NGAUGE: A decision support system to optimise N fertilisation of British grassland for economic and environmental goals
ABSTRACT The poor efficiency with which nitrogen (N) is often used on grassland farms is well documented, as are the potential consequences of undesirable emissions of nitrogen. As fertiliser represents a major input of nitrogen to such systems, its improved management has good potential for increasing the efficiency of nitrogen use and enhancing environmental and economic performance. This paper describes the development, structure and potential application of a new decision support system for fertiliser management for British grassland. The underlying empirically-based model simulates monthly nitrogen flows within and between the main components of the livestock production system according to user inputs describing site conditions and farm management characteristics. The user-friendly decision support system (‘NGAUGE’) has a user interface that was produced in collaboration with livestock farmers to ensure availability of all required inputs. NGAUGE is an improvement on existing nitrogen fertiliser recommendation systems in that it relates production to environmental impact and is therefore potentially valuable to policy makers and researchers for identifying pollution mitigation strategies and blueprints for novel, more sustainable systems of livestock production. One possible application is the simulation of the phenomenon of pollution swapping, whereby, for example, the adoption of strategies for the reduction of nitrate leaching may exacerbate emissions of ammonia and nitrous oxide. Outputs of the decision support system include a field- and target-specific N fertiliser recommendation together with farm- and field-based N budgets, comprising amounts of N in both production and loss components of the system. Recommendations may be updated on a monthly basis to take account of deviations of weather conditions from the 30-year mean. The optimisation procedure within NGAUGE enables user-specified targets of herbage production, N loss or fertiliser use to be achieved while maximising efficiency of N use. Examples of model output for a typical grassland management scenario demonstrate the effect on model predictions of site and management properties such as soil texture, weather zone, grazing and manure applications. Depending on existing management and site characteristics, simulations with NGAUGE suggest that it is possible to reduce nitrate leaching by up to 46% (compared with a fertiliser distribution from existing fertiliser recommendations), and fertiliser by 33%, without sacrificing herbage yield. The greatest improvements in efficiency are possible on sandy-textured soils, with moderate N inputs.
- SourceAvailable from: Anita Shepherd CBiol. AFRSPSoc
Conference Paper: Learning how to model ecosystem trade-offs at the farm scale[Show abstract] [Hide abstract]
ABSTRACT: The ecosystem service framework provides a forum for scientists from a range of disciplines to communicate and work together alongside other key stakeholders. However to be effective, place-based comparison of the tradeoffs of ecosystem services need further development. These place-based comparisons are vital in agricultural systems due to the increasing global demand for food production, coupled with the realization that this should be achieved with minimal negative impact on the environment. The farm is the logical unit of management in agricultural systems and hence there is a need for ecosystem tradeoff assessments at the farm scale. We have carried out a literature review of the tradeoffs in the delivery of ecosystem services from intensively managed temperate grassland systems. Building on this work, we are now setting up a farm scale experiment to examine the tradeoffs, identified from the refereed literature, as requiring further investigation due to either limited or conflicting evidence. To facilitate an improved understanding of these tradeoffs we need to learn how to model them, based on previous and current modelling frameworks and coupled with improved knowledge of international best practice. Fundamentally, this requires a dialogue between modellers and field scientists.International Congress on Environmental Modelling and Software, Ottawa 2010; 01/2010
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ABSTRACT: As much as 60% of the nitrate in water in England is thought to derive from agriculture. Legislation aims to improve water quality by limiting nitrate concentration in surface and groundwaters to 50 mg l(-1). The UK Government responded to the requirements of the EC Nitrate Directive by delineating Nitrate Vulnerable Zones (NVZs) to cover 55% of England in 2002 and increased it to 70% in 2009. In this study we assessed the cost-effectiveness of measures for implementation in livestock systems to mitigate nitrate leaching in the UK. These estimates were prepared for a range of hypothetical farms representative of typical dairy, beef and sheep farms at different locations in England and Wales and for a list of mitigation measures identified to reduce leaching. The NGAUGE and NFixCycle models were used to estimate leaching from these systems. The costs of implementation of the mitigation measures were also assessed in order to evaluate the cost-effectiveness of these measures. In general, the most effective measures to reduce leaching for all systems were the ones that involved a reduction in stocking rates and grazing time, followed by those involving improvements in fertiliser and crop management. Only in the case of the dairy system was effectiveness affected by location of the farm. The costs for implementation in the sheep system were relatively low compared with beef and dairy systems. Implementation of some of the measures with high cost-effectiveness would need to be incentivised financially or with legislation due to the high costs involved.Science of The Total Environment 02/2011; 409(6):1104-15. · 3.26 Impact Factor
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ABSTRACT: The grazing management of grassland has a direct effect on nitrogen (N) recycling. This is an important reason why management has become an alternative to improve the grassland production and quality, in turn to make it more suitable for the environment. However, the livestock system intensification induces changes in the natural dynamics of the N cycle, accelerating gas emmisions (e.g. ammonia, NH3 and nitrous oxide, N20) and leaching losses from soil under grazing. When the amount of N in the environment increases, there is an impact on smog episodes, global warming, stratospheric ozone depletion, acid rain and eutrophication of fresh water. There are different techniques to evaluate the gases emitted from the soil. This klonowledge is useful to design the strategies to reduce the negative consequences of theses gases on the environment. In this review, the effect of grazing managements on N gas emissions from soils and the current techniques for N gas emission measurements in the field and laboratories conditions are discussed.Revista de la Ciencia del Suelo y Nutricion Vegetal 12/2006; 7(3):61-99.