Loss of phosphorus and nitrogen in runoff and subsurface drainage from high and low input pastures grazed by sheep in southern Australia

Melland, A. R. and McCaskill, M. R. and White, R. E. and Chapman, D. F. (2008) Loss of phosphorus and nitrogen in runoff and subsurface drainage from high and low input pastures grazed by sheep in southern Australia. Australian Journal of Soil Research , 46 (2). pp. 161-172. ISSN 0004-9573

Abstract

High rates of fertiliser applied to boost pasture growth in the southern Australian sheep industry may lead to
eutrophication of waterways and groundwater degradation. A field study was used to investigate whether higher fertiliser and stocking rates would increase nutrient loss in runoff and subsurface flow from pastures. Phosphorus (P) and nitrogen (N) concentrations in surface and subsurface flow were measured from 1998–2000 in four 0.5-ha hillslope plots. Surface flow volume was measured directly and subsurface water flux was estimated using soil moisture data and a water balance model. A simulated rainfall study was also conducted using 0.64-m2 plots. The treatments represented were: a low-P setstocked sown pasture (SS low P), a high-P set-stocked sown pasture (SS high P), a high-P sown pasture in a 4-paddock rotation (RG 4-pdk), and an unsown set-stocked pasture (Low P volunteer). No runoff from the hillslope occurred in 1999, while the volume of runoff in 1998 and 2000 varied from 0.1 to 68 mm/year across the 4 hillslope plots. More P was lost via surface runoff (up to 0.25 kg P/ha.year) than subsurface flow
(up to 0.027 kg P/ha.year). However, N loads were greater in subsurface flows (3.2–10.6 kg N/ha.year) than surface runoff (0.04–2.74 kg N/ha.year). Phosphorus concentrations were higher in runoff from the high P treatments (0.34–0.83 mg P/L) than the set-stocked low P treatment (0.19–0.22 mg P/L). Higher TP concentrations in runoff from the high P
treatments were associated with greater labile P contents in the soil, dung, and herbage. However, the volume of runoff, rather than the pasture treatment, was the primary determinant of nutrient loss. Avoiding high nutrient inputs in seasonally waterlogged areas, sowing perennial pastures, and minimising stock camping helps minimise P losses to waterways and N losses to groundwater.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © CSIRO 2008. Permanent restricted access to published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Date Deposited: 15 Aug 2014 05:26
Last Modified: 29 Aug 2014 02:43
Uncontrolled Keywords: fertiliser; water quality; nutrient loads; soil fertility; hillslope hydrology
Fields of Research : 04 Earth Sciences > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology
07 Agricultural and Veterinary Sciences > 0799 Other Agricultural and Veterinary Sciences > 079902 Fertilisers and Agrochemicals (incl. Application)
05 Environmental Sciences > 0503 Soil Sciences > 050302 Land Capability and Soil Degradation
Socio-Economic Objective: D Environment > 96 Environment > 9614 Soils > 961402 Farmland, Arable Cropland and Permanent Cropland Soils
Identification Number or DOI: 10.1071/SR07084
URI: http://eprints.usq.edu.au/id/eprint/25775

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