Nutrient losses by surface run-off following the application of organic manures to arable land. 1. Nitrogen

Response of nutrient loss to natural erosive rainfall events under typical tillage practices of contour ridge system in the rocky mountain areas of Northern China

Changes in natural rainfall characterized by heavy precipitation and high rainfall intensity would increase the risks and uncertainty of nutrients losses. Losses of nitrogen (N) and phosphorus (P) with water erosion from agriculture-related activities has become the principal nutrients resulting the eutrophication of water bodies. However, a little attention has been paid to the loss characteristic of N and P responding to natural rainfall in widely used contour ridge systems. To explore the loss mechanism of N and P in contour ridge system, nutrient loss associated with runoff and sediment yield was observed in in situ runoff plots of sweet potato (SP) and peanut (PT) contour ridges under natural rainfall. Rainfall events were divided into light rain, moderate rain, heavy rain, rainstorm, large rainstorm, and extreme rainstorm level, and rainfall characteristics for each rainfall level were recorded. Results showed that rainstorm, accounting for 46.27% of the total precipitation, played a destructive role in inducing runoff, sediment yield, and nutrient loss. The average contribution of rainstorm to sediment yield (52.30%) was higher than that to runoff production (38.06%). Rainstorm respectively generated 43.65-44.05% of N loss and 40.71-52.42% of P loss, although light rain induced the greatest enrichment value for total nitrogen (TN, 2.44-4.08) and PO4-P (5.40). N and P losses were dominated by sediment, and up to 95.70% of the total phosphorus and 66.08% of TN occurred in sediment. Nutrient loss exhibited the highest sensitivity to sediment yield compared to runoff and rainfall variables, and a significant positive linear relationship was observed between nutrient loss and sediment yield. SP contour ridge presented higher nutrient loss than that in PT contour ridge, especially for P loss. Findings gained in this study provide references for the response strategies of nutrient loss control to natural rainfall change in contour ridge system.

A broad-scale spatial analysis of the environmental benefits of fertiliser closed periods implemented under the Nitrates Directive in Europe

Nutrient pollution from agriculture has been an ongoing challenge for decades, contributing to numerous negative environmental impacts. In the European Union policies have been developed to address nutrient pollution, including Nitrate Action Programmes under Council Directive 91/676/EEC. Although Member States report on progress on implementation, there have been few studies that explore how measures have been implemented; the environmental implications of any differences; and how they vary spatially on a European scale. This study aims to address this gap with respect to fertiliser closed periods (1155 different closed periods across 69 Nitrate Action Programmes). This included the development of an approach that can be applied using readily available spatial data. Each closed period was scored for its coverage of risk periods for losses of nitrate; organic material; nitrous oxide and ammonia. Closed periods were then matched to relevant combinations of spatial data for each environmental zone and fertiliser type. The scores for each combination were used to create maps and calculate spatial statistics. The results show that in addition to nitrate, closed periods also reduce the risk of organic material run-off, emissions of nitrous oxide and to a lesser extent ammonia. However, risk reduction is spatially variable across all the impacts and the scope for synergy is also variable (e.g. nitrate loss does not always correlate with nitrous oxide or ammonia risk reduction). Regions in the Atlantic, Lustanian and some areas within the Mediterranean zones appear to provide the greatest combined risk reduction, with other zones, especially in eastern Europe, having a lower combined risk reduction (due to a combination of different risk periods coupled with lower coverage of individual risks). The spatial analysis within this study is relatively simple; is based on a snapshot of closed periods during 2019-2020; and only explores one measure. However, it does provide some useful data and insights that could support policy development in the future. This includes scope for Member States and regions to learn from others where greater coverage of risk periods has been achieved; and highlighting how a more holistic perspective can be taken to the environmental management of nutrients. As we strive towards developing sustainable production systems, farmers and policy makers need to take a more integrated approach to incorporate additional environmental objectives; which increases the complexity of the challenge. Consequently, the demand for pragmatic approaches that take a more holistic approach is likely to increase in the future.

Isotherms, Kinetics, and Thermodynamics of NH4+ Adsorption in Raw Liquid Manure by Using Natural Chabazite Zeolite-Rich Tuff

The search for safer and sustainable management of animal manure is a global and topical challenge, in particular for the reduction of nitrogen (N) content. The use of natural adsorbents as zeolite-rich tuffs is recognized as a valid method to recover N, in the form of ammonium (NH4+), from animal manure. While the scientific literature is rich in studies performed on synthetic solutions and using clinoptilolite zeolites as adsorbent, it lacks information concerning adsorption in real liquid manure and using other types of zeolite-rich tuffs (e.g., chabazite). This work aims at exploring the NH4+ adsorption process from raw liquid swine manure, using a chabazite-rich zeolite tuff as adsorbent. The effects of temperature, contact time, and grain size have been assessed. Isotherms, kinetic models, and thermodynamic parameters have been investigated. Harkins-Jura isotherm correlates well with the observed data, in accordance with the formation of an adsorption multilayer. Kinetic data have been explained by intraparticle diffusion and pseudo-second-order models. In conclusion, the natural chabazite tuff has proven to be a valid material for NH4+ adsorption from raw liquid swine manure. In particular, to reach the highest adsorption capacities and adsorption rates, it is recommended to use it at a fine particle size and with dosages < 6 %.

Runoff water quality after low-disturbance manure application in an alfalfa-grass hay crop forage system

The impacts of low-disturbance manure application (LDMA) on runoff water quality in hay crop forages are not well known. Our objective in this study was to determine surface runoff losses of total nitrogen (TN), ammonium N (NH₄ -N), nitrate N (NO₃ -N), total phosphorus (TP), dissolved reactive P (DRP), and suspended sediment from alfalfa (Medicago sativa L.)-grass plots in central Wisconsin after surface broadcasting manure and LDMA compared with no application. Treatments were (a) surface banding (BAND), (b) surface banding with aeration (A/B), (c) shallow disk injection (INJECT), (d) surface broadcast (BCAST), and (e) a no-manure control (CONT). Runoff events were generated (n = 7) from replicated plots following a standardized rainfall simulation protocol. Although runoff was variable across plots and within treatments, mean runoff concentrations of TN (P = .03), NH₄ -N (P = .03), TP (P = .001), and DRP (P < .0001) were lower for incorporated (INJECT and A/B) vs. unincorporated (BCAST and BAND) treatments. INJECT had lower mean DRP concentration (P = .02) than A/B and was similar to CONT and had lower cumulative TN (P = .05), TP (P = .07), and DRP (P = .01) loads than A/B. Additionally, TP, TN, DRP, and NH₄ -N loads and concentrations were strongly related with soil surface manure coverage extent (R² = 0.50-0.84; P < .0001), suggesting that manure was a main source of N and P losses. Although INJECT appeared to be the most effective in mitigating nutrient loss in surface runoff, more research is needed to determine LDMA impacts on farm economics, soil properties, and runoff water quality.

Impact of agricultural farms on the environment of the Puck Commune: Integrated agriculture calculator-CalcGosPuck

Background

Leaching of nutrients from agricultural areas is the main cause of water pollution and eutrophication of the Baltic Sea. A variety of remedial actions to reduce nitrogen and phosphorus losses from agricultural holdings and cultivated fields have been taken in the past. However, knowledge about the risk of nutrient leaching has not yet reached many farmers operating in the water catchment area of the Baltic Sea.

Methods

The nutrient balance method known as “At the farm gate” involves calculating separate balances for nitrogen (N), phosphorus (P) and potassium (K). After estimating all the components of the nutrient balance, the total balance for NPK is calculated and the data obtained is expressed as the ratio of total change (surplus) to the area of arable land on a farm. In addition, the nutrient usage efficiency on a farm is also calculated. An opinion poll was conducted in 2017 on 3.6% (n = 31) of the farms located in commune of Puck. The total area of the farms including arable and grass land ranged from 5 to 130 ha with an average of 45.82 ha. The arable land was on average 30.79 ha ranging from 4.45 to 130 ha while the grassland averaged 12.77 ha and ranged from 0 to 53 ha.

Results

The average consumption of mineral fertilizer in the sample population of farms was 114.9 kg N, 9.3 kg P, and 22.9 kg K·ha⁻¹of agricultural land (AL), respectively. N balance in the sample farms being ranged from −23.3 to 254.5 kg N·ha⁻¹AL while nutrient use efficiency ranged from 0.40% to 231.3%. In comparison, P surplus in the sample farms was 5.0 kg P·ha⁻¹AL with the P use efficiency of 0.4–266.5%.

Discussion

Mean N fertilizer consumption in the tested farms was higher than the average usage across Poland and in the Pomeranian Voivodeship. However, mean consumption of potassium fertilizers was lower than mentioned averages. Mean P fertilizer consumption was higher than in the Pomeranian Voivodeship, but lower compared to the entire country. Generally, on the basis of designated research indicators of farm pressures on water quality, concentrations of total nitrogen and total phosphorus were obtained. CalcGosPuck (an integrated agriculture calculator) will help to raise farmers’ awareness about NPK flow on farm scale and to improve nutrient management.

Sorbents can tailor nitrogen release from organic wastes to match the uptake capacity of crops

Delivering nutrients from mineral or organic fertilizers out of synchrony with crop uptake causes inefficiencies and pollution. We explore methodologies for evaluating sorbents as additives to organic agricultural wastes to retain nitrogen in an exchangeable form and deliver at rates that approximate the uptake capacity of roots. Focussing on ammonium (NH₄⁺) as the main inorganic nitrogen form in the studied wastes (sugarcane mill mud, poultry litter), we tested geo-sorbents and biochar for their ability to retain NH₄⁺. Sorption capacity was ranked palagonite < bentonite, biochar, vermiculite < chabazite, clinoptilolite (5.7 to 24.3 mg NH₄⁺ g^-1 sorbent). Sorbent-waste formulations were analysed for sorption capacity, leaching and fluxes of NH₄⁺. Ammonium-sorption capacity broadly translated to sorbent-waste formulations with clinoptilolite conferring the strongest NH₄⁺ attenuation (80%), and palagonite the lowest (7%). A 1:1 ratio of sorbent:waste achieved stronger sorption than a 0.5:1 ratio, and similar sorption as a 1:1.5 ratio. In line with these results, clinoptilolite-amended wastes had the lowest in situ NH₄⁺ fluxes, which exceeded the NH₄⁺ uptake capacity (I_max) of sugarcane and sorghum roots 9 to 84-fold, respectively. Less efficient sorbent-waste formulations and un-amended wastes exceeded I_max of crop roots up to 274-fold. Roots preferentially colonized stronger sorbent-waste formulations and avoided weaker ones, suggesting that lower NH₄⁺ fluxes generate a more favourable growth environment. This study contributes methodologies to identify suitable sorbents to formulate organic wastes as next-generation fertilizers with view of a crop's nutrient physiology. Efficient re-purposing of wastes can improve nutrient use efficiency in agriculture and support the circular nutrient economy.

Using microalgae in the circular economy to valorise anaerobic digestate: challenges and opportunities

Managing organic waste streams is a major challenge for the agricultural industry. Anaerobic digestion (AD) of organicwastes is a preferred option in the waste management hierarchy, as this processcangenerate renewableenergy, reduce emissions from wastestorage, andproduce fertiliser material.However, Nitrate Vulnerable Zone legislation and seasonal restrictions can limit the use of digestate on agricultural land. In this paper we demonstrate the potential of cultivating microalgae on digestate as a feedstock, either directlyafter dilution, or indirectlyfromeffluent remaining after biofertiliser extraction. Resultant microalgal biomass can then be used to produce livestock feed, biofuel or for higher value bio-products. The approach could mitigate for possible regional excesses, and substitute conventional high-impactproducts with bio-resources, enhancing sustainability withinacircular economy. Recycling nutrients from digestate with algal technology is at an early stage. We present and discuss challenges and opportunities associated with developing this new technology.

Stimulation of N2 O emission by manure application to agricultural soils may largely offset carbon benefits: a global meta-analysis

Animal manure application as organic fertilizer does not only sustain agricultural productivity and increase soil organic carbon (SOC) stocks, but also affects soil nitrogen cycling and nitrous oxide (N₂ O) emissions. However, given that the sign and magnitude of manure effects on soil N₂ O emissions is uncertain, the net climatic impact of manure application in arable land is unknown. Here, we performed a global meta-analysis using field experimental data published in peer-reviewed journals prior to December 2015. In this meta-analysis, we quantified the responses of N₂ O emissions to manure application relative to synthetic N fertilizer application from individual studies and analyzed manure characteristics, experimental duration, climate, and soil properties as explanatory factors. Manure application significantly increased N₂ O emissions by an average 32.7% (95% confidence interval: 5.1-58.2%) compared to application of synthetic N fertilizer alone. The significant stimulation of N₂ O emissions occurred following cattle and poultry manure applications, subsurface manure application, and raw manure application. Furthermore, the significant stimulatory effects on N₂ O emissions were also observed for warm temperate climate, acid soils (pH < 6.5), and soil texture classes of sandy loam and clay loam. Average direct N₂ O emission factors (EFs) of 1.87% and 0.24% were estimated for upland soils and rice paddy soils receiving manure application, respectively. Although manure application increased SOC stocks, our study suggested that the benefit of increasing SOC stocks as GHG sinks could be largely offset by stimulation of soil N₂ O emissions and aggravated by CH₄ emissions if, particularly for rice paddy soils, the stimulation of CH₄ emissions by manure application was taken into account.

Spatial assessment of soil nitrogen availability and varying effects of related main soil factors on soil available nitrogen

To effectively understand the availability of soil nitrogen and assist in soil nitrogen control at the regional scale, it is essential to understand the accurate spatial distribution patterns of the three soil nitrogen parameters [i.e., total nitrogen (TN), available nitrogen (AN) and nitrogen availability ratio (NAR)] and explore the spatially varying influences of major impact factors on soil AN. Land use affects the spatial distributions of soil TN, AN and NAR (i.e., AN/TN). To explore the effects of different land use types and improve mapping accuracy, residual kriging with land use information and ordinary kriging (without land use information) were compared based on the sample data of soil TN and AN in Hanchuan county, China. A local regression technique, geographically weighted regression (GWR), was adopted to explore the varying relationships between soil AN and its major impact factors in soil (i.e., soil TN and soil pH), due to the advantages of GWR over the traditional ordinary least squares regression (OLS) model. The results showed that (1) land use types as auxiliary information obviously improved the prediction accuracies of the three soil nitrogen parameters; (2) GWR performed much better than OLS in terms of fitting accuracy; and (3) GWR effectively revealed the spatially varying influences of the impact factors on soil AN, which were ignored by OLS. Based on the results, suggestions for soil nitrogen control measures in different subareas were proposed.

Nutrient Runoff Losses from Liquid Dairy Manure Applied with Low-Disturbance Methods

Manure applied to cropland is a source of phosphorus (P) and nitrogen (N) in surface runoff and can contribute to impairment of surface waters. Tillage immediately after application incorporates manure into the soil, which may reduce nutrient loss in runoff as well as N loss via NH volatilization. However, tillage also incorporates crop residue, which reduces surface cover and may increase erosion potential. We applied liquid dairy manure in a silage corn ( L.)-cereal rye ( L.) cover crop system in late October using methods designed to incorporate manure with minimal soil and residue disturbance. These include strip-till injection and tine aerator-band manure application, which were compared with standard broadcast application, either incorporated with a disk or left on the surface. Runoff was generated with a portable rainfall simulator (42 mm h for 30 min) three separate times: (i) 2 to 5 d after the October manure application, (ii) in early spring, and (iii) after tillage and planting. In the postmanure application runoff, the highest losses of total P and dissolved reactive P were from surface-applied manure. Dissolved P loss was reduced 98% by strip-till injection; this result was not statistically different from the no-manure control. Reductions from the aerator band method and disk incorporation were 53 and 80%, respectively. Total P losses followed a similar pattern, with 87% reduction from injected manure. Runoff losses of N had generally similar patterns to those of P. Losses of P and N were, in most cases, lower in the spring rain simulations with fewer significant treatment effects. Overall, results show that low-disturbance manure application methods can significantly reduce nutrient runoff losses compared with surface application while maintaining residue cover better than incorporation by tillage.

Best available technology for European livestock farms: Availability, effectiveness and uptake

Concerns over the negative environmental impact from livestock farming across Europe continue to make their mark resulting in new legislation and large research programs. However, despite a huge amount of published material and many available techniques, doubts over the success of national and European initiatives remain. Uptake of the more cost-effective and environmentally-friendly farming methods (such as dietary control, building design and good manure management) is already widespread but unlikely to be enough in itself to ensure that current environmental targets are fully met. Some of the abatement options available for intensive pig and poultry farming are brought together under the European IPPC/IED directive where they are listed as Best Available Techniques (BAT). This list is far from complete and other methods including many treatment options are currently excluded. However, the efficacies of many of the current BAT-listed options are modest, difficult to regulate and in some cases they may even be counterproductive with respect to other objectives ie pollution swapping. Evaluation of the existing and new BAT technologies is a key to a successful abatement of pollution from the sector and this in turn relies heavily on good measurement strategies. Consideration of the global effect of proposed techniques in the context of the whole farm will be essential for the development of a valid strategy.

Use of Zeolite with Alum and Polyaluminum Chloride Amendments to Mitigate Runoff Losses of Phosphorus, Nitrogen, and Suspended Solids from Agricultural Wastes Applied to Grassed Soils

Diffuse pollutant losses containing phosphorus (P), nitrogen (N), and suspended solids (SS) can occur when agricultural wastes are applied to soil. This study aimed to mitigate P, N, and SS losses in runoff from grassed soils, onto which three types of agricultural wastes (dairy slurry, pig slurry, and dairy-soiled water [DSW]), were applied by combining amendments of either zeolite and polyaluminum chloride (PAC) with dairy and pig slurries or zeolite and alum with DSW. Four treatments were investigated in rainfall simulation studies: (i) control soil, (ii) agricultural wastes, (iii) dairy and pig slurries amended with PAC and DSW amended with alum, and (iv) dairy and pig slurries amended with zeolite and PAC and DSW amended with zeolite and alum. Our data showed that combined amendments of zeolite and PAC applied to dairy and pig slurries reduced total P (TP) in runoff by 87 and 81%, respectively, compared with unamended slurries. A combined amendment of zeolite and alum applied to DSW reduced TP in runoff by 50% compared with unamended DSW. The corresponding reductions in total N (TN) were 56% for dairy slurry and 45% for both pig slurry and DSW. Use of combined amendments reduced SS in runoff by 73 and 44% for dairy and pig slurries and 25% for DSW compared with unamended controls, but these results were not significantly different from those using chemical amendments only. The findings of this study are that combined amendments of zeolite and either PAC or alum reduce TP and TN losses in runoff to a greater extent than the use of single PAC or alum amendments and are most effective when used with dairy slurry and pig slurry but less effective when used with DSW.

Spatiotemporal statistical modelling of long-term change in river nutrient concentrations in England & Wales

Concentrations of nutrient nitrogen (N) and phosphorus (P) are elevated in rivers across large areas of Europe (European Nitrogen Assessment (ENA), Sutton et al., 2011). Environmental policies have been implemented over the past 20 years with the aim of reducing nitrogen inputs to surface waters. However, environmental and ecological status is still below set targets (ENA, Sutton et al., 2011). Identification of patterns in long-term change for nutrient trends in hydrological catchments in England & Wales is required to assess impacts of nutrient management policy and provide better evidence for future policy. Such information could provide essential evidence for supporting policy by combining information from the wider catchment, rather than relying on the analysis of data from individual sites. Surface water quality is subject to considerable spatial and short-period temporal variability, reflecting variability in loading and dilution. This makes it difficult to determine temporal trends at individual monitoring sites with relatively sparse sampling. Here we apply spatiotemporal statistical additive models for both nitrogen and phosphorus in river networks across England & Wales to investigate the overall pattern of nutrient concentrations in these river surface waters over the past 20-40 years. Concentrations of Orthophosphate (OP) have generally decreased over time for many of the Large Hydrological Areas with a seasonal pattern highlighting one peak in the summer months. Over the past ten years, Total Oxidised Nitrogen (Nitrate+Nitrite, TON) concentrations have generally been slowly decreasing or fairly constant. However, prior to 2000, concentrations were generally on an upward trend. The seasonal pattern highlights one trough in the summer months. The highest levels for OP and TON broadly occur in the same general areas across England & Wales. On average, over time, the lowest values are evident in the north-west and south-west (particularly for OP) and highest values are evident in the Midlands, Anglian and Southern regions.

A Review of the Use of Organic Amendments and the Risk to Human Health

Historically, organic amendments—organic wastes—have been the main source of plant nutrients, especially N. Their use allows better management of often-finite resources to counter changes in soils that result from essential practices for crop production. Organic amendments provide macro- and micronutrients, including carbon for the restoration of soil physical and chemical properties. Challenges from the use of organic amendments arise from the presence of heavy metals and the inability to control the transformations required to convert the organic forms of N and P into the minerals available to crops, and particularly to minimize the losses of these nutrients in forms that may present a threat to human health. Animal manure and sewage biosolids, the organic amendments in greatest abundance, contain components that can be hazardous to human health, other animals and plants. Pathogens pose an immediate threat. Antibiotics, other pharmaceuticals and naturally produced hormones may pose a threat if they increase the number of zoonotic disease organisms that are resistant to multiple antimicrobial drugs or interfere with reproductive processes. Some approaches aimed at limiting N losses (e.g. covered liquid or slurry storage, rapid incorporation into the soil, timing applications to minimize delay before plant uptake) also tend to favor survival of pathogens. Risks to human health, through the food chain and drinking water, from the pathogens, antibiotics and hormonal substances that may be present in organic amendments can be reduced by treatment before land application, such as in the case of sewage biosolids. Other sources, such as livestock and poultry manures, are largely managed by ensuring that they are applied at the rate, time and place most appropriate to the crops and soils. A more holistic approach to management is required as intensification of agriculture increases.

Incidental phosphorus and nitrogen loss from grassland plots receiving chemically amended dairy cattle slurry

Chemical amendment of dairy cattle slurry has been shown to effectively reduce incidental phosphorus (P) losses in runoff; however, the effects of amendments on incidental nitrogen (N) losses are not as well documented. This study examined P and N losses in runoff during three simulated rainfall events 2, 10 and 28 days after a single application of unamended/chemically amended dairy cattle slurry. Twenty-five hydraulically isolated plots, each measuring 0.9 m by 0.4 m and instrumented with runoff collection channels, were randomly assigned the following treatments: (i) grass-only, (ii) slurry-only (the study-control), (iii) slurry amended with industrial grade liquid alum comprising 8% Al₂O₃, (iv) slurry amended with industrial grade liquid poly-aluminum chloride (PAC) comprising 10% Al₂O₃, and (v) slurry amended with lime. During the first rainfall event, lime was ineffective but alum and PAC effectively reduced dissolved reactive P (DRP) (by 95 and 98%, respectively) and total P (TP) flow-weighted-mean-concentrations (by 82 and 93%, respectively) in runoff compared to the study-control. However, flow-weighted-mean-concentrations of ammonium-N (NH₄--N) in runoff were increased with alum- (81%) and lime-treated (11%) slurry compared to the study-control whereas PAC reduced the NH₄--N by 82%. Amendments were not observed to have a significant effect on NO₃--N losses during this study. Slurry amendments reduced P losses for the duration of the study, whereas the effect of amendments on N losses was not significant following the first event. Antecedent volumetric water content of the soil or slope of the plots did not appear to affect runoff volume. However, runoff volumes (and consequently loads of P and N) were observed to increase for the chemically amended plots compared to the control and soil-only plots. This work highlights the importance of considering both P and N losses when implementing a specific nutrient mitigation measure.

A novel application of natural fluorescence to understand the sources and transport pathways of pollutants from livestock farming in small headwater catchments

This paper demonstrates the application of a low-cost and rapid natural fluorescence technique for tracing and quantifying the transport of pollutants from livestock farming through a small headwater catchment. Fluorescence intensities of Dissolved Organic Matter (DOM) present in different pollutant sources and drainage waters in the Den Brook catchment (Devon, UK) were monitored through storm events occurring between January 2007 and June 2008. Contrasting fluorescence signals from different sources confirmed the technique's usefulness as a tracer of pollutants from livestock farming. Changes in fluorescence intensities of drainage waters throughout storm events were used to assess the dynamics of key pollutant sources. The farmyard area of the catchment studied was shown to contribute polluted runoff at the onset of storm events in response to only small amounts of rain, when flows in the Den Brook first-order channel were low. The application of slurry to a field within the catchment did not elevate the fluorescence of drainage waters during storm events suggesting that when slurry is applied to undrained fields the fluorescent DOM may become quickly adsorbed onto soil particles and/or immobilised through bacterial breakdown. Fluorescence intensities of drainage waters were successfully combined with discharge data in a two component mixing model to estimate pollutant fluxes from key sources during the January 2007 storm event. The farmyard was shown to be the dominant source of tryptophan-like material, contributing 61-81% of the total event flux at the catchment outlet. High spatial and temporal resolution measurements of fluorescence, possibly using novel in-situ fluorimeters, may thus have great potential in quickly identifying and quantifying the presence, dynamics and sources of pollutants from livestock farming in catchments.

Integrated assessment of nitrogen losses from agriculture in EU-27 using MITERRA-EUROPE

The high N inputs to agricultural systems in many regions in 27 member states of the European Union (EU-27) result in N leaching to groundwater and surface water and emissions of ammonia (NH(3)), nitrous oxide (N(2)O), nitric oxide (NO), and dinitrogen (N(2)) to the atmosphere. Measures taken to decreasing these emissions often focus at one specific pollutant, but may have both antagonistic and synergistic effects on other N emissions. The model MITERRA-EUROPE was developed to assess the effects and interactions of policies and measures in agriculture on N losses and P balances at a regional level in EU-27. MITERRA-EUROPE is partly based on the existing models CAPRI and GAINS, supplemented with a N leaching module and a module with sets of measures. Calculations for the year 2000 show that denitrification is the largest N loss pathway in European agriculture (on average 44 kg N ha(-1) agricultural land), followed by NH(3) volatilization (17 kg N ha(-1)), N leaching (16 kg N ha(-1)) and emissions of N(2)O (2 kg N ha(-1)) and NO(X) (2 kg N ha(-1)). However, losses between regions in the EU-27 vary strongly. Some of the measures implemented to abate NH(3) emission may increase N(2)O emissions and N leaching. Balanced N fertilization has the potential of creating synergistic effects by simultaneously decreasing N leaching and NH(3) and N(2)O emissions. MITERRA-EUROPE is the first model that quantitatively assesses the possible synergistic and antagonistic effects of N emission abatement measures in a uniform way in EU-27.

Spatial and temporal variation of nitrogen exported by runoff from sandy agricultural soils

The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N (TKN), organic matter-associated N (OM-N), NO3(-)-N, and NH4(+)-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3(-)-N, and NH4(+)-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.

Nitrogen interception in floodwater of rice field in Taihu region of China

A field experiment located in Taihu Lake Basin of China was conducted, by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen (N) export in a typical rice field through "zero-drainage water management" combined with sound irrigation, rainfall forecasting and field drying. N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations, and subsequently tended to return to the background level. Before the first field drying, total particulate nitrogen (TPN) was the predominant N form in floodwater of plots with no N input, dissolved inorganic nitrogen (DIN) on plots that received urea only, and dissolved organic nitrogen (DON) on plots treated with the mixture of urea and manure. Thereafter TPN became the major form. No N export was found from the rice field, but total nitrogen (TN) of 15.8 kg/hm2 was remained, mainly due to soil N sorption. The results recommended the zero-drainage water management for full-scale areas for minimizing N export.

Validation of the exposure assessment for veterinary medicinal products

Under the EU Directive 2004/28/EC, an environmental risk assessment of new veterinary medicinal products is required. Given the nature of risk assessment for new applications, there is a need to model exposure concentrations. Critical evaluations are essential to ensure that the use of models by regulators does not result in the propagation of misleading information. The empirical validations of soil exposure models, previously discussed in this journal, indicate that it is impossible to analyse the contribution of every model parameter to the variability in the predictions. In particular, the prediction of the slurry concentration is challenged by uncertainties concerning dilution, mixing and dissipation of residues. Surface water and groundwater models generated highly deviating results compared to the field results, questioning the usefulness of the available screening models. Animal husbandry, slurry handling and environmental conditions throughout Europe are considered in order to define realistic worst case scenarios, to be used in conjunction with distribution models for the environmental risk assessment of veterinary medicinal products at registration. Given the variability in manure management practice throughout Europe, a deterministic approach for the manure-to-soil model was selected. Both worst case and best case scenario were developed. Several modelling assumptions applied in the surface water exposure model for fish nursery effluent were validated against newly available data. Since the available data give no proof that a settling tank contributes to the removal of pesticides from waste water, it is recommended for risk assessment purposes to consider the contribution of the settling tank to removal of pesticides and medicines to be negligible. Surface water dilution factors may be considered to be rather small, a factor of 2, for low flow situations.

Long-term effects of sustained beef feedlot manure application on soil nutrients, corn silage yield, and nutrient uptake

A field study was initiated in 1992 to investigate the long-term impacts of beef feedlot manure application (composted and uncomposted) on nutrient accumulation and movement in soil, corn silage yield, and nutrient uptake. Two application strategies were compared: providing the annual crop nitrogen (N) requirement (N-based rate) or crop phosphorus (P) removal (P-based rate), as well as a comparison to inorganic fertilizer. Additionally, effects of a winter cover crop were evaluated. Irrigated corn (Zea mays L.) was produced annually from 1993 through 2002. Average silage yield and crop nutrient removal were highest with N-based manure treatments, intermediate with P-based manure treatments, and least with inorganic N fertilizer. Use of a winter cover crop resulted in silage yield reductions in four of ten years, most likely due to soil moisture depletion in the spring by the cover crop. However, the cover crop did significantly reduce NO3-N accumulation in the shallow vadose zone, particularly in latter years of the study. The composted manure N-based treatment resulted in significantly greater soil profile NO3-N concentration and higher soil P concentration near the soil surface. The accounting procedure used to calculate N-based treatment application rates resulted in acceptable soil profile NO3-N concentrations over the short term. While repeated annual manure application to supply the total crop N requirement may be acceptable for this soil for several years, sustained application over many years carries the risk of unacceptable soil P concentrations.

Irrigated mountain meadow fertilizer application timing effects on overland flow water quality

Nonpoint-source pollution from agricultural activities is currently the leading cause of degradation of waterways in the United States. Applying best management practices to flood-irrigated mountain meadows may improve agricultural runoff and return flow water quality. Prior research has focused on fertilizer use for increased hay yields, while few studies have investigated the environmental implications of this practice. We examined the effects of fertilizer application timing on overland flow water quality from an irrigated mountain meadow near Gunnison, Colorado. Application of 40 kg phosphorus (P) and 19 kg nitrogen (N) ha(-1) using monoammonium phosphate (11-52-0, N-P-K) fertilizer to plots in the fall significantly reduced concentrations of reactive P and ammonium N in irrigation overland flow compared with early or late spring fertilization. Reactive P loading was 9 to almost 16 times greater when fertilizer was applied in the early or late spring, respectively, compared with in the fall. Ammonium N followed a similar trend with early spring loading more than 18 times greater and late spring loading more than 34 times greater than loads from fall-fertilized plots. Losses of 45% of the applied P and more than 17% of the N were measured in runoff when fertilizer was applied in the late spring. These results, coupled with those from previous studies, suggest that mountain meadow hay producers should apply fertilizer in the fall, especially P-based fertilizers, to improve hay yields, avoid economic losses from loss of applied fertilizers, and reduce the potential for impacts to water quality.

Agricultural nutrient inputs to rivers and groundwaters in the UK: policy, environmental management and research needs

Losses of nitrogen (N) and phosphorus (P) in land run-off and drainage from agricultural land can impair river water quality and may pose a potential health hazard. Losses of P are up to an order of magnitude smaller than those of N, but may be more significant with respect to freshwater eutrophication. At the field scale, research suggests that rates of nutrient loss are sensitive to both nutrient and land management, in particular, where nutrient inputs continuously exceed production requirements and where farming methods increase land vulnerability to run-off and erosion. A clear distinction can be made between N and P in the timescales over which inputs of these nutrients are buffered by terrestrial ecosystems against loss, which has implications for control strategies. At the river basin scale, any targets for reducing nutrient loss are best guided by site-specific information on their likely ecological impact, but this information rarely exists for UK rivers affected by eutrophication, and only general guidelines are available. True management of the environment requires integrated approaches which include both N and P taking account of differences in their source areas and delivery mechanisms, the vulnerability of land use and adoption of safe management options in relation to landscape characteristics and the sensitivity of the watercourse along its reach. For P, the identification of vulnerable zones represents a step forward to the management of the river basin in smaller definable units, which can provide a focus for safe management practices. This requires a better understanding of the linkages between nutrient sources, transport and impacts and is considered an urgent research priority.

Nutrient losses by surface run-off following the application of organic manures to arable land. 2. Phosphorus

Phosphorus (P) surface run-off losses were studied following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farm yard manure (FYM) and inorganic nitrogen (N) and P fertiliser were compared, over a 4-year period (1993-97). N losses from the same studies are reported in a separate paper. The application of cattle FYM and, especially slurry, to the silty clay loam soil increased both particulate and soluble P loss in surface water flow. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increased application of slurry solids increased all forms of P loss via surface run-off; the results suggested that a threshold for greatly increased risk of P losses via this route, as for N, occurred at ca. 2.5-3.0 t/ha solids loading. This approximates to the 50 m3/ha application rate limit suggested for slurry within UK 'good agricultural practice'. The studies also provided circumstantial evidence of the sealing of the soil surface by slurry solids as the major mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Losses of total and soluble P, recorded for each of the 4 years of experiments, reached a maximum of only up to 2 kg/ha total P (TP), even after slurry applications initiating run-off. Whilst these losses are insignificant in agronomic terms, peak concentrations of P (up to 30,000 micrograms/l TP) in surface water during a run-off event, could be of considerable concern in sensitive catchments. Losses of slurry P via surface run-off could make a significant contribution to accelerated eutrophication on entry to enclosed waters, particularly when combined with high concentrations of NO3(-)-N. Restricting slurry application rates to those consistent with good agronomic practice, and within the limits specified in existing guidelines on good agricultural practice, offers the simplest and most effective control measure against this potentially important source of diffuse pollution.