Agriculture is a major source of nitrous oxide (N2O) emissions, a potent greenhouse gas. While direct N2O emissions from soils have been widely investigated, indirect N2O emissions from nitrogen (N) ...enriched surface water and groundwater bodies are poorly understood. In this contribution, indirect N2O emissions from subsurface agricultural field drains and headwater streams were monitored over a two-year period (2013–2015) in an intensive arable catchment in eastern England. Indirect N2O emission factors for groundwater (EF5g) and surface runoff (EF5r) were calculated for both field drain and streamwater samples, respectively, using two approaches: the N2O–N/NO3–N ratio and the IPCC (2006) methodology. Mean EF5g values derived from the N2O–N/NO3–N ratio were 0.0012 for field drains and 0.0003 for streamwater. Using the IPCC (2006) methodology, the mean EF5g values were 0.0011 for field drains and 0.0001 for streamwater. Thus, EF values derived from both methods were below the current IPCC (2006) default value of 0.0025 and a downward revision to 0.0012 for EF5g and 0.0002 for EF5r is recommended. Such revision would halve current estimates of N2O emissions associated with nitrogen leaching and runoff from agriculture for both the UK and globally.
Indirect nitrous oxide (N2O) emissions produced by nitrogen (N) leaching into surface water and groundwater bodies are poorly understood in comparison to direct N2O emissions from soils. In this ...study, dissolved N2O concentrations were measured weekly in both lowland headwater streams and subsurface agricultural field drain discharges over a 2‐year period (2013–2015) in an intensive arable catchment, Norfolk, UK. All field drain and stream water samples were found to have dissolved N2O concentrations higher than the water–air equilibrium concentration, illustrating that all sites were acting as a net source of N2O emissions to the atmosphere. Soil texture was found to significantly influence field drain N2O dynamics, with mean concentrations from drains in clay loam soils (5.3 μg N L−1) being greater than drains in sandy loam soils (4.0 μg N L−1). Soil texture also impacted upon the relationships between field drain N2O concentrations and other water quality parameters (pH, flow rate, and nitrate (NO3) and nitrite (NO2) concentrations), highlighting possible differences in N2O production mechanisms in different soil types. Catchment antecedent moisture conditions influenced the storm event mobilisation of N2O in both field drains and streams, with the greatest concentration increases recorded during precipitation events preceded by prolonged wet conditions. N2O concentrations also varied seasonally, with the lowest mean concentrations typically occurring during the summer months (JJA). Nitrogen fertiliser application rates and different soil inversion regimes were found to have no effect on dissolved N2O concentrations, whereas higher N2O concentrations recorded in field drains under a winter cover crop compared to fallow fields revealed cover crops are an ineffective greenhouse gas emission mitigation strategy. Overall, this study highlights the complex interactions governing the dynamics of dissolved N2O concentrations in field drains and headwater streams in a lowland intensive agricultural catchment.
Air pollution is an increasingly environmental problem worldwide. People from Iraq and the Kurdistan Region of Iraq (KRI) constantly complain of poor air quality in the region. Many studies have ...investigated particular aspects of air pollution in theKRI, the issue, however, has never been comprehensively discussed. This study, unlike its precedents, collects all the documents, research articles, and ground facts available concerning air pollution, and aims to thoroughly understand all dimensions of the issue and classifies its significant factors and sources. The result revealed that, compared to 40 years ago, current air quality in the KRI, specifically in the two largest cities of Erbil and Sulaimani, has deteriorated. The root causes were found to be political instability and wars in the region, a sharp increase in population, and poor public services. Similar to many other cities in the developing countries, sources such as transportation have contributed in the pollution. In addition, other significant sources such as dust storms, large and private power generators as well as household kerosene heaters which might not be present in other countries were found contributing in escalation of the pollution. It is concluded that air pollution in theKRIis the outcome of a variety of causes and sources some of which may not be common in other parts of the world.
The impact of cover crops and non-inversion tillage regimes on soil and riverine nutrient concentrations is assessed at the farm-scale.
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•A three-year farm-scale cover crop and ...non-inversion tillage trial was conducted.•Oilseed radish cover crop reduced soil water nitrate concentrations by 75–97%.•Corresponding reductions in riverine nitrate concentrations were not observed.•Non-inversion tillage alone was ineffective at reducing nutrient leaching losses.•Mitigation trial profit margins were comparable with conventional farm practice.
The efficacy of cover crops and non-inversion tillage regimes at minimising farm-scale nutrient losses were assessed across a large, commercial arable farm in Norfolk, UK. The trial area, covering 143ha, was split into three blocks: winter fallow with mouldboard ploughing (BlockJ); shallow non-inversion tillage with a winter oilseed radish (Raphanus sativus) cover crop (Block P); and direct drilling with a winter oilseed radish cover crop (Block L). Soil, water and vegetation chemistry across the trial area were monitored over the 2012/13 (pre-trial), 2013/14 (cover crops and non-inversion tillage) and 2014/15 (non-inversion tillage only) farm years. Results revealed oilseed radish reduced nitrate (NO3-N) leaching losses in soil water by 75–97% relative to the fallow block, but had no impact upon phosphorus (P) losses. Corresponding reductions in riverine NO3-N concentrations were not observed, despite the trial area covering 20% of the catchment. Mean soil NO3-N concentrations were reduced by ∼77% at 60–90cm depth beneath the cover crop, highlighting the ability of deep rooting oilseed radish to scavenge nutrients from deep within the soil profile. Alone, direct drilling and shallow non-inversion tillage were ineffective at reducing soil water NO3-N and P concentrations relative to conventional ploughing. Applying starter fertiliser to the cover crop increased radish biomass and nitrogen (N) uptake, but resulted in net N accumulation within the soil. There was negligible difference between the gross margins of direct drilling (£731ha−1) and shallow non-inversion tillage (£758ha−1) with a cover crop and conventional ploughing with fallow (£745ha−1), demonstrating farm productivity can be maintained whilst mitigating diffuse pollution. The results presented here support the wider adoption of winter oilseed radish cover crops to reduce NO3-N leaching losses in arable systems, but caution that it may take several years before catchment-scale impacts downstream are detected.
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•River Wensum Demonstration Test Catchment (DTC) established by UK government.•Impacts of conservation tillage assessed across 143 ha trial area from 2013 to 2018.•Soil properties, ...water quality and economic performance compared with ploughing.•Conservation tillage did not improve soil health or reduce diffuse water pollution.•Conservation tillage yielded improved economic performance compared to ploughing.
In 2010, the UK government launched the Demonstration Test Catchments (DTC) platform to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology whilst maintaining food production capacity. In this paper, we compare the impacts on soil health of two types of conservation tillage (direct drill and shallow non-inversion) against conventional mouldboard ploughing after five years (2013–2018) of adoption within the River Wensum DTC. Across the 143 ha conservation tillage trial area, temporal changes in the physical, chemical and biological condition of the soils were examined through the analysis of 324 soil samples, whilst the impacts on soil water chemistry were assessed through the analysis of 1176 samples of subsurface field drainage. Riverine water pollution was also explored through high-resolution (30 min) hydrochemistry measurements generated by an automated, in-situ bankside monitoring station located 650 m downstream of the trial area. Results revealed that conservation tillage did not significantly alter the soil physical, chemical or biological condition relative to conventional ploughing during the first five years. In addition, conservation tillage did not reduce nutrient leaching losses into field drainage and did not significantly impact upon river water quality, despite the trial area covering 20% of the catchment. Economically, however, conservation tillage yielded net profit margins 13% higher than conventional ploughing after five years of practice due to a combination of operational efficiency savings and improved yields. Overall, the results of this study demonstrate that conservation tillage alone is ineffective at improving the short-term environmental sustainability of farming practices in this lowland intensive arable setting and indicates that a broader, integrated approach to conservation agriculture is required incorporating aspects of cover cropping, crop rotations and precision farming techniques. The improvements in farm business performance do, however, demonstrate land managers can make important financial gains by converting to a conservation tillage system.
Mitigating agricultural water pollution requires changes in land management practices and the implementation of on-farm measures to tackle the principal reasons for water quality failure. However, a ...paucity of robust empirical evidence on the hydrological functioning of river catchments can be a major constraint on the design of effective pollution mitigation strategies at the catchment-scale. In this regard, in 2010 the UK government established the Demonstration Test Catchment (DTC) initiative to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology while maintaining food production capacity. A central component of the DTC platform has been the establishment of a comprehensive network of automated, web-based sensor technologies to generate high-temporal resolution empirical datasets of surface water, soil water, groundwater and meteorological parameters. In this paper, we demonstrate how this high-resolution telemetry can be used to improve our understanding of hydrological functioning and the dynamics of pollutant mobilisation and transport under a range of hydrometerological and hydrogeological conditions. Furthermore, we demonstrate how these data can be used to develop conceptual models of catchment hydrogeological processes and consider the implications of variable hydrological functioning on the performance of land management changes aimed at reducing agricultural water pollution. Keywords: River, Agriculture, Soil moisture, Groundwater, Surface water, Water pollution
Indirect nitrous oxide (N sub(2)O) emissions produced by nitrogen (N) leaching into surface water and groundwater bodies are poorly understood in comparison to direct N sub(2)O emissions from soils. ...In this study, dissolved N sub(2)O concentrations were measured weekly in both lowland headwater streams and subsurface agricultural field drain discharges over a 2-year period (2013-2015) in an intensive arable catchment, Norfolk, UK. All field drain and stream water samples were found to have dissolved N sub(2)O concentrations higher than the water-air equilibrium concentration, illustrating that all sites were acting as a net source of N sub(2)O emissions to the atmosphere. Soil texture was found to significantly influence field drain N sub(2)O dynamics, with mean concentrations from drains in clay loam soils (5.3 mu g N L super(-1)) being greater than drains in sandy loam soils (4.0 mu g N L super(-1)). Soil texture also impacted upon the relationships between field drain N sub(2)O concentrations and other water quality parameters (pH, flow rate, and nitrate (NO sub(3)) and nitrite (NO sub(2)) concentrations), highlighting possible differences in N sub(2)O production mechanisms in different soil types. Catchment antecedent moisture conditions influenced the storm event mobilisation of N sub(2)O in both field drains and streams, with the greatest concentration increases recorded during precipitation events preceded by prolonged wet conditions. N sub(2)O concentrations also varied seasonally, with the lowest mean concentrations typically occurring during the summer months (JJA). Nitrogen fertiliser application rates and different soil inversion regimes were found to have no effect on dissolved N sub(2)O concentrations, whereas higher N sub(2)O concentrations recorded in field drains under a winter cover crop compared to fallow fields revealed cover crops are an ineffective greenhouse gas emission mitigation strategy. Overall, this study highlights the complex interactions governing the dynamics of dissolved N sub(2)O concentrations in field drains and headwater streams in a lowland intensive agricultural catchment.
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