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The advantages and disadvantages of a winter-hardy vs. a freeze-killed cover crop mixture combined with reduced soil cultivation to a following maize crop were studied on an organic farm in Lower Austria in two consecutive experiments. Effects on soil inorganic nitrogen contents, weed density and the yield of a following maize crop were assessed. The winter-hardy compared with freeze-killed cover crop mixture, both consisting of legumes and non-legumes, reduced soil inorganic nitrogen contents over winter, leading to a reduced nitrate leaching risk, whereas the yield of a following grain maize crop was not significantly affected. Weed density was high in both cover crop treatments, presumably due to the continued reduced, non-inverting soil cultivation on the farm, and higher in the winter-hardy cover crop treatment at one of the assessment dates. Combined with an adapted soil cultivation, both the winter-hardy and the freeze-killed cover crop mixture were suitable before grain maize in this organic farming system with non-inverting soil cultivation under moderately dry site conditions, but the winter-hardy cover crop mixture seems advantageous because it reduces the nitrate leaching risk. [ABSTRACT FROM AUTHOR]

Nitrate leaching is a main nitrogen (N) loss pathway in vegetable production. Although there are numerous mitigation practices that control nitrate leaching, an integrated assessment of these measures is lacking. Thus, we conducted a meta-analysis to integrate the assessment of strategies for controlling nitrate leaching from vegetable systems in China. The main strategies included improved N fertilizer management (INFM), reduced water management (RWM), comprehensive regulation of N fertilizer and water management (CFWM), and catch crops (CCs). Each mitigation measure decreased nitrate leaching significantly and did not reduce vegetable yields. CFWM reduced nitrate leaching the most at 41% on average, followed by CCs, RWM, and INFM (35%, 24%, and 22%, respectively). The nitrate leaching scaled yields (NLSY, defined as yield divided by the quantity of nitrate leaching) were significantly increased by 87%, 44%, 32%, and 27% for CFWM, CCs, INFM, and RWM, respectively. The efficacies of the strategies were dependent on soil properties. CFWM, INFM, and RWM were more effective in soils with low pH and coarse texture than in other soils. In conclusion, the risk of nitrate leaching from vegetable production systems is high, and INFM and CFWM are suggested to decrease nitrate leaching from vegetable production. [ABSTRACT FROM AUTHOR]

Copyright of Revista Colombiana de Ciencias Hortícolas is the property of Revista Colombiana de Ciencias Horticolas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cover crops (CC) promote the accumulation of soil organic carbon (SOC), which provides multiple benefits to agro‐ecosystems. However, additional nitrogen (N) inputs into the soil could offset the CO2 mitigation potential due to increasing N2O emissions. Integrated management approaches use organic and synthetic fertilizers to maximize yields while minimizing impacts by crop sequencing adapted to local conditions. The goal of this work was to test whether integrated management, centered on CC adoption, has the potential to maximize SOC stocks without increasing the soil greenhouse gas (GHG) net flux and other agro‐environmental impacts such as nitrate leaching. To this purpose, we ran the DayCent bio‐geochemistry model on 8,554 soil sampling locations across the European Union. We found that soil N2O emissions could be limited with simple crop sequencing rules, such as switching from leguminous to grass CC when the GHG flux was positive (source). Additional reductions of synthetic fertilizers applications are possible through better accounting for N available in green manures and from mineralization of soil reservoirs while maintaining cash crop yields. Therefore, our results suggest that a CC integrated management approach can maximize the agro‐environmental performance of cropping systems while reducing environmental trade‐offs. [ABSTRACT FROM AUTHOR]

Agro-ecosystem services are the various benefits (e.g., crop yield) that people freely obtain from the properly functioning agricultural lands. The estimated changes in climatic conditions including increasing temperature, with particular attention to the summer means, together with the expected changes in the temporal precipitation distribution pose enormous challenge to the agriculture. Currently, dynamic system models are most frequently used tools that are capable of estimating the prospective effects of climate change on agro-ecosystems. A deterministic biogeochemical model is presented that is developed by Hungarian scientists within the framework of the AgroMo project. The main goal of the AgroMo project is to develop climate-smart strategies in order to mitigate the effect of potential future hazards in the context of climate change by 1) creating a complex, state-of-the-art experimental platform; 2) producing ten new, 0.1° spatial resolution climate scenarios based on the RCP (Representative Concentration Pathway) 4.5 and RCP8.5 scenarios; 3) developing an integrated assessment and modeling framework that is capable of simulating every major land use types; 4) analyzing/simulating a great number of adaptation strategies that can be used to support decision makers. Based on the preliminary simulation results, climate change will most likely expose significant negative impact on the spring sown crops in Hungary. Although, the yield losses could be avoided with irrigation or could be mitigated with earlier sowing, the role of winter crops is likely to become more significant in Hungary in the future. [ABSTRACT FROM AUTHOR]

Human activities are deeply connected with groundwater reservoirs, so protecting them from pollution has become a priority in many regions of the world. Nitrate is considered the main groundwater pollutant since it is directly linked to many human activities. Agricultural activities and domestic wastewater have been identified as the main sources of nitrate in groundwater. Nevertheless, there are some natural processes that can mitigate nitrate pollution. Together with dilution processes, the degradation of nitrate through denitrification has been acknowledge as a process that can potentially reduce nitrogen loads, in both deep and shallow aquifers. Usually these processes were not properly quantified in vulnerability assessment methods, until the introduction of LOS indices. In this study, the application of the LOS indices on 4 agricultural areas is discussed, highlighting how the LOS indices can identify portions of the landscape with higher potential denitrification and how they directly enhance the groundwater vulnerability assessment. Previous studies have shown that LOS indices are a valuable tool for proper vulnerability assessment to nitrate, however they need to be coupled with other parameters that also describe nitrate behavior in groundwater. The SINTACS-SVN and DRASTIC-PA methods that include the LOS indices, were applied for the first time in the Epanomi coastal area to evaluate the reliably of the assessment and, despite the different classes range and the weights applied, similar groundwater vulnerability assessment maps were obtained. The nitrate vulnerability maps were comparable with the observed nitrate concentrations and were found to be highly comparable with original LOS maps. Nevertheless, it should be kept in mind that vulnerability methods are only screening tools and groundwater quality observations are pivotal information for environmental management. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of urea and Nano-Nitrogen Chelate (NNC) fertilizers on yield of sugarcane (Saccharum Officinarum) and nitrate leaching from soil. The treatments included urea (U) and NNC at five levels of nitrogen (0, 80, 112, 137 and 161 kg N ha−1). This experiment was carried out during 2017 and 2018 in Khuzestan province, Iran. The results showed that the average of soil nitrate concentration during the sugarcane growth period in urea and NNC treatments were 10.2 and 12.8 mg kg−1 respectively. The highest and lowest nitrate leaching (699.0 mg l−1 and 183.0 mg l−1) belongs to the highest level of urea fertilizer and the lowest level of NNC. In urea treatments, the lowest amount of nitrate was observed in the topsoil (0-30 cm depth) whereas in NNC fertilizer maximum value was achieved in topsoil. The height of sugarcane stem in both fertilizers increased with increasing rate of fertilizer, but there was no significant difference between two types of fertilizer. Yield of sugarcane (fresh weight of stem) increased significantly by increasing of fertilizer application, but there was no significant difference between two types of fertilizer. In terms of sugar content, there was a significant difference between treatments. The order of nitrogen use efficiency (NUE) for stems and sugar yield from high to low was as NUE (fresh stem): U1 > N1 > N3 ≥ U3 ~ U2 > N4 ~ U4 > N2 and for NUE (sugar): N1 > U1 > N3 ≥ N2 > U2 ~ N4 ≥ U3 > U4. This study showed that application of nano nitrogen fertilizer (NNC) had significant effects on reducing nitrate leaching and increasing sugar production in sugarcane. However, when nitrate leaching and its effects on human health and the environment are in view, nano fertilizers are valuable. [ABSTRACT FROM AUTHOR]

Fertilized temperate croplands export large amounts of reactive nitrogen (N), which degrades water and air quality and contributes to climate change. Fertilizer use is poised to increase in the tropics, where widespread food insecurity persists and increased agricultural productivity will be needed, but much less is known about the potential consequences of increased tropical N fertilizer application. We conducted a meta‐analysis of tropical field studies of nitrate leaching, nitrous oxide emissions, nitric oxide emissions, and ammonia volatilization totaling more than 1,000 observations. We found that the relationship between N inputs and losses differed little between temperate and tropical croplands, although total nitric oxide losses were higher in the tropics. Among the potential drivers we studied, the N input rate controlled all N losses, but soil texture and water inputs also controlled hydrological N losses. Irrigated systems had significantly higher losses of ammonia, and pasture agroecosystems had higher nitric oxide losses. Tripling of fertilizer N inputs to tropical croplands from 50 to 150 kg N ha−1 year−1 would have substantial environmental implications and would lead to increases in nitrate leaching (+30%), nitrous oxide emissions (+30%), nitric oxide (+66%) emissions, and ammonia volatilization (+74%), bringing tropical agricultural nitrate, nitrous oxide, and ammonia losses in line with temperate losses and raising nitric oxide losses above them. [ABSTRACT FROM AUTHOR]

Autumn grazing of high-yielding forage crops such as fodder beet (FB) has increased in popularity in many regions of New Zealand. During grazing, large amounts of urinary nitrogen (N) is returned to the soil which is at risk of leaching. This study evaluated using two different catch crops of oats or Italian ryegrass ('Italian RG') to reduce the risk of N leaching both after FB grazing by lactating dairy cows and after lifting (i.e. un-grazed FB) in autumn. During FB grazing, cows grazed either (i) high [40% of diet dry matter (DM), with pasture; FB40] or (ii) low (25% of diet DM, with pasture; FB25) FB allocations. Both Italian RG and oats reduced soil mineral N (0–90 cm depth) by 16%–37% by August, and 53%–58% by October, compared with a fallow control (115 and 100 kg N ha−1 for August and October, respectively). The greatest reductions in soil mineral N were from oats, largely attributed to higher DM yields resulting in greater N uptake. Furthermore, the total amounts of soil mineral N in the soil after grazing differed between FB allocation treatments and lifted FB (FB25 > FB40 > lifted FB), in proportion to urinary-N inputs and associated dietary N intake. [ABSTRACT FROM AUTHOR]

Nitrogen (N) leaching losses from grazed pasture systems pose a risk to the environment with mitigation strategies urgently required to achieve regulatory limits. There has been increased interest in alternative forages to manipulate excretion of urinary-N of livestock. This review summarises research on key forage attributes which affect the pattern of urine-N excretion. The literature showed an opportunity to alter both N concentration and moisture concentration of forages to reduce urine patch N loading. Complementary mitigations of extending the grazing rotation and reducing fertiliser were tested in simulations in addition to a diuresis effect on nitrate leaching in pastoral dairy systems. Findings suggested that forage species alone could not substantially reduce (by more than 20%) nitrate leaching. Combining all forage, management and systems-based solutions led to the greatest reductions in nitrate leaching, 59 and 31% for Waikato and Canterbury. Nonetheless, reductions in N loss came at the expense of pasture productivity which will likely affect profitability and farmer adoption of this suite of solutions in the absence of other drivers. The role of plant secondary metabolites in microbial dynamics has implications on N recycling in soil and rumen environments and this was identified as an area for further research. [ABSTRACT FROM AUTHOR]

A short-term, dairy cow, grazing experiment was conducted in late-lactation (autumn) to determine the effect of fodder beet (FB) and maize silage supplementation on dry matter and nitrogen (N) intake, urinary N excretion and milk solids (MS; milk fat + milk protein) production. Seventy-two multiparous, lactating (224 ± 20.0 DIM; mean ± SD) Holstein-Friesian cows were randomly assigned (n = 24 per treatment; 8 per replicate) to one of three groups. Control animals were offered pasture (11 kg DM/cow/day) with maize silage (4 kg DM/cow/day; 'Maize'). The other two groups were either offered pasture (11 kg DM/cow/day) with 25% FB (4 kg DM/cow/day; 'FB25') or pasture (9 kg DM/cow/day) with 40% FB (6 kg DM/cow/day; 'FB40'). At the same supplement DM intake, diets containing maize silage or grazed FB had similar urinary nitrogen (UN) concentrations, but FB increased milk solids (MS) production. At 40% FB inclusion UN excretion was reduced but this came at the expense of MS production. Farmers need to exhibit caution when feeding fodder beet to lactating dairy cows to minimise the risk of adverse animal health effects. Feeding fodder beet allocations high enough to achieve significant environmental benefit is likely to compromise animal health and milk production. [ABSTRACT FROM AUTHOR]

Four levels of plantain (0%, 25%, 50% and 75% on DM basis) inclusion rate to ryegrass-clover pasture and three target heifer mature live weights, 444 kg (representing Jersey), 529 kg (Friesian), and 492 kg (cross bred Jersey × Friesian) were tested in this modelling exercise for a 30 ha farm and 24-month analysis. The annual average growth rates were 30 kg DM/ha/day and 23 kg DM/ha/day for plantain and perennial ryegrass-white clover, respectively. Feeding plantain increased animal live weight gain, but on a whole farm level, total live weight gain was similar between the three target weight treatments. Stocking rate was identified as a major driver of nitrogen leaching in this study, which resulted in a decreased nitrogen leaching with increased target live weight groups. Increased annual nitrogen leaching value was found from feeding plantain to animals, which contrasts to previous speculation from animal studies. [ABSTRACT FROM AUTHOR]

Nitrate ( N O 3 − ) leaching is a leading process of nitrogen (N) loss in agricultural ecosystems. The present research focused on N O 3 − leaching and transport in soil from the packed soil columns at different depths (0–20, 0–40, 0–60 and 0–90 cm) under saturated or unsaturated conditions for a lateritic soil. The leached N O 3 − collected from the bottom of column was analyzed with colorimetric method and was assessed for its variance in concentration (mg/L) with variable depths (20–90 cm). The leaching of N O 3 − was more in saturated condition than in unsaturated conditions. The cumulative N O 3 − concentration detected were 23, and 17 mg/L in a saturated condition for two N applications 15 mg and 7.5 mg, respectively, and were 2.10, and 1.36 mg/L in an unsaturated condition for two N applications 19.5 mg and 9.5 mg, respectively. Depth-wise analysis of N O 3 − leached indicated that at a 20 cm depth leached 16, 29 and 43% higher N O 3 − in a saturated condition whereas 21, 38, 52% higher N O 3 − in the unsaturated condition in comparison to 40, 60 and 90 cm depths, respectively. The N O 3 − concentrations with variable depths for both conditions were analyzed with principal component analysis (PCA) and PC (Pearson correlation) scores of 99.93% and 76.41% for unsaturated and saturated conditions were obtained and clarified that N application with more water results in more N O 3 − being leached out. Further, the study suggests that N O 3 − leaching can be restricted even with limited amount of nutrient and water. [ABSTRACT FROM AUTHOR]

Approximately two percent of the world's energy is consumed in the production of ammonia from hydrogen and nitrogen gas. Ammonia is used as a fertilizer ingredient for agriculture and distributed in the environment on an enormous scale to promote crop growth in intensive farming. Only 30–50 % of the nitrogen applied is assimilated by crop plants; the remaining 50–70 % goes into biological processes such as nitrification by microbial metabolism in the soil. This leads to an imbalance in the global nitrogen cycle and higher nitrous oxide emissions (a potent and significant greenhouse gas) as well as contamination of ground and surface waters by nitrate from the nitrogen‐fertilized farmland. This Review gives a critical overview of the current knowledge of soil microbes involved in the chemistry of ammonia nitrification, the structures and mechanisms of the enzymes involved, and phytochemicals capable of inhibiting ammonia nitrification. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the impacts of fertigation strategies on nitrate leaching and its uptake into maize plants. Field experimental data were employed to calibrate a numerical model (HYDRUS 2D/3D) for a surface drip irrigation system in a sandy clay loam soil. The calibrated model was used to simulate nitrate plant uptake and its leaching in different fertigation scenarios based on various fertigation durations and different start times of fertigation. Finally, nitrogen plant uptake was compared with maize N requirement during growth stages in two fertigation frequency scenarios. These simulations were also performed in sandy loam soil. The results show that, if fertigation is done at the end of irrigation, nitrate leaching in shorter fertigation duration will be less than the leaching in longer fertigation duration. However, in the case of fertigation at the beginning of irrigation, the nitrate leaching is higher if the fertigation duration is short, and vice versa. Furthermore, reducing the number of fertigation events in the sandy clay loam soil increases the nitrate plant uptake. However, in the sandy loam soil, a lesser number of fertigation events reduce nitrate uptake. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Key aspects of nitrogen (N) cycle were investigated in a 1 ha irrigated wheat-maize rotation field at Luancheng in the North China Plain to estimate the N balance. The main N output items including ammonia volatilization, nitrate leaching, denitrification-nitrification loss, and nitrogen uptake by crop above ground were measured to assess the magnitude of N cycle by different pathway. The main N input items were also investigated, including applied N fertilizer, N in irrigated water and rainfall and N in residue retained to field.The total NH3 volatilization loss was 19.7 kg N ha-1 under wheat and 46.7 kg N ha-1 under maize, accounting for 7.9% and 27.4% of the applied fertilizer N, respectively. Denitrification-nitrification loss was 4.8~7.9 kg N ha-1 for the maize phase, accounting for 2.8%~4.6% of the applied fertilizer N, which was slightly higher than that from the wheat phase (1.0%~1.4%). While the cumulative nitrate leaching losses were 32 kg N ha-1 under wheat and 24 kg N ha-1 under maize, accounting for 12.8% and 14.1% of applied N, respectively.The total N input was 558.5 kg N ha-1y-1, while the total N output was 488.7~492.9 kg N ha-1y-1. N uptake by crop was the main item of N output, accounting for about 73% of the total N output. The total N loss to the environment was 129.7~133.9 kg N ha-1y-1 and ammonia volatilization and nitrate leaching were the main pathways of fertilizer N loss.

Nitrogen (N) supply is a major factor controlling the yield and quality of vegetables. The purpose of the present study was to determine the effects of different rates of controlled-release N fertilizers (CRFs) and urea applications with cow manure on a) yield (Brassica napa L.), b) nitrate leaching from soil, and c) N2O flux in surface soil. The fertilizers were applied according to the following 6 type-rate combinations: 1) CM-CDU 450 (kg ha-1), 2) LP 450, 3) urea 450, 4) CM-CDU 360, and 5) LP 360, and 6) control (no fertilizer). Yield was significantly higher in theCM-CDU 450 and LP 450 whereas other fertilizer treatments did not show significant differences. The total amounts of leaching nitrate from soils were significantly higher in the urea treatment than in the CM-CDU and LP. Total amount of nitrous oxide (N2O) emission in the urea treatment was highest among the treatments during three cropping seasons. Emission factor (EF) in every treatment ranged from 0.2 to 0.3%.

A container experiment was conducted to simulate the raised bed cultivation system in upland blueberry production and to identify the major loss pathways of N from the root zone amended with different soil organic matter. Treatments were: PM -Tateyama brown forest soil + peat moss (1:1), SC – soil + sawdust sewage sludge compost (1:1) + ferrous sulfate, and SO – soil only. The response of each treatment to ammonium sulfate fertilization was remarkably different. The nitrous oxide emission was largest in the SO and PM treatments (0.41, 0.31 mg N2O/m2/hour, respectively) and lowest in the SC treatment (0.05 N2O/m2/hour) after fertilizer application. The drainage water nitrate concentration was relatively high in SO and PM (159 and 80 mg L-1 respectively) after fertilization. The highest cumulative berry fresh weight was recorded in SC (816 g) followed by PM (85 g) and SO (81 g). According to these results, the sawdust compost treatment may be most suitable due to lower environmental risks and higher yield.

• Bioelectro-barriers based on electroactive bacteria were first constructed. • Bioelectro-barriers achieved nearly 100 % nitrate interception through DNRA. • Periodic application of weak electricity can consistently prevent nitrate leaching. • Bioelectro-barriers were universal for nitrate interception in more diverse areas. • G. sulfurreducens was found to efficiently secrete nitrite reductase for rapid DNRA. Groundwater, the main freshwater resource for humans, has been widely contaminated with nitrate from fertilizers. Here, we report a new and chemical-free strategy to prevent nitrate leaching from soil based on the enrichment of electroactive bacteria, mainly of the genus Geobacter , with bioelectro-barriers, which leads to a nearly 100 % interception of nitrate and partly conserves reactive nitrogen in the form of weakly mobile ammonium by dissimilatory nitrate reduction to ammonium (DNRA). G. sulfurreducens was recognized to efficiently secrete nitrite reductase (NrfA) for rapid DNRA because it lacks nitrate reductase, which inhibits DNRA by competing with nitrite and producing toxic intracellular nitric oxide. With an increase in G. sulfurreducens abundance, near-zero nitrate leaching and 3-fold greater N retention was achieved. Periodic application of weak electricity to the bioelectro-barrier ensured the dominance of G. sulfurreducens in the microbial community and therefore its ability to consistently prevent nitrate leaching. The ability of G. sulfurreducens to intercept nitrate was further demonstrated in more diverse agricultural soils, providing a novel way to prevent nitrate leaching and conserve bioavailable nitrogen in the soil, which has broader implications for both sustainable agriculture and groundwater protection. [Display omitted] [ABSTRACT FROM AUTHOR]

The deep fertilizer application (DF) has been recommended as an effective strategy for promoting crop growth and yield formation. However, the controversial discussion revolves on the challenge of effectively using DF to simultaneously increase crop nitrogen (N) uptake and minimize residual nitrate contents to enhance N utilization efficiency. Based on a precipitation manipulation experiment conducted during 2019–2022 in a semi-humid area, we examined how annual precipitation amount during wheat growing season (125 mm = dry year; 200 mm = normal year; 275 mm = wet year) and the soil water storage before sowing (500 mm, SWSS 500 ; 400 mm, SWSS 400 ; 300 mm, SWSS 300) variability affected the N uptake, N utilization efficiency, yield, and residual soil nitrate content in wheat fields treated with N fertilization at different depths (conventional surface fertilization depth of 5 cm: D5; 15 cm: D15; 25 cm: D25; 35 cm: D35). A complementary field experiment was also performed under natural rainfall condition using the 15N tracer technique to quantify the fate of fertilizer-N and 15N use efficiency (15NUE). 15N analyses showed that DF (D15, D25 and D35) significantly increased 15NUE by improving wheat 15N uptake (5.8–15.3%) and reducing potential 15N loss (9.6–12.3%) compared with D5, but the residual soil 15N in the 0–1.0 m layer increased (13.2–26.3%) as the fertilization depth increased (p < 0.05). The simulated precipitation experiment showed that compared with D5, DF significantly increased wheat N uptake, N utilization efficiency and yield by 1.4–16.4%, 1.4–14.0% and 3.3–21.5%, respectively, in the dry and normal years. In the wet year, N uptake, N utilization efficiency and yield under D15 increased by 1.9–9.8%, 2.1–11.1% and 2.2–13.4% compared to other fertilization depth treatments (p < 0.05). SWSS 500 and SWSS 400 significantly increased the N uptake (9.8–65.0%) and yield (0.6–69.3%) under all fertilization depth treatments irrespective of the annual precipitation amount than SWSS 300 (p < 0.05). DF increased the residual NO 3 –-N concentration (0–2.0 m soil layer) by 2.2–7.3% compared to D5 across all annual precipitation amounts and SWSS levels, and D35 increased the maximum downward movement of NO 3 –-N to 1.4 m under wet year within SWSS 500. DF at the depth of 14–20 cm effectively improved wheat N uptake and yield as well as minimizing the residual soil NO 3 –-N content. Applying moderate DF can enhance sustainable wheat production with high efficiency and yields in semi-humid regions. [Display omitted] ● DF is verified to yield high 15N utilization but soil 15N residues by 15N tracer. ● A framework to assess DF performance on eco-benefits and its dynamics is proposed. ● DF enhances wheat production offsetting by soil residual nitrate. ● Water scenarios contribute to the performance of DF and its optimal depth. ● The robustness of the findings is validated by field trial under natural rainfall. [ABSTRACT FROM AUTHOR]

Pasture-based dairy farming is a source of nitrate (NO 3 -) leaching to Irish water bodies. Nitrate leaching can lead to excess nitrogen in water bodies that causes eutrophication leading to a reduction of oxygen levels, which ultimately can have a negative human health and environmental impacts. The objectives of this study were to review relevant literature pertaining to nitrate leaching and methods of leaching measurement in relation to Irish grassland dairy farming and to identify the main factors associated with leaching. Data from ceramic cup, lysimeter, hydrologically isolated drainage plots and groundwater borehole studies were evaluated. Recorded leaching from ceramic cup studies was found to be highly variable. Lysimeter studies did not account for paddock scale grazing and growth effects. Drainage studies provided consistent data but were not suitable for well-drained soils. Borehole studies were found to be the most reliable method of assessing leaching to groundwater on well-drained soils. Factors that influence leaching such as soil type, climate, nutrient load and stocking rate were analysed. Farm nitrogen surplus per hectare and its interaction with climate were found to be important factors that affect leaching. More long term studies that combine root zone and groundwater measurements methods across a range of spatial scales (farm – catchment), which account for climate, nitrogen surplus, soil type and grassland management effects were recommended. Targeted precision grassland management strategies are recommended to reduce nitrogen surplus and leaching while increasing nitrogen use efficiency. • Significant relationships between leaching and above ground activity were found. • N surplus and climate effects are significant drivers of N leaching. • More long-term studies measuring root zone and groundwater leaching recommended. • Studies to account for leaching at a range of spatial scales are proposed. • Targeted responses are required to reduce leaching from farms on high risk soils. [ABSTRACT FROM AUTHOR]

Setting nitrogen (N) emission targets for agricultural systems is crucial to prevent to air and groundwater pollution, yet such targets are rarely defined at the county level. In this study, we employed a forecasting-and-back casting approach to establish human health-based nitrogen targets for air and groundwater quality in Quzhou county, located in the North China Plain. By adopting the World Health Organization (WHO) phase I standard for PM 2.5 concentration (35 μg m−3) and a standard of 11.3 mg NO 3 −-N L−1 for nitrate in drinking water, we found that ammonia (NH 3) emissions from the entire county must be reduced by at least 3.2 kilotons year−1 in 2050 to meet the WHO's PM 2.5 phase I standard. Additionally, controlling other pollutants such as sulfur dioxide (SO 2) and nitrogen oxides (NO x) is necessary, with required reductions ranging from 16% to 64% during 2017–2050. Furthermore, to meet the groundwater quality standard, nitrate nitrogen (NO 3 −-N) leaching to groundwater should not exceed 0.8 kilotons year-1 by 2050. Achieving this target would require a 50% reduction in NH 3 emissions and a 21% reduction in NO 3 −-N leaching from agriculture in Quzhou in 2050 compared to their respective levels in 2017 (5.0 and 2.1 kilotons, respectively). Our developed method and the resulting N emission targets can support the development of environmentally-friendly agriculture by facilitating the design of control strategies to minimize agricultural N losses. • A novel method was developed for establishing human-health-oriented nitrogen targets. • This approach was implemented in Quzhou County, the North China Plain. • Reducing agricultural ammonia emissions by at least 50% can meet PM 2.5 standard. • Decreasing nitrate leaching by at least 21% can meet water quality standards. • It provides a way to optimize regional agricultural nitrogen management. [ABSTRACT FROM AUTHOR]

The stormwater biofilter is a prevailing green infrastructure for urban stormwater management, but it is less effective in dissolved nitrogen removal, especially for nitrate. The mechanism that governs the nitrate leaching and performance stability of stormwater biofilters is poorly understood. In this study, a water quality model was developed to predict the ammonium and nitrate dynamics in a biochar-pyrite amended stormwater biofilter. The transport of dissolved nitrogen species was described by advection-dispersion models. The kinetics of adsorption and pyrite-based autotrophic denitrification are included in the model and simulated with a steady-state saturated flow. The model was calibrated and validated using eleven storm events. The modeling results reveal that the contribution of pyrite-based autotrophic denitrification to nitrate leaching alleviation improves with the increased drying duration. The nitrate removal efficiency was affected by a series of design parameters. Pyrite filling rate has a minor effect on nitrate removal promotion. Service area ratio and submerged zone depth are the key parameters to prevent nitrate leaching, as they influence the emergence and discharge time of nitrate breakthrough. The high inflow volume (high service area ratio) and small submerged zone can lead to earlier and increased discharge of peak nitrate otherwise the peak nitrate could be retained in the submerged zone and denitrified during the drying period. The developed mechanistic model provides a useful tool to evaluate the treatment ability of stormwater biofilters under varying conditions and offers a guideline for biofilter design optimization. [Display omitted] • The synergistic effect of adsorption and degradation was considered in the model. • Contribution of autotrophic denitrification increases with prolonged drying period. • Pyrite filling rate has a minor effect on nitrate removal promotion. • Service area ratio and submerged zone depth are key to preventing nitrate leaching. [ABSTRACT FROM AUTHOR]

Nitrogen is an element present on Earth in different forms, such as gaseous in the air, dissolved in water, immobilized in the soil, as well as biologically bound in all living organisms. The transition from one form to another constitutes the nitrogen cycle. Current agricultural systems rely on nitrogen fertilizers, which represent the reactive or biologically available nitrogen in soil. The excessive presence of reactive nitrogen in the environment has become a threat to soil, water, and air. The increasing demands for food in the world are associated with significant increase in nitrogen fertilizers inputs which threatens the environment and living organisms. The quantities of nitrogen used per capita in developed countries exceed those in developing countries. However, developed countries are regulated by restrictions of fertilizers inputs in agriculture, whereas such regulations do not exist in most of the developing countries. The need to resort to alternative and eco-sustainable strategies to mitigate the pollution related to human activities, is increasingly evident. This review aims to highlight the fate of nitrogen through the main agricultural practices in modern agriculture. Special attention was given to rocket (Eruca sativa) which is considered a nitrate hyper-accumulator and was used as a case study in the present review. Finally, some eco-sustainable solutions, useful for mitigating or preventing the excessive release of harmful forms of nitrogen into the environment, were also discussed.

Fertilizer coating can increase the efficiency of N fertilizers and reduce their negative impact on the environment. This may be achieved by the utilization of biodegradable natural coating materials instead of polyurethane-based polymers. The aim of this study was to detect the effect of calcium ammonium nitrate (CAN) fertilizer coated with modified conventional polyurethane enhanced with vegetable oils on the yield and quality of Brassica napus L. compared to CAN fertilizer with a vegetable oil-based polymer and to assess the risks of nitrogen loss. Three types of treatments were tested for both coated fertilizers: divided application (CAN, coated CAN), a single application of coated CAN, and a single application of CAN with coated CAN (1:2). A single application of coated CAN with both types of coating in the growth stage of the 9th true leaf significantly increased the yield, the thousand seed weight, and oil production compared to the uncoated CAN. The potential of using coated CAN may be seen in a slow nitrogen release ensuring the nitrogen demand for rapeseed plants throughout vegetation and eliminating the risk of its loss. The increased potential of NH4+ volatilization and NO3− leaching were determined using the uncoated CAN fertilizer compared to the coated variants. Oil-based polymer coatings on CAN fertilizer can be considered as an adequate replacement for partially modified conventional polyurethane.

The use of urease inhibitors in irrigated systems decreases both soil ammonium (NH4+) and nitrate (NO3−) availability, and, thus, could be an easy tool to reduce N loss due to ammonia volatilization and NO3− leaching. The main goal of this experiment was to assess the effect of urease inhibitors on N use efficiency, N losses, and their economic impact in a maize-wheat field experiment. In this study, 10 treatments were compared, combining the urea fertilizer with or without urease inhibitor, applied in one or two dressings, and under optimal or sub-optimal irrigation. A single application of urease inhibitor (IN1d), coupled with the conventional urea, helped to reduce the nitrate leaching risk both during the maize period (even when compared to the two dressing treatment) and after harvest. In addition, this improvement was achieved together with an increase in economic benefit, even when compared with the application of the same amount of regular urea split into two dressings. Under low water availability systems, the benefits of applying urease inhibitors increased with respect to the application of regular urea, making this technique a very promising strategy for adaptation to climate change in arid and semiarid regions.

The nitrate (NO3−) leaching assessment from extensive fertilizer nitrogen (N) applications to croplands is crucial to optimize fertilizer-N recommendations that do not threaten the quality of drinking groundwater. SWAP (Soil Water Atmosphere Plant), a water balance model, was linked with ANIMO (Agricultural NItrogen MOdel), a nitrate leaching model and the Geographical Information System (GIS) to assess the spatial and temporal leaching of NO3−-N from fields under rice-wheat cropping system in the riparian wetlands in the Punjab in north-western India. The results revealed that NO3−-N concentration in the groundwater exceeded the 10 mg NO3−-N L−1 limit set by the World Health Organization (WHO) for drinking water only during December–January. The verification of these results using measured values indicated that the SWAP-ANIMO model satisfactorily predicted NO3−-N concentrations in the leachate in the vadose zone. A low value of the mean absolute error (0.5–1.4) and a root mean square error (0.6–1.5) was observed between the measured and the predicted NO3−-N concentration across the soil profile during the validation at five sampling sites. The NO3−-N predictions revealed that in the long-term, the ongoing fertilizer-N management practices in the riparian wetlands will not significantly change the average NO3−-N concentration in the groundwater. The modeling approach was satisfactory for an efficient quantitative assessment of NO3−-N pollution in groundwater while accounting for the spatial and temporal variability.

Objective The study aimed to assess the N use efficiency (NUE) of pig slurry (in comparison with chemical fertilizer) for each regrowth yield and annual herbage production and their nutritive value. Methods Consecutive field experiments were separately performed using a single application with a full dose of N (200 kg N/ha) in 2014 and by four split applications in 2015 in different sites. The experiment consisted of three treatments: i) control plots that received no additional N, ii) chemical fertilizer-N as urea, and iii) pig-slurry-N with five replicates. Results The effect of N fertilization on herbage yield, N recovery in herbage, residual inorganic N in soil, and crude protein were significantly positive. When comparing the NUE between the two N sources (urea and pig slurry), pig slurry was significantly less effective for the earlier two regrowth periods, as shown by lower regrowth dry matter (DM) yield, N amount recovered in herbage, and inorganic N availability in soil at the 1st and 2nd cut compared to those of urea-applied plots. However, the effect of split application of the two N sources was significantly positive at the last two regrowth periods (at the 3rd and 4th cut). The two N sources and/or split application had little or no influence on neutral detergent fiber (NDF) content, acid detergent fiber (ADF) content, and in vitro DM digestibility, whereas cutting date was a large source of variation for these variables, resulting in a significant increase in in vitro DM digestibility for the last two regrowth periods when an increase in NDF and ADF content occurred. Split application of N reduced the N loss via nitrate leaching by 36% on average for the two N sources compared to a single application. Conclusion The pig slurry-N was utilized as efficiently as urea-N for annual herbage yield, with a significant increase in NUE especially for the latter regrowth periods.

The management of soil organic matter, an important issue in reducing nitrate leaching to groundwater. Description of the subject. The nitrate concentration in half of the groundwater bodies of the Walloon Region (Belgium) has justified their classification as vulnerable zones under the Nitrates Directive (ND). This vulnerable area has a relatively high diversity of agro-soil environments. Thus, the nitrogen content of agricultural soils can vary locally by a factor 4. Objectives. This study aimed to establish whether the carbon content of a soil is a significant risk factor in nitrate leaching to groundwater. Method. The article is based on measurements of nitrate nitrogen residue (APL) and soil total organic carbon (TOC) at the beginning of the leaching period. The measurements were made in 2012 in 1,500 plots, during inspections organized by the Wallonia Public Service. This was as part of the application of the Program for the Sustainable Management of Nitrogen in Agriculture, the scheme for implementing the ND within the Walloon region. Results. Examination of the results showed both that the APL was positively correlated to the TOC and that plots with "noncompliant" APL results had a significantly higher average TOC than the other plots. Conclusions. Since APL is an environmental indicator of the risk of nitrate leaching, it appears that the TOC may constitute a risk of groundwater contamination by nitrate. It is therefore advisable to improve the inclusion of this parameter in advice regarding nitrogen fertilization and secondly, in the case of summer harvest, to better manage the sowing of catch crops.