The environmental and socioeconomic benefits of optimized fertilization for greenhouse vegetables.

China produces more than half of global vegetables with greenhouse farms contributes approximately 35 % to the country's overall vegetable supply. The average nitrogen (N) application rate of greenhouse vegetable production exceeds 2000 kg N ha-1 yr-1, considerably contributing to global agricultural GHG emissions and reactive N (Nr) losses. Optimizing the N fertilizer utilization in greenhouse vegetable production is essential for mitigating environmental pollution and promoting sustainable development nationally and globally. In this study, we estimated the N footprint (NF), social costs (SC, which includes ecosystem and human health damage costs caused by Nr losses to the environment) and net ecosystem economic income (NEEI, which balances between the fertilizers input cost, yield profit, and social costs) of different greenhouse vegetables (tomato, pakchoi, lettuce, cabbage) under farmers' practice (FP) and reduced fertilization treatment (R). Results showed that compared with FP, the NF of tomato, pakchoi, lettuce and cabbage in the R treatment decreased by 61 %, 29 %, 46 % and 36 %, respectively, and the social costs were decreased by 60 %, 48 %, 57 % and 50 %, respectively. On the regional scale, the reduction in N fertilizer use for greenhouse vegetables in Beijing only could save the fertilizer input cost by 1-5 million USD, and avoided SC would increase by 1-14 million USD. As a result, this increased the NEEI by 2-19million USD. This study has demonstrated that adopting reduced fertilization practices represents a cost-effective measure that not only ensures yields but also decrease social costs, NF, and improve the benefits to help achieve sustainable development of greenhouse vegetable production.

Cost-effective mitigation of nitrogen pollution from global croplands.

Cropland is a main source of global nitrogen pollution1,2. Mitigating nitrogen pollution from global croplands is a grand challenge because of the nature of non-point-source pollution from millions of farms and the constraints to implementing pollution-reduction measures, such as lack of financial resources and limited nitrogen-management knowledge of farmers3. Here we synthesize 1,521 field observations worldwide and identify 11 key measures that can reduce nitrogen losses from croplands to air and water by 30-70%, while increasing crop yield and nitrogen use efficiency (NUE) by 10-30% and 10-80%, respectively. Overall, adoption of this package of measures on global croplands would allow the production of 17 ± 3 Tg (1012 g) more crop nitrogen (20% increase) with 22 ± 4 Tg less nitrogen fertilizer used (21% reduction) and 26 ± 5 Tg less nitrogen pollution (32% reduction) to the environment for the considered base year of 2015. These changes could gain a global societal benefit of 476 ± 123 billion US dollars (USD) for food supply, human health, ecosystems and climate, with net mitigation costs of only 19 ± 5 billion USD, of which 15 ± 4 billion USD fertilizer saving offsets 44% of the gross mitigation cost. To mitigate nitrogen pollution from croplands in the future, innovative policies such as a nitrogen credit system (NCS) could be implemented to select, incentivize and, where necessary, subsidize the adoption of these measures.

Abating ammonia is more cost-effective than nitrogen oxides for mitigating PM2.5 air pollution.

Fine particulate matter (PM2.5, particles with a mass median aerodynamic diameter of less than 2.5 micrometers) in the atmosphere is associated with severe negative impacts on human health, and the gases sulfur dioxide, nitrogen oxides, and ammonia are the main PM2.5 precursors. However, their contribution to global health impacts has not yet been analyzed. Here, we show that nitrogen accounted for 39% of global PM2.5 exposure in 2013, increasing from 30% in 1990 with rising reactive nitrogen emissions and successful controls on sulfur dioxide. Nitrogen emissions to air caused an estimated 23.3 million years of life lost in 2013, corresponding to an annual welfare loss of 420 billion United States dollars for premature death. The marginal abatement cost of ammonia emission is only 10% that of nitrogen oxides emission globally, highlighting the priority for ammonia reduction.

Uncertainty of nitrogen budget in China.

The accuracy of the nitrogen (N) budget is of great importance for evidence-based decision-making to address both food security and environmental protection challenges. This study attempts to advance understanding of uncertainties in China's N budget using the Coupled Human And Natural Systems (CHANS) model and Monte Carlo simulation from 1980 to 2018. Results show that the spatial and temporal variations in agricultural and industrial activities and insufficient knowledge on N cycling parameterization are the two dominant causes of uncertainties in the N budget in China. Uncertainties of N inputs generally are <10%, while they are <30% for N outputs and >30% for N accumulations. Uncertainty of nitrogen oxides emission is more sensitive to energy consumption due to the large contributions from industry and transportation. While the uncertainty of ammonia emission is predominantly affected by agricultural activity. Combining surface measurements, satellite observations, and atmospheric simulation models enables cross-check of N fluxes in multiple systems and reduces uncertainties of N budget.

Challenges and opportunities for quantifying greenhouse gas emissions through dairy cattle research in developing countries.

The global dairy sector is facing the challenge of reducing greenhouse gas (GHG) emissions whilst increasing productivity to feed a growing population. Despite the importance of this challenge, many developing countries do not have the required resources, specifically funding, expertise and facilities, for quantifying GHG emissions from dairy production and research. This paper aims to address this challenge by discussing the magnitude of the issue, potential mitigation approaches and benefits in quantifying GHG emissions in a developing country context. Further, the paper explores the opportunities for developing country dairy scientists to leverage resources from developed countries, such as using existing relevant GHG emission estimation models. It is clear that further research is required to support developing countries to quantify and understand GHG emissions from dairy production, as it brings significant benefits including helping to identify and implement appropriate mitigation strategies for local production systems, trading carbon credits and achieving the nationally determined contribution obligations of the Paris Agreement.

Societal benefits of halving agricultural ammonia emissions in China far exceed the abatement costs.

Mitigating agricultural ammonia (NH3) emissions in China is urgently needed to avoid further damage to human and ecosystem health. Effective and feasible mitigation strategies hinge on integrated knowledge of the mitigation potential of NH3 emissions and the associated economic costs and societal benefits. Here we present a comprehensive analysis of marginal abatement costs and societal benefits for NH3 mitigation in China. The technical mitigation potential of agricultural NH3 emissions is 38-67% (4.0-7.1 Tg N) with implementation costs estimated at US$ 6-11 billion. These costs are much lower than estimates of the overall societal benefits at US$ 18-42 billion. Avoiding unnecessary fertilizer use and protein-rich animal feed could provide 30% of this mitigation potential without additional abatement costs or decreases in agricultural productivity. Optimizing human diets with less animal-derived products offers further potential for NH3 reduction of 12% by 2050.

What are the social costs and benefits of lignite application to reduce ammonia emissions in intensive feedlot?

Recent studies demonstrated that lignite application in feedlot can mitigate ammonia (NH3) emission from intensive livestock production, which is an important source of environmental pollution. However, the use of lignite on feedlot requires mining and transport of lignite, which are themselves sources of greenhouse gas and other gaseous pollutants. There is a need for an integrated assessment on the gas emissions to determine the potential impact of those additions to the production chain. Using a case study in Victoria, Australia, carbon dioxide (CO2) and NH3 were identified as key emission changes compared to business as usual (BAU). Social costs and benefits analysis indicated that these changes in emissions translate to social benefits of AUD$11 - $151 and $18 - $256 per cattle per year at lignite application rate of 3 and 6 kg m-2 respectively, while the corresponding social costs of the additional gaseous emissions are AUD$2 - $19 and $3 - $28 per cattle per year per 200 km. Our results indicate that the use of lignite in feedlot to mitigate NH3 can be targeted at feedlots located in proximity to lignite source, population centre and/or vulnerable ecosystems to maximise social benefits and minimise social costs. More broadly, estimating the social costs and benefits of changing manure management practice to mitigate NH3 emission generates information that can be used to evaluate alternative policies for N management.

Policy distortions, farm size, and the overuse of agricultural chemicals in China.

Understanding the reasons for overuse of agricultural chemicals is critical to the sustainable development of Chinese agriculture. Using a nationally representative rural household survey from China, we found that farm size is a strong factor that affects the use intensity of agricultural chemicals across farms in China. Statistically, a 1% increase in farm size is associated with a 0.3% and 0.5% decrease in fertilizer and pesticide use per hectare (P < 0.001), respectively, and an almost 1% increase in agricultural labor productivity, while it only leads to a statistically insignificant 0.02% decrease in crop yields. The same pattern was also found using other independently collected data sources from China and an international panel analysis of 74 countries from the 1960s to the 2000s. While economic growth has been associated with increasing farm size in many other countries, in China this relationship has been distorted by land and migration policies, leading to the persistence of small farm size in China. Removing these distortions would decrease agricultural chemical use by 30-50% and the environmental impact of those chemicals by 50% while doubling the total income of all farmers including those who move to urban areas. Removing policy distortions is also likely to complement other remedies to the overuse problem, such as easing farmer's access to modern technologies and knowledge, and improving environmental regulation and enforcement.

A new cost-effective method to mitigate ammonia loss from intensive cattle feedlots: application of lignite.

In open beef feedlot systems, more than 50% of dietary nitrogen (N) is lost as ammonia (NH3). Here we report an effective and economically-viable method to mitigate NH3 emissions by the application of lignite. We constructed two cattle pens (20 × 20 m) to determine the effectiveness of lignite in reducing NH3 emissions. Twenty-four steers were fed identical commercial rations in each pen. The treatment pen surface was dressed with 4.5 kg m(-2) lignite dry mass while no lignite was applied in the control pen. We measured volatilised NH3 concentrations using Ecotech EC9842 NH3 analysers in conjunction with a mass balance method to calculate NH3 fluxes. Application of lignite decreased NH3 loss from the pen by approximately 66%. The cumulative NH3 losses were 6.26 and 2.13 kg N head(-1) in the control and lignite treatment, respectively. In addition to the environmental benefits of reduced NH3 losses, the value of retained N nutrient in the lignite treated manure is more than $37 AUD head(-1) yr(-1), based on the current fertiliser cost and estimated cost of lignite application. We show that lignite application is a cost-effective method to reduce NH3 loss from cattle feedlots.

The potential for carbon sequestration in Australian agricultural soils is technically and economically limited.

Concerns about increasing concentrations of greenhouse gases in the atmosphere, primarily carbon dioxide (CO2), have raised worldwide interest in the potential of agricultural soils to be carbon (C) sinks. In Australia, studies that have quantified the effects of improved management practices in croplands on soil C have generally been inconclusive and contradictory for different soil depths and durations of the management changes. We therefore quantitatively synthesised the results of Australian studies using meta-analytic techniques to assess the technical and economic feasibility of increasing the soil C stock by improved management practices. Our results indicate that the potential of these improved practices to store C is limited to the surface 0-10 cm of soil and diminishes with time. None of these widely adopted practices is currently financially attractive under Australia's new legislation known as the Carbon Farming Initiative.

Spatial variability of shallow groundwater level, electrical conductivity and nitrate concentration, and risk assessment of nitrate contamination in North China Plain.

In recent years, nitrate (NO3) contamination of groundwater has become a growing concern for people in rural areas in North China Plain (NCP) where groundwater is used as drinking water. The objective of this study was to evaluate groundwater resource level, to determine groundwater quality and to assess the risk of NO3 pollution in groundwater in Quzhou County in the NCP. Ordinary Kriging (OK) method was used to analyze the spatial variability of shallow groundwater level, groundwater electrical conductivity (EC) and NO3-N concentrations, and Indictor Kriging (IK) method was used to analyze the data with NO3-N concentrations equal or greater than the groundwater NO3 pollution threshold (20 mg L(-1)). The results indicated that groundwater level averaged 9.81 m, a level 6 m lower than in 1990. The spatial correlation distances for groundwater level, EC and NO3-N concentration were 21.93, 2.19 and 3.55 km, respectively. The contour map showed that shallow groundwater level areas extended from north to south across the County. Groundwater EC was above 3 dS m(-1) in the most part of the northern county. Groundwater NO3 pollution (NO3-N> or =20 mg L(-1)) mainly occurred in the County Seat areas due to wastewater irrigation and excessive fertilizer leaching from agricultural fields. At Henantuang town, besides suburban of the County Seat, groundwater was also contaminated by NO3 shown by the map generated using the IK method, which was not reflected in the map generated using the OK method. The map generated using the OK method could not reflect correctly the groundwater NO3 pollution status. The IK method is useful to assess the risk of NO3 pollution by giving the conditional probability of NO3 concentration exceeding the threshold value. It is suggested that risk assessment of NO3 pollution is useful for better managing groundwater resource, preventing soil salinization and minimizing NO3 pollution in groundwater.