Nitrogen Footprint Research Articles

Identifying and assessing effectiveness of alternative low-effort nitrogen footprint reductions in small research institutions

Concern over the ecological damage of excess nitrogen has brought increased attention to the role of research institutions and universities in contributing to this problem. Institutions often utilize the concept of the ecological ‘footprint’ to quantify and track nitrogen emissions resulting from their activities and guide plans and commitments to reduce emissions. Often, large-scale changes and commitments to reduce nitrogen footprints are not feasible at small institutions due to monetary and manpower constraints. We partnered with managers in the dining and facilities departments at the Marine Biological Laboratory (MBL), a small research institution in Woods Hole, Massachusetts, to develop five low-effort strategies to address nitrogen emissions at the institution using only resources currently available within those departments. Each proposed strategy achieved emissions reductions in their sector and in the overall nitrogen footprint of the MBL. If all modelled strategies are applied simultaneously, the MBL can achieve a 7.7% decrease in its nitrogen footprint. Managers at MBL considered strategies that required no monetary input most feasible. The intersection of carbon and nitrogen emissions also means the modelled strategies had the co-benefit of reducing the MBL’s carbon footprint, strengthening the argument for applying these strategies. This paper may serve as a model for similar institutions looking to reduce the ecological impact of their activities.

The nitrogen and phosphorus footprints of food products in Yemen over the last 57 years.

Food nitrogen (N) and phosphorus (P) footprints are indicators for determining the losses of N and P over food production (FP) and food consumption (FC) chain. Yemen is an interesting case because, given the country's heavy dependence on food imports, food insecurity, and poverty, the N footprint (NF) and P footprint (PF) could affect its future development. However, NF and PF over time have not yet been studied in Yemen. Therefore, this is the first paper to compute the NF and PF in Arabian Peninsula (a case study from Yemen) by an adjusted model of N-Calculator, by computing virtual N (VNFs) and virtual P (VPFs) factors for main foodstuffs. The NF (kg N cap-1 year-1) and PF (kg P cap-1 year-1) elevated from 5.56 and 1.20 in the 1960s to 15.2 and 4.79 during 2011-2017, respectively, while the national NF (Gg [109 g] N year-1) and national PF (Gg P year-1) increased from 27.7 and 6.77 in the 1960s to 358 and 122 during 2011-2017, respectively. Cereal was the largest contributor to the NF and PF in Yemen over the past 57 years. FP contributes approximately 80% and 86% of the total NF and PF during 2011-2017. Therefore, if possible, the best way for consumers and farmers in Yemen to decrease NF and PF is to focus efforts on increasing FP and FC of foodstuffs with less VNFs and VPFs. The consumption of vegetable-fruit, legumes, starchy, eggs, poultry, and fish should be increased as their NF and PF are low. However, people in Yemen suffer from shortage of resources and lack of awareness, and thus they do not have the opportunity to choose foodstuffs that are low in NF and PF. Accordingly, policymakers should encourage integrated approaches that introduce powerful tools for controlling crop and livestock production in conjunction with enhancements in nutrient use efficiency.

Managing the trade-offs among yield, economic benefits and carbon and nitrogen footprints of wheat cropping in a semi-arid region of China

It is critical to understand how farming practices affect the carbon and nitrogen footprints of agricultural production. Grain yield, economic return, and carbon and nitrogen footprints of spring wheat (Triticum aestivum L.) were examined under different tillage-mulch practices. Wheat was grown over 15 years (2002–2016) in the semi-arid region of the western Loess Plateau of China under six tillage-mulch practices: traditional plough with no straw mulching (T), no-till without straw mulching (NT), traditional plough with straw mulching (TS), no-till without straw mulching (NTS), traditional plough with plastic mulching (TP), no-till with plastic mulching (NTP). Average wheat yield over 15 years under NTS, NTP, TP and TS was increased by 28, 24, 22, and 13%, respectively, compared to T. Average net return was greatest under NTS and lowest under TP. The soils under all six tillage-mulch practices gained a considerably large amount of soil organic carbon (SOC) over the 15 yr. The increase in SOC in the 0–30 cm soil layer was greatest under NTS and lowest under T. When changes in soil C were included in the calculations, treatments of NT, TS, NTS, and NTP sharply reduced total greenhouse gas (GHG) emission compared to T. Compared to T, the carbon footprint was decreased by 180, 44, and 123% under NTS, NT, and TS, respectively, but was increased by 153% under TP. Compared to T, the nitrogen footprint was 24–26% lower in TP and NTP, but was not significantly different under NTS, NT, and TS. Therefore, NTS enhanced yield and net return, and reduced GHG and the carbon footprint without increasing the nitrogen footprint, and should be adopted to mitigate the environmental impacts of wheat production in the semiarid Loess Plateau.

Carbon and nitrogen footprints accounting of peanut and peanut oil production in China

The peanut sector has significant potential for decreasing greenhouse gas (GHG) emissions and reactive nitrogen (Nr) loss from agricultural production activity in China. This study calculated the carbon (C) and nitrgen (N) emissions of the peanut sector in China by jointly using the carbon footprint (CF) and nitrogen footprint (NF) methods based on the national statistical data from 2008 to 2017. The results showed that the average area-based CF (CFa) and NF (NFa) of peanut cropping in China were 1912.58 kg CO2-eq ha−1 and 41.19 kg N-eq ha−1, respectively. The average yield-based CF (CFy) and NF (NFy) of peanut oil reached 1.38 kg CO2-eq kg−1 and 28.23 g N-eq kg−1, respectively. The CFa of the peanut cropping subsystem in China increased from 2008 to 2017, while the NFa presented a reduction feature during 2009–2011 and during 2015–2017. Based on the results above, the total GHG emissions and Nr losses caused by the peanut sector in China were estimated to reach average values of 8.33 million tons (Mt) CO2-eq year−1 and 0.15 Mt N-eq year−1, respectively, during 2009–2017. Moreover, peanut cropping in Fujian showed the highest CF and NF, while that in Anhui and Chongqing presented the lowest CF and NF, implying that optimizing peanut layout in China would be of significant importance to developing the peanut sector with fewer environmental consequences. Fertilizer production and application were continuously the largest sources of CF and NF in the peanut sector in China, which should be given more attention for reducing the environmental consequences in the future. This study provides policy guidance for clean production in peanut industrial chain in the China.

Cutting environmental footprints of maize systems in China through Nutrient Expert management

Excessive fertilizer consumption, poor management, and intense pollution currently restrict sustainable agriculture in China. To address these problems, two 9-year experiments involving typical maize production systems in Northcentral China (summer maize) and Northeast China (spring maize) were conducted to evaluate the effectiveness of Nutrient Expert (NE) management, a Nutrient Decision Support System which combines 4 R nutrient management with improved varieties and optimized plant density, on reducing carbon (C) and nitrogen (N) footprints. The mean grain yields under NE were 7.4 and 11.5 tons ha−1, which were 3.9% and 6.9% higher than those of local farmers’ practices (FP) in the summer and spring maize systems, respectively; the N-derived (affected by N fertilization) yield accounted for 21.7% and 73.5% of the total yield under NE, respectively. Compared with FP, NE achieved 21.8% and 16.0% lower reactive nitrogen (Nr) losses, 18.4% and 20.9% lower greenhouse gas (GHG) emissions, 24.8% and 21.4% smaller N footprints (9.1 and 2.3 kg N ton−1 grain), and 21.5% and 26.0% smaller C footprints (436 and 206 kg CO2 eq ton−1 grain) in summer and spring maize, respectively. NE reduced the N-derived N and C footprints by 30.3% and 27.2% in summer maize and 22.9% and 28.0% in spring maize, respectively, as a result of greater yields and optimal N management. Moreover, compared with summer maize, spring maize showed significantly smaller N-derived N (12.6-fold) and C (7.2-fold) footprints. The results demonstrated the ability of long-term NE management to sustain maize yields, reduce Nr losses and GHG emissions, and cut C and N footprints, indicating its potential suitability as an alternative management for sustainable agriculture. Moreover, the summer maize system still had considerable potential for environmental footprints reduction even when current NE management practices were adopted.

The nitrogen and carbon footprints of vegetable production in the subtropical high elevation mountain region

Mountain vegetable production has become a critical source of low heat-resistance vegetables in summer in subtropical regions, but evaluations based on life-cycle assessment (LCA) that are relevant to the environment and economics have not been reported. We conducted a survey to compare the cabbage yield and resource inputs for small-holder farms at a high (HEL, 900–1500 m) and low (LEL, 200–600 m) elevations in a subtropical region in Southwest China. We used LCA to quantify the nitrogen (N) and carbon (C) footprints, and used the yield and environmental impacts gap method to determine the potential to mitigate the environmental impacts of farming at HELs and LELs. The results show that the respective average reactive N (Nr) and greenhouse gas (GHG) emissions for the HEL and LEL were 137.0 kg N ha−1 and 6785 kg CO2-eq ha−1, and 126.7 kg N ha−1 and 6153 kg CO2-eq ha−1, respectively. The N and C footprints for the HEL were 17.3% and 16.2% lower, respectively, than those for the LEL due to the higher yield at the HEL. The average cabbage yield was 26.5% greater at the HEL (53.2 t ha−1) than at the LEL (42.0 t ha−1). The average total N application rate at the HEL was 455 kg N ha−1, which was 6.0% greater than that at the LEL. There was great potential for yield increases and the mitigation of N and C footprints by farmers at both the HEL and LEL. Compared to the average of all surveyed farmers for HEL and LEL, those farmers whose yields and N fertilizer production efficiency were both higher than the average of all surveyed farmers (HH groups) reduced their N and C footprints by 44.7–49.4% and 44.4–51.2%, respectively, with 34.4–52.3% higher yield and 9.2–19.8% lower N application rate. This study indicates that high yield, low environmental cost, and high economic benefit can be achieved by advancing agronomic management based on the best farmers’ practices for vegetable production in a subtropical high-elevation mountain region.

Nitrogen loss to the environment due to various nitrogen-use efficiencies during milk and beef production in Japan

Reactive nitrogen (Nr) is essential to livestock production, but its excess use can become a source of environment pollution, the extent of which can be evaluated by using a nitrogen (N) footprint model. Such a model provides a useful indicator linking consumers’ activity with Nr loss to the environment. To reduce Nr losses, it is crucial to reduce the use of ‘new-Nr,’ namely Nr chemically (synthetic-Nr) and biologically (BNF-Nr) fixed from the atmosphere, by recycling manure-Nr for crop production. When estimating the N footprint associated with the N use efficiency (NUE) of animal products and virtual N factor (VNF), namely the ratio of Nr released to the environment during the food production and consumption processes per unit Nr consumed, Nr flows from feed production in fields to milk and beef consumption by humans should be quantified. Here, we estimated the national-scale NUE of milk and beef production in Japan and quantified the VNF and N footprint, namely Nr losses to the environment per capita through milk and beef consumption by humans. Crop NUE (i.e. feed-Nr/(new-Nr + manure-Nr)) was greater in paddy fields and grassland than in upland fields. Milk NUE (i.e. consumed-Nr/new-Nr) and milk VNF were 15% and 5.6, respectively. Beef NUEs (i.e. consumed-Nr/new-Nr) and beef VNFs were 4.0% and 24.2 for dairy bullocks, 3.2% and 29.8 for crossbred cattle, and 2.4% and 41.5 for beef breeds, respectively. The length of the fattening period was an important determinant of beef NUE and beef VNF. When the components of slaughtered cattle (the three types previously mentioned + culled cattle) in Japan were considered, beef NUE and beef VNF were 3.7% and 26.3, respectively. We hope that providing consumers with this information will prompt them to choose more environmentally sustainable animal products and thus substantially reduce the worldwide N footprint.

The food nitrogen footprint for African countries under fertilized and unfertilized farms

Although nitrogen (N) is a limiting factor for food production (FP) in Africa, and African food security is seriously threatened by the phenomenon of soil N depletion, there is a dearth of information that shows the points to focus on throughout the chain of FP and food consumption (FC) in all African countries to minimize N loss while securing food N supply. Food N footprint (NF) is an indicator for tracing the losses of reactive N (Nr) with regard to the FP and FC chain. This is the first study to calculate the food NF for all African countries under fertilized and unfertilized farms, by calculating two sets of virtual N factors (VNFs; kg Nr released to the environment kg−1 N in consumed product): one for unfertilized farms (the unfertilized scenario) and one for fertilized farms (the fertilized scenario). The fertilized and unfertilized VNFs were utilized to calculate a weighted average set of VNFs (the combined scenario). From the percentage of farms that utilize N fertilizer, and the N percentage in production that comes from soil depletion, the proportion used for the combined scenario was determined. Soil N depletion factors (SNDFs; kg N taken from the unfertilized soil kg−1 N in food consumed) were also computed to identify the quantity of N extracted from the soil for food production. We have also provided the changes in N inputs, N outputs, and N use efficiency (NUE) for North Africa and Sub-Saharan Africa (SSA) during the last 57 years. The average total N input to croplands increased from 24 and 19 kg N ha−1 yr−1 in 1961–1965 to 100 and 42 kg N ha−1 yr−1 in 2010–2017 for North Africa and SSA, respectively. The NUE declined from 109% and 67% (1961–1965) to 47% and 63% (2010–2017) for North Africa and SSA, respectively. The total average per-capita food NF was 11 and 5.8 kg N cap−1 yr−1 in unfertilized farms; 21 and 14 kg N cap−1 yr−1 in fertilized farms; and 19 and 7.5 kg N cap−1 yr−1 under the combined scenario for North Africa and SSA, respectively. Vegetable-fruit and beef have the highest SDNFs in Africa. FP in Africa contributes approximately 70% of the total food NF. Therefore, if possible, the best way for Africans to reduce soil N depletion and N emissions is to encourage the production and consumption of livestock and crops products with less VNF and SNDF. However, African people do not have this luxury of choice because of poverty and ignorance. Therefore, African policy-makers must adopt integrated approaches that provide effective tools to control the production of animals and crops in conjunction with the improvement of NUE. Trying to completely change the African agricultural system is impossible, but strategies must be developed to reduce soil depletion in a gradual way, as well as a shift towards low-VNF foods.

Differences between Holstein dairy cows in renal clearance rate of urea affect milk urea concentration and the relationship between milk urea and urinary nitrogen excretion

Urine and fecal excretions from cattle contribute to global nitrogen (N) emissions. The milk urea nitrogen (MUN) concentration in dairy cows is positively correlated with urinary urea N (UUN) emissions, and both decline with the reduction in crude protein intake. However, MUN concentration may differ between individual cows despite feeding the same ration. Thus, we hypothesized that due to differences in endogenous N utilization cows with high MUN concentration excrete more UUN than cows with a low MUN concentration. The objective of the present study was to elucidate N partitioning and urea metabolism in dairy cows with divergent MUN concentrations fed two planes of crude protein. Twenty Holstein dairy cows with high (HMU; n = 10) and low (LMU; n = 10) milk urea concentrations were fed two isocaloric diets with a low (LP) and normal (NP) crude protein level. Methane and ammonia emissions were recorded in respiration chambers. Feed intake, feces and urine excretions and milk yield were recorded for four days and subsamples were analyzed for total N and N-metabolites. A carbon-13 labeled urea bolus was administered intravenously followed by a series of plasma samplings. Total N and UUN excretions and ammonia emissions from excreta were lower on the LP diet, however, methane emissions, urinary N excretions and ammonia emissions were comparable between groups. Although plasma and salivary urea concentrations, urea pool size and urea turnover were higher, HMU cows had lower renal urea clearance rates. Additionally, HMU cows had lower renal clearance rates for creatinine, uric acid and creatine and excreted less uric acid (on the LP diet only) and creatine with urine. In conclusion, contrary to our hypothesis, HMU cows did not excrete more UUN than LMU cows. The lower urinary creatine excretion of HMU cows suggests that these animals have a lower environmental nitrogen footprint.

Ammonia mitigation effects from the cow housing and manure storage chain on the nitrogen and carbon footprints of a typical dairy farm system on the North China Plain

Atmospheric ammonia is an important air pollutant, while dairy production is a significant source of ammonia emissions. The aim of the present dairy manure management study was to analyze: 1) the impacts of acidification of the manure surface and/or a vermiculite cover on ammonia, nitrous oxide and methane emissions from animal housing and manure storage stages, 2) the potential influence on the reactive nitrogen (N) and carbon (C) footprints of milk from cradle-to-farm-gate. It was based on a consecutive incubation trial and a life cycle assessment approach for a typical dairy farm system on the North China Plain. Trial results showed that surface-acidification of manure under a slatted floor could reduce ammonia emission by 98 and 22% from housing (one day) and storage stages (38 days), respectively, with small effects on nitrous oxide and methane emissions. The vermiculite cover (storage stage only) reduced ammonia emissions by 98% and methane by 58%, but increased nitrous oxide emissions from storage by almost six times with small absolute losses. The combination of the two mitigations retained 90% of the manure N post-storage relative to that at the start of the housing stage. Life cycle assessment indicated that the reactive-N footprint (NF, i.e. reactive N loss per kg fat- and protein-corrected milk) of milk production was dominated by ammonia emissions and was reduced by 10, 33 and 38% in the manure acidification, manure cover and combination treatments, respectively. Acidification of the manure surface, the vermiculite cover and combination treatments decreased the C footprint (CF, i.e. total greenhouse gas emissions per kg fat- and protein-corrected milk) by 1.0, 1.9 and 2.4%, respectively. This holistic analysis, combining incubation trials and life cycle assessment, indicates that surface-acidification of manure under the slatted floor and a vermiculite cover during manure storage can reduce ammonia emission from a dairy farm system, with an overall positive influence on reduction of NF and CF for dairy farm systems.

Exploring the Widespread Impacts of Ongoing Nitrogen Pollution

The release of reactive nitrogen into the environment is having severe and ongoing ecosystem, economic, and human health impacts. How can we reduce our nitrogen footprint?

Mapping the environmental footprints of nations partnering the Belt and Road Initiative

Over the past few years, the Belt and Road Initiative (BRI) proposed by China has made a notable contribution to the rapid growth of cross-border trade. This however has been accompanied by unexpected burden shifting of resource extractions and environmental emissions to less developed countries. Given that little attention has been paid to the trade-embodied resources and emissions throughout the BRI, this paper, for the first time, accounts for the water, land, carbon, nitrogen and phosphorus footprints of 65 BRI nations and traces the flows embodied in international trade between the BRI and remaining 124 economies by employing a global multi-regional input–output model. Overall, distribution of the BRI's environmental footprints shows strong spatial heterogeneity, amongst China, India and Russia have the highest total environmental footprints. Furthermore, reverse patterns of spatial distribution can be observed between the total and per capita footprints of BRI nations. When it comes to the global scale, the BRI as a whole is found to be a net exporter of trade-embodied flows except for virtual water. Remarkably, 29% of the BRI nations experience a role transition in supply chains across scales, either from net exporters on the BRI level to net importers on the global level, or in reverse. Our findings provide a holistic picture of environmental footprints at scales ranging from single nations, regions, BRI, and even globe, highlighting the significance of a global view in finding ways to tackle environmental challenges and fulfill the Sustainable Development Goals throughout the BRI countries by 2030.

Sub-Saharan Africa's food nitrogen and phosphorus footprints: A scenario analysis for 2050

The current study presents the first nitrogen (N) and phosphorus (P) footprints calculator for Sub-Saharan Africa during 1961–2017 using an adjusted N-Calculator model, by calculating two sets of virtual N factors (VNFs) or virtual P factors (VPFs): one for fertilized farms and one for unfertilized farms. We furthermore calculated the future food footprints of N (NF) and P (PF) under five scenarios include: 1) business as usual [BAU], 2) achieve an equitable diet (EqD) while the plant N and P uptake and all other food losses would be constant at 2017 level [S1], 3) follow the EqD without any changes in plant N and P uptake, but the current ratio of other food losses would increase by 50% [S2], 4) follow the EqD with a 5% less in plant N and P uptake than the current ratio, and the current ratio of other food losses would increase by 50% [S3], and 5) follow the EqD with a 10% greater in plant N and P uptake than the current ratio, while the current ratio of other food losses would decrease by 50% [S4]. NF (kg N cap−1 yr−1) and PF (kg P cap−1 yr−1) increased from 6.7 and 1.1 to 8.3 and 1.5 during 1961–2017, respectively. The national NF (Tg N yr−1) and PF (Tg P yr−1) increased from 1.6 and 0.26 to 7.7 and 1.4, respectively. In 2050, NF would be 9.7, 21.7, 24.1, 27.7, and 15.5 kg N cap−1 yr−1 for the BAU, S1, S2, S3, and S4 scenarios, respectively. While, PF would be 1.8, 5.1, 5.6, 7.3, and 3.0 kg P cap−1 yr−1, respectively. S4 scenario results in much less NF and PF. We suggest applying the S4 scenario with a change of dietary style by reducing the foods consumption with high VNFs and VPFs by 2050.

The Projected Effect of Including Teaching on Sustainability Issues in a University Nutrition Class: Projected Reduction in Nitrogen Footprint

List the main consumer's contributions to reactive nitrogen in the environment and understand the impact of teaching the relationship between consumer choices and environmental health.

Plastic mulching reduces nitrogen footprint of food crops in China: A meta-analysis

Sustainably feeding the growing population amid rising global temperatures and dwindling resources is a grand challenge facing mankind. Plastic mulching (PM) is widely used in China aiming to the increase of crop productivity. However, the impact of PM on reactive nitrogen (Nr) emissions and nitrogen (N) footprint has not been explicitly described. In this study, we collected 4051 observations from 394 published papers for potato (Solanum tuberosum L.), maize (Zea mays L.), and wheat (Triticum aestivum L.), and used meta-analysis to investigate how PM affected crop yield, net economic return, Nr emissions, and N footprints including nitrogen footprint per unit of output energy (NFo) and nitrogen footprint per unit of net economic return (NFe) at regional scale and across a range of precipitation and N fertilization gradients in China. The meta-analysis showed that compared to non-PM practice, PM increased grain yield by 25, 27, and 20% in potato, maize, and wheat, respectively, and enhanced net economic return by 19, 29, and 22%, respectively, with corresponding reduction in NFo of 24, 36, and 18% and NFe of 19, 37, and 19%, respectively. Potato and maize had greater energy output and net economic return than wheat. Plastic mulching was more effective in improving net economic return (or energy output) and reducing N footprints (i.e., NFe and NFo) in the semiarid region (i.e., annual precipitation <600 mm) when N was applied at 100–200 kg N ha−1, especially in potato and maize. Our analysis suggests that the use of PM enhanced grain yield and net economic return while lowering the N footprint without increasing Nr emission. Therefore, PM has great potential to mitigate Nr loss in China when crop species, N fertilization rate, and local environmental factors (i.e., growing region and annual precipitation) are appropriately considered.

Optimized crop rotations increase biomass production without significantly changing soil carbon and nitrogen stock

To meet the growing challenges for food security, renewable resource production and climate change adaptation, optimized crop rotations (OCRs) should aim to maximize biomass production and export from the field while minimizing carbon (C) and nitrogen (N) footprints. However, the effects of OCRs on aboveground biomass production and soil C and N stock as well as the potential links between them remain poorly understood. In this study in Denmark, we harvested all aboveground biomass and simultaneously investigated soil C and N content and stock in two continuous monocultures (CMs) as well as in four OCRs. Across five-year continuous observations, OCRs significantly increased cumulative aboveground biomass production by 23% compared to CMs. There was no significant difference between OCRs and CMs in soil C and N content in any of the soil layers (0–20, 20–50, and 50–100 cm) after the five years. Moreover, OCRs had no effect on top layer soil C and N stock compared to CMs, even when examined by equivalent soil mass. Slight reductions in soil C and N stock after five years in both OCRs and CMs did not relate to the changes in aboveground biomass production. Our results highlight that it is feasible to produce more biomass for biorefineries in OCRs than in CMs and the reductions in soil C and N stock over time seem similar for the two systems. Longer-term continuous observations are called for to underpin these results.

Evaluation of carbon, nitrogen footprint and primary energy demand under different rice production systems

Abstract Ground cover rice production system (GCRPS) has been widely proved to enhance rice yield and save irrigation water. However, information on the environmental impacts and energy consumption of GCRPS remains unknown. In this study, a two-year field experiment was conducted in Hubei Province of China including conventional paddy (W1) and GCRPS (W2, maintaining saturated soil water content; W3, maintaining 80% of the field capacity), factorially combined with different N management practices (N1, zero-N application; N2, single urea application; N3, split application of urea for W1 treatments; manure substitution for W2 and W3 treatments). By combining a soil-crop model simulation with a footprint analysis method, a life cycle inventory was built to evaluate yield-scaled carbon footprint (CF), nitrogen footprint (NF), and primary energy demand (PED) of different rice production systems. Results showed that, compared to conventional flooding paddy, GCRPSs significantly reduced CF, NF, and PED by 31%–35%, 37%–40%, and 17%–18% respectively. Across different N treatments under GCRPS, manure substitution reduced the CF (20%–22%), NF (11%–37%), and PED (25%–27%) compared to the single urea treatments. The hotspot’s contribution of N2O to CF, NH3 to NF, and N-fertilizer production to PED under GCRPS can be reduced by 77%, 33%, and 51% respectively compared to the single urea treatments. Therefore, W3N3 was recommended as the best management practice achieving less CF of 541.4 kg CO2 eq t−1, NF of 2.4 kg N eq t−1, and PED of 2440.0 MJ t−1 meanwhile maintaining high rice yield of 8526 kg ha−1 in the study region.

A community nitrogen footprint analysis of Baltimore City, Maryland

The nitrogen footprint tool (NFT) provides a novel way for communities to understand the environmental impacts of their collective activities and consumption. Reactive nitrogen (Nr; all N species except N2) is created by the Haber–Bosch process for food production and as a by-product of fossil fuel combustion and two natural processes, biological nitrogen fixation and lightning. While it is a vital input for food production, too much Nr has a negative effect on the environment. Calculating the amount of Nr released to the environment as a result of an entity’s resource consumption is the first step in reducing those Nr losses. The nitrogen (N) footprint method has previously taken this approach at the personal and institution scale. In this study, the approach is extended, for the first time, to the spatial patterns of the community nitrogen footprint within a large city, through the integration of diverse geographic information to calculate the N footprint distribution within the City of Baltimore, Maryland, USA. The total N footprint of Baltimore City was ∼19 000 MT N or 30 kg N per capita in 2016, dominated by the food production sector (73%), followed by the energy and transportation sectors (15% combined). There was geographic variability among census block groups’ per capita N footprint within Baltimore City; driven primarily by economic and development factors. Several management scenarios were assessed to better understand what actions may reduce the Baltimore N footprint at the city and community scale over time. The study explored the effect and efficacy of reducing meat consumption based on differences in city consumption patterns, increasing the use of renewable energy sources, and reducing electricity consumption on the city’s total N footprint. The model for the Baltimore City N footprint calculation can be applied to other communities in the United States at the spatial grain of the census block group or any country with this level of data to provide an indicator of nitrogen sustainability.

Integrated systematic approach increase greenhouse tomato yield and reduce environmental losses

High input - high output greenhouse vegetable systems are responsible for nutrient surpluses and environmental losses. Integrated strategies that improve soil, crop and nutrient management are needed to ensure more sustainable production systems. We conducted a two-year field experiment to evaluate the potential of integrated soil-crop system management (ISSM) practices to improve the productivity and environmental outcomes from an intensive greenhouse tomato production system in the Yangtze River Basin, China. Four treatments were tested: i) farmers' practice (FP); ii) soil remediation (SR), where lime nitrogen with compost addition was the only management strategy; iii) a treatment that combined soil remediation with optimized crop planting density (SRCO), which increased planting density for improving crop yield; and iv) integrated soil-crop system management (ISSM), as a systematic integrated approach, which included the combined optimization of soil remediation, crop optimization, and nutrient management. In the integrated soil-crop system management treatment, nutrient management was optimized through adoption of the most appropriate type (formula) of fertilizer for the crop, rate and application timing of synthetic fertilizer, and by substituting poultry manure with compost. Our results indicated that the fruit yield of the integrated soil-crop system management treatment was 104 t ha−1, 13.4%–37.3% higher than that of the other three treatments. The mean reactive nitrogen loss (81.1 kg N ha−1) and the greenhouse gas emissions (6495 kg CO2-eq ha−1) in the farmers' practice treatment were much higher than in the other three treatments (reactive nitrogen loss: 47.9–54.3 kg N ha−1; and greenhouse gas emissions: 4926–5468 kg CO2-eq ha−1, respectively). The mean nitrogen and carbon footprints of the integrated soil-crop system management treatment were significantly lower than those of other treatments, as a result of both the lower fertilizer nitrogen use and the greater yield. This study indicates that integrated soil-crop system management could produce greater yields and increase net profit with reduced nitrogen inputs, whilst reducing the environmental cost associated with conventional farmers’ practice in plastic-greenhouse vegetable production systems.

Incorporating the WHCNS model to assess water and nitrogen footprint of alternative cropping systems for grain production in the North China Plain

Water shortage and reactive N (Nr) release from excessive fertilization are major challenges for sustainable grain production in the North China Plain (NCP). Alternative cropping systems in this region must be explored because traditional winter wheat and summer maize (WW-SM) rotation is maintained at the cost of high consumption of irrigation water and N loss to the environment. In this study, a soil–crop system model (WHCNS, soil water heat carbon and N simulator) and a life cycle assessment were integrated to analyze and evaluate water footprint (WF) and N footprint (NF) for alternative cropping systems of wheat and maize (2H1Y_FP, two harvests in 1 year with farmer’s practice; 2H1Y_RI, two harvests in 1 year with reduced inputs; 1H1Y, one harvest in 1 year with reduced inputs; and 3H2Y, three harvests in 2 years with reduced inputs) in the NCP. Results showed that NH3 volatilization and NO3− leaching are the main hot spots of NF for different crops. For the composition of WF, blue and green WF contributed largely to the total WF of wheat and maize, respectively, and the proportion of gray WF for maize could be decreased by 30% with the reduction in fertilizer amount. The yearly average NF (kg N-eq t−1 y−1) showed the following order: 1H1Y (2.65) <3H2Y (3.41) <2H1Y_RI (6.15) <2H1Y_FP (17.46), and the yearly average WF (m3 t−1 y−1) showed the same order as follows: 1H1Y (565.22) <3H2Y (830.15) <2H1Y_RI (1162.19) <2H1Y_FP (1633.18). Among the compared cropping systems, the 1H1Y and 3H2Y modes as potential alternatives to traditional WW-SM cropping systems showed advantages of sustaining groundwater exploitation and mitigating groundwater nitrate contamination in the NCP. However, the two modes compromised 33%–37% and 20%–25% of crop yield in comparison with those of 2H1Y systems. By considering the site-specific climate and soil conditions, the WHCNS model-based WF and NF analyses could serve as an accurate and effective tool for screening various cropping systems in clean agricultural production.