Nr Losses Research Articles

Fertilization strategies for abating N pollution at the scale of a highly vulnerable and diverse semi-arid agricultural region (Murcia, Spain)

Overuse of N fertilizers in crops has induced the disruption of the N cycle, triggering the release of reactive N (Nr) to the environment. Several EU policies have been developed to address this challenge, establishing targets to reduce agricultural Nr losses. Their achievement could be materialized through the introduction of fertilizing innovations such as incorporating fertilizer into soils, using urease inhibitors, or by adjusting N inputs to crop needs that could impact in both yields and environment. The Murcia region (southeastern Spain) was selected as a paradigmatic case study, since overfertilization has induced severe environmental problems in the region in the last decade, to assess the impact of a set of 8 N fertilizing alternatives on crop yields and environmental Nr losses. Some of these practices imply the reduction of N entering in crops. We followed an integrated approach analyzing the evolution of the region in the long-term (1860–2018) and considering nested spatial- (from grid to region) and systems scales (from crops to the full agro-food system). We hypothesized that, even despite reduction of N inputs, suitable solutions for the abatement of Nr can be identified without compromising crop yields. The most effective option to reduce Nr losses was removing synthetic N fertilizers, leading to 75% reductions in N surpluses mainly due to a reduction of 64% of N inputs, but with associated yield penalties (31%–35%). The most feasible alternative was the removal of urea, resulting in 19% reductions of N inputs, 15%–21% declines in N surplus, and negligible yield losses. While these measures are applied at the field scale, their potential to produce a valuable change can only be assessed at regional scale. Because of this, a spatial analysis was performed showing that largest Nr losses occurred in irrigated horticultural crops. The policy implications of the results are discussed.

Yield- and protein-neutral reduction in fertilizer rate for wheat, maize and rice can reduce the release of reactive nitrogen and greenhouse gas emissions in China

Seeking food security, contemporary Chinese agriculture has followed a trajectory of overfertilization and associated environmental problems, hence the need for nitrogen-balancing practices that do not compromise yield and quality. Here we present a national meta-analysis using 224 studies with 1972 comparisons to quantify the potential to reduce nitrogen (N) fertilization to improve environmental outcomes while maintaining yield and grain protein. We calculated a nitrogen reduction ratio (NRR), as 100 × (N C − N T)/N C; where N is N fertilizer rate and subscripts indicate farmer practice (C) and reduced N rate treatment (T). Our meta-analysis showed that the NRR that maintained yield and grain protein content at the level of current practice was up to 10% in wheat and up to 30% in maize and rice. Larger yield-neutral NRR could be achieved in more fertile, heavier-textured soils, and with practices including enhanced-efficiency N fertilizer, combined application of organic and inorganic N fertilizer, and incorporated straw. Assuming a reduction in N fertilizer usage by 10% for wheat and by 30% for maize and rice in the current cropping area, there is a potential to save 5.7 Mt N yr−1; reduce loss of reactive nitrogen by 1.26 Mt N yr−1, equivalent to 63% of annual total Nr losses for rice in China, reduce N-related greenhouse emissions by 75.2 Mt CO2-eq yr−1, equivalent to 14.5%–25% of the emissions associated with the N fertilizer chain in China; and improve N use efficiency by 23%. Our results highlight the feasibility of maintaining yield and grain protein, and achieving substantial environmental benefits with reduced fertilization rate, and the environmental and agronomic scenarios where these outcomes are more likely.

Attribution and driving force of nitrogen losses from the Taihu Lake Basin by the InVEST and GeoDetector models

Quantifying temporal and spatial changes in reactive nitrogen (Nr) losses from a watershed and exploring its main drivers are the key to watershed water quality improvements. Huge Nr losses continue to threaten the safety of the water environment in the Taihu Lake Basin (TLB). Here, the InVEST and GeoDetector models were combined to estimate Nr losses in the TLB from 1990 to 2020 and explore driving forces. Different scenarios for Nr losses were compared, showing that Nr loss peaked at 181.66 × 103 t in 2000. The key factors affecting Nr loss are land use, followed by elevation, soil, and slope factors, and their mean q-values were 0.82, 0.52, 0.51, and 0.48, respectively. The scenario analysis revealed that Nr losses increased under the business-as-usual and economic development scenarios, while ecological conservation, increased nutrient use efficiency, and reduced nutrient application all contribute to a reduction in Nr losses. The findings provide a scientific reference for Nr loss control and future planning in the TLB.

Sustainability assessment on paddy-upland crop rotations by carbon, nitrogen and water footprint integrated analysis: A field scale investigation

Nutrients of carbon, nitrogen and water of farmland ecosystem are essential foundation to guarantee crop production, but also environmental flows associated greenhouse gas (GHG), reactive nitrogen (Nr) releases, and water consumption. Their flow characteristics serve as a crucial starting point for creating efficient management practices and mitigation measures. Therefore, the objectives of this study are to quantify the carbon footprint (CF), nitrogen footprint (NF), water footprint (WF), and comprehensive environmental footprint (ComF) of six paddy-upland rotation systems, including fallow-paddy rice (FA-PR), Chinese milk vetch-paddy rice (CMV-PR), wheat-paddy rice (WH-PR), rapeseed-paddy rice (RA-PR), green forage wheat-paddy rice (WF-PR), and vicia faba bean-paddy rice (FB-PR), as well as to analysis their relationships and define driving factors. Results showed that the lowest area-scaled CF of 3.74 t CO2-eq ha−1 were observed in the CMV-PR rotation, which were 41% lower than that for WH-PR (the highest CF, 9.13 t CO2-eq ha−1) when soil carbon change was taken into account. It is of importance that soil carbon sequestration in CMV-PR rotation could offset up to around 57% of its CF, while the WH-PR rotation only offset 25%. The RA-PR rotation had the highest area-scaled NF and WF, which was 1.8 and 1.9 times greater than those of the lowest rotation in FA-PR. In terms of comprehensive environmental effects, the six rotation systems showed the order of FA-PR < CMV-PR < FB-PR < RA-PR < WF-PR < WH-PR, with NH3 volatilization accounting 60.7%–66.7% and blue-green WF for 17.5%–26.6% of the total. Therefore, priority should be given to optimizing N fertilizer application and water consumption for paddy-upland rotation systems. The study also suggested that appropriate inter-annual adjustment of rotation system could contribute to achieving GHG mitigations and Nr losses.

Exploring a sustainable rice-cropping system to balance grain yield, environmental footprint and economic benefits in the middle and lower reaches of the Yangtze River in China

Environmental degradation and resource scarcity are serious challenges faced by global rice production. Although rice production is crucial to ensure global food security, it is also one of the principal sources of greenhouse gas (GHG) and reactive nitrogen (Nr) emissions. Exploring rice-cropping systems with a low environmental footprint and high grain yield and economic benefits is a crucial strategy to improve the sustainability of rice production. Here, life cycle assessment was used to compare the performance of middle-season rice (MR), double-season rice (DR) and ratoon rice systems (RR) based on farmer-reported data in the middle and lower reaches of the Yangtze River of China. The average annual grain yields of DR, MR, and RR were 13.68, 8.96 and 11.97 t ha−1, respectively. Although RR produced 12.5% lower grain yield, it had 41.2% lower global warming potential (GWP) and 33.8% smaller eutrophication potential (EP) than DR, which resulted in lower greenhouse gas intensity (GHGI) and reactive nitrogen intensity (NrI). The lower GWP and EP in RR were mainly attributed to lower agricultural inputs, smaller CH4 and N2O emissions and less Nr losses. Compared with MR, RR had higher GWP and EP, but significantly higher grain yield (33.6%) in RR contributed to lower GHGI and similar NrI. In all three cropping systems, CH4 emissions and NH3 volatilization had the highest contributions to GWP and EP, respectively. Compared with the other two cropping systems, RR exhibited the highest net economic income (NEI), benefit-cost ratio and eco-efficiency. Overall, our results suggested that RR is a sustainable rice-cropping system that can coordinate grain yield, environmental footprint and economic benefits.

Optimal nitrogen rate strategy for sustainable rice production in China.

Avoiding excessive agricultural nitrogen (N) use without compromising yields has long been a priority for both research and government policy in China1,2. Although numerous rice-related strategies have been proposed3-5, few studies have assessed their impacts on nationalfood self-sufficiency and environmental sustainability and fewer still have considered economic risks faced by millions of smallholders. Here we established an optimal N rate strategy based on maximizing either economic (ON) or ecological (EON) performance using new subregion-specific models. Using an extensive on-farm dataset, we then assessed the risk of yield losses among smallholder farmers and thechallengesof implementing the optimal N rate strategy. We find that meeting national rice production targets in 2030 is possible while concurrently reducing nationwide N consumption by 10% (6-16%) and 27% (22-32%), mitigating reactive N (Nr) losses by 7% (3-13%) and 24% (19-28%) and increasing N-use efficiency by 30% (3-57%) and 36% (8-64%) for ON and EON, respectively. This study identifies and targets subregions with disproportionate environmental impacts and proposes N rate strategies to limit national Nr pollution below proposed environmental thresholds, without compromising soil N stocks or economic benefits for smallholders. Thereafter, the preferable N strategy is allocated to each region based on the trade-off between economic risk and environmental benefit. To facilitate the adoption of the annually revised subregional N rate strategy, several recommendations were provided, including a monitoring network, fertilization quotas and smallholder subsidies.

Optimizing N Application for Forage Sorghum to Maximize Yield, Quality, and N Use Efficiency While Reducing Environmental Costs

Investigating the responses of forage crop yield, quality, and nitrogen (N) use efficiency to different N application rates is beneficial for guiding proper N fertilization regimes and for reducing reactive N environmental pollution. A field experiment was conducted to investigate the effects of different N application rates on above-ground dry matter yield, forage quality, crop N uptake, N use efficiency (NUE), and ecosystem economic benefits (EEBs) of forage sorghum cultivated on the Longdong Loess Plateau in 2019 and 2020. Five N application rates were tested, namely 0, 80, 160, 240, and 320 kg·ha−1 (referred to as N0, N80, N160, N240, and N320, respectively). The maximum above-ground dry matter yield (22.3 t·ha−1 in 2019 and 18.0 t·ha−1 in 2020) was obtained at an N application of 160 kg·ha−1. Forage sorghum crude protein (CP) content increased significantly with increasing N application rates (the CP content at N320 was 7.4% and 8.6% in 2019 and 2020, respectively). In contrast, neutral detergent fiber (NDF) and acid detergent fiber (ADF) were only affected by high N application rates (NDF and ADF were significantly higher in N320 compared with N0 and N90). The relative feed value (RFV) was significantly higher in N0 compared with N320. Crop N uptake was significantly higher in N160 compared with N0 (25.7% increase to 249.4 kg·ha−1 in 2019 and 40.5% increase to 247.4 kg·ha−1 in 2020, respectively). NUE decreased linearly as N rates increased, but NO3−–N residue (0–200 cm), reactive N loss (Nr loss), and greenhouse gas (GHG) emissions increased. Private profitability and EEB were the largest at N160 (private profitability at N160 was 514.2 USD·ha−1, and EEB at N160 was 392.7 USD·ha−1). Above-ground yield and optimum forage quality must be maximized, while simultaneously safeguarding farmer income and reducing environmental pollution from N fertilizers. Therefore, the optimum N application rate for forage sorghum cultivation in the dry areas of the Loess Plateau is recommended at 160 kg·ha−1.

Mitigation of nitrogen losses and greenhouse gas emissions in a more circular cropping-poultry production system

There is a global need to improve the environmental performances and circularity of livestock production systems. This relates also to poultry production systems in China, however, the benefits of optimized, more circular systems have not been quantified. Here, we applied a substance flow analysis to estimate the reactive nitrogen (Nr) losses and greenhouse gas (GHG) emissions from housing, manure processing and manure application to cropland in a conventional decoupled and an optimized coupled crop-poultry system. We hypothesized that an optimized coupled system has lower Nr losses and GHGs emissions, and a higher economic return for farmers. We used data from experimental measurements, a farm survey, literature and local market prices to estimate the farm performance for both systems. In the conventional system the manure was only partly (58%) utilized and the remaining 42% was wasted and discharged into the environment. In the optimized system a series of emission mitigation measures was adopted, including low-protein feeding, manure composting with additives and a partial replacement of synthetic fertilizers by manure. The optimized system produced 24% more products per 100 units of N input, leading to a whole-system nitrogen use efficiency (NUE) increase from 33% to 50%. The Nr losses per unit of product-N decreased by 55%, whereas the GHG emissions (N2O and CH4) decreased by 35%. Moreover, the net economic benefit increased by 21%. Evidently, the optimized and more circular system had significant economic and environmental benefits compared to the conventional one. These benefits will be drivers for the transformation to more sustainable production systems, but governmental policy incentives will be needed to remove current cultural and institutional barriers.

Gaseous reactive nitrogen losses of agricultural systems in China influenced by crop trade

China plays an important role in the international trade of agricultural commodities. Considering the dynamic reactive nitrogen (Nr) losses of agricultural systems in China, a hypothesis was proposed that crop conversion in China would be correlated with the extent of crop trade, influencing Nr losses in agricultural systems. The objective of this study was to verify the hypothesis based on a hybrid approach, which incorporated life cycle analysis (LCA), copula–Markov chain Monte Carlo (MCMC) simulation, and copula sampling. The approach was proven to be of benefit in (a) evaluating Nr losses in crop planting based on a LCA framework, (b) identifying dependencies and co-movements of the correlated variables in planting structures and crop trade using copula–MCMC simulations, and (c) recognizing fluctuations in Nr losses of crop planting in the future using copula-based sampling method. The planting structures and international trade of four types of crops (i.e. wheat, soybeans, maize, and rice) in 20 provinces of China indicated significant correlations, thus supporting the initial hypothesis. With the improvement of self-sufficiency in crop production, especially soybeans, Nr losses from the crop production of China in 2025 and 2030 would decrease by 8.43% and 4.26%, compared with those in 2018 (i.e. 1916.74 kt N).

Mitigating environmental impacts using net energy system in feed formulation in China's pig production

As the world's largest pork producer, China is facing substantial environmental pressures caused by pig production and the relevant feed production. The net energy (NE) system is promoted as a new evaluation method to evaluate energy content in feed and energy requirements of pigs, but its application lacks of comprehensive and comparative evaluation from the environmental perspective. To identify influence factors and to develop mitigation strategies, the carbon and nitrogen footprints and land use (LU) of pigs (25–120 kg) in China were explored through scenario analysis and cradle-to-farm gate life cycle assessment (LCA). Functional unit (FU) was defined as 1 kg of live weight increase in pig. Among all the procedures of pig production, feed crop production and manure management were the principal contributors to the greenhouse gas (GHG) and nitrogen emissions. As for the carbon footprint, the GHG emissions ranged from 2.37 to 2.55 kg CO2-eq. FU−1 for scenarios using the NE system, 2 % lower than that of the metabolizable energy (ME) system. Cottonseed meal-based scenario generated the lowest GHG emissions, and anaerobic digestion achieved the same effects as other manure management methods. As for the nitrogen footprint, reactive nitrogen (Nr) emissions ranged from 53.4 to 66.2 g Nr FU−1 for scenarios using the NE system, 4 % lower than that of the ME system. Peanut-based scenario won the lowest Nr losses. Moreover, arable LU ranged from 4.63 to 5.85 m2 FU−1 for scenarios using the NE system, 4 % lower than that of the ME system, and economic advantage by using the NE system was also proved. Sensitivity analysis and data quality assessment were conducted to quantify the uncertainties of the above models. In conclusion, the application of the NE system in feed formulation was an effective strategy to improve the environmental sustainability of China's pig production.

Maintaining higher grain production with less reactive nitrogen losses in China: A meta-analysis study

Managing reactive nitrogen (Nr) in agricultural production is crucial for addressing the triple challenges of food security, climate change and environmental degradation. Intensive work has been conducted to investigate the effects of mitigation strategies on reducing Nr losses by ammonia emission (Nr-NH3), nitrous oxide emission (Nr-N2O) and nitrate leaching (Nr-NO3-) separately. This meta-analysis evaluated the efficiency of each strategy in mitigating Nr losses coupled with grain yield responses. The results indicate that producing one Megagram (Mg) of wheat grains caused higher Nr losses, twice that of rice and 17% that of maize. The Nr-NH3 and Nr-NO3- were the dominant sources of Nr losses of the three crops (96%), while Nr-NH3 only presented 86% of the total Nr losses for rice. Reducing the N rate strategy decreased the yield by 33% and the Nr losses by 62% compared with the conventional rate (150–250 kg N ha−1) as an average of the three crops. In contrast, increasing the N rate higher than 250 kg N ha−1 amplified the yield by 15% but also caused a 71% increase in Nr losses compared with the conventional rate. Although subsurface application decreased Nr losses by 5%, this study rejected this approach as an effective strategy due to a 4% yield decline on average of the grain crops. Slow-release fertilizers decreased Nr-NH3 and Nr-N2O losses by 41–58% and 54–89%, respectively, of the highest losses under urea in the three crops, but also led to yield reductions. Organic amendments achieved the highest drop in Nr-NO3- loss by 66% in maize coupled with yield declines. Biochar increased wheat and maize yields by 0.3 and 0.1 Mg, respectively, coupled with 1 kg reduction in Nr losses. On average, inhibitors augmented the grain yields by 0.2 Mg ha−1 for each 1 kg decline in Nr losses. In conclusion, for sustainable agricultural intensification, biochar (for wheat only) and inhibitors (for the three crops) are strongly recommended as mitigation strategies for Nr losses from grain crop production systems in China.

Single application of a new polymer-coated urea improves yield while mitigates environmental issues associated with winter wheat grown in rice paddy soil

Rainfed winter wheat grown in rice paddy suffers from a relatively low yield and severe nitrogen (N) losses. Reduction in N application and/or single use of controlled release N fertilizer (CRNF) have been proposed to address these challenges. A new CRNF, known as nano-Fe III -tannic acid-modified waterborne polymer-coated urea (NWU), has the ability to avoid initial quick release and prolong N availability, which is assumed to synchronize with winter wheat N uptake. Here, we conducted a field experiment spanning three wheat growing seasons to examine the efficacy of single application of NWU on grain yield, N uptake, N use efficiency (NUE), reactive nitrogen (Nr) losses, and net ecosystem economic benefit (NEEB) under two N application rates (160 and 240 kg ha −1 ). Basal application of NWU increased grain yield by 15.7 %, NUE by 51.1 % and NEEB by 45.1 %, while reducing Nr losses by 35.7 % compared to three-split applications of urea at 240 kg ha −1 . Moreover, single application of NWU with a reduced N rate by one-third could even maintain high grain yield and NEEB comparable to that of conventional N practices, meanwhile reducing Nr losses by 58.8 %. Single application of NWU can address high yield and environmental protection simultaneously for wheat grown in paddy soil. • The priority is to use CRNF for wheat grown in paddy fields. • Nano- Fe III -tannic acid modified displayed more synchronized nitrogen supply. • Single use of the modified CRNF achieved largest yield and economic benefit. • Single use of the modified CRNF coupled with N reduction minimized Nr loss.

Coupling the environmental impacts of reactive nitrogen losses and yield responses of staple crops in China

Cropland reactive nitrogen losses (Nr) are of the greatest challenges facing sustainable agricultural intensification to meet the increases in food demand. The environmental impacts of Nr losses and their yield responses to the mitigation strategies were not completely evaluated. We assessed the environmental impacts of Nr losses in China and coupled the efficiency of mitigation actions with yield responses. Datasets about Nr losses in China were collected, converted into potentials of acidification (AP), global warming (GWP), and aquatic eutrophication (AEP), and analyzed by a meta-analysis program. Results showed that producing 1 Mg of rice grains had the highest AP (153 kg acid equiv.), while wheat had the highest GWP and AEP (74 kg CO2 equiv. and 0.37 kg PO4 equiv., respectively). Using the conventional rates (averagely, 200, 230, and 215 kg N ha−1) of urea as a surface application to produce 131.4, 257.2, and 212.1 Tg of wheat, maize, and rice resulted in 17–33 Tg, 7–10 Tg, and 6–87 Gg of AP, GWP, and AEP, respectively. For their balanced effect on reducing AP, GWP, and AEP while maximizing yields, inhibitors, and subsurface application could be set as the best mitigation strategies in wheat production. Inhibitors usage and biochar are strongly recommended strategies for sustainable production of maize. None of the investigated strategies had a balanced effect on rice yield and the environment, thus new mitigation technologies should be developed.

Responses of crop productivity and reactive nitrogen losses to the application of animal manure to China's main crops: A meta-analysis

The effective utilization of manure in cropland systems is essential to sustain yields and reduce reactive nitrogen (Nr) losses. However, there are still uncertainties regarding the substitution of mineral nitrogen (N) fertilizer with manure in terms of its effects on crop yield and Nr losses. We conducted a comprehensive meta-analysis of wheat, maize, and rice applications in China and discovered that substituting mineral N fertilizer with manure increased wheat and maize yields by 4.9 and 5.5 %, respectively, but decreased rice yield by 1.7 %. The increase of yield is larger at low N application and low mineral N substitution rates ((SR) ≤30 %) for silt soils, warm regions, and acidic soils. High SR (>70 %) decreased rice yield as well as the N use efficiency of wheat and maize. Substitution of mineral N fertilizer with manure resulted in lower NH3 volatilization for wheat (48.7 %), lower N2O and NH3 emissions, and N runoff for maize (12.8, 49.6, and 66.7 %, respectively), and lower total Nr losses for rice (11.3–26.5 %). The loss of Nr was significantly and negatively correlated with soil organic carbon content. The rate of N application, soil properties, and climate were critical factors influencing N2O and NH3 emissions and N leaching, whereas climate or soil properties were the dominant factors influencing response in N runoff. We concluded that in silt soils, warm regions, and neutral soils, a ≤ 50 % substitution of mineral N fertilizer with manure can sustain crop yields while mitigating Nr losses.

Reactive N emissions from cropland and their mitigation in the North China Plain

Excessive application of chemical nitrogen (N) fertilizer and inefficient N management are still common in the North China Plain, leading to large reactive N (Nr) losses and pollution, threatening environmental security and public health. Three improved N management practices (33% reduction in N applied (OU), OU combined with partial organic fertilizer substitution (UOM) and the urea in UOM amended with a urease inhibitor (ULOM)) together with no N application (CK) and farmers’ conventional practice (CU) were tested on a maize-wheat rotation at Quzhou, Hebei, North China Plain (NCP). Nr emissions were related to WFPS (Water Filled Pore Space), soil mineral N (NH4+-N and NO3−-N) and soil temperature. Nr emissions and yield-scaled Nr emissions were significantly reduced by partial substitution of organic fertilizer for chemical fertilizer: NH3 emissions were reduced by 55.8–62.4%. Using a urease inhibitor (Limus®), further reduced NH3 emissions by 40.2–64.5%. Yield-scaled NH3 emissions were, on average, reduced by 60.0% and 55.2% in the maize and wheat growing season, respectively, relative to the UOM treatment. Long-term application of organic fertilizer had a significant positive effect on N use efficiency (NUE). Overall, the study shows that appropriated N management such as reducing the N application rate, partial substitution of chemical N by organic N and using a urease inhibitor can reduce Nr emissions and promote NUE in the North China Plain. The methods corresponding to the ULOM and UOM treatments were the most and second most effective, respectively, with high net economic benefits.

Biochar and organic substitution improved net ecosystem economic benefit in intensive vegetable production

Biochar amendment and substituting chemical fertilizers with organic manure (organic substitution) have been widely reported to increase crop production and decrease reactive nitrogen (Nr) loss including nitrous oxide (N2O), nitric oxide (NO), and ammonia (NH3) emissions, and N runoff and leaching. However, few comprehensive evaluations have been performed on the environmental and economic aspects of biochar amendment or organic substitution. Here, we studied the comprehensive effects of biochar amendment, organic substitution, and biochar amendment combined with organic substitution on crop production, Nr loss, and net ecosystem economic benefit (NEEB) in intensive vegetable production by integrating life-cycle assessment for Nr footprints, empirical models for NH3 volatilization and N runoff and leaching derived from peer-reviewed publications and validated by the current measurements and direct field measurement for N2O and NO emissions during 5 consecutive years of vegetable crop rotations. Five fertilization treatments were applied (SN: synthetic fertilizer application; SNB: SN plus 20 t ha−1 biochar amendment; SNM: substituting 50% of chemical N fertilizer with organic manure; SNMB: SNM plus 20 t ha−1 biochar amendment; and CK: no fertilizer or biochar addition). Compared with the SN, the SNB increased vegetable yield (28.4%, p < 0.05; interannually varying from − 10 to 74.9%) and nitrogen use efficiency (29.2%, interannually varying from − 39.7 to 150.4%), and decreased field Nr loss (45.4%, p < 0.01; interannually varying from − 40.3 to 78.4%), and thus improved NEEB by 7.1%; meanwhile, the SNM increased vegetable yield (11.6%, interannually varying from − 5.4 to 27.1%) and nitrogen use efficiency (45.7%, p < 0.05; interannually varying from 2.3 to 154%), reduced field Nr loss (34.9%, p < 0.01; interannually varying from 8.4–39.0%), and thus improved NEEB by 17.8% (p < 0.05) compared to the SN, being 56.0 × 103 Chinese Yuan (CNY) ha−1 crop−1. Due to the high foreground Nr loss during organic manure production and high input costs of biochar production, the SNMB decreased the NEEB by 8.0% as compared to the SN. Moreover, the SNB and SNM improved vegetable qualities by increasing protein, soluble sugar, and vitamin C contents while decreasing nitrate content (p < 0.05). Therefore, single application of biochar amendment or organic substitution would achieve better NEEB and product quality in vegetable production.Graphical

Optimizing Nitrogen Application for Chinese Ratoon Rice Based on Yield and Reactive Nitrogen Loss

Ratoon rice (RR) has been regarded as a labor-saving and beneficial production system. Nitrogen (N) surplus and reactive N losses (Nr losses) are effective environmental indicators used to evaluate the performance of N management. Few studies have assessed N surplus and Nr losses for Chinese RR. In this study, Chinese RR planting areas were divided into South China (SC), the southern part of East China (SEC), Central China (CC), the northern part of East China (NEC), and Southwest China (SW). N surplus and Nr losses were also calculated based on 782 studies using a quadratic model under optimized N management for the highest yield (OPT-yield), the highest N-use efficiency (NUE) (OPT-NUE), and the highest grain N uptake (OPT-N uptake). The RR yields in the five regions ranged from 9.98 to 13.59 t ha−1. The high-yield record was observed in SEC, while the low-yield record was observed in NEC. The highest and the lowest Nr losses were found in NEC and SC, respectively. N surplus was reduced, while the yield was maintained in SEC, CC, NEC, and SW under OPT-yield and OPT-N uptake, and N surplus and Nr losses were reduced in the five regions when targeting the highest NUE. Farmers should be encouraged to plant RR in SEC and CC. RR was also a good choice when N management measures were conducted in three other regions. To achieve a win–win situation for both yield and the environment, OPT-yield could serve to improve the N management of current conventional practices.

Spatio‐temporal assessment of greenhouse gas emission from rapeseed production in China by coupling nutrient flows model with LCA approach

AbstractRapeseed (Brassica napus L.) production experienced a considerable increase during the past decades, and there is growing concern about how to realize the dual objectives of meeting the increasing demand for rapeseed and reducing the associated greenhouse gas (GHG) emissions. Most reported studies on crop‐sourced GHG emissions to date were aimed at optimizing crop management to reduce emission, but often without a detailed spatio‐temporal assessment of GHG emissions for layout management practices. Herein, we used a newly developed modelling approach that integrates the NUtrient Flows in food chains, Environment, and Resource use (NUFER) model with a dynamic reactive nitrogen (Nr) loss module for rapeseed and Life Cycle Assessment (LCA) approach to assess the GHG emissions from rapeseed production in China, where produces 18% of the world's rapeseed. Results showed that the GHG emissions from rapeseed production in China increased by 1.90% yearly from 2004 to 2018, largely due to increased inputs of agricultural materials, especially diesel. Further, carbon footprints of rapeseed production were found vary greatly between production regions, due to diverse climatic conditions, field management practices and the level of mechanization. Scenario analysis showed that adoption of both optimized nutrient and layout management practice is required to mitigate the current resource and environmental burdens, and to achieve edible oil security. Thus, our study provides new insights for policymakers on the formulation of management practices to reduce crop‐sourced GHG emissions, going along with an increase of food demand in the future.

Environmental impacts, human health, and energy consumption of nitrogen management for maize production in subtropical region.

Over-application of fertilizers could not improve crop yield and agronomic efficiency, but result in increasing nitrogen (N) surplus and adverse effects on the ecosystem sustainability. Although some previous studies have addressed one or a few environmental aspects in crop production, an integrated assessment for the effects of N fertilizer on multiple environmental impacts, and the optional steps of normalization and weighting is required. A consecutive 2-year plot-based field experiment was conducted with five N fertilizer levels (0, 90, 180, 270, and 360kgNha-1) in maize production at three sites in Southwest China, to evaluate the environmental performance and sustainability through joint use of life cycle assessment (LCA) and energy consumption analysis. Results demonstrated that the optimal N rate (180kgNha-1) showed greater potential for maintaining high yield (achieved 86% of the yield potential) and reducing the global warming (- 31%), acidification (- 47%), eutrophication (- 44%) compared to farmers' practice, and energy depletion potentials, by reducing pollutants emission during the production and transportation of N fertilizer and Nr losses at farm stage. Optimal N treatment indirectly reduced the land use, life-cycle human toxicity, aquatic eco-toxicity, and terrestrial eco-toxicity potentials by improving grain yield and agronomic efficiency. In addition, the optimal N treatment reduced the energy consumption by enhancing the energy use efficiency (EUE) (+ 74%) and reducing non-renewable energy form (- 45%) than the farmer's practice. This study will provide comprehensive information for both scientists and farmers involved in maize production and N management in subtropical region.

Bottom-up estimates of reactive nitrogen loss from Chinese wheat production in 2014

Excessive use of synthetic nitrogen (N) for Chinese wheat production results in high loss of reactive N loss (Nr; all forms of N except N2) into the environment, causing serious environmental issues. Quantifying Nr loss and its spatial variations therein is vital to optimize N management and mitigate loss. However, accurate, high spatial resolution estimations of Nr from wheat production are lacking due to limitations of data generation and estimation methods. Here, we applied the random forest (RF) algorithm to bottom-up N application rate data, obtained through a survey of millions of farmers, to estimate the Nr loss from wheat production in 2014. The results showed that the average total Nr loss was 52.5 kg N ha−1 (range: 4.6-157.8 kg N ha−1), which accounts for 26.1% of the total N applied. The hotspots for high Nr loss are the same as those high applied N, including northwestern Xinjiang, central-southern Hebei, Shandong, central-northern Jiangsu, and Hubei. Our database could guide regional N management and be used in conjunction with biogeochemical models.