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Modelling Nitrogen Losses from Sheep Grazing Systems with Different Spatial Distributions of Excreta

Author

Listed:
  • Matthew J. Bell

    () (Melbourne School of Land and Environment, University of Melbourne, Vic. 3010, Australia)

  • Brendan R. Cullen

    () (Melbourne School of Land and Environment, University of Melbourne, Vic. 3010, Australia)

  • Ian R. Johnson

    () (Melbourne School of Land and Environment, University of Melbourne, Vic. 3010, Australia)

  • Richard J. Eckard

    () (Melbourne School of Land and Environment, University of Melbourne, Vic. 3010, Australia)

Abstract

The aim of this study was to assess the effect that the randomised versus even distribution of excreta (dung and urine) may have on modelling nitrogen (N) losses by leaching, volatilisation and denitrification from a grazing system. A range of stock densities (from 200 to 2000 sheep/ha, equivalent to an annual stocking rate of 3 to 33 dry sheep equivalent (DSE)/ha respectively) were simulated to represent an increasing application of N excreta to a grazed 1 hectare area either distributed randomly or uniformly. This study found that the proportion of annual N inputs lost by denitrification were significantly lower and leaching N losses were higher at high stocking densities compared to if excreta was distributed uniformly. The results of this study indicate that N losses from a sheep grazing system could be adequately modelled assuming uniform distribution of excreta at stocking densities up to 1200 sheep/ha (equivalent to an annual stocking rate of 20 DSE/ha). But at higher stock densities, when N loads are high, the spatial distribution of excreta is important and models need to explicitly deal with the distribution of dung and urine N returns.

Suggested Citation

  • Matthew J. Bell & Brendan R. Cullen & Ian R. Johnson & Richard J. Eckard, 2012. "Modelling Nitrogen Losses from Sheep Grazing Systems with Different Spatial Distributions of Excreta," Agriculture, MDPI, Open Access Journal, vol. 2(4), pages 1-13, September.
  • Handle: RePEc:gam:jagris:v:2:y:2012:i:4:p:282-294:d:20287
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    References listed on IDEAS

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    1. anonymous, 1990. "Agriculture: bank lending," Cross Sections, Federal Reserve Bank of Richmond, issue fall, pages 1-15.
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    More about this item

    Keywords

    distribution; excreta; grazing system; modelling; nitrogen losses;

    JEL classification:

    • Q1 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture
    • Q10 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - General
    • Q11 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Aggregate Supply and Demand Analysis; Prices
    • Q12 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets
    • Q13 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Agricultural Markets and Marketing; Cooperatives; Agribusiness
    • Q14 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Agricultural Finance
    • Q15 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Land Ownership and Tenure; Land Reform; Land Use; Irrigation; Agriculture and Environment
    • Q16 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - R&D; Agricultural Technology; Biofuels; Agricultural Extension Services
    • Q17 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Agriculture in International Trade
    • Q18 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Agriculture - - - Agricultural Policy; Food Policy

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