Modelling Nitrogen Losses from Sheep Grazing Systems with Different Spatial Distributions of ExcretaReport as inadecuate




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





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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. View Full-Text

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





Author: Matthew J. Bell * , Brendan R. Cullen, Ian R. Johnson and Richard J. Eckard

Source: http://mdpi.com/



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