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Phosphorus (P) is a non-renewable resource, therefore ensuring global food and environmental security depends upon sustainable P management. To achieve this goal, sustainable P management in the upstream and downstream sectors of agriculture from mineral extraction to food consumption must be addressed systematically. The innovation and feasibility of P sustainability are highlighted from the perspective of the whole P-based chain, including the mining and processing of P rock, production of P fertilizers, soil and rhizosphere processes involving P, absorption and utilization of P by plants, P in livestock production, as well as flow and management of P at the catchment scale. The paper also emphasizes the importance of recycling P and the current challenges of P recovery. Finally, sustainable solutions of holistic P management are proposed from the perspective of technology improvement with policy support.

The processes of urbanization and industrialization within geological phosphorus-rich mountains (GPMn) have resulted in water degradation within southwest China. Lake Dianchi, one of the most eutrophicated lakes in China, has epitomized this issue. Clear understandings of phosphorus (P) mitigation efforts, the evolution of P budgets, and possible risks in the Dianchi system will benefit future eutrophication control, providing valuable lessons for other plateau freshwater lakes. In this study, we applied systematic review methodology to investigate the above questions, and then compared the results with other lakes worldwide. Generally, meta-analytical approaches have indicated P levels remain a key factor in causing algal blooms. Post-2015, the P budget of the Dianchi system, especially in Caohai section, was modified. However, it's still experiencing high pressures from P enrichment (Caohai: 0.4 mg·l−1; Waihai: 0.2 mg·l−1). The flux of P in Dianchi remains high, both through the external P load (556 ton·a−1), and an internal cycle (304 ton·a−1 associated with the absorption, deposition and removal of algae biomass; and 380 ton·a−1 associated with sediment exchange). Meanwhile, significant P retention has been observed in the lake, in particular within the Waihai section (211 ton·a−1). Currently, water diversion (from external watersheds), sewage diversion, and sediment-dredging projects have benefited Dianchi. However, continuous urbanization and GPMn ecological degradation could introduce hundreds of tons of additional P, leading to subsequent algal blooms. Furthermore, beyond Lake Dianchi, other lakes and reservoirs in southwest China are facing similar issues regarding P mitigation, especially in GPMn regions, though corresponding knowledge is still limited. Therefore, effective and flexible sub-regional protection strategies and research related to external and internal P mitigations have become key requirements for Lake Dianchi management. Meanwhile, ecologically sensitive approaches to GPMn regions, as well as city development within basin and market driven treatments, should be incorporated into regional water source protection for southwest China.

With an increasing population and changing diet structure, summer maize is increasingly becoming an important energy crop in China. However, traditional farmer practices for maize production are inefficient and unsustainable. To ensure food security and sustainable development of summer maize production in China, an improved, more sustainable farmer management system is needed. Establishing this system requires a comprehensive understanding of the limitations of current farming practice and the ways it could be improved. In our study, 235 plots from three villages in the North China Plain (NCP) were monitored. Maize production on farms was evaluated; our results showed that the maize yield and nitrogen partial factor productivity (PFPN) were variable on smallholder farms at 6.6–13.7 t ha−1 and 15.4–88.7 kg kg−1, respectively. Traditional farming practices also have a large environmental impact (nitrogen surplus: −64.2–323.78 kg ha−1). Key yield components were identified by agronomic diagnosis. Grain yield depend heavily on grain numbers per hectare rather than on the 1000-grain weight. A set of improved management practices (IP) for maize production was designed by employing a boundary line (BL) approach and tested on farms. Results showed that the IP could increase yield by 18.4% and PFPN by 31.1%, compared with traditional farmer practices (FP), and reduce the nitrogen (N) surplus by 57.9 kg ha−1. However, in terms of IP effect, there was a large heterogeneity among different smallholder farmers' fields, meaning that, precise technologies were needed in different sites especially for N fertilizer management. Our results are valuable for policymakers and smallholder farmers for meeting the objectives of green development in agricultural production.

Sustainable feeding of the growing population in China without ecological destabilization is a grand challenge. In this populous country where agriculture is dominated by smallholder farming, developing innovative technology and translating scientific knowledge into action for smallholder farmers is a crucial step in addressing this challenge. Here, we present a novel approach for technology innovation and dissemination to achieve sustainable intensification in the fields of smallholder farmers. The Science and Technology Backyard (STB) is a hub in a rural area that links knowledge with practices to promote technology innovation and exchange. In this study, the framework and functions of STB are introduced, and the key implications for sustainable intensification across millions of smallholder farmers are explicitly stated: (i) develop innovative technology based on stated demands of farmers; (ii) disseminate technology by innovative social service models though combined top-down approaches with bottom-up measures to enable smallholders in rural areas. This paper provides a perspective on transformation of small-scale agriculture toward sustainable intensification in China and useful knowledge applicable to other developing countries.

Increasing plant density is an effective and important way to reduce maize yield gaps in Northeast China. However, the fact is that a significant plant density gap exists between optimum plant density and actual plant density in farmers' fields. To quantify the density gap between planned planting density and final harvest plant density (HPD), we studied 60 farmers' fields on three types of soil for three crop seasons from 2015 to 2017 by measuring their plant-plant distance, actual seedlings density (ASD), final HPD and yield. We also explored the potential causes of density loss by digging the places where the seedlings were missing for two consecutive years in 2016–2017. Results show that the three-year average HPD in farmers' fields was 59 699 plants ha−1, which was significantly lower than the planned density, including both the machine setting density (MSD; 67 962 plants ha−1) and theoretical plant density (TPD; 67 467 plants ha−1). No significant difference was found in HPD between years and soil types. However, for MSD and TPD, the average value in 2015 was significantly higher than that in 2016 and 2017. No significant difference between soil types was observed. Furthermore, the results from 2016 till 2017 indicated that a lack of seeds in the soil, a failure to germinate due to low-quality seeds, and a lack of seedlings breaking out of the soil due to environmental problems explained approximately 60.88, 10.33 and 28.80% of density loss, respectively. According to our survey, 63% of farmers did not know their own TPD and HPD, and 54% of farmers did not know the density loss. Therefore, we argue that farmers' limited knowledge of density and density loss is an urgent problem that needs to be solved in maize production. These observations will be useful for determining best management practices for maize production and for providing helpful suggestions for machine improvement.

Stringent emission controls during the Asia Pacific Economic Cooperation Summit (APEC; November 5–11, 2014) provide a valuable opportunity to examine the impact of such measures on the chemical properties of PM2.5 and other air pollutants. Here, we measured the water-soluble inorganic ions (WSII) and carbonaceous species in PM2.5, NH3 and NO2 at multiple sites in Beijing between September and November 2014. Relative to the pre-APEC period (September and October 2014), significant reductions in the average concentrations of WSII (69% for NO3−, 68% for SO42−, 78% for NH4+, and 29–71% for other species), elemental carbon (EC, 43%) and organic carbon (OC, 45%) in PM2.5 were found during the APEC period. The contributions of secondary inorganic ions (SIA, including SO42−, NO3−, and NH4+) to PM2.5 were significantly lower during the APEC period (9–44%), indicating a combination of lower gaseous precursor emissions and a relative weak secondary aerosol formation. Ion-balance calculations indicated that the PM2.5 sample in the pre-APEC period was alkaline but was acidic during the APEC period. Relatively lower mean concentrations of EC (1.5 μg m−3), OC (10.5 μg m−3), secondary organic carbon (SOC, 3.3 μg m−3), secondary organic aerosol (SOA, 5.9 μg m−3) and primary organic aerosol (POA, 10.0 μg m−3) appeared during the APEC period. The average concentrations of NH3 and NO2 at all road sites were significantly reduced by 48 and 60% during the APEC period, which is consistent with clear reductions in satellite NH3 columns over Beijing city in the same period. This finding suggests that reducing traffic emissions could be a feasible method to control urban NH3 pollution. During the APEC period, concentrations of PM2.5, PM10, NO2, SO2 and CO from the Beijing city monitoring network showed significant reductions at urban (20–60%) and rural (18–57%) sites, whereas O3 concentrations increased significantly (by 93% and 53%, respectively). The control measures taken in the APEC period substantially decreased PM2.5 pollution but can increase ground O3, which also merits attention.

Macadamia (Macadamia spp.) has been widely planted in southern China and has been now developed into an important industry. China has the largest area of macadamia plantation in the world but provides only 3% production of the world. Current farming systems have a fertilizer surplus of about 73 g of nitrogen (N), 103 g of phosphorus (P), and 24 g of potassium (K) per macadamia plant per year in southern China. Optimizing fertilization recommended for macadamia improves production by about 5 kg per plant. Macadamia develops cluster roots (i.e., proteoid roots) in a P-starvation environment. Overuse of P fertilizers restrains the development of cluster roots as well as rhizosphere processes, thus decreasing the P-use efficiency. Excessive fertilization, especially P fertilization, is one of the major limiting factors in China macadamia production. This study is the first to analyze current management practices and then discuss approaches of improving nutrient management based on the specific root biology of macadamia. For a sustainable macadamia industry, it is imperative to develop appropriate nutrient management by integrating root-zone soil nutrient supply, fertilizer application, and rhizosphere processes.

Developing sustainable food systems is essential, especially for emerging economies, where food systems are changing rapidly and affect the environment and natural resources. We explored possible future pathways for a sustainable food system in China, using multiple environmental indicators linked to eight of the Sustainable Development Goals (SDGs). Forecasts for 2030 in a business as usual scenario (BAU) indicate increases in animal food consumption as well as increased shortages of the land available and the water needed to produce the required food in China. Associated greenhouse gas emissions and nitrogen and phosphorus losses could become 10-42% of global emissions in 2010. We developed three main pathways besides BAU [produce more and better food (PMB), consume and waste less food (CWL), and import more food (IMF)] and analyzed their impacts and contributions to achieving one or more of the eight SDGs. Under these scenarios, the demand for land and water and the emissions of GHG and nutrients may decrease by 7-55% compared to BAU, depending on the pathway followed. A combination of PMB and CWL was most effective, while IMF externalizes impacts to countries exporting to China. Modestly increasing feed or food imports in a selective manner could ease the pressure on natural resources. Our modeling framework allows us to analyze the effects of changes in food production-consumption systems in an integrated manner, and the results can be linked to the eight SDGs. Despite formidable technological, social, educational, and structural barriers that need to be overcome, our study indicates that the ambitious targets of China's new agricultural and environmental strategy appear to be achievable.

Increasing plant density is a key measure to close the maize (Zea mays L.) yield gap and ensure food security. However, there is a large plant density difference in the fields sown by agronomists and smallholders. The primary cause of this phenomenon is the lack of an effective methodology to systematically analyze the density loss. To identify the plant density loss processes from experimental plots to smallholder fields, a research methodology was developed in this study involving a farmer survey and measurements in a smallholder field. The results showed that the sowing density difference caused by farmer decision-making and plant density losses caused by mechanical and agronomic factors explained 15.5%, 5.5% and 6.8% of the plant density difference, respectively. Changing smallholder attitudes toward the value of increasing the plant density could help reduce this density loss and increase farm yields by 12.3%. Therefore, this methodology was effective for analyzing the plant density loss, and to clarify the primary causes of sowing density differences and plant density loss. Additionally, it was beneficial to identify the priorities and stakeholders who share responsibility for reducing the density loss. The methodology has wide applicability to address the sowing density differences and plant density loss in other areas to narrow crop yield gaps and ensure food security.

Pig production contributes considerably to land use and greenhouse gas (GHG) and reactive nitrogen (Nr) emissions. Land use strategies were widely proposed, but the spillover effects on biological flow are rarely explored. Here, we simultaneously assessed the carbon (C), nitrogen (N), and cropland footprints of China's pig production at the provincial scale in 2017. The environmental impacts of land use strategies were further evaluated. Results show that one kg live-weight pig production generated an average of 1.9 kg CO2-equiv and 59 g Nr emissions, occupying 3.5 m2 cropland, with large regional variations. A large reduction in GHG (58-64%) and Nr (12-14%) losses and occupied cropland (10-11%) could be achieved simultaneously if combined strategies of intensive crop production, improved feed-protein utilization efficiency, and feeding co-products were implemented. However, adopting a single strategy may have environmental side-effects. Reallocating cropland that pigs used for feed to plant food alternatives would enhance human-edible energy (3-20 times) and protein delivery (1-5 times) and reduce C and N footprints, except for rice and vegetables. Reallocating cropland to beef and milk production would decrease energy and protein supply. Therefore, a proper combination of land use strategies is essential to alleviate land use changes and nutrient emissions without sacrificing food supply.

A link between microbial life history strategies and soil organic carbon storage in agroecosystems is presumed, but largely unexplored at the gene level. We aimed to elucidate whether and how differential organic material amendments (manure versus peat-vermiculite) affect, relative to sole chemical fertilizer application, the link between microbial life history strategies and soil organic carbon storage in a wheat-maize rotation field experiment. To achieve this goal, we combined bacterial 16S rRNA gene and fungal ITS amplicon sequencing, metagenomics and the assembly of genomes. Fertilizer treatments had a significantly greater effect on microbial community composition than aggregate size, with soil available phosphorus and potassium being the most important community-shaping factors. Limitation in labile carbon was linked to a K-selected oligotrophic life history strategy (Gemmatimonadetes, Acidobacteria) under sole chemical fertilizer application; defined by a significant enrichment of genes involved in resource acquisition, polymer hydrolysis, and competition. By contrast, excess of labile carbon promoted an r-selected copiotrophic life history strategy (Cytophagales, Bacillales, Mortierellomycota) under manure treatment; defined by a significant enrichment of genes involved in cellular growth. A distinct life history strategy was not observed under peat-vermiculite treatment, but rather a mix of both K-selected (Acidobacteria) and r-selected (Actinobacteria, Mortierellomycota) microorganisms. Compared to sole chemical fertilizer application, soil organic carbon storage efficiency was significantly increased by 26.5% and 50.0% under manure and peat-vermiculite treatments, respectively. Taken together, our results highlight the importance of organic material amendments, but in particular a one-time peat-vermiculite application, to promote soil organic carbon storage as a potential management strategy for sustainable agriculture.

The soil microbiome, existing as interconnected communities closely associated with soil aggregates, is the key driver in nutrient cycling. However, the underlying genomic information encoding the machinery of the soil microbiome involved in nutrient cycling at the soil aggregate scale is barely known. Here comparative metagenomics and genome binning were applied to investigate microbial functional profiles at the soil aggregate scale under different organic material amendments in a long-term field experiment. Soil samples were sieved into large macroaggregates (2 mm), macroaggregates (0.25-2 mm) and microaggregates (0.25 mm). Microbial taxonomic and functional alpha diversity were significantly correlated to soil NO

Improved recycling of animal manure may contribute to reduce synthetic fertilizer use in cropland, thereby to mitigate environmental and human health threats. However, the potential impacts of such strategies are not well-quantified, and the socioeconomic-cultural barriers are not well-understood, which limit the effectiveness of policy measures, especially in rapidly developing countries. We used a combination of scenario analyses and a farm survey among 1500 farmers across China to explore the impacts of replacing fertilizer by manure and to assess the existence of possible technical, socioeconomic, cultural barriers. We estimated the use of nitrogen fertilizer may be reduced by 3 to 32%, via increased manure recycling from 30% in 2015 to 34 to 70% in 2050, depending on fertilization measures and cropping system. However, only 55% of the interviewed farmers actually used manures. Eight out of 38 factors were evaluated as key barriers to manure use, which involved in the perceived high economic costs of manure use, lack of suitable application technology, and unknown manure quality and availability. Cereal farmers perceived greater barriers than cash crop growers. Several key actions have to be prioritized to achieve the high reduction in fertilizer use. There is need for a transparent manure exchange market, with manure-use advisors, accurate information on the composition and price of manure products, middle man for transporting manure from specialized livestock farms and distant crop farms, and contractors with manure application machinery. This requires specific policy incentives and outreach and control strategies.

Crop and livestock production are essential to maintain food security. In China, crop and livestock production were integrated in the past. Today, small backyard systems are still integrated but the larger livestock farms are landless and largely geographically separated from crop production systems. As a result, there is less recycling of animal manures and there are lower nutrient use efficiencies in the Chinese food production systems. This, in turn, results in considerable losses of nutrients, causing water pollution and harmful algal blooms in Chinese lakes, rivers and seas. To turn the tide, there is a need for agricultural "green" development for food production through reintegrating crop and livestock production. An additional wish is to turn the Chinese water systems "blue" to secure clean water for current and future generations. In this paper, current knowledge is summarized to identify promising interventions for reintegrating crop and livestock production toward clean water. Technical, social, economic, policy and environmental interventions are addressed and examples are given. The paper highlights recommended next steps to achieve "green" agriculture and "blue" water in China.

Insight in the phosphorus (P) flows and P balances in the food chain is largely unknown at county scale in China, being the most appropriate spatial unit for nutrient management advice. Here, we examined changes in P flows in the food chain in a typical agricultural county (Quzhou) during 1980–2017, using substance flow analyses. Our results show that external P inputs to the county by feed import and fertilizer were 7 times greater in 2017 than in 1980, resulting in a 7-fold increase in P losses to the environment in the last 3 decades, with the biggest source being animal production. Phosphorus use efficiency decreased from 51% to 30% in crop production (PUEc) and from 32% to 11% in the whole food chain (PUEf), but increased from 4% to 7% in animal production (PUEa). A strong reduction in P inputs and thus increase in PUE can be achieved by balanced P fertilization, which is appropriate for Quzhou considering a current average adequate soil P status. Fertilizer P use can be reduced from 7276 tons yr−1 to 1765 tons yr−1 to equal P removal by crops. This change would increase P use efficiency for crops from 30% to 86% but it has a negligible effect on P losses to landfills and water bodies. Increasing the recycling of manure P from the current 43%–95% would reduce fertilizer P use by 17% and reduce P losses by 47%. A combination of reduced fertilizer P use and increased recycling of manure P would save fertilizer P by 93%, reduce P accumulation by 100% and P loss by 49%. The results indicate that increasing manure-recycling and decreasing fertilizer-application are key to achieving sustainable P use in the food chain, which can be achieved through coupling crop-livestock systems and crop-based nutrient management.

Earth's water resources are critical for supporting livelihoods and food security but are being increasingly overexploited to support global agriculture. Diversifying cropping systems could potentially resolve unsustainable water use but trade‐offs with other aspects of sustainability and food security have not yet been assessed. We performed a detailed analysis of 31 different field crop rotations conducted during 1990–2019 in the North China Plain, to assess the potential impact of crop diversification on actual evapotranspiration (ETa), changes in regional groundwater table, grain yield, economic output, and water use efficiency (WUE) and to identify configurations that can achieve co‐benefits across multiple dimensions. We found that a combination of lowering the cropping index (i.e., harvest frequency), incorporating fallow periods, and introducing higher‐value crops into the currently dominant winter wheat–summer maize double cropping system can reduce growing season ETa by as much as 31%, mitigate groundwater decline by 19% or more, and increased economic output and economic WUE by more than 11% and 3%, respectively. We also found that multiple diversified wheat‐maize–based rotations—all with rotation lengths greater than 2 years—achieve co‐benefits across all evaluated dimensions. This study provides new empirical evidence of the opportunities for diversified crop rotations to balance the multiple objectives of food production, sustainable groundwater use, and farmer profitability. Extending this solution to other water‐stressed agricultural regions could be an effective strategy in achieving more sustainable food production system globally.

Ensuring national food security amidst ongoing economic development whilst both protecting the environment and reducing the dependence on fossil fuels are significant challenges for Chinese sustainable development. The main objectives of this study were to reveal irrigated crop (wheat, maize, and sunflower) performance in terms of energy, economic, and environmental aspects in China&rsquo, s largest designed irrigation area, Hetao irrigation district (HID), and to evaluate agricultural suitability based on plant structure. An integrated indicator and comprehensively assessment method were used to evaluate the above objectives based on the results from in-person surveys. The results show that maize exhibits the best overall performance compared to two other major crops (wheat and sunflower), which supports the government policy of adjust and optimize the planting structure program (AOPST), an effective way to achieve the multiple-objectives for sustainable agricultural development. However, reducing fertilizer remains a more critical factor than AOPST. These study results provide useful guidance for policy-makers and relevant stake-holders both in a regional context for the HID and at the global agricultural governance and management level.

High yield and efficient use of nitrogen is one of the major target for maize breeding worldwide. Both yield potential and nitrogen use efficiency (NUE) of maize is lower in China compared to that in the US. In this study, we analyzed the change of the plant traits related to high yield and NUE of maize cultivars registered and planted in China and US during the past 40 decades. Compared to the cultivar released in the US, Chinese cultivar are less tolerant to high planting density, higher ratio of ear height to plant height, low grain filling rate, more stay-green and longer growth period. We suggest an ideal plant architecture of maize for high yield and NUE. To achieve high yield and high NUE under intensive production conditions (medium and high nitrogen input, high density planting), an ideotype plant architecture is proposed which includes compact plant architecture, low ratio of ear height to plant height (around 0.36–0.38, close to the golden rate.), medium ear, small tassel, medium root size, one-layer brace root, half stay-green, efficient N remobilization, fast grain filling rate etc. The parameters can be utilized to guide future breeding.

Harnessing soil microbiomes is a major demand for development of sustainable and productive agriculture. Here we aimed to assess the impact of two different types of organic material amendments in combination with chemical fertilizer on the plant-soil microbiota in maize farming and its link to soil fertility and crop productivity. Soils and roots were collected from a long-term wheat-maize rotation system involving three experimental treatments: chemical fertilizer (CF); chemical fertilizer plus seasonal application of manure (OM); and chemical fertilizer plus one-time application of peat and vermiculite (PV). Crop residues were returned in all three treatments each season. Bacterial 16S rRNA gene and fungal ITS sequencing were conducted to elucidate the treatment-specific response of the microbiota in bulk soil, rhizosphere soil, and root compartment. Relative to CF and OM treatments, PV amendment led to significant increases in soil organic carbon (SOC) content, aboveground plant biomass, and grain yield over the five-year field study. The PV-induced changes in microbial composition involved the greatest treatment-specific “effect size” on indicator ASVs (amplicon sequence variants) in bulk and rhizosphere soils. The number of interactions was more than doubled in the PV co-occurrence network relative to those in the CF and OM co-occurrence networks. Potential beneficial microbes, such as Glomeromycota (arbuscular mycorrhiza), Basidiomycota, and various members of the Actinobacteria and Burkholderiales, were most enriched in the root compartment of the PV treatment. Peat-vermiculite enhanced microbiota-driven soil fertility and crop productivity, thereby providing new insights into plant-soil-microbiota interactions that can be harnessed for smart farming.

Producing high economic benefits and high grain yields with limited environmental impacts is crucial for feeding the world's growing population. Yet it remains challenging to improve the performance of one objective without creating unintended consequences for other objectives. This is especially difficult for smallholders navigating a diverse array of environmental and personal demands. This study demonstrates how combining participatory research through the Science and Technology Backyards (STB) approach with Pareto‐based ranking modeling can increase smallholder production while also reducing environmental impact. Through an intensive farmer survey in a 1 × 1 km grid in Quzhou County, we demonstrate that farmers engaged in STBs performed better according to multiple objectives (i.e., optimizing overall grain yield, benefit‐cost ratio, and GHG emissions, without compromising any one of these objectives) than farmer's not engaged in STBs. Moreover, we used a Pareto optimization approach (OPT) to determine the optimal smallholder scenario. We found that under OPT, grain yield could reach 9.5 t/ha, with a benefit‐cost ratio of 2.1, a 100% N recovery efficiency, and 7,395 kg CO2eq ha−1 GHG emissions. With OPT as a final goal, our research team worked with STB farmers to improve economic and environmental outcomes without compromising yield. Our findings demonstrate that no significant difference was obtained between farmers engaged in STBs and these under OPT. Compared with non‐STB farmers, STB farmers’ grain yield improved by 18%, benefit‐cost ratio improved by 26% due to improved N recovery efficiency, and GHG emissions were reduced by 31%. These improvements demonstrate the power of scientist–farmer engagement for optimizing wheat production. Such engagement allows farmers to modify their agronomic practices to more closely match Pareto optimal conditions, thus improving environmental and economic benefits without compromising yield. Our results provide solid evidence of the potential for sustainable wheat production by combining modeling with participatory research., We found that smallholders engaged with scientists through STBs came closer to these Pareto optimal conditions on average than smallholders. These results show that multi‐objective optimization in wheat production can be achieved by modifying agronomic practices through engagement between scientists and farmers. These improvements demonstrate the power of scientist–farmer engagement for optimizing wheat production. Such engagement allows farmers to modify their agronomic practices to more closely match Pareto optimal conditions, thus improving environmental and economic benefits without compromising yield. Our results provide solid evidence of the potential for sustainable wheat production by combining modeling with participatory research.

Feeding the world's growing population, while producing economic benefits with limited environmental effects, is a major challenge faced by global food supply chains. This is especially apparent when the production stage is predominated by smallholders as they each face varying economic and environmental demands, making it difficult to mobilize them on the ground. This study investigated how the environmental and economic sustainability of wheat supply chains could be improved by analyzing the performance of all stakeholders, especially the smallholders. Results showed that 77% of GHG emissions came from wheat cultivation, and less than 8% of the total economic benefits were recouped during this stage. In contrast, smallholders in the Science and Technology Backyards, reduced their GHG emissions by 16.4% and improved their economic benefits by 1.3- fold. Furthermore, a 2.6-fold increase in profit (1808 USD) with GHG emission reduction was achieved simultaneously by integrating all individual stages as a whole. This study found that the sustainability of the wheat supply chain was mainly affected by wheat cultivation. It also demonstrated the potential efficacy of empowering smallholders and integration of all individual stages as a whole to improve the sustainability of food supply chains., Graphical abstract Image 1, Highlights • A complete supply chain analysis for steamed bread was undertaken. • Wheat planting is the major limiting stage for sustainability of wheat supply chain. • Approaches to improve food supply chain sustainability have been developed.

This special issue contains a collection of papers dealing with various aspects of Integrating livestock and crop production systems in different parts of the world. Drafts of some papers were presented and discussed at a 2-day international workshop in Quzhou, Hebei, China, during October 9-12, 2019. The workshop was combined with a 2-day field trip to visit dairy and poultry farms and rural villages in Hebei. The workshop was organized by the National Academy of Agriculture Green Development of China Agricultural University. There were 13 Chinese and 11 international scientists (from five continents) and 20 Chinese postdoctoral researchers and PhD students participating in the workshop.The objectives of the workshop were (1) to discuss experiences with integrated/integrating crop and livestock production systems across the world, (2) to discuss institutions, markets and technologies needed for integrating crop and livestock production, and (3) to discuss and identify knowledge gaps, and to explore opportunities for joint research.Integrating livestock and crop production systems is one of the four research themes of the National Academy of Agriculture Green Development of the China Agricultural University in Beijing. The overall objective of this research theme is “To lay the scientific foundation for integrating crop and livestock production systems in China, which are (a) productive and competitive, (b) ecologically sound and (c) accepted by the society[1].” The research theme reflects the need of developing more sustainable livestock production systems in China, where the changes in livestock production have been huge over recent decades[2,3]. Livestock production has strongly increased, and production systems have dramatically changed over the last 20 years (Fig. 1). The dependence on feed imports has greatly increased, while manure management practices pollute the environment, and biosecurity is often at stake. Integrating livestock and crop production systems is seen as a way to develop more sustainable livestock and crop production.This editorial briefly explains the broader background of the workshop, and summarizes the main experiences of participants with integrating crop and livestock production systems. In addition, it briefly summarizes the outcome of a survey of participant’s views on integrating crop and livestock production systems.

International audience; Inclusion of cover crops (CCs) in cropping systems can improve soil quality, reduce agricultural inputs, and improve environmental sustainability. While CCs have been widely promoted in China in recent years, a quantitative assessment of CC effect on crop yield across China is lacking. There is also no overarching analysis on factors explaining variation in yield effects. Here, we carried out a meta-analysis to evaluate the effects of CCs on subsequent primary crop yield in China, based on 53 published studies reporting 442 yield ratios with and without CCs. We found that CCs increased subsequent primary crop yields by 9.7 % on average when compared with fallow across China. The effects of CC varied with different factors related to climatic zone, field management and soil properties. CC type (legume or not), CC season (growing in winter or summer) and nitrogen input were factors substantially influencing primary crop yield. We identified high yield benefits in subtropical rice systems with winter CCs (12.9 +/- 3.9 %) but no significant yield benefits in temperate wheat systems with summer CCs (1.9 +/- 6.6 %). Within subtropical rice systems, both legume and non-legume CCs were tested widely, and the effects of legume CCs (14.6 +/- 4.0 %) on primary crop yield were greater than those of nonlegume CCs (7.9 +/- 3.7 %). The yield benefits of CCs decreased with increasing fertilizer inputs. These results may be used for developing policy recommendations to improve primary crop yield by integrating targeted CCs associated with nitrogen management into cropping systems in China.

Orchards account for about 5% of the agricultural land in the world, however the amount of nitrogen (N) fertilizer input in orchards is relatively large. Little is known about N input and its impact in orchards at the global scale. Therefore, in this study we systematically evaluated reactive nitrogen (Nr) loss in global orchards. A meta-analysis of 97 studies reported from 2000 to 2021 from different countries showed that the mean global N fertilizer input in orchards was 303 kg N ha

Atmospheric nitrogen (N) deposition is a vital component of the global N cycle. Excessive N deposition on the Earth’s surface has adverse impacts on ecosystems and humans. Quantification of atmospheric N deposition is indispensable for assessing and addressing N deposition-induced environmental issues. In the present review, we firstly summarized the current methods applied to quantify N deposition (wet, dry, and total N deposition), their advantages and major limitations. Secondly, we illustrated the long-term N deposition monitoring networks worldwide and the results attained via such long-term monitoring. Results show that China faces heavier N deposition than the United States, European countries, and other countries in East Asia. Next, we proposed a framework for estimating the atmospheric wet and dry N deposition using a combined method of surface monitoring, modeling, and satellite remote sensing. Finally, we put forth the critical research challenges and future directions of the atmospheric N deposition. Capsule: A review of quantification methods and the global data on nitrogen deposition and a systematic framework was proposed for quantifying nitrogen deposition.

Phosphorus (P) recovery from swine manure by hydrothermal processes has recently attracted considerable interest; however, research has been limited by knowledge gaps and challenges in understanding the mechanisms of soluble and insoluble P transformations and the evaluation of the effects of the reaction conditions. In this study, the transformation mechanisms were investigated and the soluble and insoluble phosphorus distributions in swine manure during the hydrothermal processes were modelled. By increasing the severity of the exogenous conditions, P transformed from insoluble to soluble, and then polymerized with the formation of orthophosphates; meanwhile, the formation of hydrochar was enhanced thereby facilitating further P reclamation. The effects of the endogenous conditions showed there may be a threshold of calcium content, which limited the combination of Ca and P. Calcium ions mainly reacted with P in the form of hydroxyapatite and octacalcium phosphate. The modelling and prediction results showed that a coalification model gives a good fit (RSP2 = 0.9205 and RIP2 = 0.8559) for changes in the concentrations of solid total P and liquid inorganic P. The prediction level of mean absolute error was good as well (MAESP = 0.74 mg g−1 and MAEIP = 0.62 mg g−1). These findings provide a range of scientific opportunities for achieving a comprehensive understanding of the basis of sustainable utilisation of P.

Transforming apple production to one with high yield and economic benefit but low environmental impact by improving P-use efficiency is an essential objective in China. However, the potential for multi-objective improvement for smallholders and the corresponding implications for horticultural practices are not fully appreciated. Survey data collected from 99 apple producers in Quzhou County of Bohai Bay Region were analyzed by the Pareto-based multi-objective optimization method to determine the potential of multi-objective improvement in apple production. With current practices, apple yield was 45 t ha&minus, 1, and the economic benefit was nearly 83,000 CNY ha&minus, 1 but with as much as 344 kg P ha&minus, 1 input mainly from chemical fertilizer and manure. P gray water footprint was up to 27,200 m3 ha&minus, 1 due to low P-use efficiency. However, Pareto-optimized production, yield, and economic benefit could be improved by 38% and 111%, respectively. With a concurrent improvement in P-use efficiency, P gray water footprint was reduced by 29%. Multi-objective optimization was achieved with integrated horticultural practices. The study indicated that multi-objective optimization could be achieved at a smallholder scale with realistic changes in integrated horticultural practices. These findings serve to improve the understanding of multi-objective optimization for smallholders, identify possible constraints, and contribute to the development of strategies for sustainable apple production.

Sugarcane is the second largest bioenergy crop in the world and it accounts for 80% of global sugar production. Grown mostly in wet and warm tropics with relatively high nitrogen (N) fertiliser input and crop residue retention, sugarcane production is a significant source of nitrous oxide (N2O) emission. Yet, a global evaluation of research on N2O emission from sugarcane crop is lacking. Here, we conducted a meta-analysis using data from 141 measurements compiled from 15 sugarcane field studies reported from different countries to i) quantify N2O emissions and emission factors (EFs) globally, and for tropics and sub-tropics, and ii) identify the key factors that promote N2O emission. Our analysis shows that the global mean total N2O emission from sugarcane production reached 2.26 (CI: 1.93–2.62) kg N2O-N ha−1 yr−1 with an estimated EF of 1.21% (CI: 0.971–1.46%). N2O emissions increased exponentially with increase in N fertiliser rate, questioning the adequacy of Intergovernmental Panel on Climate Change (IPCC) default EF value (1%) for sugarcane N2O emission estimation. Mean total N2O emissions and EFs in tropics and sub-tropics did not vary significantly. Supplementing synthetic N fertiliser (SN) with organic amendments (OA) significantly increased mean N2O emission (~1.4-fold) and EF (~2.5-fold) compared to SN. A remarkable reduction in N2O emission (38.6%) and EF (61.5%) was evident when enhanced efficiency fertilisers (EEF) replaced SN. In contrast, crop residue removal had little impact on N2O emission and EF, but both parameters showed an upward trend with irrigation and increased rainfall. Soil carbon content and pH were emerged as key regulators of sugarcane N2O emission and EF. It is concluded that global sugarcane N2O emission could be significant and that there is considerable prospect for mitigating the emission through innovative nutrient formulations and precision agriculture that help meet crop nutrient demand without compromising environmental imperatives.

The environmental sustainability of the largest citrus plantation globally is facing a great challenge in China. Further, there is a lack of quantitative, regional hotspot studies. In this study, the life cycle assessment (LCA) was used to quantify the environmental cost of citrus production based on 155 farmers’ surveys from typical citrus orchards in Danling County, southwest China, which produced 0.65% of the country’s total citrus production. The results showed that the average values of environmental risk indicated by global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP) were 11,665 kg CO2-eq ha−1, 184 kg SO2-eq ha−1, and 110 kg PO4-eq ha−1, respectively. The production and utilization of fertilizer ranked the first contribution to the environmental impacts among all the environmental impacts, which contributed 92.4−95.1%, 89.4−89.8%, and 97.8−97.9% to global warming potential, acidification potential, and eutrophication potential, respectively. Specific to the contribution of fertilizers to environmental costs, the production and utilization of nitrogen (N) fertilizer accounted for more than 95% of the total environmental costs. Thus, the spatial distribution of environmental costs in this county was well matched with that of N input. Compared with the average values of investigated 155 orchards, the high yield and high N use efficiency (HH) orchard group with younger and better educated owners achieved a higher citrus yield and N use efficiency with less fertilizer input and lower environmental costs. Five field experiments conducted by local government and Danling Science and Technology Backyard were used to further certify the reduction potential of environment costs. These field results showed that the local recommendation (LR) treatment increased citrus yield and N use efficiency by 1.9−49.5% and 38.0−116%, respectively, whereas decreased environmental costs by 21.2−35.2% when compared with the local farmer practice in the HH orchard group. These results demonstrated that an optimum nutrient management based on the local field recommendation in citrus-producing areas is crucial for achieving a win-win target of productivity and environmental sustainability in China and other, similar countries.

The role of cereal grain zinc (Zn) in human health has been intensively studied in dietary structure, but limited information is available on the transfer of Zn from soil to crop grain for wheat grown in the intensive production system, especially the effect from management practices such as applications of fertilizer Zn, nitrogen (N) and phosphorus (P). Using wheat as a model crop in the intensive agriculture system, we have found that more Zn supply is needed to achieve the high yield goal. The critical levels for soil DTPA-Zn and shoot Zn concentration at anthesis for maximum grain yield are identified as 1.98 and 29.4 mg kg− 1, which were greater than those of the previous reports. Increasing N supply improved wheat Zn uptake due to increased root length and surface area. In contrast, fertilizer P application significantly decreased wheat Zn uptake, which was mainly attributed to the reduction of root colonization by arbuscular mycorrhizal fungi. Applying strategies such as foliar and soil application of Zn fertilizers can enhance grain Zn bioavailability, depending on the application method and the amount of available soil Zn. For Zn biofortification, foliar application of Zn has great superiority due to its benefits on grain Zn, low cost, and high adaptation to environment and crop production systems. In conclusion, N and P fertilizations can be optimized to combine with Zn fertilizer application as a double-win strategy to simultaneously achieve high grain yield and grain Zn bioavailability for wheat grown in the intensive production system.

Intercropping exploits species complementarities to achieve sustainable intensification by increasing crop outputs per unit land with reduced anthropogenic inputs. Cereal/legume intercropping is a classical case. We carried out a global meta-analysis to assess land and fertilizer N use efficiency in intercropping of maize and soybean as compared to sole crops, based on 47 studies reported in English and 43 studies reported in Chinese. The data were extracted and analyzed with mixed effects models to assess land equivalent ratio (LER) of intercropping and factors affecting LER. The worldwide average LER of maize/soybean intercropping was 1.32 ± 0.02, indicating a substantial land sparing potential of intercropping over sole crops. This advantage increased as the temporal niche differentiation between the two species was increased by sowing or harvesting one crop earlier than the other as in relay intercropping, i.e. with only partial overlap of the growing periods of the two species The mean fertilizer N equivalent ratio (FNER) was 1.44 ± 0.03, indicating that intercrops received substantially less fertilizer N than sole crops for the same product output. These fertilizer savings are mainly due to the high relative maize yield and the lower N input in the intercrop compared to the input in sole maize. This meta-analysis thus shows that exploiting species complementarities by intercropping maize and soybean enables major increases in land productivity with less fertilizer N use. Both LER and FNER increased as the difference in growth duration increased for maize and soybean, but were not affected by fertilizer N rate. LER increased when soil organic matter increased but FNER did not change with soil organic matter.

Intercropping is known to increase the efficiency of land use, but no meta-analysis has so far been made on the yield gain of intercropping compared to sole cropping in terms of absolute yield per unit area. Yield gain could potentially be related to a relaxation of competition, due to complementarity or facilitation, and/or to the competitive dominance of the higher yielding species. The contributions of competitive relaxation and dominance were here estimated using the concepts of complementarity effect (CE) and selection effect (SE), respectively. We compiled a dataset on intercropping of grain-producing crops from China, a hotspot of strip intercropping in the world. We quantified the yield gain and its components and analysed the contribution to yield gain of species traits (C3, C4, legume, non-legume), complementarity in time and nutrient input. Total yield in intercrops exceeded the expected yield, estimated on the basis of sole crop yields, by 2.14 ± 0.16 Mg ha−1 (mean ± standard error). Ninety percent of this yield gain was due to a positive CE while the remaining 10 % was due to SE. The net yield gain increased with temporal niche differentiation (TND) which is the proportion of the total growing period of the crop mixture during which species grow alone. The mechanism underlying yield gain shifted from competitive dominance of the higher yielding species when there was more overlap in growth period between the two species, to competitive relaxation when there was less overlap, while competitive relaxation remained the major component of the yield gain. The yield gain was substantially greater in intercrops with maize than in intercrops without maize, but there was no difference in yield gain between systems with and without legumes. The yield gain increased with nitrogen (N) input in maize/C3-cereal intercrops but not in cereal/legume intercrops, illustrating the ability of legumes to compensate for low N input, and highlighting the need for N input for high productivity in intercropping systems without legumes. Yield gain did not respond to phosphorus (P) input. We conclude that competitive relaxation is the main contributing factor to yield gain in the investigated Chinese intercropping systems, which were mostly relay strip intercropping systems. The underlying drivers of yield gain were related to presence of maize and species complementarity in time, but we did not find strong evidence for the selection effect.

Following its 40-year reform and 'Open Door' policy, China has recently proposed a new approach to green development and rural revitalization—the idea of Agriculture Green Development (AGD), with the key feature of creating a green eco-environment. In this mini-review we introduce the definition, theory, framework and major components of a green eco-environment as a key part of the AGD. We define a green eco-environment as including four key elements or measures: (1) a green eco-environmental indicator system; (2) environmental monitoring and warning networks; (3) emission standards and environmental thresholds for key pollutants; (4) emission controls and pollution remediation technologies. We have used Quzhou County (a typical county in the center of the North China Plain) as an example to show how detailed air, water and soil monitoring networks, as well as improved farmer practices and pollution control measures (especially ammonia emission mitigation and PM2.5 pollution reduction), can begin to create a green eco-environment in China and that AGD is possible. We conclude by stressing the need to improve the framework and practice for a green eco-environment, especially the importance of linking proposals and practices for a green eco-environment with the United Nations high priority Sustainable Development Goals.

Intercropping, the simultaneous production of multiple crops on the same field, provides opportunities for the sustainable intensification of agriculture if it can provide a greater yield per unit land and fertilizer than sole crops. The worldwide absolute yield gain of intercropping as compared with sole crops has not been analysed. We therefore performed a global meta-analysis to quantify the effect of intercropping on the yield gain, exploring the effects of crop species combinations, temporal and spatial arrangements, and fertilizer input. We found that the absolute yield gains, compared with monocultures, were the greatest for mixtures of maize with short-grain cereals or legumes that had substantial temporal niche differentiation from maize, when grown with high nutrient inputs, and using multirow strips of each species. This approach, commonly practised in China, provided yield gains that were (in an absolute sense) about four times as large as those in another, low-input intercropping strategy, commonly practised outside China. The alternative intercropping strategy consisted of growing mixtures of short-stature crop species, often as full mixtures, with the same growing period and with low to moderate nutrient inputs. Both the low- and high-yield intercropping strategies saved 16-29% of the land and 19-36% of the fertilizer compared with monocultures grown under the same management as the intercrop. The two syndromes of production in intercropping uncovered by this meta-analysis show that intercropping offers opportunities for the sustainable intensification of both high- and low-input agriculture.

Atmospheric reactive nitrogen (N r ) has been a cause of serious environmental pollution in China. Historically, China used too little N r in its agriculture to feed its population. However, with the rapid increase in N fertilizer use for food production and fossil fuel consumption for energy supply over the last four decades, increasing gaseous N r species (e.g. NH 3 and NO x ) have been emitted to the atmosphere and then deposited as wet and dry deposition, with adverse impacts on air, water and soil quality as well as plant biodiversity and human health. This paper reviews the issues associated with this in a holistic way. The emissions, deposition, impacts, actions and regulations for the mitigation of atmospheric N r are discussed systematically. Both NH 3 and NO x make major contributions to environmental pollution but especially to the formation of secondary fine particulate matter (PM 2.5 ), which impacts human health and light scattering (haze). In addition, atmospheric deposition of NH 3 and NO x causes adverse impacts on terrestrial and aquatic ecosystems due to acidification and eutrophication. Regulations and practices introduced by China that meet the urgent need to reduce N r emissions are explained and resulting effects on emissions are discussed. Recommendations for improving future N management for achieving ‘win-win’ outcomes for Chinese agricultural production and food supply, and human and environmental health, are described. This article is part of a discussion meeting issue ‘Air quality, past present and future’.

Nitrogen (N) fertilizer-induced soil acidification in Chinese croplands is well-known, but insight in the impacts of different N fertilizer management approaches (fertilizer type and rate) on soil acidification rates is very limited. Here, we conducted a field experiment on a moderate acid soil to quantify soil acidification rates in response to N fertilization by different fertilizer types and N rates through monitoring the fate of elements (mainly nutrients) related to H+ production and consumption. Two N fertilizer types (urea and NH4Cl) and three N rates (control, optimized and conventional, 0/120/240 kg N ha−1 for wheat, 0/160/320 kg N ha−1 for maize) were included. Nitrogen addition led to an average H+ production of 4.0, 8.7, 11.4, 29.7 and 52.6 keq ha−1 yr−1, respectively, for the control, optimized urea, conventional urea, optimized NH4Cl and conventional NH4Cl plots. This was accompanied with a decline in soil base saturation of 1–10% and in soil pH of 0.1–0.7 units in the topsoil (0–20 cm). Removal of base cations by crop harvesting and N transformations contributed ~70% and ~20% to the H+ production in the urea treated plots, being ~20% and ~75% in the NH4Cl treated plots, respectively. The large NH4+ input via fertilization in the NH4Cl treated plots strongly enhanced the H+ production induced by N transformations. The low contribution of N transformations to the H+ production in the urea treated plots was due to the limited NO3− leaching, induced by the high N losses to air caused by denitrification. Increased N addition by urea, however, strongly increased H+ production by enhanced plant uptake of base cations, mainly due to a large potassium uptake in straw. Our results highlight the important role of optimizing fertilizer form and N rate as well as straw return to the field in alleviating soil acidification.

Recycling of livestock manure to agricultural land may reduce the use of synthetic fertilizer and thereby enhance the sustainability of food production. However, the effects of substitution of fertilizer by manure on crop yield, nitrogen use efficiency (NUE), and emissions of ammonia (NH3 ), nitrous oxide (N2 O) and methane (CH4 ) as function of soil and manure properties, experimental duration and application strategies have not been quantified systematically and convincingly yet. Here, we present a meta-analysis of these effects using results of 143 published studies in China. Results indicate that the partial substitution of synthetic fertilizers by manure significantly increased the yield by 6.6% and 3.3% for upland crop and paddy rice, respectively, but full substitution significantly decreased yields (by 9.6% and 4.1%). The response of crop yields to manure substitution varied with soil pH and experimental durations, with relatively large positive responses in acidic soils and long-term experiments. NUE increased significantly at a moderate ratio (

Organic fertilizer is an effective substitute for mineral fertilizer that improves crop yield and is environmentally friendly. However, the effects of substitution often vary due to complicated interactions among the organic fertilizer substitution rate (Rs), total nutrient supply, and type of cropping system used. We performed a meta-analysis of 133 maize studies, conducted worldwide, to assess maize yield and environmental performance with substitution of mineral fertilizer with organic fertilizer. At an equivalent nitrogen (N) rate, substituting mineral fertilizer with organic fertilizer increased maize yield by 4.22%, reduced NH3 volatilization by 64.8%, reduced N leaching and runoff by 26.9%, and increased CO2 emissions by 26.8%, however, it had no significant effect on N2O or CH4 emissions. Moreover, substitution with organic fertilizer increased the soil organic carbon sequestration rate by 925 kg C ha&minus, 1 yr&minus, 1 and decreased the global warming potential by 116 kg CO2 eq ha&minus, 1 compared with mineral fertilizer treatment. The net global warming potential after organic fertilizer substitution was &minus, 3507 kg CO2 eq ha&minus, 1, indicating a net carbon sink. Furthermore, the effect of organic fertilizer substitution varied with the fertilization rate, Rs, and treatment duration. Maize yield and nitrogen use efficiency tended to increase with increasing N application rate following substitution of mineral fertilizer with organic fertilizer. Full substitution reduced N losses more than partial substitution. Further analysis revealed that the yield-optimal Rs for organic N in maize production was 40&ndash, 60%. Moreover, maize yield and nitrogen use efficiency were further increased after long-term (&ge, 3 years) combined use of organic and mineral fertilizers. These findings suggest that rational use of organic and mineral fertilizers improves maize productivity, increases soil organic carbon sequestration, and reduces N and C losses.

Chinese agriculture needs to become less dependent on fertilizer inputs to enhance sustainability. Cereal/legume intercropping is a potential pathway to lower fertilizer inputs, but there is insufficient knowledge on the nitrogen (N) response in species mixtures. Here, we investigated N response in maize/peanut intercropping. Maize showed a stronger yield response to N input than peanut both in sole cropping and in intercropping, and so did sole crops relative to intercrops. Maize yield was the highest at the maximum level tested: 360 kg N/ha. Agronomic efficiency (AE) of sole maize was 7.8 kg/kg N input, averaged across five N levels (0, 90, 180, 270, and 360 kg/ha). Partial land equivalent ratios (pLERs) for maize decreased with N input, from 0.70 at zero to 0.64 at 360 kg/ha. Sole peanut showed an optimum yield response to N input, with the highest yield at 270 kg/ha and lower yield at 360 kg/ha. The average AE of sole peanut was 1.3 kg/kg. The pLER of peanut declined from 0.43 at zero to 0.32 at 360 kg/ha while the overall LER decreased from 1.13 to 0.96, indicating relative better performance of intercropping at low than at high N input. Apparent recovery (RE) for N was 27.2% for sole maize, 12.4% for sole peanut, and 7.2% for intercrops. Mean N uptake was 179 kg/ha in sole maize, 199 kg/ha in intercropping, and 264 kg/ha in sole peanut. Partial economic budgeting indicated that with the current low Chinese N fertilizer prices, gross margin is maximized with high N input in sole crops; however, for intercropping, the highest gross margin was attained at intermediate N inputs of 180 or 270 kg/ha. Fertilizer price incentives may facilitate a transition to intercropping at moderate N input in China.