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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. [ABSTRACT FROM AUTHOR]

Straw retention and wheat-soybean rotation play critical role in maintaining soil quality. However, the correlation between bacterial diversity and community structure, and soil nutrients is unknown, and a systematic understanding of their responses to straw retention is lacking. In the field experiment, the straw retention treatments included no straw (NS), half straw (HS), and total straw (TS) retention during long-term wheat-soybean rotation. The mean contents of soil total nitrogen (TN), nitrate-N (NO3−-N), and microbial biomass nitrogen (MBN) increased by 15.06%, 21.10%, and 38.23%, respectively, with straw retention relative to NS, while that of ammonium-N (NH4+-N) reduced by 3.68%. The concentration of carbon components increased as straw retention increased. The levels of soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), and soil organic carbon (SOC) increased by 4.34%, 7.63%, and 9.34%, respectively, with straw retention relative to NS. Soil bacterial alpha diversity was reduced with straw retention. Soil pH and nutrient content were identified as the main factors affecting the soil microbial diversity and structure at the phylum level. Accordingly, straw retention and soybean-wheat rotation enable sustainable agriculture in the dryland of northern China. [ABSTRACT FROM AUTHOR]

Straw retention is an effective method to conserve soil water content and improve soil carbon stocks. However, how soil carbon dynamics respond to different straw retention practices remains unclear. In this study, we investigated soil respiration and soil carbon sequestration at depths of 0–100 cm. We conducted a two-year field experiment with three crop rotation treatments and three straw retention treatments in northwest China. The straw retention treatments included no straw retention (NS), retention of half the straw (HS), and retention of the total amount of straw (TS). The crop rotations treatments included winter wheat plus summer soybean (WS), winter wheat plus summer maize (WM), and winter wheat plus summer fallow (WF). Mean soil respiration rates under WS, WM, and WF treatments were 5.14, 6.53, and 5.49 μmol·m-2·s-1; and 5.67, 5.47, and 6.03 μmol·m-2·s-1 under TS, HS, and NS treatments. The mean soil water content were 15.50%, 15.57%, and 15.74% under WS, WM, and WF rotations, and 15.81%, 15.41%, and 15.50% under TS, HS, and NS treatments. The soil organic carbon (SOC) concentration was higher with increased straw retention, and lower at deeper soil depths. Mean SOC concentrations under different rotations and straw treatments of TS, HS, and NS, respectively were as follows: WS: 6.91, 6.63, 6.39 g/kg; WM: 6.90, 6.72, 6.57 g/kg; and WF: 6.49, 6.52, 6.37 g/kg. Soil temperature was the main determinant of soil respiration rates. We conclude that WS rotation resulted in lower soil respiration, WM rotation resulted in a higher soil carbon sequestration potential, and WF rotation resulted in higher soil water content. However, continued, long-term monitoring is needed to confirm the effect of rotations and straw retention on soil respiration and carbon sequestration in dryland cropping systems in northern China. [ABSTRACT FROM AUTHOR]

Field experiments were conducted to study soil properties, soil enzymes activities, water use efficiency (WUE) and crop productivity after six years of soya bean straw mulching in the semi‐arid conditions of China. The experiment included four treatments: CK (Control), N (240 kg N ha‐1), H (soya bean straw mulching at half rate 700 kg ha‐1 with 240 kg N ha‐1) and F (soya bean straw mulching at full rate 1,400 kg ha‐1 with 240 kg N ha‐1). Soil organic carbon (SOC), soil labile organic carbon (LOC), soil available N (AN), available P (AP) and enzyme activities were analysed after wheat harvesting in 2016 and 2017. Results show that straw amounts had positive effects on the soil fertility indices being higher for treatment F. The SOC, LOC, AN, AP and enzyme activities (i.e. saccharase, urease and alkaline phosphatase) were in the order of F > H > N > CK. High wheat grain yield and WUE were observed for F treatment. A total of six years mulching along with 240 kg ha‐1 nitrogen fertilizer application is sufficient for wheat yield stability and improving soil properties except urease activities in the semi‐arid condition of China. However, the straw mulching amount should be further studied with minimum nitrogen fertilizer for an environment‐friendly and effective approach for improving the soil biological properties with adequate crop production on a sustainable basis in the semi‐arid region of China. [ABSTRACT FROM AUTHOR]

In the Loess Hilly Region of China, the widespread conversion of cropland to forestland and grassland has resulted in great increased in organic carbon (C), nitrogen (N) and phosphorus (P) stocks in the shallow soil layers. However, knowledge regarding changes in C, N, and P in deep soil is still limited. To elucidate the responses of deep soil C, N, and P stocks and stoichiometry in response to changes in land use, the soil from a 0–200 cm soil profile was collected from the following three typical land use patterns in the heartland of the region: forestland, grassland, and cropland. Compared with cropland, forestland and grassland had improved soil organic carbon (SOC) and total nitrogen (TN) contents and stocks at most soil depths but decreased total phosphorus (TP) contents and stocks. At soil depths of 0–200 cm in the forestland and grassland, the cumulative SOC stocks were improved by 34.97% and 7.61%, respectively, and the TN stocks were improved by 54.54% and 12.47%, respectively. The forestland had higher SOC, TN and TP contents and stocks compared to the grassland in almost all soil layers. The soil depths of 100–200 cm contained the highest percentages of SOC, TN and TP stocks (47.80%–49.93%, 46.08%–50.05% and 49.09%–52.98%, respectively). Additionally, the forestland and grassland showed enhanced soil C:P, N:P and C:N:P ratios, and the forestland had higher C:P, N:P and C:N:P ratios compared to the grassland. Furthermore, the SOC and TN stocks had significant impacts on the soil C:N, C:P and N:P ratios. It was concluded that afforestation was the best choice for soil nutrient restoration of degraded land, and deep soil provided an extremely important resource for evaluating soil C, N and P pools and cycling. [ABSTRACT FROM AUTHOR]

Energy crisis is receiving attention with regard to the global economy and environmental sustainable development. Developing new energy resources to optimize the energy supply structure has become an important measure to prevent energy shortage as well as achieving energy conservation and emission reduction in China. This study proposed the concept of energy agriculture and constructed an energy agricultural technical support system based on the analysis of energy supply and demand and China’s foreign dependence on energy resources, combined with the function of agriculture in the energy field. Manufacturing technology equipment and agricultural and forestry energy, including crop or forestry plants and animal feces, were used in the system. The current status and future potential of China’s marginal land resources, energy crop germplasm resources, and agricultural and forestry waste energy-oriented resources were analyzed. Developing the function of traditional agriculture in food production may promote China’s social, economic, and environmental sustainable development and achieve energy saving and emission reduction. [ABSTRACT FROM AUTHOR]

Abstract: It is not known if the species composition of herbaceous plant assemblies within tree-fall gaps is determined stochastically or whether it follows species-specific and environmentally-determined patterns. We applied three methods, fitting species abundance distribution models, comparing community similarities, and testing species–environmental variable association, to evaluate the relative importance of chance and deterministic rules in controlling herbaceous composition within canopy gaps in the Abies–Betula forests of Mt. Taibai, Central China. Herbaceous species abundance within canopy gaps was well fit by a neutral model, showing that relative abundance was qualitatively consistent with stochastic processes. Although species composition in gaps significantly differed from closed canopy sites (ANOSIM, R =0.509, p =0.001), there were no significant differences among gaps of different age groups (ANOSIM, R =0.035, p =0.191) or gaps of different size groups (ANOSIM, R =0.089, p =0.057). Similarly, gaps of similar age and size did not show significantly higher similarity (χ 2 =2.30, df =3, p =0.513) in species composition than gaps of distinct age or size. Moreover, there were only eight species, including two light-demanding species, confined to larger gaps among the 69 species, and only an additional seven species found more commonly in larger gaps, whereas most herbaceous species were gap size generalists. Canonical correspondence analysis and random permutation tests suggested that only 27% of species with abundance ⩾5 were associated with environmental variables in gaps. In summary, the species composition in gaps was not constrained significantly by gap traits; rather species were distributed stochastically, likely through by random dispersal and recruitment limitation of species from the surrounding available species pool. Measures that introduce gap disturbance, such as selective harvesting, are still recommended when the maintenance of total biodiversity in forests is a concern. [Copyright &y& Elsevier]

• A productive equipment for sorting famous tea raw materials was designed. • The sorting scheme consists of classification, control and process scheme. • Higher grades of fresh tea leaves have a longer horizontal throwing trajectory. • The sorting effect of high-grade raw material is better under the optimal parameters. • Improving the classification performance of the model using genetic algorithms. Famous tea is a pillar of China's tea industry and must be processed using fresh leaves of consistent tenderness and size. However, equipment with high accuracy and efficiency are unavailable for sorting fresh tea leaves (FTLs). Therefore, in this study, we designed a machine-vision platform for sorting FTLs. This platform subjects FTLs to a horizontal tossing motion and change trajectory by blowing air, thereby achieving the sorting of different types of FTLs. The overall sorting scheme consists of classification scheme, control scheme, and process scheme. We found that different types of FTLs have different flight trajectories when subjected to horizontal tossing. And have different optimal classification features and sorting parameters. When sorting high-grade FTLs (low-grade FTLs), the classification feature used is area and mean saturation (equivalent diameter, major-axis length and G variance), the designed platform achieved a recognition rate, purity, selection rate, and integrity rate of 100% (98.5%), 94.32% (87.47%), 91.67% (90.67%), and 100% (100%), respectively. Under optimal parameters, the production efficiency of the platform reached 25 kg/h. Overall, the results of this study indicate that the designed platform can meet the small-scale production requirements for famous tea. [ABSTRACT FROM AUTHOR]

Addition of organic material, such as crop straw mulch in most soils is considered a strategy for sustainable agricultural production. We conducted a two-year experiment in 2015 and 2016 to determine changes in soil biochemical properties and maize yield in response to treatment with wheat-straw mulch. The treatments consisted of the addition of different levels of wheat-straw mulch (S1: 0, S2: 2500, S3: 5000 kg ha −1 ). Soil samples from four depths (0.1, 0.2, 0.3, and 0.4 m) were collected and analyzed. Soil enzymes, such as invertase, phosphatase, urease, and catalase, were significantly higher in the S3 treatment than in the S1 treatment. Values were greater for the samples collected at 0.1 m soil depth than those collected from deeper soil layers. Regarding soil properties, soil organic carbon (SOC), available nitrogen (AN), available phosphorus (AP), total nitrogen (TN), total phosphorus (TP), and soil water content (SWC) were significantly higher in S3 at 0–0.1 m soil depth than in other treatments. Compared with the (S1), an average increase in SOC, AN, AP, TN, TP, and SWC in 0–0.4 m soil depth with full straw mulch (S3), were 32.4, 31.9, 32.0, 11.8, 16.7, and 18.5%, higher, respectively. On average, urease, phosphatase, invertase, and catalase increased by 15.1, 11.0, 88.4, and 24.0%, respectively in the S3 treatment compared with that in the S1 treatment at 0–0.1 m depth, and decreased with increasing soil depth. The S3 treatment had increased grain yield (7%), biomass yield (28%), and water use efficiency (8%), compared with the S1 treatment. Overall, our results suggested that the S3 straw mulch treatment (5000 kg ha −1 ) could be used to sustain maize productivity and promote a better relationship between soil enzymes and soil properties in the semi-arid conditions of the Guanzhong area. [ABSTRACT FROM AUTHOR]

Straw incorporation with half-plastic film mulch is a promising approach for enhancing soil quality in dryland farming. However, its effects on soil greenhouse gas (GHG) and NH 3 emissions remain poorly understood. This study aims to optimize the mulch practice to balance the plastic film input with comprehensive benefits and examine the temporal dynamics and influencing factors of soil GHG and NH 3 emissions. A 3-year field experiment was conducted in a wheat-maize cropping system in north-western China with a complete randomized design including three treatments replicated thrice: (a) no straw incorporation or half-plastic film mulch (CT), (b) straw incorporation without half-plastic film mulch (S), and (c) straw incorporation with half-plastic film mulch (SP). The study revealed that S treatment significantly enhanced crop yield and soil cumulative N 2 O, CO 2 , and NH 3 emissions during the maize season by 8.26%, 113.51%, 31.78%, and 64.92%, respectively, compared to CT treatment. SP treatment significantly decreased N 2 O and NH 3 emissions by 30.66% and 23.74%, respectively, and slightly stimulated CO 2 emissions by 8.73% relative to S treatment throughout the three maize seasons. The average maize yield gap between S and SP treatments ranged from 517 to 800 kg ha−1. N 2 O and NH 3 emissions were significantly associated with soil water content (SWC), soil N components, and enzyme activity (nitrate and nitrite reductase), whereas CO 2 emissions were significantly influenced by soil temperature. Compared with S treatment, half-plastic film mulch increased SWC (16.77%), reduced soil N content and inhibited activity of nitrate (12.15%) and nitrite reductase (8.40%), eventually mitigated straw incorporation-induced N 2 O and NH 3 emissions by 30.66% and 23.74%, respectively. Overall, we demonstrated that straw incorporation with half-plastic film mulch is an innovative practice for enhancing the sustainability of dryland farming by increasing maize yield and mitigating N 2 O and NH 3 emissions. [Display omitted] • Nitrogen cycle- related enzyme activities are key to regulating gas emissions. • S significantly increased N 2 O, CO 2 , and NH 3 emissions compared with CT. • SP significantly reduced N 2 O and NH 3 emissions and increased yield compared to S. • SP is an innovative practice for promoting the sustainability of dryland farming. [ABSTRACT FROM AUTHOR]

• Compared impacts of 5 tillage systems on Calcic Cambisol erosion in Loess Plateau. • Measured soil physicochemistry, microbial diversity, and soybean yield over 9 y. • Ascomycota and Basidiomycota abundances correlated with soybean yield. • Ascomyta and Gemmatimonadetes correlated with available K and N, respectively. • BP neural network showed that ridge-furrow plastic mulching optimal for this region. Soil erosion has caused substantial nutrient losses in the hilly-gully area of the Loess Plateau in China. Consequently, traditional tillage provides little ecological benefit there, and conservation tillage is required instead. To identify a suitable conservation tillage mode for this region, we set up no-tillage (NT), straw mulching (SM), plastic mulching (PM), and ridge-furrow plastic mulching (RPM) systems, used conventional tillage (CT) as a control, and monitored all systems for nine years. We measured and compared relative soil physicochemical properties, fungal and bacterial community diversity and composition, and microbial responses to the various environmental factors. Based on the measured soil quality indicators, we used a back propagation (BP) artificial neural network to perform a comprehensive evaluation of the various treatments to identify the conservation tillage mode that provided the greatest ecological benefits. Long-term RPM was the most highly efficacious at preventing water erosion. Relative to CT, conservation tillage methods significantly increased soil available N and available K levels and, by extension, the soybean grain yields. Neither fungal nor bacterial alpha diversity indices were significantly different among the tillage treatments, but the relative abundances of the dominant bacterial and fungal phyla significantly differed among treatments, and these relative abundances were significantly correlated with both yield, soil available K, and available N contents. Based on the results of our other analyses, bulk density, water and soil conservation capacity, available N, available K, and yield were selected as the appropriate BP neural network model inputs. We then used the output, the comprehensive evaluation value of each cultivation mode, to generate comprehensive simulations. The regression coefficient of the expected and the actual output value reached 0.99. The model disclosed that all types of conservation tillage (except NT) were superior to traditional tillage and that RPM conferred the greatest comprehensive benefits. Based on BP neural network analysis, we established that ridge-furrow plastic mulching is the optimal conservation measure for the study region. The present study serves as a reference and provides guidance for selecting the ideal methods of cultivation for hillsides in the Loess Plateau of China. Our results are relevant for the mitigation of soil erosion in other similar agricultural regions worldwide. [ABSTRACT FROM AUTHOR]

Soil microbial nutrients and resource availability improve with mulching in agroecosystems, resulting in changes of soil microbial nutrient utilization strategies. However, the responses of soil microorganisms to nutrient utilization processes to regulate community assembly and thus maintain resource availability have not been clarified. Here, we performed a long-term field experiment with mulching measures, including no-mulching (NM), straw mulching (SM), plastic mulching (PM), and ridge mulching (RM), conducted on the Loess Plateau of China, to explore the community assembly process in response to microbial nutrient utilization. Microbial nutrient utilization strategies were analysed by measuring soil nutrients, microbial biomass, and extracellular enzyme activities. The results showed that PM and RM acquired C and N nutrients by secreting C- and N-extracellular enzymes in response to C:N- and C:P imbalances in soil chemistry, thereby reducing the nutrient limitation on microbial metabolism and improving microbial C utilization efficiency (CUE). Soil extracellular enzymatic stoichiometry increased and N utilization efficiency (NUE) decreased under mulching and drove an increase in beta-diversity and dominant species abundance in fungal communities. Mulching measures promoted the modular distribution of sensitive microorganisms and aggregation of fungal networks under PM and RM by reducing the stoichiometric imbalance and extracellular enzymatic N:P. At the same time, the microbial community assembly gradually changed from a stochastic to a deterministic process in response to the alleviation of soil C:P imbalance and changes in microbial nutrient utilization, in which the fungal community was dominant. In conclusion, soil microorganisms adaptively responded to changes in soil microbial nutrient utilization through the enhancement of aggregation of fungal co-occurrence networks and deterministic assembly processes. This study provides a better understanding of the impact of mulching on microbial nutrient utilization strategies from a community assembly perspective. • Microbial community composition change under mulching in loess soil was examined. • Absent mulching, community assembly was dominated by stochasticity. • Under mulching, change from stochastic to deterministic assembly was promoted. • Nutrient imbalance drove adaptive regulation of phylogenetic turnover. • Under nutrient imbalance, fungal community assembly was driven by N limitation. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Integrated TPB and PMT to study farmers' environmental behavior. • Subjective norm had the greatest effect on farmers' environmental intention. • Attitude and subjective norm mediate the effects of threat appraisal on intention. • Pro-environmental behavior should be facilitated through comprehensive measures. [ABSTRACT FROM AUTHOR]

The goal of this study was to determine the dynamics of physicochemical properties and biological activities of soil, and their relationship following afforestation. Soil samples were collected at 0–10 cm from five Pinus tabulaeformis plantation forests restored for 15, 25, 30, 45, and 70 years, as well as a millet ( Setaria italica ) farmland in the Damaiji catchment area. These five afforested lands were converted from similar farmlands. The activities of catalase (CAT), saccharase (SAC), urease (URE) and alkaline phosphatase (ALP), microbial biomass, soil water content, pH, soil bulk density, soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen, nitrate nitrogen, total phosphorus (TP), and available phosphorus (AP) were measured. The results revealed that the contents of SOC, TN, AP, microbial biomass C, N, and P, CAT, SAC, URE, and ALP in the P . tabulaeformis forest soil were significantly higher than those in the farmland by 64.97%–262.02%, 75.44%–254.28%, 46.63%–114.21%, 125.95%–554.83%, 101.35%–464.21%, 15.80%–167.35%, 22.57%–49.95%, 96.78%–145.73%, 6.98%–56.08% and 89.15%–177.89%, respectively. The soil properties, microbial biomass, enzymatic activities, and C:P and N:P ratios in soil and microbial biomass improved with increasing plantation chronosequence. Variations in C:N:P stoichiometry and higher C:P and N:P ratios in the soil and microbial biomass revealed the P limitation. Simultaneously, N:P ratios included more serviceable information that reflected the relationship between soil and microbes. Soil enzymatic activities had a high correlation with soil nutrient cycling and could be indicators of soil fertility status, particularly for ALP. The significant correlation between SOC, TN, enzymatic activities, and microbial biomass revealed that the substrate availability of carbon and nitrogen could influence the activity of soil enzymes and microorganisms. This study demonstrated that soil enzymatic activities and microorganisms respond to the process of afforestation and hence have the potential to affect nutrient balance and quality of soil. [ABSTRACT FROM AUTHOR]

In order to provide a clear guidance for biogas development in rural China, the progress and current status of rural biogas, critical factors influencing biogas development in rural areas, and probable biogas transformations are discussed in this paper. Rural biogas in China experiences rapid development in the past fifteen years and subsidies and policies from Chinese government are two main driving forces for promoting this development. For the recent days, the growth rate of household biogas decreased and that of Medium-to-large biogas projects (MLBPs) obviously increased. Several surveys showed that the utilization rate of household biogas greatly decreased and more and more digesters were discontinued. The underlying reasons for these changes come from the development of large-scale livestock farms, agricultural modernization and urbanization, which deeply affect the agricultural and social environment in rural China. The development of these agricultural and social factors all create positive conditions for MLBPs, but they negatively affect household biogas projects in terms of biomass supply and their participation in modern agricultural processes. Ongoing transformations and developments in local agriculture and rural society significantly influence the patterns of biogas projects. For future biogas development, MLBPs should be encouraged and the reduction of household biogas projects should be allowed to continue. However, recommendations on probable biogas development transformations suggest that the decision for expanding or abandoning the household projects in certain regions should be consistent with the developments and trends of local agriculture and society. For MLBPs, suitable developing models and reasonable operating mechanisms should be fully considered for assuring their benefits and continuous operation. [ABSTRACT FROM AUTHOR]

Abstract: As a renewable energy source, biogas not only alleviates energy shortage in rural areas but also effectively reduces the environmental risk associated with agricultural waste management. This study presents a comprehensive overview of development of household bio-digesters and medium and large-scale biogas plants (MLBPs) in China, and discusses the advantages and disadvantages of both biogas systems in terms of environmental performance, role in agriculture, economic benefit, government support, energy efficiency, societal influence, and resident living mode. Both systems have their relative strengths and weaknesses. The operation and maintenance of household bio-digesters are easier, and their environmental and economic performances are superior compared to those of MLBPs. However, MLBPs have higher energy efficiency and better social effect. Thus, the choice of a biogas generation system depends on the local circumstances. Household bio-digesters are suitable for undeveloped regions where the rural residents live far apart from each other, whereas MLBPs are suitable for developed regions where people live close together. The government can play a positive role in preventing the negative impacts of rural social structural change, such as those of urban migration of adults, on household biogas development. Additionally, establishment of scientific and technological support and service systems is recommended for further development of biogas in rural China. [Copyright &y& Elsevier]

• N limitation for microbe increased with increasing elevation. • The rates of SOC decomposition and microbial respiration decreased with elevation. • Global warming relieve microbial N limitation and lead to increased soil carbon release. • DOC:TDN explained more variation for microbial N limitation and microbial processes. Soil microbes have a great influence on the feedbacks of carbon (C)-climate, and their metabolic activities are limited by resource availability. Altitudinal gradients strongly affect soil microbial communities, but the effects on microbial resource limitation and their regulation for C dynamics remain unclear. In this study, we designed an altitudinal gradient experiment that included six altitudinal sites from 1308 m to 2600 m in the Qinling Mountains, China. The enzymatic stoichiometry was determined and modeled to investigate microbial resource limitations and major microbial metabolism processes (e.g., organic C decomposition rate and microbial respiration rate) along the elevation gradient. Other environmental variables including mean annual temperature (MAT) and mean annual precipitation (MAP), the C: nitrogen (N): phosphorus (P) ratio in soil total nutrients, available nutrients, and microbial biomass were also measured. The results showed that soil microbes suffered from N limitation in our study and microbial N limitation significantly increased with increasing elevation. But the rates of both organic C decomposition and microbial respiration greatly decreased with increased elevation. These trends suggest that warming induced by elevation change might relieve N limitation for microbes and lead to increased soil C release. Redundancy analysis (RDA) showed that MAT and soil nutrient stoichiometry, particularly for the DOC: TDN ratio, explained more variations for changes in microbial N limitation and major microbial processes. Collectively, our study demonstrated that the higher microbial N limitation at high elevation may be beneficial to soil carbon accumulation by changing the C: N ratio, which provided insights into microbially mediated soil carbon release under global warming. [ABSTRACT FROM AUTHOR]

The positive impact of straw incorporation (S 1) on mitigating global warming potential due to increase soil organic carbon sequestration can be offset by the straw-induced greenhouse gas (GHG) emissions. Therefore, this study advocated an optimal straw-based system, i.e. straw incorporation plus half plastic film mulch (SP), to mitigate the straw-induced GHG emissions in northwest China. A two-year field experiment was conducted to investigate effects of no straw inputs (S 0), S 1 and SP on yields, GHG emissions and soil labile carbon (C) and nitrogen (N) pools, and identify the relationship between GHG emissions and soil labile C and N pools. Results showed that SP significantly enhanced maize yield by 14.5 and 7.0% in 2018 and 2019, respectively, as compared to S 0 , mainly due to the increased soil inorganic nitrogen (SIN) and dissolved organic nitrogen (DON) contents. In addition, SP considerably mitigated the straw-induced CO 2 emission by 77.8 and 67.1% in 2018 and 2019, respectively, mainly attributed to the reduced dissolved organic carbon (DOC)/DON, microbial biomass carbon (MBC)/SIN and DOC/SIN. Moreover, SP significantly lessened the straw-induced N 2 O emission by 43.6 and 59.5% in 2018 and 2019, respectively, due to significant decreased DOC content during seeding to jointing, the major N 2 O emission period. Our results indicated that SP, as a kind of straw-based system, enhanced the sustainability of summer maize ecosystem because of mitigating the straw-induced GHG emissions and simultaneously enhancing maize yield. • SP significantly enhanced maize yield due to increased soil inorganic nitrogen, and dissolved organic nitrogen contents. • SP mitigated soil CO 2 emissions attributed to the reduced soil DOC/DON, MBC/SIN and DOC/SIN. • SP mitigated soil N 2 O emissions because of the decreased soil DOC during seeding to jointing. [ABSTRACT FROM AUTHOR]

• Afforestation varied the soil physical-chemical properties and nosZ -type microbial community structure. • Shannon and Simpson indices were strongly correlated with soil physicochemical properties. • There are some differences of dominant species in different land use types. • AN was the key environment factor to influence the composion of microorganisms. Microbial denitrification is an important part of the soil nitrogen cycling process and is the main way that naturally-fixed nitrogen returns to the atmosphere. Research to date has mainly focused on the effects of temperature, pH and carbon sources on denitrification, with the effects of different vegetation types thought to be relatively small. This study investigated the soil denitrification process in the Loess hilly region of China. Four typical land-use types were selected: farmland (FL), abandoned land (AL), Caragana korshinskii (CK), and Robinia pseudoacacia (RP). The functional gene nosZ , which regulates nitrous oxide reductase (N 2 OR), was selected as the target primer. High-throughput sequencing was carried out and the composition of soil properties was determined. The physicochemical properties of soil, including nitrate nitrogen and organic carbon levels, were studied to explore soil microbial compositions and species diversities and their main influences. Compared with FL, the content of ammonium nitrogen (AN) in AL, CK, and RP soils was 28.5%, 29.7% and 28.8% higher, respectively, while nitrate nitrogen was 1.39-, 1.96-, and 1.55-fold higher, respectively. The Shannon index showed that the microbial diversity of the nosZ gene in RP was greater than that in FL. Nonmetric multidimensional scaling analysis showed that the FL distribution was much different from those of AL, CK, and RP; meanwhile, the AL, CK, and RP distributions tended to overlap, which indicates that there were only small differences in species compositions. Redundancy analysis showed that AN is a key environmental factor affecting the nosZ type microorganisms composition in different taxonomic levels, and the contribution rates can reach 74.3% (p = 0.006), 73.2% (p = 0.004), and 62.6% (p = 0.008), respectively (from phylum to order). This study revealed the α- and β -diversities of nosZ type microorganisms and the key environmental influences on the composition of microorganisms with the land-use change. It provides a reference for further study on the heterogeneity of nitrogen output processes in different land use types. [ABSTRACT FROM AUTHOR]

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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

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.

Nitrogen fertilization significantly increases greenhouse gases (GHGs) emission, when applied from inorganic or organic sources. Minimizing GHGs from agroecosystems without compromising crop yield for stabilization of green production systems remains a challenge. Being an integral component of wheat production technology, the nitrogen (N) application deems to be indispensable. Thus, to reduce the application of N fertilizer and keep in view the minimization of GHGs emission, without compromising soil fertility and wheat production, field experiments were performed with treatments included maize straw mulch (S1: 0, S2: 4500, S3: 9000 kg ha -1 ) and nitrogen fertilizer (N1: 0, N2: 192 and N3: 240 kg ha -1 ) during 2015-17. Results showed that the cumulative CO 2 and N 2 O emission from 9000 kg ha -1 of maize straw mulch with 192 kg N ha -1 (S3N2) significantly decreased by 0.67% and 33.7%, respectively, averaged over two years compared with that of 9000 kg ha -1 of maize straw mulch with 240 kg N ha -1 (S3N3). Likewise, the average soil moisture content significantly increased by 10% and 10.6% for S3N2 and S3N3 treatments at 0-10 cm soil depth, respectively, compared to S1N1. Similarly, the S3N2 and S3N3 treatments had lowered the soil temperature by 0.2 and 0.1 °C, respectively, over S1N1 in wheat grown fields. The grain yield of wheat was increased by 45% and 45% under S3N3 and S3N2 treatments than S1N1, respectively. The S3N2 treatment was more economical than S3N3 for wheat crop. Therefore, maize straw mulch (S3) combined with 20% less N fertilizer (N2) from commercial source were considered as a viable production technology to improve crop yield, and reduce soil CO 2 and N 2 O emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The evaluation of tea quality tended to be subjective and empirical by human panel tests currently. A convenient analytical approach without human involvement was developed for the quality assessment of tea with great significance. In this study, near-infrared hyperspectral imaging (HSI) combined with multiple decision tree methods was utilized as an objective analysis tool for delineating black tea quality and rank. Data fusion that integrated texture features based on gray-level co-occurrence matrix (GLCM) and short-wave near-infrared spectral features were as the target characteristic information for modeling. Three different types of supervised decision tree algorithms (fine tree, medium tree, and coarse tree) were proposed for the comparison of the modeling effect. The results indicated that the performance of models was enhanced by the multiple perception feature fusion. The fine tree model based on data fusion obtained the best predictive performance, and the correct classification rate (CCR) of evaluating black tea quality was 93.13% in the prediction process. This work demonstrated that HSI coupled with intelligence algorithms as a rapid and effective strategy could be successfully applied to accurately identify the rank quality of black tea., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The use of crop residues as mulching materials or organic fertilizer, instead of burning, can help improve the soil organic carbon (SOC) and crop grain yield. An experiment was conducted for three consecutive seasons from 2013 to 2016, to study the effect of no straw (S0), S1/2 (700 kg/ha soybean straw, and 3000 kg/ha wheat straw), and S1 (1400 kg ha -1 soybean straw, and 6000 kg/ha wheat straw) treatments in wheat-soybean multi-crop system. The randomized complete block design was used with three repeats. Compared with the S0 regime, a significant increase of 0.5%-8.7% and 1.4%-27.7% in soil CO 2 emission was observed in the S1 regime during all growth stages of summer soybean and winter wheat, respectively. Soil temperature of S1/2 and S1 was 0.1-1.1 °C and 0.3-1.4 °C higher than that of S0 during the seeding stage and greening stage for wheat, during 2013 to 2016. During wheat season, soil moisture was higher in the S1 than in the S0 treatment. Likewise, wheat, soybean crop resulted the same results. Soil CO 2 emissions increase with the increasing in soil temperature, and 73.4-73.9% of the variation could be explained by seasonal variation in soil temperature in wheat season. Similarly, 69.5-74.7% of the variation in soil CO 2 emissions is recorded by seasonal variation in soil temperature in summer soybean season. Meanwhile (S1) increased the SOC and grain yield of wheat and soybean when compared to S0. Straw input increasing soil CO 2 , grain yield and SOC content, considering the benefits of straw inputs to crops yield and SOC content, It is concluded that the addition of straw improve agriculture production. However, the types of straw inputs in order to promote the sequestration of soil organic carbon with the decrease in greenhouse gas emission is the future research direction for agriculture development in Guanzhong region of China., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This study applies the environmental Kuznets curve to test the relationship between the regional economic growth and the different types of agricultural nonpoint source pollution loads in the Ningxia Yellow River irrigation area by using the Johnes export coefficient method. Results show that the pollution load generated by crop cultivation and livestock-breeding industries in the Ningxia Yellow River irrigation area shows an inverted U-shaped feature; however, this feature is absent in living-sewage pollution load. Crop pollution has shown a decreasing trend since 1997 because of the increased per capita income of farmers. Livestock-breeding pollution load reached its turning point when the per capita income of farmers reached 8386.74 RMB. Therefore, an increase in the per capita income of farmers corresponds to an increase in the livestock-breeding pollution load in the Ningxia Yellow River irrigation area.