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Observations of the inadequacy of existing tools and approaches to address these challenges provided the motivation for the Environmental Virtual Observatory pilot (EVOp), an innovation from the UK Natural Environment Research Council (NERC). The EVOp is currently exploring the use of a cloud-based infrastructure in catchment science by developing an exemplar to explore N and P fluxes to inland and coastal waters in the UK from catchment to national scale. The objective for this exemplar is to demonstrate the ways in which ensemble modelling of the major nutrient cycles, together with scenario analysis and prediction within an uncertainty framework at various scales, supported by a cloud environment, may be used to address a range of research questions pertinent to environmental policy in the UK.
2. Materials & Methods The export coefficient model (Johnes, 1996), adapted to function on a geoclimatic basis (e.g. Johnes and Butterfield, 2002), and using a range of high resolution, geo-referenced digital datasets within a cloud environment comprises initial demonstration of the capabilities of N and P flux modelling in the EVOp. Geoclimatic regions, landscape units displaying homogenous or quasi-homogenous functional behaviour in terms of process controls on N and P cycling, are key to this approach; ten regions have been defined across the UK using GIS manipulation of spatial data describing hydrogeology, runoff, topographical slope and soil parent material. The export coefficient model operates within a regional framework, providing mapped, tabulated and statistical outputs at various UK Government reporting scales: river catchment, WFD RBD, coastal drainage and OSPAR zone.
Model estimations are assessed against national monitoring data for the UK.
3. Results & Discussion Model outputs demonstrate significant patterns in N and P flux to waters at differing scales and generated a range of summary statistics. Moreover, model uncertainty varies across space. These results can be used to further explore the primary drivers for spatial variation and identify waterbodies at risk, especially in unmonitored catchments. The technical and computational support of a cloud-based infrastructure also facilitates scenario analysis exploring potential water quality impacts of future mitigation strategies. Current research involves derivation of a regional framework to support a fully coupled N/P and hydrological modelling.
Nitrogen Workshop 2012
4. Conclusion The use of cloud-based modelling to integrate national datasets and mathematical models has provided new information on variations in N and P fluxes across the UK at various scales.
Furthermore, improved access to data and models for use by catchment managers and policy makers prioritises the advancement of effective catchment science.
References Johnes, P.J. 1996. Evaluation and management of the impact of land use change on the nitrogen and phosphorus load delivered to surface waters: the export coefficient modelling approach. Journal of Hydrology 183(3-4): 323-349.
Johnes, P.J. and Butterfield, D. 2002. Landscape regional and global estimates of nitrogen flux from land to ocean:
errors and uncertainties. Biogeochemistry 57 ⁄ 58, 429-47
Sims, J.T., Bergström, L., Bowman, B.T. and Oenema, O. 2005. Nutrient management for intensive animal agriculture:
Policies and practices for sustainability, Soil Use and Management 21(Suppl.): 141-151.
Vitousek P.M., Naylor R., Crews T., David, M.B., Drinkwater L.E., Holland, E., Johnes, P.J., Katzenberger, J., Martinelli, L. A., Matson, P.A., Nziguheba,G., Ojima, D., Palm, C. A., Robertson, G.P., Sanchez, P. A., Townsend, A.R. and Zhang, F.S. 2009. Nutrient imbalances in agricultural development. Science 324, 1519-1520
Nitrogen Workshop 2012
The use of Integrated Constructed Wetlands (ICW) in the management of nitrogen (N) enriched effluents.
Harrington, R.a, Carroll, P.a, McInnes, R.b, Everard,M.c, Harrington, C.d, e a Waterford County Council, Adamstown, Waterford, Ireland b RM Wetlands & Environment Ltd, 6 Ladman Villas, Littleworth, Faringdon, Oxfordshire, SN7 8EQ, UK c M.Everard, Evidence Directorate, Environment Agency, Horizon House, Deanery Road, Bristol BS1 5AH d Institute for Infrastructure and Environment, School of Engineering, The University of Edinburgh, William Rankine Building, The King’s Buildings, Edinburgh EH9 3JL, Scotland, United Kingdom e Teagasc, Johnstown Castle Research Centre, County Wexford, Ireland
AbstractAir, water and soil are inextricably linked through biogeochemical processes evolved over
3.8 billion years (Paul, 2007). The interfaces whereby these processes occur are various and there is increasing evidence to suggest that wetland ecosystems, especially those that support dense helophytic vegetation are particularly capable of supporting these processing capacities (van der valk, 2007). Over the past 15 years and building on earlier efforts in riparian restoration ecology, the capacity of shallow helophytic wetlands has become better understood and applied to a range of nutrient enriched effluent streams including amongst others, that of farmyard and municipal wastewater (Harrington and McInnes, 2009;
Harrington and Scholz, 2010). Originating from its basis in restoration ecology, the approach taken has been one that has focused on overall ecosystem function and consequently incorporated an understanding of the need to explicitly integrate water management with that of biodiversity and landscape-fit/aesthetic needs and is now known as the Integrated Constructed Wetland (ICW) concept (Harrington and Ryder, 2002; Harrington and Scholz, 2007). The capacity of these systems to manage water vectored nitrogen (N) in a manner that is socially, economically and environmentally coherent is presented. Emphasis is placed upon distinguishing between the accumulating recyclable organic-bound N in the detritus and necromass, and that in solution, which is denitrified at each stage from the through- flowing water in multi-cell ICW systems. Emphasis is placed upon understanding and mitigating any potential untoward environmental impacts while simultaneously facilitating efficient agricultural practice. The capacities of ICW-type wetlands to manage various types of watervectored animal wastes are also presented. Furthermore, the wider benefits derived from the placement of ICW infrastructure in the rural landscape are presented, particularly those that might be brought into the mainstream of water, land and biodiversity management and that are especially relevant to the management of N.
References Harrington, C. and Scholz, M. 2010. Assessment of pre-digested piggery wastewater treatment operations with surface flow integrated constructed wetland systems. Bioresource Technology 101(20), 7713-7723.
Harrington, R. and McInnes, R. 2009. Integrated Constructed Wetlands (ICW) for livestock wastewater management. Bioresource Technology 100(22), 5498-5505.
Paul E.A. 2007. Soil microbiology and biochemistry (3rd edition), Oxford, United Kingdom.
Van der Valt, A.G. 2006. The Biology of Freshwater Wetlands. Oxford University Press, Oxford.
Harrington, R. and Ryder, C. 2002. The use of integrated constructed wetlands in the management of farmyard
runoff and waste water. In “Proceedings of the National Hydrology Seminar on Water Resource Management:
Sustainable Supply and Demand”, The Irish National Committees of the International Hydrological Programme and International Commission on Irrigation and Drainage, Tullamore, Offaly, pages 55-63.
Tools to improve N cycle models Betteridge, K., Li, F.Y., Costall, D.C.
AgResearch Grasslands, Private Bag 11008, Palmerston North, New Zealand
1. Background & Objectives Return of urinary nitrogen (N) to grazed pastures predominates over faecal N return by a factor of about 2. While recent N models recognise that urinary N return is heterogeneous, few if any acknowledge the temporal variability in urinary N concentration (UN) and urine volume (UV) from individual cows or variability amongst cows grazing the same pasture. We hypothesise that urination events with large volumes or high urinary N concentrations will have a disproportionately high risk of N leaching due to the non-linear relationship between N load and N leaching. The purpose of our research is to develop a framework that handles spatio-temporal variability in urinary output by grazing cattle to predict potential errors of modelling without this variability. We also report on a new urine sensor for grazing cows that estimates urine volume and urinary N concentration of each urination event. With a GPS, the location of these urine patches can be used to determine the consequence of strongly skewed urine return by cattle to campsites, especially in hill pastures, on N leaching and nitrous oxide emissions. This work will assist us to develop efficient targeted N loss mitigation strategies.
2. Methods and Materials We developed a framework to estimate N leaching where effects of variations in Uv and UN on N load in urine patches as well as the proportion of the paddock area affected by urine can be estimated. Two contrasting pumice soils from the Lake Taupo catchment, New Zealand, were used for this study and ryegrass/white clover pastures were rotationally grazed 9 times/yr to a residual stubble of 1250 kg DM/ha. Weather data (1975-2005) from the north Taupo region (-38.525S,
175.825E) were obtained from interpolated virtual climate station data. Mean annual rainfall is 1484 mm and mean temperature 11.6˚C. Urine data used in this study were taken from Betteridge et al., (1986) who measured UN and estimated UV of each urination event of two steers over three 24 h periods. Urination frequency ranged between 13 and 73 events/day, UV from 7.6 to 51.2 L/day and UN ranged between 0.8 to 14.1 mg N/L. These data were used to develop probability density curves that are described by lognormal functions for both UN and UV. We modelled situations where UV and UN varied; and where UV or UN alone was varied with the other parameter held constant. For comparison, estimated N leaching from a base-line scenario using an average UN of 7.5 g N/L and average UV of 2.5 L was also determined. APSIM 7.3 (Keating et al., 2003) was used to estimate N leaching. This involves AgPasture to simulate pasture growth and N uptake, SurfaceOM to simulate residue decomposition at the soil surface, SoilN2 to simulate soil carbon-nitrogen dynamics, and SWIM2. All modules, with the exception of SWIM2, perform the calculations on a daily time-step, so as to simulate the fast infiltration of urine after deposition. We also developed a module to add urine within the soil profile to a given depth in a wetted soil volume shaped as an inverted cone.
Using this framework and N leaching curves in response to N load, we estimate the N leaching losses at the patch level and then up-scaled the estimates to the paddock level. Effects of variations in the N load and urine patch area on N leaching are evaluated by comparing the estimates using variable urine patches with the base-line scenario. In all simulations the amount of urine-N returned each year was held constant with grazing intensity varied ensure this. Sensitivities of N leaching to varying UV or UN were assessed by varying either UV or its UN separately in the analysis.
Nitrogen Workshop 2012
Novel urine sensor This sensor fits to the rear of a cow to estimate UN and UV of each urination event. UV is estimated by integrating pressure head over time within a slotted chamber through which urine passes to the ground. Refractive index of the urine, that we calibrate against urea-N and glycine in artificial urine, is determined at the base of this chamber. A ZigBee radio transmitter system and four ZigBee nodes around the perimeter of the paddock determines the position of each urination event within the paddock. Real time transmission of urine and position data to a base computer is possible.
3. Results & Discussion We found that for the same amount of urinary N deposited and the same number of urination events per year, N leaching losses at paddock scale were 7.6% and 4.7% higher where UV and UN varied as opposed to where average UV and UN values were used, for the two pumice soils. This finding probably reflects the substantially higher N loss as UN increases, as occurs with early morning urination events, compared to a low loss from dilute urine that is often passed in the afternoon (Betteridge et al., 1986). At the paddock scale, N leaching increased logarithmically with increased average UV or UN, whereas at the patch level N leaching increased exponentially with N deposition rate. Where average UV was held constant but UN varied, estimated N leaching was higher than where UN was constant while UV varied. Leaching loss was highly sensitive to UV when UN was constant such that by halving volume from 2.5 L to 1.25 L/event leaching was reduced by an average 16% in the two soils. Halving UN while UV was held constant resulted in an even larger leaching reduction of 25% across these soils. Thus salt, given cattle as a diuretic, will increase urination frequency and possibly lower UV, and will reduce UN to substantially reduce N leaching.
Our findings support the need to have a better understanding of UV and UN of individual urination events to more accurately estimate N emissions to the environment. Our urine sensor is capable of measuring these parameters in grazing cows and will enable urine patches of known urine characteristics to be quickly located and used for N emission studies. The combination of the framework model and urine sensor will greatly assist in evaluating mitigation strategies that are expressed through changed urination characteristics. Initial data from one cow over 4 days shows a coefficient of variation for volume of 36% and for urinary nitrogen concentration of 28% amongst individual urination events.
4. Conclusion The framework model demonstrated that estimated N leaching was more sensitive to changing UN than to changing UV at the patch level whereas at the paddock level, the effects of urine volume and N concentration were more similar. Mitigation strategies that result in urination events that are more frequent, of lower concentration or lower volume will reduce N losses to the environment. Salt fed as a diuretic is one such strategy that may provide these criteria.