Composting is very robust and efficient for the biodegradation of organic waste; however secondary pollutants, namely greenhouse gases (GHGs) and odorous emissions, are environmental concerns during ...this process. Biochar addition to compost has attracted the interest of scientists with a lot of publication in recent years because it has addressed this matter and enhanced the quality of compost mixture. This review aims to evaluate the role of biochar during organic waste composting and identify the gaps of knowledge in this field. Moreover, the research direction to fill knowledge gaps was proposed and highlighted. Results demonstrated the commonly referenced conditions during composting mixed biochar should be reached such as pH (6.5–7.5), moisture (50–60%), initial C/N ratio (20–25:1), biochar doses (1–20% w/w), improved oxygen content availability, enhanced the performance and humification, accelerating organic matter decomposition through faster microbial growth. Biochar significantly decreased GHGs and odorous emissions by adding a 5–10% dosage range due to its larger surface area and porosity. On the other hand, with high exchange capacity and interaction with organic matters, biochar enhanced the composting performance humification (e.g., formation humic and fulvic acid). Biochar could extend the thermophilic phase of composting, reduce the pH value, NH3 emission, and prevent nitrogen losses through positive effects to nitrifying bacteria. The surfaces of the biochar particles are partly attributed to the presence of functional groups such as Si–O–Si, OH, COOH, CO, C–O, N for high cation exchange capacity and adsorption. Adding biochars could decrease NH3 emissions in the highest range up to 98%, the removal efficiency of CH4 emissions has been reported with a wide range greater than 80%. Biochar could absorb volatile organic compounds (VOCs) more than 50% in the experiment based on distribution mechanisms and surface adsorption and efficient reduction in metal bioaccessibilities for Pb, Ni, Cu, Zn, As, Cr and Cd. By applicating biochar improved the compost maturity by promoting enzymatic activity and germination index (>80%). However, physico-chemical properties of biochar such as particle size, pore size, pore volume should be clarified and its influence on the composting process evaluated in further studies.
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•Using biochar as an additive improved the performance and quality of composting.•Biochar affects the dynamic and structure of the microbial community during composting.•Biochar reduced the availability of heavy metals and odorous gases emissions.•Biochar improved the compost maturity by promoting enzymatic activity and germination index.
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•DRASTIC was modified specifically for porous aquifers and nitrates.•The qualitative parameters were replaced by quantitative.•The class range and rating of the parameters were ...validated using grading methods.•Nitrogen losses were used for the specific vulnerability and pollution risk to nitrates.•The correlation with nitrate concentration improved by 78%.
In the present study the DRASTIC method was modified to estimate vulnerability and pollution risk of porous aquifers to nitrate. The qualitative parameters of aquifer type, soil and impact of the vadose zone were replaced with the quantitative parameters of aquifer thickness, nitrogen losses from soil and hydraulic resistance. Nitrogen losses from soil were estimated based on climatic, soil and topographic data using indices produced by the GLEAMS model. Additionally, the class range of each parameter and the final index were modified using nitrate concentration correlation with four grading methods (natural breaks, equal interval, quantile and geometrical intervals). For this reason, seventy-seven (77) groundwater samples were collected and analyzed for nitrate. Land uses were added to estimate the pollution risk to nitrates. The two new methods, DRASTIC-PA and DRASTIC-PAN, were then applied in the porous aquifer of Anthemountas basin together with the initial versions of DRASTIC and the LOSN-PN index. The two modified methods displayed the highest correlations with nitrate concentrations. The two new methods provided higher discretisation of the vulnerability and pollution risk, whereas the high variance of the (ANOVA) F statistic confirmed the increase of the average concentrations of NO3−, increasing from low to high between the vulnerability and pollution risk classes. The importance of the parameters of hydraulic resistance of the vadose zone, aquifer thickness and land use was confirmed by single-parameter sensitivity analysis.
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•Zeolites increased soil water retention.•Zeolites generally have a positive effect on the growth and yield of plants.•Zeolites can be an additive to fertilizers with a slow release ...of nutrients.
Zeolites are porous aluminosilicates with a crystalline structure that contain a system of interconnected chambers and channels. The geometrical parameters of zeolites are one of the most important characteristics responsible for their adsorption capacity. As a result, zeolites can not only serve as a sorbent for pollutants in the environment, but also as a reservoir of water and nutrients for plants (anions and cations). Due to their unique properties, zeolites have become more and more popular in recent years and find practical application in many branches of the economy. The study results to date prove that zeolites are safe for the environment and living organisms, and their multidirectional use in agriculture results primarily from their high porosity, sorption-ion-exchange capacity and well-developed specific surface area. A direct application of zeolites to soil not only has a beneficial effect on the soil sorption capacity, but also reduces soil acidification and increases the efficiency of nutrient use. Better utilisation of nutrients from fertilisers gives higher yields and reduces nutrient dispersion in the environment. Another advantage of zeolites is that they can be obtained by synthesis from various waste materials (e.g. ashes), making their production cost relatively low. This meets the principles of sustainable development and is part of the closed-loop economy and the retardation of environmental resources. Given that zeolites are the subject of many researches, the present study was prepared as a review of the current possibilities of using these materials in agriculture, mainly for the production of fertilisers.
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•New sensors have to be more sensitive, selective, low-cost and user-friendly.•Agricultural environments are high interference environments for current sensors.•Spectroscopic sensors ...provide selective measurements, allowing interference modelling.•Spectroscopic sensors can be automated and miniaturized to offer real-time data.•Electrochemical sensors require better sensitivity at room temperature.•Photoacoustic sensors require new advances in electronics to lower their cost.
Reducing ammonia emissions is one of the most difficult challenges for environmental regulators around the world. About 90% of ammonia in the atmosphere comes from agricultural sources, so that improving farm practices in order to reduce these emissions is a priority. Airborne ammonia is the key precursor for particulate matter (PM2.5) that impairs human health, and ammonia can contribute to excess nitrogen that causes eutrophication in water and biodiversity loss in plant ecosystems. Reductions in excess nitrogen (N) from ammonia are needed so that farms use N resources more efficiently and avoid unnecessary costs. To support the adoption of ammonia emission mitigation practices, new sensor developments are required to identify sources, individual contributions, to evaluate the effectiveness of controls, to monitor progress towards emission-reduction targets, and to develop incentives for behavioural change. There is specifically a need for sensitive, selective, robust and user-friendly sensors to monitor ammonia from livestock production and fertiliser application. Most currently-available sensors need specialists to set up, calibrate and maintain them, which creates issues with staffing and costs when monitoring large areas or when there is a need for high frequency sampling. This paper reports advances in monitoring airborne ammonia in agricultural areas. Selecting the right method of monitoring for each agricultural activity will provide critical data to identify and implement appropriate ammonia controls. Recent developments in chemo-resistive materials allow electrochemical sensing at room temperature, and new spectroscopic methods are sensitive enough to determine low concentrations in the order of parts per billion. However, these new methods still compromise selectivity and sensitivity due to the presence of ambient dust and other interferences, and are not yet suitable to be applied in agricultural monitoring. This review considers how ammonia measurements are made and applied, including the need for sensors that are suitable for routine monitoring by non-specialists. The review evaluates how monitoring information can be used for policies and regulations to mitigate ammonia emissions. The increasing concerns about ammonia emissions and the particular needs from the agriculture sector are addressed, giving an overview of the state-of-the-art and an outlook on future developments.
The combined application of organic and synthetic nitrogen (N) fertilizers is being widely recommended in China’s vegetable systems to reduce reliance on synthetic N fertilizer. However, the effect ...of substituting synthetic fertilizer with organic fertilizer on vegetable productivity (yield, N uptake and nitrogen use efficiency) and reactive nitrogen (Nr) losses (N2O emission, N leaching and NH3 volatilization) remains unclear. A meta-analysis was performed using peer-reviewed papers published from 2000 to 2019 to comprehensively assess the effects of combined application of organic and synthetic N fertilizers. The results indicate that overall, the vegetable yield, N2O emission and NH3 volatilization were not significantly changed, whereas N leaching was reduced by 44.6% and soil organic carbon (SOC) concentration increased by 12.5% compared to synthetic N fertilizer alone. Specifically, when synthetic N substitution rates (SRs) were ≤70%, vegetable yields and SOC concentration were increased by 5.5%–5.6% and 13.1–18.0%, and N leaching was reduced by 41.6%–48.1%. At the high substitution rate (SR>70%), vegetable yield was reduced by 13.6%, N2O emission was reduced by 14.3%, and SOC concentration increased by 16.4%. Mixed animal-plant sources of organic N preferentially increased vegetable yield and SOC concentration, and reduced N2O emission and N leaching compared with single sources of organic-N. Greenhouse gas (GHG) emission was decreased by 28.4%–34.9% by combined applications of organic and synthetic N sources, relative to synthetic N fertilizer alone. We conclude that appropriate rates (SR ≤ 70%) of combined applications of organic and synthetic N fertilizers could improve vegetable yields, decrease Nr and GHG emission, and facilitate sustainable development of coupled vegetable-livestock systems.
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•Yields increased when substitution rate of synthetic N with organic source was ≤70%.•Substitution of synthetic N fertilizer with organic fertilizers reduced N leaching loss.•Substitution of synthetic N fertilizer with organic fertilizers increased soil carbon sequestration.•Combined applications of organic and synthetic N fertilizers decreased net GWP at field level.
Capsule: Appropriate substitution of synthetic N fertilizer with organic fertilizers could increase vegetable yields and SOC concentration, and reduce N leaching and GHG emission.
To ensure global food security, agriculture must increase productivity while reducing environmental impacts associated with chemical nitrogen (N) fertilisation. This necessitates towards more ...sustainable practices such as recycling organic waste to substitute chemical fertiliser N inputs. However, hitherto how such strategy controls the succession of microbial communities and their relationship with crop yields and environmental impacts have not been comprehensively investigated. We conducted a field experiment with vegetable production in China examining partial substitution (25–50%) of chemical fertiliser with organic forms (pig manure or municipal sludge compost) considering key sustainability metrics: productivity, soil health, environmental impacts and microbial communities. We demonstrate that partial organic substitution improved crop yields, prevented soil acidification and improved soil fertility. Treatments also reduced detrimental environmental impacts with lower N2O emission, N leaching and runoff, likely due to reduced inorganic nitrogen surplus. Microbial communities, including key genes involved in the N cycle, were dynamic and time-dependent in response to partial organic substitution, and were also important in regulating crop yields and environmental impacts. Partial organic substitution increased bacterial diversity and the relative abundance of several specific microbial groups (e.g. Sphingomonadales, Myxococcales, Planctomycetes, and Rhizobiales) involved in N cycling. Additionally, partial organic substitution reduced the number of bacterial ammonia oxidizers and increased the number of denitrifiers, with the proportion of N2O-reducers being more pronounced, suggesting a mechanism for reducing N2O emissions. Comprehensive economic cost-benefit evaluation showed that partial organic substitution increased economic benefit per unit area by 37–46%, and reduced agricultural inputs and environmental impacts per unit product by 22–44%. Among them, 50% substitution of pig manure was the most profitable strategy. The study is crucial to policy-making as it highlights the potential advantages of shifting towards systems balancing chemical and organic fertilisers with economic benefits for farmers, reduced environmental damage and an efficient way for organic waste disposal.
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•Organic amendment improved crop yields and reduced environmental impacts.•Soil properties and microbial communities jointly regulated crop yield and environmental impacts.•Organic amendment increased bacterial diversity and proportion of N2O-reducing community.•Nutrition cycling related taxa were enriched in organic amended soils.
Nitrification inhibitors (NIs) such as dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP) provide an opportunity to reduce losses of reactive nitrogen (Nr) from agricultural ecosystems. To ...understand the fate and efficacy of these two inhibitors, laboratory-scale experiments were conducted with 14C-labelled DCD and DMPP to determine the relative rates of mineralization, recovery in soil extracts and sorption in two agricultural soils with contrasting pH and organic matter content. Concurrently, the net production of soil ammonium and nitrate in soil were determined. Two months after NI addition to soil, significantly greater mineralization of 14C-DMPP (15.3%) was observed, relative to that of 14C-DCD (10.7%), and the mineralization of both NIs increased with temperature, regardless of NI and soil type. However, the mineralization of NIs did not appear to have a major influence on their inhibitory effect (as shown by the low mineralization rates and the divergent average half-lives for mineralization and nitrification, which were 454 and 37days, respectively). The nitrification inhibition efficacy of DMPP was more dependent on soil type than that of DCD, although the efficacy of both inhibitors was lower in the more alkaline, low-organic matter soil. Although a greater proportion of DMPP becomes unavailable, possibly due to physico-chemical sorption to soil or microbial immobilization, our results demonstrate the potential of DMPP to achieve higher inhibition rates than DCD in grassland soils. Greater consideration of the interactions between NI type, soil and temperature is required to provide robust and cost-effective advice to farmers on NI use.
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•DCD and DMPP mineralization was slow and did not affect their nitrification inhibition efficacy.•Relative to DCD, less DMPP was sorbed to the solid phase and more was mineralized.•Inhibition efficacy of DCD and particularly DMPP decreased in the calcareous soil.•Both DCD and DMPP mineralization and inhibition efficacy were strongly influenced by temperature.
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-FeIII-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.
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•The priority is to use CRNF for wheat grown in paddy fields.•Nano- FeIII-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.
Estimating regional soil nitrogen (N) balance in croplands is critical to improve management practices, reduce environmental risks and develop sustainable agriculture. In this study, spatial and ...temporal variations of soil N balance were evaluated from 1984 to 2014 in China's croplands. Results indicated that the total soil N balance was in surplus and increased by 7.3 Tg N (130.4%) between 1984 and 2014, which was attributed to the increased N input of 29.3 Tg N, compared with the increased N output of 22.1 Tg N. Soil N balance continually increased from the 1980s (1984–1989) to the 2000s (2000–2009), and then decreased in the 2010s (2010–2014). Meanwhile, N use efficiency decreased gradually from the 1980s to the 2000s, but it increased in the 2010s. The N loss (N2, N2O, NO, NH3, NO3− leaching and runoff) increased significantly from the 1980s to the 1990s, while the increasing trend gradually reduced from the 1990s to the 2010s. The spatial-temporal distribution of the N balance at the regional scale showed that the total highest and lowest N balance was in the middle and lower reaches of Yangtze River (2.1–3.7 Tg N) and northeast of China (0.3–1.0 Tg N), but the highest and lowest N balance per cropping area was in the southeast (93.4–129.7 kg N ha−1) and northeast (19.6–43.9 kg N ha−1) regions respectively from the 1980s to the 2010s. The N balance decreased for all regions from the 2000s to the 2010s, excluding the southeast and southwest of China due to higher increased rate of N input than the lower increased rate of N output. Reducing the use of chemical fertilizer N would improve cop productivity, decrease soil surplus N and environmental risks of N gas emissions, nitrate leaching and runoff.
•Spatial and temporal variations of soil N balance were evaluated in China's croplands.•Total soil N balance was in surplus and increased by 7.3 Tg N between 1984 and 2014.•N use efficiency decreased from the 1980s to the 2000s which then increased in the 2010s.•The total highest and lowest N balances were in the MLYR and NE regions, respectively.
Nitrogen non-point pollution and greenhouse gas (GHG) emission are major challenges in rice production. This study examined options for both economic and environmental sustainability through ...optimizing water and N management. Field experiments were conducted to examine the crop yields, N use efficiency (NUE), greenhouse gas emissions, N losses under different N and water management. There were four treatments: zero N input with farmer's water management (N0), farmer's N and water management (FP), optimized N management with farmer's water management (OPTN) and optimized N management with alternate wetting and drying irrigation (OPTN+AWD). Grain yields in OPTN and OPTN+AWD treatments increased by 13.0–17.3% compared with FP. Ammonia volatilization (AV) was the primary pathway for N loss for all treatments and accounted for over 50% of the total losses. N losses mainly occurred before mid-tillering. N losses through AV, leaching and surface runoff in OPTN were reduced by 18.9–51.6% compared with FP. OPTN+AWD further reduced N losses from surface runoff and leaching by 39.1% and 6.2% in early rice season, and by 46.7% and 23.5% in late rice season, respectively, compared with OPTN. The CH4 emissions in OPTN+AWD were 20.4–45.4% lower than in OPTN and FP. Total global warming potential of CH4 and N2O was the lowest in OPTN+AWD. On-farm comparison confirmed that N loss through runoff in OPTN+AWD was reduced by over 40% as compared with FP. OPTN and OPTN+AWD significantly increased grain yield by 6.7–13.9%. These results indicated that optimizing water and N management can be a simple and effective approach for enhancing yield with reduced environmental footprints.
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•Optimized N and water management reduced environmental footprints without yield penalty.•Reduced amount and delayed timing of N application helped to improve NUE and reduce N losses.•Increasing N and water use efficiency can reduce greenhouse gas emission and N losses.
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