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Sustainable N management in agriculturally intensive regions is critically important with respect to crop productivity, private profitability, ecological protection, and human health. This study articulates the benefits of N fertilizer use to ecological (e.g., in terms of the gross revenue from yield minus the costs of N fertilizer, eutrophication, soil acidification, and global warming) and social (e.g., in terms of the benefits of ecological systems minus the costs to human health) systems based on 156 farm sites with five different N levels. Agronomically (AOR), privately (POR), ecologically (EOR) and socially (SOR) optimized N rates were derived with the minimum N rate achieving maximum benefits from N-derived yields, private profitability, ecological and social systems. Compared with the traditional AOR and POR, use of the EOR resulted in a decrease in the N rate by 24–37%, and reduced Nr losses by 31–51% without yield losses. The SOR further decreased the N rate by 36–47%, and lowered the Nr losses by 44–60%, while decreasing the grain yield by only 4.4–4.9%. Furthermore, in groups with both high soil productivity and better management, the yield was highest with the EOR and SOR (7.72–7.86 Mg ha −1 ), and the Nr losses intensity remains low relative to other three groups. Compared with farmers' practice ( n = 2938), utilizing the EOR and SOR can increase the grain yield by 10–12%, reducing Nr losses by 54–63%. N management using the EOR and SOR provides a win-win opportunity, and should be prioritized in agricultural research and practice.

Post-silking N accumulation positively correlates with maize (Zea mays L.) grain yield in production, but the effect of N management post-silking is unclear. This study was to evaluate maize yield and physiological changes in response to in-season nitrogen management (INM) with respect to post-silking N fertilization of maize. Optimal nitrogen rates (ONR) were determined for INM by subtracting soil nitrate-N content measured at the maize root layers from the target N value. Other treatments included a zero N (0N) post-silking control with the same N application pre-silking as ONR and excessive N treatment (Exc. N) with the same N application pre-silking as ONR plus an additional application of 50% of the target N value post-silking. The grain yield with ONR of the INM was 10.9 Mg ha–¹, 17% higher than the 9.3 Mg ha–¹ obtained with the 0N control post-silking. The Exc. N treatment post-silking did not increase maize yield, but resulted in a high residual soil Nₘᵢₙ after harvest. The high grain yield obtained with ONR showed markedly higher dry matter (DM) production and N accumulation post-silking, with higher net photosynthesis and green leaf area than obtained with the 0N control post-silking. Additional N application post-silking also improved root development, as evidenced by the 18, 20, and 9% increase in root dry matter, root length, and root surface area densities for ONR compared to the 0N control. Results suggested that INM can synchronize soil N supply and plant N uptake throughout the growing season, thereby increasing maize grain yield.

SUMMARYOptimal nitrogen (N) management for maize in the film-mulched production systems that are widely used in dryland agriculture is difficult because top-dressing N is impractical. The current research determined how matching N supply and demand was achieved before and after silking stages, when single applications of controlled release urea (CRU) were combined with conventional urea in film-mulched maize production. The CRU: urea mixture was applied in a 1 : 2 or 2 : 1 ratio and all three fertilizer regimes (urea alone and CRU: urea at 1 : 2 or 2 : 1) were applied at N rates of 180 and 240 kg/ha over 2 years. The 1 : 2 CRU: urea mixture, applied once at 180 kg N/ha, was found to synchronize N supply with demand, thereby reducing N losses. The highest grain yields (11·8–12·0 t/ha), N uptake (232–239 kg/ha), N recovery (65·8–67·7%) and high net economic return were achieved with this regime. These results indicate that a single application of a mixture of CRU and urea can synchronize N supply with demand and provide higher yields and profits than conventional N fertilization in film-mulched maize systems.

Drip irrigation under plastic mulch (DIPM) has been used to achieve high maize yields in China, but N use efficiency is often low and N losses are high. Here, we designed a DIPM system with optimal N management to close the maize yield gap with high NUE and low N loss and used it in Northeast China in 2014 and 2015. The amount and timing with optimal N rate (ONR) were designed to close the maize yield gap based on the N requirement. Grain yield using the ONR treatments averaged 13.8 Mg ha −1 during 2014 and 2015, which was 90% of the yield potential simulated by the Hybrid-Maize Model. When N treatment was less than the ONR (70% ONR), grain yield decreased from 13.8 to 11.6 Mg ha −1 . When additional N fertilizer (130% ONR) was applied, no gain in yield was achieved, but N losses increased significantly from 65 to 121 kg N ha −1 . Grain yield was significantly lower in the farmers’ typical N practice treatment than that in the ONR treatment. Although 30% more N was applied with farmers’ practice, the lowest N use efficiency and greatest N losses were observed. In conclusion, DIPM with optimal N management increased yield potential with high N use efficiency and low N losses in a water-limited region.

Tuberculosis caused by Mycobacterium tuberculosis continues to pose a serious global health threat. The attenuated Mycobacterium bovis bacillus Calmette–Guérin, as the only licensed vaccine, has limited protective efficacy against TB. The development of more effective antituberculosis vaccines is urgent and demands for further identification and understanding of M. tuberculosis Ags. MPT83 (Rv2873), a secreted mycobacterial lipoprotein, has been applied into subunit vaccine development and shown protective effects against M. tuberculosis infection in animals; however, the understanding of the underlying mechanism is limited. In present study, we systematically studied the effect of MPT83 on macrophage apoptosis by constructing Mycobacterium smegmatis strain overexpressing MPT83 (MS_MPT83) and purifying rMPT83 protein. We found that MPT83 induced apoptosis in both human and mouse macrophages. MPT83 induced cyclooxygenase-2 (COX-2) expression at both the transcriptional and protein levels in macrophages, whereas silencing or inhibiting COX-2 blocked rMPT83-induced apoptosis or the enhanced apoptotic response to MS_MPT83 in comparison with M. smegmatis transfected with pMV261 vector (MS_Vec), indicating that COX-2 is required for MPT83-induced apoptosis. Additionally, tlr2 deficiency led to significant reduction of COX-2 expression, accompanied by less apoptosis in macrophages stimulated with rMPT83 or infected with MS_MPT83. Moreover, the activation of p38 accounted for MPT83-induced COX-2 expression. Finally, lower bacteria burdens in the lungs and spleens and enhanced survival were observed in mice i.v. infected with MS_MPT83 compared with MS_Vec. Taken together, our results established a proapoptotic effect of MPT83 and identified the TLR2/p38/COX-2 axis in MPT83-induced macrophage apoptosis.

Better understanding of the factors that influence crop nitrogen (N) requirement plays an important role in improving regional N recommendations for rice (Oryza sativa L.) production. We collected data from 1 280 plot-level measurements in different reaches of the Yangtze River, China to determine which factors contributed to variability in N requirement in rice. Yield, variety, and cropping system were significantly related to N requirement. The N requirement remained consistent at about 18.6 kg N Mg−1 grain as grain yield increased from 7 to 9 Mg ha−1, then decreased to 18.1, 16.9, and 15.9 kg N Mg−1 grain as yield increased to 9–10, 10–11, and > 11 Mg ha−1, respectively. The decreased requirement for N with increasing yield was attributable to declining N concentrations in grain and straw and increased harvest index. Super rice variety had lower N requirement (17.7 kg N Mg−1 grain) than ordinary inbred and hybrid varieties (18.5 and 18.3 kg N Mg−1 grain, respectively), which was a result of lower grain and straw N concentrations of super rice. The N requirements were 19.2, 17.8, and 17.5 kg N Mg−1 grain for early, middle, and late rice cropping systems, respectively. In conclusion, the rice N requirement was affected by multiple factors, including yield, variety, and cropping system, all of which should be considered when planning for optimal N management.

Decreasing nutrient losses from excessive synthetic fertilizer inputs is the direct and valid way to address low nutrient use efficiency and the related environmental consequences. Here, we established a comprehensive database of nitrogen (N), phosphorus (P), and carbon (C) losses from rice paddy fields in China, which we used to evaluate fertilization-induced losses and the impact of environmental factors, and to mitigate losses by adopting alternative fertilization options and setting input thresholds. Our results showed that most N-loss pathways had exponential increases with additional N input. In average, 23.8% of the N applied was lost via NH3 (16.1%), N2O (0.3%), leaching (4.8%), and runoff (2.6%). Total P loss was approximately 2.7% of the input, composed of leaching (1.3%) and runoff (1.4%). C lost as CH4 accounted for 4.9% of the organic C input. A relative importance analysis indicated that climate or soil variation rather than fertilizer rate was the dominant factor driving N and P leaching, and CH4 emissions. Based on the sensitivity of multiple N-loss pathways to N fertilization, we propose upper thresholds for N inputs of 142–191 kg N ha−1 across four rice types, which would avoid dramatic increases in N losses. Compared to conventional chemical fertilization, alternative fertilization options had diverse performances: enhanced-efficiency N fertilizer reduced N loss rate by 7.8 percent points and the global warming potential (GWP, considering N2O and CH4 emissions) by 28.8%; combined manure and chemical N fertilizer reduced N loss rate by 9.0 percent points but increased the GWP by 56.9%; straw return had no effect on total N loss but almost doubled the GWP. Using nutrient sources most appropriate to site-specific conditions is demonstrated as a robust way to decrease nutrient losses. Setting nutrient input thresholds would also contribute to the mitigation of environmental pollution, especially in regions with poor fertilization recommendation systems.

Sustainably feeding the growing population amid a changing climate and dwindling resources is a grand challenge facing mankind. Decades-long advancement in crop breeding has progressively elevated yield potential, markedly enhancing global food production capacity. However, relevant impact on reactive N (Nr) emissions associated with crop variety improvement has not been explicitly described. Here, we report multitiered evidence that newer and select maize, wheat, and rice varieties developed in China have the capacity to substantially lower Nr losses while producing more grain. First, we pooled studies featuring side-by-side comparison of different varieties, totaling 269 paired observations, to demonstrate that collectively, relatively newer varieties of maize, wheat, and rice had less Nr emissions (9.6%-23.5%) while yielding more grains (7.3%-11.2%) compared to older varieties under wide-ranging conditions. Next, we built an extended database (142 field studies with 833 observations) and comprehensively evaluated the Nr-loss reduction potential of newer varieties (2000 and after) versus older ones (1985-1999). We found that newer varieties had Nr emission factors (N loss as a percentage of N applied after correcting for background emissions) 18.2%-75.7% less for N2 O, 18.3%-75.7% less for NO 3 - , and -8.5% to 22.8% less for NH3 , while producing more grains (16.0%-24.4%). Individual varieties differed markedly in yield-emission scores. A nationwide farmer survey (2.47 million responses) indicated tremendous opportunities for a new way of management intervention. Coupling variety selection with sound N and other agronomic management can help lower N footprint while producing more grain.

Agriculture affects climate change and contributes directly and indirectly to greenhouse gas (GHG) emissions. However, no reports have fully quantified the GHG emissions from different crop systems in China. In this study, the carbon emission and carbon sequestration inventories and the carbon footprint (CF) of 16 major crop systems in China from 2001 to 2018 were analyzed with a cradle-to-farm gate life cycle analysis approach for the first time. The results showed that the largest farm CF and product CF were vegetables (11.9 t CO2 eq ha−1) and tea (4.6 t CO2 eq t−1), respectively. From the perspective of crop emissions and processes, the main crop systems influencing the national total net carbon emissions (NTCE) from crop production are rice, maize, wheat, fruits and vegetables, accounting for 87.3–90.4%; the key emission processes for NTCE are fertilization and irrigation, accounting for 73.7–76.8%. The NTCE has increased by 410.4 Mt CO2 eq from 2001 to 2018, of which maize, fruits and vegetables were the main crops that explained 99.0%, while fertilization and irrigation were the key factors and explained 91.9% of these increases. Scenario analysis indicated that increasing the straw return rate and partially replacing chemical fertilizers with manure have a minimal impact on NTCE. In contrast, reducing the loss of reactive nitrogen is the most effective single strategy to alleviate agricultural GHG emissions in the future. Our results will provide a fresh perspective for the development of more effective GHG emission reduction strategies for agricultural green development.

Losses of nitrogen (N) fertilizers applied in the fields lead to adverse impacts on the environment quality, human and ecosystem health. Quantifying the integrated effects of N fertilizer on the environment, human health, and ecosystem economic benefits (EEB) is critical to developing sustainable N-management strategies. In this study, the life cycle assessment (LCA) and EEB evaluation of winter wheat under five N fertilizer levels for 12 years on the North China Plain (NCP) were performed. The LCA results demonstrated that, compared to the conventional N (Con. N) treatment, the optimal N treatment (Opt. N, 165 kg N ha−1 on average) based on in-season root-zone N management, substantially reduced greenhouse gas emissions, acidification, eutrophication, and energy consumption potentials per Mg of grain produced by reducing life-cycle pollutants emissions. Moreover, the increase in crop yield in the Opt. N indirectly reduced the life-cycle land use, water use, human toxicity, aquatic ecotoxicity, and terrestrial ecotoxicity potentials per Mg of grain produced compared to lower N application treatments. Consequently, Opt. N had the lowest aggregated environmental indicator (0.39 EcoX Mg−1). Also, Opt. N reduced the negative effects on human health by 28% and 31% compared to the without N treatment (CK) and Con. N treatments. In addition, the average N-derived EEB considering the cost from N fertilizer, ecosystem and human health effects was highest with Opt. N (1493 $ ha−1). This study demonstrates that long-term optimal N management in wheat production can increase ecosystem economic benefits while reducing harm to the ecosystem and human health, and the integrated assessment of this study could provide a more comprehensive view on sustainable N management strategy to the policy-makers and stake-holders.

Excessive phosphorus (P) fertilization in intensive agricultural areas in China has caused resource waste and serious environmental problems, resulting in a need to evaluate P use efficiency to develop reasonable, sustainable P use strategies. This study summarizes the yield response to P (YRP) and the agronomic efficiency of P (AEP) in maize (Zea mays L.) in the primary maize-producing regions of China. We collated data from 7025 field experiments performed between 2005 and 2010 in these regions to quantify the effects of different soil properties (soil type, pH, Olsen-P, organic matter, Ava-N, and Ava-K) and management practices (variety and planting system) on the YRP and AEP and to clarify their relative importance to the YRP and AEP. The average P fertilizer application rate, YRP and AEP of maize in China were 92.3 kg ha−1, 16.58 % and 12.69 kg kg−1, respectively. The YRP and AEP of maize in red soil were significantly lower than those in other soil types. In addition, the YRP and AEP of maize increased with increasing soil pH. At soil Olsen-P levels below 15 mg kg−1, the YRP and AEP decreased with increasing soil Olsen-P; however, the YRP and AEP remained relatively stable at higher soil Olsen-P levels. The YRP and AEP of ‘Haiyu 6’ and ‘Xianyu 335’ were higher than those of other maize varieties. Among the different planting systems, spring maize with irrigation achieved the highest YRP and AEP (23.52 % and 14.37 kg kg−1, respectively). In addition, random forest analysis indicated that the maize variety should be prioritized over soil fertility indicators and P application rates when integrated P management strategies are formulated for maize. It was suggested that YRP and AEP can be improved by altering such soil properties and management practices, furthermore, variety is the most important factor affecting YRP and AEP in maize production systems in China.

Efficient use of nitrogen (N) is important for crop production, environmental sustainability, and food security. To make improvements, the use of N needs to be carefully analyzed based on efficiency potentials, local production, and regional socio-economy. The utilization of N fertilizer in maize, wheat, and rice production was evaluated for countries with different socio-economic developments, and alternative improvement strategies were developed in relation to the United Nation's sustainable development goals for 2050. A meta-analysis of data from 2095 peer-reviewed papers published involving 52 countries showed that the efficiency of fertilizer N utilization, expressed as recovery efficiency of N (REN), was 36%, 38%, and 29% in the world for maize, wheat, and rice, respectively, compared to 76%, 67%, and 66% potentials. Observed REN differed substantially among countries with different socio-economic development stages, suggesting that different strategies are needed for improvements. Developed countries had REN approaching potentials, and technology innovation that can lead to higher production and environmental safety is the key for further improvements. Rapidly developing countries had large N surpluses, and REN and production can be increased through integrated managements. Slowly developing countries used little fertilizer and had low production, and need to focus on fundamental agriculture in inputs and managements to obtain production sustainability. This study provided an outlook for N fertilizer utilization and crop production by 2050 and approaches that can be taken to reach the goals. This analysis might be useful for countries with different socio-economic developments in developing strategies to achieve the United Nation's sustainable development objectives.

It is essential to identify the main components that limit crop yield to achieve high crop yields. We collected data from 156 experimental field plots over six crop seasons to determine the degree to which wheat yield is limited by spike number and to further understand the effects of different sowing dates, seeding rates, and nitrogen (N) management on population development and yield. High yields in plots (>8.5 t ha−1) were attributable to increased spike numbers associated with elevated pre-winter stem numbers and higher percentage of productive stems. An early sowing date with a seeding rate of 350 seeds m−2 significantly produced higher spike numbers than a late sowing date with a seeding rate of 540 seeds m−2. High basal N fertilizer rate and dressing N at the regreening stage, typical of farmers’ N practices, markedly decreased productive stem percentage compared to an optimal basal N rate and N dressing at the stem-elongation stage. A dressing N rate of 120 kg N ha−1 at stem-elongation stage increased spike number compared to applications of 0 or 60 kg N ha−1. Based on our results, we designed an integrated crop-N management (ICM-N) for generating high yields and high N use efficiency. The ICM-N strategy increased grain yield by 33% (p < 0.05) while using a 27% lower N fertilizer rate led to an 87% increase in N use efficiency over three crop seasons compared to a standard farmers’ management strategy.

Understanding grain yield response to potassium fertilizer supply and potassium uptake requirements is essential for devising optimized potassium fertilizer management policies in China. Currently, potassium fertilization is often ignored due to high natural levels of potassium in the soil. We conducted 836 on-farm experiments at 209 sites in China to quantify wheat ( Triticum aestivum L.) grain yield response to potassium application rates, and evaluate potassium uptake requirements with increasing grain yield. Across all 209 sites, wheat grain yield increased by 70% from 3.3 Mg ha −1 at a control level to 5.6 Mg ha −1 for recommended potassium treatments (RKR, 102 kg K 2 O ha −1 ). With 150% RKR treatments, no yield gains were achieved, while there was a notable decrease in potassium use efficiency. The potassium uptake requirements per Mg of grain (K req ) increased from 21.1 kg with RKR treatments to 21.9 kg with 150% RKR treatments, which indicated that a luxury potassium uptake occurred under excessive potassium application. Under RKR treatments, K req decreased from 23.8 kg with −1 to 20.2 kg with >7.5 Mg ha −1 , which was attributed to the increase of the harvest index (from 45.5% to 48.6%) and decline in grain potassium concentrations (from 4.7 g kg −1 to 4.0 g kg −1 ). When the grain yield was −1 , potassium accumulation during post-anthesis was lower than that at pre-anthesis, by −78.5 kg ha −1 and −30.8 kg ha −1 with −1 and 6–7.5 Mg ha −1 yield ranges, respectively, but higher than that at pre-anthesis when the grain yield was >7.5 Mg ha −1 and by 18.2 kg ha −1 . In summary, potassium fertilization can increase wheat grain yield in China and total potassium uptake requirements were shown to decrease with increasing grain yield. This suggests that potassium optimization must be taken into account in management decisions for high-yielding wheat production in China.

Achieving both high yield and high nitrogen use efficiency (NUE) simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. As the greatest consumers of N fertilizer in the world, Chinese farmers have overused N, and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship. To address this problem, this study evaluated the total and dynamic N requirement for different yield ranges of two major crops (maize and wheat), and suggested improvements to N management strategies. Whole-plant N aboveground uptake requirement per grain yield (Nreq) initially deceased with grain yield improvement and then stagnated, and yet most farmers still believed that more fertilizer and higher grain yield were synonymous. When maize yield increased from 12.0 Mg ha−1, Nreq decreased from 19.8 to 17.0 kg Mg−1 grain. For wheat, it decreased from 27.1 kg Mg−1 grain for grain yield 9.0 Mg ha−1. Meanwhile, the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield, which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages. We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.

Agriculture in China has been smallholder based. Tempted by a large food demand, smallholders have been using excessive fertilizer to obtain high yields. This type of production has impaired the country's food production and environmental sustainability. There are, however, some innovative smallholders who are more adaptive to new technologies, have become more successful in production and nutrient utilization. In this study, we analysed the outlook of transforming smallholder agriculture in China into sustainable food production. First, we collected a database from a survey of 6.6 million smallholders engaged in the production of a total of 54 crops, which were categorized into cereals, fruits, vegetables, and others. From the database we assessed the extent of nitrogen (N) overuse by counties. Then we identified the top 10% performers in crop yield and N efficiency as prime producers. These prime producers were 15.3–35.4% higher in crop yield but 16.0–21.0% lower in N fertilizer use than their cohorts, and consequently 17.2–37.6% higher in economic returns. Replicating the success of the prime producers in agriculture in China would enable the country to reduce N use by 32.9% and land use by 11% without changing production. In the meantime, nitrate leaching from cropland would be brought down below the threshold for water safety. Based on the data we developed a model for transforming smallholder agriculture to sustainable food production through co-operation with stakeholders. This model could be used as a reference for producers, investors, and policy makers.

Decision-making related to nitrogen (N) applications based solely on historic experience is still widespread in China, the country with the largest rice production and N fertilizer use. By connecting N application rates with target N uptake, indigenous N supply, and N loss estimates collected from 1078 on-farm experiments, we determined regional N application rates for five rice-based agroecosystems, including a quantification of the reduction potential of application rates when using low-loss N sources, such as organic N and slow-release N. Based on our results, the moderate regional N application rates were 165, 180, 160, 153, and 173 kg N ha−1 for single, middle-CE (Central and Eastern China), middle-SW (Southwestern China), early, and late rice, respectively; lower (99–148 kg N ha−1) and upper (195–217 kg N ha−1) limits of N application rates were developed for situations with sufficient and insufficient indigenous N supplies, respectively. The depletion of soil N mineralization was quantified as 46.8–67.3 kg ha−1, and straw return is determined to be a robust measure to maintain soil N balance. Substituting manure or slow-release N for conventional N fertilizer significantly decreased N losses via NH3 volatilization, leaching, runoff, and N2O emissions. Overall, we observed 7.2–11.3 percent point reductions of N loss rate for low-loss N sources when compared to conventional N applications. On average, total N application rates could be theoretically reduced by 27 kg N ha−1 by using a slow-release N fertilizer, or by 30 kg N ha−1 when using manure due to their effectiveness at decreasing system N losses. Greater productivity, sustainable soil fertility, and a lower risk of N pollution would result from the ideal N application rate coupled with appropriate management practices. Widespread adoption of using low-loss N sources could become a key solution for future reduction in environmental N pollution and agricultural N inputs.

Phosphorus (P) is an essential and limiting nutrient for agricultural systems, where the demand for agricultural products such as food, feed, and bio-fuel are the major drivers of the intensification of agricultural production systems. Globally, maize is one of three main cereal crops, a main feedstock for animal production and a substrate for the production of bio-ethanol. This study investigated P flows through the multiple utilization systems of maize (as represented by the subsystems of food, feed and energy production) at a crop level of 2016 as reference year and made future predictions of P flows for the year 2030 based on different scenarios for food-feed-energy systems in China. For 2016, the subsystem of animal production resulted in the highest waste of P due to inappropriate manure management, but the subsystem of value-added products (Bio-fuel production, distillers dried grains with solubles (DDGS), maize-oil) showed the lowest P use efficiency (39%). From the value-added subsystem, 17% of P from the process flow to the subsystem of animal production as DDGS, and 61% of P is wasted associated with wastewater and sludge. Future scenarios of structural adjustments in the maize consumption system predict that the supply of maize for animal feed will be threatened if the policy of the Biofuel National Promotion before 2020 is fully implemented in China, as current maize production will not meet the future demand of food, feed and energy simultaneously. The results emphasized the use of P waste resources and better sludge management from a systems perspective. This also implied the importance of exploring coordinated development and integrated strategies for sustainable P flow management in multiple utilization systems.

Understanding water productivity (WP) on a regional scale is useful for identifying and managing inefficiencies in irrigated crop production systems. However, relevant WP analyses are not available for maize production systems in China. A meta-analysis was conducted of maize WP in Northern China that included 2354 observations from 282 articles published between January 2000 and March 2018. Our goal was to quantify the current WP and its constraining factors, and estimate the boundary function for WP in the different maize agro-ecological zones of Northern China. The Northern China average WP across the large set of field experiments was 22.3 kg ha–1 mm–1, with Northeast China (NE, 25.8 kg ha–1 mm–1) > North China Plain (NCP, 22.3 kg ha–1 mm–1) ≈ Northwest China (NW, 21.6 kg ha–1 mm–1). The boundary function for WP had slopes of 42.5, 36.8 and 40.4 kg ha−1 mm−1 for NW, NCP and NE, respectively. The WP was significantly correlated with latitude, vapor pressure deficit, N application rate, seasonal average temperature, experimental regions and years. WP was increased by optimal irrigation, soil surface with plastic mulch, deep tillage, straw incorporation into the soil, ridge planting, and the application of super absorbent polymer. In this study, we provided both reference WP values, recommendations to achieve higher WP and identification of regions with opportunities for improvement.

To achieve food and water security, it is as important to close the water productivity (WP) gap (which was defined as the difference between the maximum attainable WP and the currently achieved WP at the field scale) as it is to close yield gaps. However, few studies have provided quantitative estimates of existing WP gaps and constraining factors for global maize production. Using a meta-analysis of 473 published studies covering 31 countries and 5,553 observations (932 site-years), we found the global average WP value for irrigated maize was 18.6 kg ha−1 mm−1. These WPs varied by factors such as seasonal precipitation, irrigation regimes, soil organic matter and soil pH. In current production systems, there exists a huge scope for improvement in maize WP, but the reported field experiments achieved only 20–46% of potential WP across all countries. Considering the future, raising WP to 85% of potential WP by 2050, a 100% increase in maize production could be achieved with 20% less planted area and 21% less water consumption than in 2005. Closing the WP gap may be critical to ensuring food security and achieving sustainable global agriculture.

The concept of high yield with a goal of minimum environmental cost has become widely accepted. However, the trade-offs and complex linkages among agronomic, economic, and environmental factors are not yet well understood. In this study, reactive nitrogen (Nr) losses were estimated using an empirical model, and an economic indicator and an evaluation model were used to account for the environmental costs of N fertilizer production and use. The minimum N rate to achieve the maximum yield benefit (agronomically optimal N rate), maximum economic benefit (economically optimal N rate: economic benefit was defined as yield benefit minus N fertilizer cost), and maximum net benefit (ecologically optimal N rate: net benefit was defined as yield benefit minus N fertilizer and environmental costs) were estimated based on 91 on-farm experiment sites with five N levels for summer maize production on the North China Plain. Across all experimental sites, the agronomically, economically, and ecologically optimal N rates (Nagr, Neco, and Necl, respectively) averaged 289, 237, and 171 kg N ha−1, respectively. Necl management increased net benefit by 53% with a 46% decrease in total environmental costs, and a 51% decrease in Nr loss intensity from N fertilizer use (47, 65, and 38% for N2O emission, N leaching, and NH3 volatilization, respectively) and maintained grain yield, compared with Nagr management. Compared with Neco management, Necl increased net benefit by 12%, with a 31% decrease in total environmental costs and a 33% decrease in Nr loss intensity from N fertilizer use, and maintained economic benefit and grain yield. No differences in Necl were observed between soil types or years, but significant variation among counties was revealed. Necl increased with the increase in N-derived yield with an R2 of 0.83. In conclusion, Necl was primarily affected by N-derived yield and could enhance profitability as well as reduce Nr losses associated with the maize grain yield.

Global estimates of soil nitrate leaching of applied nitrogen (N) in agricultural production systems are not imprecise; however, the results of some field experiments have suggested that nitrate leaching responds exponentially rather than linearly to increasing N inputs. In this study, we compiled field data on nitrate leaching for 324 site-year combinations extracted from 86 peer-reviewed articles to test the hypothesis that in response to N fertilizer addition, soil nitrate leaching emission factors (EF) do not remain constant, but rather increase rapidly with increasing rates of N application. The averaged overall results showed that the proportional change in the EF response to increasing N input (ΔEF, %) was 0.042. Because this value was positive and significantly different from zero, our results demonstrate that EF is not constant, but rather increases with N addition. We compared our ΔEF response pattern with other constant EF patterns, and found that the 30% EF estimate of the Intergovernmental Panel on Climate Change and the 19% EF used in another published model were too high. A global estimate of soil nitrate leaching in arable uplands calculated with our ΔEF pattern was substantially lower than other estimates calculated with other procedures. In conclusion, our ΔEF pattern provided a globally applicable procedure for more accurate estimation of leaching loss and potential environmental costs incurred by various N application gradients.

Mycobacterium tuberculosis (Mtb)-derived components are usually recognized by pattern recognition receptors to initiate a cascade of innate immune responses. One striking characteristic of Mtb is their utilization of different type VII secretion systems to secrete numerous proteins across their hydrophobic and highly impermeable cell walls, but whether and how these Mtb-secreted proteins are sensed by host immune system remains largely unknown. Here, we report that MPT53 (Rv2878c), a secreted disulfide-bond-forming-like protein of Mtb, directly interacts with TGF-β-activated kinase 1 (TAK1) and activates TAK1 in a TLR2- or MyD88-independent manner. MPT53 induces disulfide bond formation at C210 on TAK1 to facilitate its interaction with TRAFs and TAB1, thus activating TAK1 to induce the expression of pro-inflammatory cytokines. Furthermore, MPT53 and its disulfide oxidoreductase activity is required for Mtb to induce the host inflammatory responses via TAK1. Our findings provide an alternative pathway for host signalling proteins to sense Mtb infection and may favour the improvement of current vaccination strategies.

Increasing maize (Zea mays L.) yields depends on understanding the dynamics of biomass and N accumulation such that N demand and N supply can be synchronized and N management improved. Biomass and N accumulation data were collected at the six-leaf (V6) stage, the flowering (VT) stage, and harvest from nine field experiments at eight sites in four key summer maize domains on the North China Plain. The data were used to investigate how grain yield and the N uptake requirement per Mg grain yield (Nreq) were related to differences in N management. Grain yield averaged 9.0 Mg ha–¹ and ranged from 1.9 to 16.3 Mg ha–¹; the highest grain yield (9.6 Mg ha–¹) was achieved with optimal N rates (N = OPT). In N = OPT plots, increases in grain yield from 10 Mg ha–¹ were associated with substantial increases in biomass and N accumulation during grain filling. In N = OPT plots with >10 Mg ha–¹ yield, plants had a high stover N content and maintained a high green leaf area index and SPAD, which contributed to a high harvest index, high kernel number per plant, and high thousand kernel weight. Our results indicate that farmers on the North China Plain should apply less total N fertilizer and should apply a substantial proportion of the N fertilizer after stage V6.

Although the interaction between phosphorus (P) and zinc (Zn) in crop production has long been a focus of plant nutrition research, the effects of P on the Zn content of cereal crops remains unclear, especially in intensive agricultural systems with high rates of P application and low levels of available Zn. The current study of a high-yielding winter wheat system on the North China Plain compared the effects of P application (0, 25, 50, 100, 200, and 400 kg ha −1 ) on yield, biomass accumulation, Zn accumulation, Zn uptake during all crop stages, and Zn remobilization. In two growing seasons (2011–2012 and 2012–2013), the results indicated that P application significantly increased wheat grain yield and shoot biomass. Phosphorus application also significantly increased the P concentration and decreased the Zn concentration in shoots. Phosphorus application increased P accumulation (kg ha −1 ) throughout the growing season but the effect of P application on Zn accumulation (g ha −1 ) depended on crop stage. Zn accumulation increased with increasing P application rates at the jointing stage. Zn accumulation at the flowering and maturity stage increased with application of 25 and 50 kg P ha −1 but decreased with application of 100–400 kg P ha −1 in both cropping seasons. The Zn harvest index and the ratio of pre-anthesis to post-anthesis Zn accumulation were not greatly affected by P application rate. Zn remobilization into grain increased with application of 0–50 kg P ha −1 but then decreased with the further application of 50–400 kg P ha −1 in both cropping seasons. Overall, the effects of P application on Zn nutrition depended on P rate and crop stage. Lower P application rates ( −1 ) increased Zn accumulation especially after the flowering stage and increased Zn remobilization to grain. High rates of P (>50 kg ha −1 ), in contrast, significantly decreased Zn accumulation and remobilization in this high-yielding winter wheat system. The results indicate that optimal P management in intensive agricultural systems is needed to ensure both high wheat yields and high levels of Zn in grain required for human nutrition.

Substantial gaps have been reported between the average farmer’s maize yield and yield potential in China, especially the North China Plain (NCP). This maize yield gap as identified by previous studies indicates large opportunities for raising yield by improving agronomy. Agronomic factors are either transient or persistent. Transient factors, which explain yield differences depending on unpredictable weather conditions, can have significantly different optimums from one year to another. While those transient factors are difficult to improve without reliable forecasts, persistent factors influence yield more consistently and therefore represent the best near-term targets for shrinking yield gaps. In this study, multi-year satellite images are used to quantify field-scale maize yield variation in Quzhou County of NCP, and this variation is then analyzed to determine the role of soil type and persistent management factors in explaining yield gaps. Results indicate that (i) remote sensing can provide reasonably reliable estimates of maize yields in this region; (ii) soil type has a clear effect on maize yields, and one that interacts strongly with growing season rainfall amounts; and (iii) on average roughly 20% of yield differences that appear within any one year are related to factors that persist in other years. Overall, the study presents a generalizable methodology of assessing yield gap as well as the proportion arising from persistent factors using satellite data. Our results suggest that the majority of yield gap is dominated by transient factors, and shrinking this gap may require high quality forecasts to make informed optimal management decisions.

Overestimation of the P requirement has been a driving force in the overuse of P fertilization in intensively managed agricultural systems and the resulting extensive environmental pollution. A database comprising 2157 measurements was developed from 2000 to 2013 using 45 on-farm and station trials to evaluate the relationship between aboveground P uptake and grain yield with different P fertilizer (Pf) treatments and to quantify P requirements per megagram of grain at different grain yield levels. Winter wheat (Triticum aestivum L.) yield ranged from 0.9 to 11.7 Mg ha–¹. The P requirement per megagram of grain yield (Pᵣₑq) increased with Pf supply from 4.1 kg under the treatment without Pf to 4.8 kg under the Pf surplus treatment. These results imply that excessive P application generally does not lead to greater P use efficiency and poses a potential environmental threat. Under the optimal Pf (Pf = Opt) treatment, the average Pᵣₑq was 4.5 kg, and it declined from 4.7 kg in the yield range of 9 Mg ha–¹ due to the increasing harvest index (from 45.7 to 48.2%) and the diluting effect of declining grain P concentrations (from 3.8 to 3.2 g kg–¹). The largest variation in shoot biomass and P accumulation under Pf = Opt treatment occurred from the stem elongation to anthesis growth stages, suggesting that, in addition to Pf supply, crop management during the early growth season is also important for achieving higher yields.

Cellulosomes are multi-enzyme complexes assembled by cellulases and hemicellulases through dockerin-cohesin interactions, which are the most efficient system for the degradation of lignocellulosic resources in nature. Recent genomic analysis of a cellulosome-producing anaerobe Clostridium clariflavum DSM 19732 revealed that two expansin-like proteins, Clocl_1298 and Clocl_1862, contain a dockerin module, which suggests that they are components of the cellulosome. Bacterial expansin-like proteins do not have hydrolytic activities, but can facilitate the degradation of cellulosic biomass via synergistic effects with cellulases. In this study, the synergistic effect of the expansin-like proteins with both native and designer cellulosomes was investigated. The free expansin-like proteins, including expansin-like domains of Clocl_1298 and Clocl_1862, as well as a well-studied bacterial expansin-like protein BsEXLX1 from Bacillus subtilis, promoted the cellulose degradation by native cellulosomes, indicating the cellulosomal expansin-like proteins have the synergistic function. When they were integrated into a trivalent designer cellulosome, the synergistic effect was further amplified. The sequence and structure analyses indicated that these cellulosomal expansin-like proteins share the conserved functional mechanism with other bacterial expansin-like proteins. These results indicated that non-catalytic expansin-like proteins in the cellulosome can enhance the activity of the cellulosome in lignocellulose degradation. The involvement of functional expansin-like proteins in the cellulosome also implies new physiological functions of bacterial expansin-like proteins and cellulosomes.

SUMMARYUnderstanding the physiological mechanisms of biomass accumulation and partitioning in the grain, and the nitrogen (N) uptake associated with different plant densities and N management strategies, is essential for achieving both high yield and N use efficiency (NUE) in maize plants. A field experiment was conducted in 2013 and 2014, using five rates of N application and three plant densities (6·0, 7·5 and 9·0 plants/m2) in Quzhou County on the North China Plain (NCP). The objective was to evaluate whether higher plant density can produce more biomass allocated to the grain to achieve higher grain yield and to determine the optimal N management strategies for different plant densities. The highest grain yield and NUE were achieved in the 7·5 plants/m2 treatment; both the sub-optimal (6·0 plants/m2) and supra-optimal (9·0 plants/m2) plant densities resulted in diminished yield and NUE. Compared to 6·0 plants/m2, the 7·5 plants/m2 treatment displayed higher biomass accumulation during the grain-filling period and also exhibited more biomass allocated to kernels with similar total biomass accumulation compared with the 9·0 plants/m2 treatment, which contributed to its higher grain yield. The N uptake in the 7·5 plants/m2 treatment was similar to that in the 9·0 plants/m2 treatment up to pre-silking. However, the post-silking N uptake of the 7·5 plants/m2 treatment was 66·4 kg/ha, which was 29·1% higher than that of the 9·0 plants/m2 treatment. Furthermore, the highest maize grain yield was achieved in the 0·7 × optimal N rate (ONR × 0·7), ONR and ONR × 1·3 treatments for 6·0, 7·5 and 9·0 plants/m2, respectively, which suggests that different N management strategies are needed for different plant densities. In conclusion, selecting a planting density of 7·5 plants/m2 with an in-season root zone N management is a potentially effective strategy for achieving high grain yield and high NUE for maize production on the NCP.

By understanding the relation between maize ( Zea mays L.) grain yield and phosphorus (P) uptake requirements it is possible to reduce both cost and environmental impact of maize production. The goal of this study was to determine P uptake requirements and patterns of P accumulation, pre- and post-silking, at different maize grain yield levels. A database comprising measurements in 955 plots in 44 on-farm and research station experiments during the period 2000–2012 on the North China Plain was used for the analyses. The P requirement (P req. , the P content Mg −1 grain yield on the basis of 155 g kg −1 moisture content) increased significantly from 2.84 kg in the P Opt. treatment. In the Optimal P treatment, average P req. values were 3.41, 3.15, 3.09, and 2.94 kg for grain yields ranging from 12.0 Mg ha −1 , respectively. The decrease in P req. values with increasing grain yield was mainly attributable to the increase in the harvest index from 0.47 to 0.53 and the decrease in grain P concentrations from 2.73 to 2.42 g kg −1 . A larger proportion of the P was accumulated post-silking when grain yields were higher than 10 Mg ha −1 (48%) and 8–10 Mg ha −1 (44%) than when yields were less than 8 Mg ha −1 (35%). Using this knowledge of P uptake requirements should improve assessments of global P balance, and help optimize P management, especially in high-yielding maize system.

The large consumption of groundwater for irrigating winter wheat has resulted in a continuous decline in the groundwater table on the North China Plain in recent decades. Alternative cropping systems have been proposed to substitute for the conventional winter wheat–summer maize rotation system for the sustainable use of groundwater in the future. However, the impact of these cropping systems on net global warming potential (net GWP), and greenhouse gas emissions on the basis of per unit of yield (greenhouse gas intensity, GHGI) is poorly documented. Measurements of greenhouse gases were conducted over a four-year period to gain insight into net GWP and GHGI on a crop rotation scale based on an ongoing long-term field experiment on the North China Plain. The cropping systems investigated include one conventional winter wheat–summer maize system (Chem. W/M) as the control and four alternative cropping systems, namely an optimized winter wheat–summer maize system (Opt. W/M), two winter wheat–summer maize (or soybean)–spring maize system with three crops in two years (W/M–M, W/S–M), and a single spring maize per year (M). Compared with the Chem. W/M control, the grain yields in Opt. W/M increased significantly by 19% while the net GWP, GHGI and fertilizer N decreased by 29%, 40% and 40%, respectively, but still consumed as much groundwater (264 mm yr−1) as Chem. W/M. In the two-year rotation cycle fertilizer N, groundwater use, net GWP and GHGI in W/M–M, W/S–M and M declined by 56–70%, 43–63%, 50–58% and 30–50%, respectively, compared to Chem. W/M. Moreover, these cropping systems consumed only 108–159 mm yr−1 groundwater for irrigation, a value close to the theoretical value of 150 mm yr−1 to avoid a continuing decline in the groundwater table in this region. However, W/S–M treatment had grain yield reductions of −23% and M treatment had −30%, and only W/M–M maintained grain yields relative to Chem. W/M. We therefore recommend the W/M–M management package as a preferred option to maintain grain yields together with low GWP and GHGI while mitigating the decline in the groundwater table in areas with a high water deficit.

Global analysis of expression profiles using DNA microarrays was performed between a reference strain H37Rv and two clinical extensively drug-resistant isolates in response to three anti-tuberculosis drug exposures (isoniazid, capreomycin, and rifampicin). A deep analysis was then conducted using a combination of genome sequences of the resistant isolates, resistance information, and related public microarray data. Certain known resistance-associated gene sets were significantly overrepresented in upregulated genes in the resistant isolates relative to that observed in H37Rv, which suggested a link between resistance and expression levels of particular genes. In addition, isoniazid and capreomycin response genes, but not rifampicin, either obtained from published works or our data, were highly consistent with the differentially expressed genes of resistant isolates compared to those of H37Rv, indicating a strong association between drug resistance of the isolates and genes differentially regulated by isoniazid and capreomycin exposures. Based on these results, 92 genes of the studied isolates were identified as candidate resistance genes, 10 of which are known resistance-related genes. Regulatory network analysis of candidate resistance genes using published networks and literature mining showed that three two-component regulatory systems and regulator CRP play significant roles in the resistance of the isolates by mediating the production of essential envelope components. Finally, drug sensitivity testing indicated strong correlations between expression levels of these regulatory genes and sensitivity to multiple anti-tuberculosis drugs in Mycobacterium tuberculosis. These findings may provide novel insights into the mechanism underlying the emergence and development of drug resistance in resistant tuberculosis isolates and useful clues for further studies on this issue.

Although importance of high-yielding maize system for food security has been extensively studied and discussed worldwide, more must be done in the context of improving yield while simultaneously reducing agricultural environmental costs to achieve sustainable intensification (SI). Using China's maize production as an example, we discussed the system with equal emphasis on high yield and high nitrogen (N) use efficiency in regards to SI. Through yield potentials and gaps analysis with the help of crop modeling, the high-yielding maize system was designed and developed to make maximum use of solar energy and growing season with favorable temperatures via genetics × environment × management (G × E × M) interactions. In this high-yielding system compared with the low-yielding traditional farmers system, total dry matter increased with stable harvest index, aboveground plant N uptake requirement per grain yield deceased largely, and the percentage of the dry matter and N accumulation during the middle-late growing season increased significantly. Accordingly, an in-season root-zone N management was developed for high-yielding maize system to match the total N requirement by crop in application amount, placement, and timing for nonlimiting N supply with minimum losses to the environment. The high-yielding system showed great potential for SI which reduced N2O and other greenhouse gas emission intensity by 10%–30%. Moreover, we suggest future research direction for high-yielding maize system to address multiply challenges in a changing world including climate change, resource depletion and shortage, and soil constrains and degradation to ensure food security.

Genetic code expansion is a key objective of synthetic biology and protein engineering. Most efforts in this direction are focused on reassigning termination or decoding quadruplet codons. While the redundancy of genetic code provides a large number of potentially reassignable codons, their utility is diminished by the inevitable interaction with cognate aminoacyl-tRNAs. To address this problem, we sought to establish an in vitro protein synthesis system with a simplified synthetic tRNA complement, thereby orthogonalizing some of the sense codons. This quantitative in vitro peptide synthesis assay allowed us to analyze the ability of synthetic tRNAs to decode all of 61 sense codons. We observed that, with the exception of isoacceptors for Asn, Glu, and Ile, the majority of 48 synthetic Escherichia coli tRNAs could support protein translation in the cell-free system. We purified to homogeneity functional Asn, Glu, and Ile tRNAs from the native E. coli tRNA mixture, and by combining them with synthetic tRNAs, we formulated a semisynthetic tRNA complement for all 20 amino acids. We further demonstrated that this tRNA complement could restore the protein translation activity of tRNA-depleted E. coli lysate to a level comparable to that of total native tRNA. To confirm that the developed system could efficiently synthesize long polypeptides, we expressed three different sequences coding for superfolder GFP. This novel semisynthetic translation system is a powerful tool for tRNA engineering and potentially enables the reassignment of at least 9 sense codons coding for Ser, Arg, Leu, Pro, Thr, and Gly.

Understanding the inherent characteristics of cultivars with different spike types based on biomass and biomass partitioning with optimal nitrogen (N) management is important to achieve both high wheat yield and N use efficiency (NUE). A field experiment was conducted over 3 years using five N rates and two winter wheat cultivars (a larger spike cultivar (TN) and a multiple spike cultivar (LX)) in the North China Plain (NCP) to evaluate whether larger spike cultivar can accumulate more post-anthesis biomass and achieve higher yields and to determine the optimal N management strategies for the two cultivars. In both cultivars over 3 years, the optimal N rate (ONR) based on in-season root zone N management (INM) reduced the N rate by 140 kg N ha−1 from 300 to 160 kg N ha−1 without any yield losses, while it increased the N uptake efficiency from 32% to 64% compared with typical farmer's N practice (FNP). Furthermore, under ONR treatment, the grain yield and N physiological efficiency of TN significantly was higher 6 and 10% over 3 years than that of the multiple spike cultivar LX, respectively. The yield increase of TN was attributed mainly to the increased harvest index (7%) and similar total biomass. The higher 11% leaf N concentration at anthesis and 10% grain number m−2 of TN significantly increased the post-anthesis biomass by 24% under ONR, which played an important role in increasing the harvest index (HI). In addition, the grain yield of 70% ONR significantly decreased by 12% and 8% for TN and LX over 3 years, respectively, while no significant increase in grain yield was observed for 130% ONR, suggesting that the ONR was optimal in practice. Changes in N management may not be required for the two cultivars, because the ONR according to INM is close to the economically optimal N rate (EONR) based on grain yield response curves. In conclusion, selecting a larger spike cultivar with optimal N management could be a useful strategy to achieve high yield and high NUE for wheat production in the NCP, especially using optimal crop management practices.

Increasing grain zinc (Zn) concentration of cereals for minimizing Zn malnutrition in two billion people represents an important global humanitarian challenge. Grain Zn in field-grown wheat at the global scale ranges from 20.4 to 30.5 mg kg−1, showing a solid gap to the biofortification target for human health (40 mg kg−1). Through a group of field experiments, we found that the low grain Zn was not closely linked to historical replacements of varieties during the Green Revolution, but greatly aggravated by phosphorus (P) overuse or insufficient nitrogen (N) application. We also conducted a total of 320-pair plots field experiments and found an average increase of 10.5 mg kg−1 by foliar Zn application. We conclude that an integrated strategy, including not only Zn-responsive genotypes, but of a similar importance, Zn application and field N and P management, are required to harvest more grain Zn and meanwhile ensure better yield in wheat-dominant areas.

Realizing sustainable development has become a global priority. This holds, in particular, for agriculture. Recently, the United Nations launched the Sustainable Development Goals (SDGs), and the Nineteenth National People’s Congress has delivered a national strategy for sustainable development in China—realizing green development. The overall objective of Agriculture Green Development (AGD) is to coordinate “green” with “development” to realize the transformation of current agriculture with high resource consumption and high environmental costs into a green agriculture and countryside with high productivity, high resource use efficiency and low environmental impact. This is a formidable task, requiring joint efforts of government, farmers, industry, educators and researchers. The innovative concept for AGD will focus on reconstructing the whole crop-animal production and food production-consumption system, with the emphasis on high thresholds for environmental standards and food quality as well as enhanced human well-being. This paper addresses the significance, challenges, framework, pathways and potential solutions for realizing AGD in China, and highlights the potential changes that will lead to a more sustainable agriculture in the future. Proposals include interdisciplinary innovations, whole food chain improvement and regional solutions. The implementation of AGD in China will provide important implications for the countries in developmental transition, and contribute to global sustainable development.

A thorough understanding of reactive N (Nr) losses from N fertilization applications and the factors that influence it is necessary to better evaluate various Nr losses mitigation scenarios and improve N management practices. The objectives of this study were to develop empirical models to calculate Nr losses using meta-analysis and to evaluate trade-offs among grain yield, N recovery efficiency (REN), and Nr loss intensity for in-season N management for intensive summer maize (Zea mays L.) production in China. A meta-analysis with 55 studies and 170 observations suggested that both N2O emissions and N leaching increased exponentially with the N application rate or N surplus, while NH3 volatilization increased linearly with the N application rate. According to regression curves, models based on the N rate (N-R) and N surplus (N-S) were used to estimate Nr losses. Because the N-R did not account for large variations in REN or grain yield across farmers’ fields for difference competence in N management, estimated Nr losses were a little higher than those estimated by the N-S, especially for high-yield, high-REN systems. Across 162 on-farm experimental sites, an in-season root-zone N management strategy with a 39% lower N application rate and 6% higher grain yield increased the REN by 98% (from 16% to 31%) and reduced Nr loss intensity (based on the N-S) by 45% (from 13.6 to 7.5 kg N Mg−1) compared to farmers’ typical N practices. In conclusion, the reconciliation of food security with greater environmental protection for the future can be driven by improved agronomic management to increase grain yield as well as REN, rather than by solely focusing on optimizing the N application rate.

In an experiment across China to test integrated soil–crop system management for rice, wheat and maize against current practice, improvements in grain yield are equivalent to high-input techniques, but nutrient use, nutrient loss and greenhouse gas emissions are lower than current practice. Integrated soil–crop system management is a technique that aims to maximize yield and minimize environmental impact by adapting cropping systems to local conditions through optimal nutrient application, seasonal timing and the use of the best crop varieties. Fusuo Zhang and colleagues report the results of a China-wide test of this technique for the three main cereal crops — rice, wheat and maize. In comparisons with current practice and high input techniques, the authors find that the integrated system achieves yield improvements equivalent to high input techniques but with lower nutrient use, nutrient loss and greenhouse gas emissions than those found with the current practice. Agriculture faces great challenges to ensure global food security by increasing yields while reducing environmental costs1,2. Here we address this challenge by conducting a total of 153 site-year field experiments covering the main agro-ecological areas for rice, wheat and maize production in China. A set of integrated soil–crop system management practices based on a modern understanding of crop ecophysiology and soil biogeochemistry increases average yields for rice, wheat and maize from 7.2 million grams per hectare (Mg ha−1), 7.2 Mg ha−1 and 10.5 Mg ha−1 to 8.5 Mg ha−1, 8.9 Mg ha−1 and 14.2 Mg ha−1, respectively, without any increase in nitrogen fertilizer. Model simulation and life-cycle assessment3 show that reactive nitrogen losses and greenhouse gas emissions are reduced substantially by integrated soil–crop system management. If farmers in China could achieve average grain yields equivalent to 80% of this treatment by 2030, over the same planting area as in 2012, total production of rice, wheat and maize in China would be more than enough to meet the demand for direct human consumption and a substantially increased demand for animal feed, while decreasing the environmental costs of intensive agriculture.

Understanding the dynamics of biomass and nitrogen (N) accumulation in maize cultivars and the relationship of these parameters to N management is essential to improve our ability to increase maize grain yield and grain N concentration (GNC). We conducted a field experiment in 2010 and 2011, using five rates of N application and three maize hybrids (YD13, ZD958, and XY335) in Quzhou County, the North China Plain, to evaluate grain yield and GNC under different N managements and with different hybrids. The maximum grain yield in 2010–2011 averaged 8.85 and 8.90 Mg ha−1 for ZD958 and XY335, respectively, which was approximately 45% higher than the yield of YD13 (6.10 Mg ha−1). GNC in XY335 was highest among the three hybrids. The maximum GNC for 2010–2011 averaged 1.62% for XY335, 1.42% for ZD958, and 1.48% for YD13. Compared to YD13, XY335 and ZD958 had higher biomass and N accumulation during the grain-filling period and at harvest, and the apparent amount of N remobilization from stover (leaf plus stem) after silking was greater in XY335 than in ZD958, which contributed to high yield and GNC in XY335. The optimal N application rate (ONR) based on in-season N management was 149 kg ha−1, and split at the 3-leaf (V3), 6-leaf (V6), and 10-leaf (V10) stages. All maize hybrids achieved their maximum grain yield and >95% of their maximum GNC with ONR treatment. Selection of appropriate hybrids such as XY335 in combination with optimal N management can increase grain yield and GNC obtained on the North China Plain.

Understanding population establishment associated with different cultivars and N management practices is essential to optimize populations and achieve a high yield for wheat production. A field experiment was conducted in 2012 and 2013 using five N levels and two winter wheat ( Triticum aestivum L.) cultivars: a low-tillering cultivar (TN) and a high-tillering cultivar (LX) in the North China Plain (NCP). The objective of this study was to evaluate grain yield and population establishment of the two cultivars in relation to the different N rates, and to determine the best N management practice and cultivar selection. Grain yield in TN was 5% higher than that of LX in 2013 ( p −1 , and the grain yield using ONR averaged 8.0 t ha −1 for 2 years for both cultivars. Addition of N beyond the ONR did not increase yield, and treatments receiving 70% of the ONR had a 7.9% reduction in yield compared with the ONR treatment. The farmers’ practice N rate (300 kg N ha −1 ) promoted unproductive tillers in the spring and inhibited productive tillers growth before winter, especially for the low-tillering cultivar of TN. In conclusion, selection of a low-tillering cultivar combined with optimal N management in the NCP could be a strategy useful to optimize population quantity, quality, and achieve a high yield, especially when using best crop management practices.

Nitrogen (N) nutrition is a critical factor in root uptake and deposition of zinc (Zn) into wheat grain. However, little is known about how the root system in the soil profile responds to various N supplies under field conditions. A two-year field experiment was conducted to investigate the temporal and spatial distributions of winter wheat roots and relationships between root morphological traits and root Zn uptake with different N supplies. Results showed that an increasing N supply improved root length density (RL), surface area (RSA) and root dry weight (DW), thereafter, resulting in an increased root Zn uptake. For example, root Zn uptake significantly and positively correlated with RL, RSA and root DW at jointing (r = 0.608*, 0.540* and 0.785***, respectively) and flowering (r = 0.611*, 0.602* and 0.876***, respectively) stages. Furthermore, substantial root DW (80–92%) and root Zn uptake (85–96%) were mainly recovered from the upper 30 cm of soil layer irrespective of N supply, showing a good spatial matching. The increased ratios of shoot-to-root Zn concentration and shoot-to-total Zn content with the increasing N supply indicate improving N supply promotes the root-to-shoot Zn transport and increases shoot Zn nutrition. Shoot Zn content was positively correlated with final grain yield and grain Zn concentration. Thus, a combination of optimum N supply with breeding for a better root system could be a promising approach to improve root uptake and accumulation of Zn in grain to maintain relatively higher grain Zn for human nutrition.

To achieve food and environmental security, closing the gap between actual and attainable N-use efficiency should be as important as closing yield gaps. Using a meta-analysis of 205 published studies from 317 study sites, including 1332 observations from rice, wheat, and maize system in China, reactive N (Nr) losses, and total N2O emissions from N fertilization both increased exponentially with increasing N application rate. On the basis of the N loss response curves from the literature meta-analysis, the direct N2O emission, NH3 volatilization, N leaching, and N runoff, and total N2O emission (direct + indirect) were calculated using information from the survey of farmers. The PFP-N (kilogram of harvested product per kilogram of N applied (kg (kg of N)(-1))) for 6259 farmers were relative low with only 37, 23, and 32 kg (kg of N)(-1) for rice, wheat, and maize systems, respectively. In comparison, the PFP-N for highest yield and PFP-N group (refers to fields where the PFP-N was within the 80-100th percentile among those fields that achieved yields within the 80-100th percentile) averaged 62, 42, and 53 kg (kg of N)(-1) for rice, wheat, and maize systems, respectively. The corresponding grain yield would increase by 1.6-2.3 Mg ha(-1), while the N application rate would be reduced by 56-100 kg of N ha(-1) from average farmer field to highest yield and PFP-N group. In return, the Nr loss intensity (4-11 kg of N (Mg of grain)(-1)) and total N2O emission intensity (0.15-0.29 kg of N (Mg of grain)(-1)) would both be reduced significantly as compared to current agricultural practices. In many circumstances, closing the PFP-N gap in intensive cropping systems is compatible with increased crop productivity and reductions in both Nr losses and total N2O emissions.