plantations on the Loess Plateau. Our results showed that SOC, easily oxidizable organic C, dissolved organic C, and microbial biomass C increased significantly during the decomposition process. Litter decomposition significantly decreased soil hydrolase activity, but slightly increased oxidase activity. Correlation analysis results showed that SOC fractions were significantly positively correlated with the litter mass, lignin, soil moisture, and oxidase activity, but significantly negatively correlated with cellulose content and soil pH. Partial least squares path models revealed that soil C-degrading enzymes can directly or indirectly affect the changes of soil C fractions. The most direct factors affecting the SOC fractions of topsoil during litter decomposition were litter lignin and cellulose degradation, soil pH, and C-degrading enzymes. Furthermore, regression analysis showed that the decrease of SOC stability in litter decomposition was closely related to the decrease of soil hydrolase to oxidase ratio. These results highlighted that litter degradation-induced changes in C-degrading enzyme activity significantly affected SOC fractions. Furthermore, the distribution of soil hydrolases and oxidases affected the stability of SOC during litter decomposition. These findings provided a theoretical framework for a more comprehensive understanding of C turnover and stabilization mechanisms between plant and soil.

Analysis of the environmental behavior of farmers for non-point source pollution control and management: An integration of the theory of planned behavior and the protection motivation theory.

Agricultural non-point source (NPS) pollution in water source protection areas poses serious challenges for governments in developing countries. It is important to consider the environmental behavior of farmers when exploring the causes of NPS pollution as well as when establishing scientific controls and management measures. However, the poor understanding of factors influencing the environmental behavior of farmers and the lack of a suitable environmental socio-psychological model limit the application of the environmental behavior of farmers in NPS pollution management. In this study, we therefore integrated the theory of planned behavior (TPB) and the protection motivation theory (PMT) to identify the main determinants of the NPS pollution-related environmental behavior and intention of farmers in the Water Source Area of the Middle Route of the South-to-North Water Diversion Project in China. Results indicated that the integrated model provided a better understanding of the environmental behavior and intention of farmers than that provided by each component when used individually, and revealed that farmers perceived that the susceptibility and severity of threats caused by water deterioration influenced environmental intention through the mediating effects of subjective norm and attitude toward adopting pro-environmental behavior. At the same time, the perceived vulnerability of farmers was relatively high and their perceived severity was relatively low. Furthermore, the subjective norm, attitude, self-efficacy (i.e., the perceived behavioral control), and response efficacy positively and significantly influenced intention. However, response cost had a significantly negative effect on intention. Among them, subjective norm had the largest effect on intention. Intention was the key determinant for the actual environmental behavior of farmers, while self-efficacy also had a significantly positive effect on behavior. Managing and controlling agricultural NPS pollution requires a multi-disciplinary and comprehensive approach. Therefore, an integrated theoretical framework was developed in this study by integrating TPB and PMT to gain insight into the environmental behaviors and intention of farmers. The results provided a theoretical basis for NPS pollution control.

Research on the food security condition and food supply capacity of Egypt.

Food security is chronically guaranteed in Egypt because of the food subsidy policy of the country. However, the increasing Egyptian population is straining the food supply. To study changes in Egyptian food security and future food supply capacity, we analysed the historical grain production, yield per unit, grain-cultivated area, and per capita grain possession of Egypt. The GM (1,1) model of the grey system was used to predict the future population. Thereafter, the result was combined with scenario analysis to forecast the grain possession and population carrying capacity of Egypt under different scenarios. Results show that the increasing population and limitations in cultivated land will strain Egyptian food security. Only in high cultivated areas and high grain yield scenarios before 2020, or in high cultivated areas and mid grain yield scenarios before 2015, can food supply be basically satisfied (assurance rate ≥ 80%) under a standard of 400 kg per capita. Population carrying capacity in 2030 is between 51.45 and 89.35 million. Thus, we propose the use of advanced technologies in agriculture and the adjustment of plant structure and cropping systems to improve land utilization efficiency. Furthermore, urbanization and other uses of cultivated land should be strictly controlled to ensure the planting of grains.

Straw Retention with Reduced Fertilization Enhances Soil Properties, Crop Yields, and Emergy Sustainability of Wheat-Soybean Rotation.

Cereal + legume rotation is an integrated system that facilitates soil fertility and sustainable agricultural production. However, research on the management compatibility affecting soil physico-chemical properties yields overall agro-ecosystem sustainability, but profitability is lacking, especially under straw retention and potential reductions in fertilizer application. An 11-year field experiment investigated three treatments: no straw retention + traditional mineral fertilization (TNS), straw retention + traditional mineral fertilization (TS), and straw retention + reduced mineral fertilization (DS). Compared with TNS, TS significantly improved soil physico-chemical properties, including macro-aggregates (R > 0.25 mm), porosity, field water capacity (FWC), soil organic carbon (SOC) storage, total nitrogen storage, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) by 17.3%, 3.2%, 13.0%, 5.5%, 3.2%, 15.5%, and 13.8%, respectively. TS also significantly increased total (wheat + soybean) yields (TYs), economic profits, and emergy sustainability index (ESI) by 15.8%, 25.0%, 3.7 times that of TNS, respectively. Surprisingly, compared with TS, DS further significantly improved R > 0.25 mm, porosity, FWC, SOC storage, MBC, MBN, TY, economic profits, and ESI by 11.4%, 1.5%, 6.1%, 3.0%, 10.6%, 7.2%, 5.7%, 11.1%, and 36.5%, respectively. Overall, retaining straw with reduced fertilization enhances soil properties, yields, and emergy sustainability in wheat-soybean rotation systems.

Response surface optimization of methane potentials in anaerobic co-digestion of multiple substrates: dairy, chicken manure and wheat straw.

Dairy manure (DM), chicken manure (CM) and wheat straw were used to investigate the possibility of optimizing the methane (CH4) potentials in anaerobic co-digestion of multiple substrates. Response surface methodology (RSM) was used to evaluate the individual and interactive effects of four variables [carbon/nitrogen (C/N) ratio, the feeding composition (DM/CM), initial substrate loading and inoculum-to-substrate ratio (ISR)] in the digestion process. All four variables had significant effects on CH(4) potentials. Interactive effects of C/N and DM/CM ratios, C/N ratio and ISR, initial substrate loading and ISR were significant The optimum conditions were a C/N ratio of 26.31, a DM/CM ratio of 42.96:57.04, an initial loading of 15.90 g volatile solids (VS)/l and an ISR ratio of 2.34, with the maximum CH4 potential being 394 ml/g VS. The RSM model was appropriate for optimizing CH4 production in the process of anaerobic co-digestion of multiple substrates.

Combining Straw Mulch with Nitrogen Fertilizer Improves Soil and Plant Physio-Chemical Attributes, Physiology, and Yield of Maize in the Semi-Arid Region of China.

Mulching and nitrogen (N) fertilization are the main drivers for sustainable crop production. The sole use of nitrogen fertilizer threatened both the physiology and production of maize in rain-fed areas. Therefore, we proposed that wheat straw mulching with N fertilization would increase maize yield by improving soil fertility, physiology, and nitrogen use efficiency. A two-year field study evaluated the effects of CK (control), N (nitrogen application at 172 kg ha-1), HS (half wheat straw mulch, 2500 kg ha-1), HS+N (half wheat straw, 2500 kg ha-1 plus 172 kg N ha-1), FS (full wheat straw, 5000 kg ha-1), and FS+N (full wheat straw, 5000 kg ha-1 plus 172 kg N ha-1) on maize growth, physiology, and biochemistry. Compared with the control, the FS+N treatment resulted in the increase of 56% photosynthetic efficiency, 9.6% nitrogen use efficiency, 60% nitrogen uptake, 80% soluble sugar, 59% starches, 48% biomass, and 29% grain yield of maize. In addition, the FS+N regime increased 47%, 42%, and 106% of soil organic carbon and available P and N content in comparison with the control. Maize grain and biomass yields were positively correlated with N uptake, photosynthesis, soil organic carbon, and soil available N and P contents. Conclusively, the use of wheat straw at 5000 kg ha-1, along with 172 kg N ha-1, is a promising option for building a sustainable wheat-maize cropping system to achieve optimal crop yield and improved plant and soil health in a semi-arid region of China.

Differential effects of petroleum-based and bio-based microplastics on anaerobic digestion: A review.

The number of plastics is increasing owing to the rapid development of the plastics industry. Microplastics (MPs) are formed during the use of both petroleum-based plastics and newly developed bio-based plastics. These MPs are inevitably released into the environment and are enriched in wastewater treatment plant sludge. Anaerobic digestion is a popular sludge stabilization method for wastewater treatment plants. Understanding the potential impacts of different MPs on anaerobic digestion is critical. This paper provides a comprehensive review of the mechanisms of petroleum-based MPs and bio-based MPs in anaerobic digestion methane production and compares their potential effects on biochemical pathways, key enzyme activities, and microbial communities. Finally, it identifies problems that must be solved in the future, proposes the focus of future research, and predicts the future development direction of the plastics industry.

[Mineralization Characteristics of Soil Organic Carbon and Its Relationship with Organic Carbon Components in Artificial Robinia pseudoacacia Forest in Loess Hilly Region].

In order to explore the characteristics of organic carbon mineralization and the variation law of organic carbon components of an artificial forest in a loess hilly area, an artificial Robinia pseudoacacia forest restored for 13 years and the adjacent slope farmland were selected as the research objects, and indoor culture experiments under three different temperature treatments (15, 25, and 35℃) were carried out. The results indicated that the mineralization rate of soil organic carbon decreased sharply at first and then stabilized. The cumulative release of organic carbon increased rapidly in the initial stage of culture and gradually slowed in the later stage. Soil organic carbon mineralization in sloping farmland was more sensitive to temperature change, and its temperature sensitivity coefficient Q10 was 1.52, whereas that in R. pseudoacacia forest land was only 1.38. According to the fitting of the single reservoir first-order dynamic equation, the soil mineralization potential Cp of R. pseudoacacia forest land and slope farmland was between 2.02-4.32 g·kg-1 and 1.25-3.17 g·kg-1, respectively, that is, the mineralization potential of the R. pseudoacacia forest was higher. During the cultivation period, the content of various active organic carbon components decreased with time, and that in the R. pseudoacacia forest land was greater than that in the slope land. The cumulative carbon release of soil was significantly positively correlated with the contents of MBC and DOC (P<0.05), and Q10 (15-25℃) was negatively correlated with the contents of SOC, EOC, and SWC (P<0.05). These results could provide some reference for the study of soil carbon sequestration in loess hilly regions under climate change.

Changes in the material characteristics of maize straw during the pretreatment process of methanation.

Pretreatment technology is important to the direct methanation of straw. This study used fresh water, four bacterium agents (stem rot agent, "result" microbe decomposition agent, straw pretreatment composite bacterium agent, and complex microorganism agent), biogas slurry, and two chemical reagents (sodium hydroxide and urea) as pretreatment promoters. Different treatments were performed, and the changes in the straw pH value, temperature, total solid (TS), volatile solid (VS), and carbon-nitrogen ratio (C/N ratio) under different pretreatment conditions were analyzed. The results showed that chemical promoters were more efficient than biological promoters in straw maturity. Pretreatment using sodium hydroxide induced the highest degree of straw maturity. However, its C/N ratio had to be reduced during fermentation. In contrast, the C/N ratio of the urea-pretreated straw was low and was easy to regulate when used as anaerobic digestion material. The biogas slurry pretreatment was followed by pretreatments using four different bacterium agents, among which the effect of the complex microorganism agent (BA4) was more efficient than the others. The current study is significant to the direct and efficient methanation of straw.

Spatiotemporal Evolution of Non-Grain Production of Cultivated Land and Its Underlying Factors in China.

Food security is the foundation of development. We comprehensively characterized the spatiotemporal patterns of non-grain production (NGP) areas in China and elucidated the underlying factors driving NGP. Our objectives were to map NGP on cultivated land (NGPCL) in China, and to quantify its spatiotemporal patterns, to investigate the factors underlying NGP spatial differentiation, and to provide a scientific basis for developing NGP management policies and reference points for protecting cultivated land in other countries. We mapped NGPCL in China from 2000 to 2018 using remote sensing and geographic information system data. The spatiotemporal evolution of the NGP rate (NGPR) was also investigated. The dominant factors driving NGP progression and associated interactions were identified using geographic detectors. From 2000 to 2018, the NGPR gradually decreased from 63.02% to 52.82%. NGPR was high in the west and low in the east, and its spatial differentiation and clustering patterns were statistically significant. Precipitation, temperature, altitude, and soil carbon content were the dominant factors affecting the spatial differentiation in NGPR. The interaction between these factors enhanced the spatial differentiation.

Landscape Ecological Risk Assessment Based on Land Use Change in the Yellow River Basin of Shaanxi, China.

The Yellow River Basin in Shaanxi (YRBS) has a relatively fragile ecological environment, with severe soil erosion and a high incidence of natural and geological disasters. In this study, a river basin landscape ecological risk assessment model was constructed using landscape ecology principles to investigate the temporal and spatial evolution, as well as the spatial autocorrelation characteristics of landscape ecological risks in the YRBS over a 20-year period. The main findings from the YRBS were that the land use types changed significantly over the span of 20 years, there was spatial heterogeneity of the landscape pattern, and the ecological risk value was positively correlated. The threat of landscape ecological risks in YRBS is easing, but the pressure on the ecological environment is considerable. This study provides theoretical support administrative policies for future ecological risk assessment and protection, restoration measures, and control in the Yellow River Basin of Shaanxi Province.

Soil ecoenzymatic stoichiometry reveals microbial phosphorus limitation after vegetation restoration on the Loess Plateau, China.

Exploring the limitations of soil microbial nutrient metabolism would help to understand the adaptability and response mechanisms of soil microbes in semi-arid ecosystems. Soil ecoenzymatic stoichiometry is conducive to quantifying the nutrient limitations of microorganisms. To quantify microbial nutrient limitation during plant restoration, we measured soil physicochemical properties, microbial biomass, and the activities of four enzymes (ꞵ-1,4-glucosidase, leucine aminopeptidase, ꞵ-1,4-N-acetylglucosaminidase, and alkaline phosphatase) in the soils of the northern Loess Plateau. Vegetation restoration patterns significantly affected soil properties, microbial biomass, enzymatic activity, and associated stoichiometry. Soil enzymatic activity increased significantly after vegetation restoration, especially in Robinia pseudoacacia plantations (RP). Correlation analysis showed that soil nutrients (C and N), moisture and pH were significantly correlated with ecoenzymatic activities and their stoichiometries. Vector-threshold element ratio (VT) model analysis revealed that microbial nutrient metabolism was limited by P, and soil microbial C limitation was significantly weakened after vegetation restoration, particularly in RP. Correlation analysis indicated that microbial nutrient limitations represented by the VT model were significantly correlated with soil moisture, nutrients, and associated stoichiometry. Therefore, the soil microbial community was mainly limited by P rather than N in vegetation restoration on the Loess Plateau via the VT model, and this limitation was primarily associated with the variation in soil properties. In addition, the soil microbial C limitation was significantly negatively correlated with microbial nutrient (P or N) limitation, which illustrated that soil microbial nutrient metabolism has strong stoichiometric homeostasis.

[Effects of Straw Returning and Fertilizer Application on Soil Nutrients and Winter Wheat Yield].

In order to explore the effects of straw returning combined with fertilizer on soil nutrients and winter wheat yield in the Guanzhong area, an experimental split plot design was utilized. The main plot consisted of no straw returning (S0) and straw returning (S). The sub-regions consisted of no fertilizer (WF), nitrogen fertilizer (NF), and nitrogen and phosphate fertilizer (NPF). Ecological stoichiometry was used to study the relationship between soil carbon, nitrogen, phosphorus content, and yield under straw returning combined with nitrogen and phosphorus fertilizer conditions. The results showed that straw and fertilization interactions had significant effects on soil organic carbon, total nitrogen, and total phosphorus contents in the surface layer (0-20 cm) (P<0.05). Compared with that in the S0WF treatment, the SNPF treatment significantly increased soil organic carbon and total nitrogen contents in the surface layer (0-20 cm) (P<0.05). The interaction between straw and year had significant effects on soil total nitrogen content in the surface layer (0-20 cm) (P<0.05). With the increase in straw returning time, the total nitrogen content of soil 0-20 cm under the SWF treatment was significantly higher than that under the S0WF treatment (P<0.05). Straw and fertilization and their interaction had no significant effects on organic carbon and total nitrogen contents in the 20-40 cm soil layer (P>0.05). Straw and straw interaction with fertilization significantly affected total P content in 20-40 cm soil (P<0.05). Compared with that in the SWF treatment, the SNPF treatment significantly increased the total phosphorus content in the 20-40 cm soil layer (P<0.05). Straw returning combined with chemical fertilizer also had a significant effect on soil stoichiometry. Compared with that in the S0WF treatment, the S0NPF treatment decreased soil C:N in the surface layer (0-20 cm) and increased soil C:P and N:P in the surface layer (0-20 cm). Compared with that in the SWF treatment, the SNF treatment reduced soil C:N in the surface layer (0-20 cm). Straw returning combined with chemical fertilizer also had a significant effect on winter wheat yield. In 2020 and 2021, the SNPF treatment increased production by 24.23% and 28.9%, respectively, compared with that of the S0WF treatment. Correlation analysis showed that yield was significantly positively correlated with C:N (P<0.05) and C:P (P<0.01). At the same time, total nitrogen and N:P were positively correlated with treatment years (P<0.001). In conclusion, straw returning and that combined with nitrogen and phosphate fertilizer (SNPF) can improve soil nutrient characteristics, change soil stoichiometric characteristics, and increase yield in the Guanzhong area. Therefore, the results of this study indicate that straw returning combined with nitrogen and phosphate fertilizer (SNPF) is an effective way to optimize regional farmland nutrient management and improve grain production capacity.

Soil microbial nitrogen-cycling gene abundances in response to crop diversification: A meta-analysis.

Single planting structure has a significant impact on the maintenance of nitrogen in managed ecosystems. Although the effect of crop diversity on soil nitrogen-cycling microbes is mainly related to the influence of environmental factors, there is a lack of quantitative research. This study aims to determine the effect of diversified cropping mode on the abundance of functional genes in the soil nitrogen cycle based on the quantitative integration of a meta-analysis database containing 189 observation data pairs. The results show that the soil nifH (nitrogenase coding gene), nirS and nirK (nitrite reductase coding gene), and narG (nitrate reductase coding gene) abundances are positively affected by the diversity of plant species, whereas the amoA (ammonia monooxygenase coding gene) and nosZ (nitrous oxide reductase coding gene) show no response. Diversification duration and ecosystem type are important factors that regulate soil nitrogen fixation and nitrification gene abundances. Denitrification genes are mainly affected by categorical variables such as the planting pattern, soil layer, application species, duration, and soil texture. Among them, the long-term continuous diversification is mainly manifested in the reduction of soil nifH and increase of nirK abundances. Soil organic carbon and nitrogen linearly affect the responses of nifH, amoA, nirS, and nirK. Therefore, to maintain the soil ecological function, diversity of planting patterns needs to be applied flexibly by regulating the abundance of nitrogen-cycling genes. Our study draws conclusions in order to provide theoretical references for the sustainability of nitrogen and improvement of management measures in the process of terrestrial managed ecosystem diversification.

Redeploy manure resources to enhance the agro-pastoral cycle.

Returning manure to the land is a critical link in the internal cycle of agricultural systems, but excess manure leads to water eutrophication. The traditional manure re-use method brings pathogenic microorganisms, heavy metals, antibiotic resistance genes (ARGs), insect eggs, and other contaminants into the soil, posing a great threat to the ecological environment and human health. Clarifying the spatial distribution patterns of manure nutrient supply and farmland nutrient demand can help guide a more efficient and harmless way to return manure to farmland. This work counted data on cultivation and breeding in 356 cities on the Chinese mainland from 2015 to 2019 and calculated the livestock breeding volume (LB), total environmental capacity (C), and remaining environmental capacity (RC) accordingly. The Spatial Autocorrelation Model (SAC) was used to analyze the distribution patterns of the three. Data results show that China currently has the potential to double LB, but most cities in the west have excess manure due to the mismatched distribution of LB and C. The hot spot analysis results demonstrate the priority/general areas of manure management and the export/import areas of manure resources. The results of the outlier analysis show that some cities located at the boundary of RC Cold/Hot spot areas (e.g., Chengdu City) can perform resource replacement nearby to relieve local environmental pressure. This study analyzes the potential and realistic resistance to utilizing manure as an organic nutrient resource and provides a reference for developing manure management links.

Oxygen-containing groups in cellulose and lignin biochar: their roles in U(VI) adsorption.

The adsorption behaviors of cellulose and lignin biochar depend on the evolution of their oxygen-containing groups to some extent. In this study, cellulose-rich pakchoi and lignin-rich corncob were selected to prepare the pyrolytic biochar at variable temperatures, named PBC and CBC, respectively. Their structure-function relationships were in-depth studied via the combination of the adsorption experiments of U(VI) and comprehensive spectral analyses. The maximal adsorption capacity of PBC 300, obtained at 300 °C, was measured as 46.62 mg g-1 for U(VI), which was ⁓1.3 times higher than 35.60 mg g-1 of CBC 300. U(VI) adsorption on PBC and CBC were predominantly ascribed to the coordination interaction between oxygen-containing groups and U(VI). Interestingly, the main complexation groups were distinct in both biochars due to the different inherent evolutions of cellulose and lignin. Volatile d-glucose chains in cellulose were apt to degrade rapidly, and the formed carboxyls acted as the most important sites in PBC. However, the stable aromatic network in lignin led to a slow degradation, and more hydroxyls thus remained in CBC, which controlled U(VI) adsorption. In this study, we obtained greatly cost-effective adsorbents of U(VI) and provided some essential insights into understanding the structural evolution-function relationship of cellulose and lignin biochar.

[Changes in Soil Microbial Carbon-Degrading Enzymes and Their Relationships with Carbon Pool Components During the Restoration Process of Robinia pseudoacacia].

To reveal the change in the characteristics of soil microbial C-degrading enzyme activities and the response to the components of C during the restoration process of Robinia pseudoacacia forests in the Loess Plateau, the components of the soil C pool, C-degrading enzyme activities, and microbial metabolic entropy of R. pseudoacacia in different restoration stages were studied, and the response relationship between C-degrading enzymes and soil C components was explored. The results showed that the microbial respiration (MR) first increased and then decreased with the restored years. We found that the microbial metabolic entropy (qCO2) decreased significantly with the restored years, but the microbial entropy (qMB) increased. Soil C-degrading enzymes increased significantly in the early-stage restoration of R. pseudoacacia; however, oxidizing enzymes (PO and PER) and cellobiohydrolase (CBH) decreased in the late stage of restoration. The soil organic C and recalcitrant organic C increased significantly with the restored years; however, there was no significant difference for the labile organic C. Correlation analysis and the partial least squares-path model (PLS-PM) showed that soil C-degrading enzymes and C components were significantly correlated with microbial respiration and entropy (qCO2 and qMB), respectively. The hydrolytic enzyme (BG+CBH) was significantly positively correlated with SOC, microbial biomass C, qMB, and recalcitrant and labile organic C. The oxidizing enzyme (PO+PER) was significantly positively correlated with the soil clay and qCO2. In addition, the recalcitrant organic C was the key driver of soil microbial metabolism affected by vegetation restoration. Overall, the ecosystem of R. pseudoacacia plantations would gradually stabilize with the increase in restored years and significantly increase the sequestration effect of soil C. These results will be helpful to understand the transformation rule and regulation mechanism of the soil C pool in vulnerable habitats and provide scientific basis for the restoration and management of vegetation in the Loess Plateau.

[Effects of Straw Returning and Biochar Application on Summer Maize Yield and Soil N2O Emission in Guanzhong Plain].

Here, we investigated the effects of straw returning combined with biochar application on summer maize yield and soil nitrous oxide (N2O) emissions, based on a field location trial in the Guanzhong Plain from 2019 to 2020. The soil N2O emission rates were monitored using the static chamber-chromatography method. A comprehensive analysis of summer maize yields, soil N2O emissions, and soil labile nitrogen components was conducted to clarify the effects of straw returning combined with biochar application on improving soil fertility, increasing summer maize yield, and reducing greenhouse gas emissions. The three treatments were no straw returning (S0), straw returning (S), and straw returning combined with biochar application (SB). The results showed that the peak of N2O emissions from each treatment occurred 10 d after the straw return, and the rate of soil N2O emissions remained at a low level after 30 d of straw return. The rate of soil N2O emissions showed highly significant positive correlations (P<0.05) with ammonium nitrogen (NH4+-N), inorganic nitrogen (SIN), microbial nitrogen (MBN), and dissolved organic nitrogen (DON) contents. S significantly increased summer maize yield, cumulative N2O emissions, yield-scaled N2O intensity, and total nitrogen (TN) content by 7.4%-13%, 65.8%-132.2%, 54.6%-103%, and 27.8%-33%, respectively, compared to those in S0. Although the trend for SB to increase summer maize yield (2.5%-3.3%) compared to that in S was not significant (P>0.05), SB significantly reduced cumulative N2O emissions and yield-scaled N2O intensity by 24.0%-27.3% and 26.4%-29.2%, respectively, compared to that in S. SB significantly reduced the rate of soil N2O emissions by 45.1%-69.6% at the peak of N2O emissions compared to that in S. Biochar application mitigated soil N2O emissions induced by straw return and had a peak-shaving effect. SB significantly increased soil total N by 9.1%-12.2% compared to that in S. Combining summer maize yield, soil N2O emissions, and TN content, SB not only improved soil fertility and summer maize yield but also reduced yield-scaled N2O intensity, making it a suitable management practice that can be replicated to balance crop yield and environmental friendliness.

Global scaling the leaf nitrogen and phosphorus resorption of woody species: Revisiting some commonly held views.

Leaf nutrient resorption is one of the important mechanisms for nutrient conservation in plants. Element stoichiometry is crucial to characterizing nutrient limitations and terrestrial ecosystem function. Here, we use nitrogen (N) and phosphorus (P) resorption efficiencies (NRE and PRE) and their stoichiometry to evaluate the response patterns of leaf nutrient resorption efficiency (NuRE) to plant functional groups, species traits, climate, and soil nutrients on the global scale. In light of the findings from the global data set of published literature on N and P resorption by woody plants, we revisit the commonly held views that: The strong N fixation ability of N-fixers weakened the NRE, which was consistent with the general views. The NuRE was linearly negatively correlated with plant growth rate. The higher NuRE of evergreen species than deciduous plants revealed how leaf life span constrains nutrient conservation. From the perspective of NRE, PRE and their ratios, woody plants were limited by P in the tropical zone and the limiting nutrient gradually transformed into N in the temperate zone (23.43-66.57°). The NuRE of woody plants in the frigid zone was the largest than that of others implied that low temperature may limit the nutrient absorption by plant roots, thereby enhancing the retranslocation of nutrients by senesced leaves. Furthermore, Akaike weights analysis found that mean annual precipitation (MAP) and temperature (MAT), N-fixers, soil nutrients, and leaf life span have significant effects on nutrient resorption patterns, sequentially. Overall, these results showed that the plasticity of plant nutrient resorption patterns was strongly sensitive to plant functional groups and soil nutrients, but the regularity of NuRE on a global scale was controlled by temperature and precipitation. And the resorption stoichiometry pattern better interprets plant nutrient limitation and the synergy effect of N and P in plant and soil on multiple scales.

Dynamic interaction mechanism of environment, microorganisms, and functions in anaerobic digestion of food waste with magnetic powder supplement.

The reutilisation of food waste for the production of clean energy was promoted by supplementing magnet powder in anaerobic digestion (AD). This study found that adding 5% magnet powder optimally increased the amount of biogas produced by 61.9%, and the pH and volatile fatty acids (VFA) content had the greatest correlation with biogas production. A further metagenomics analysis in the early, middle, and late stages of the AD revealed that interaction between bacteria and archaea had highest explanation rate for pH and VFA changes rather than enzymes. Moreover, the 5% magnet powder increased the proportion of the CO2 methanogenesis and decreased the acetate methanogenesis on day 15 of peak biogas production. And it was an innovative discovery that conversion of tetrahydromethanopterin S-methyltransferase to methane increased, which is an important common node of methanogenesis metabolic and may be the fundamental reason for the increase in biogas production caused by magnetic powder.