Using gypsum to reduce phosphorus in runoff from subcatchments in South Australia
Date
2005
Authors
Cox, J.
Varcoe, J.
Chittleborough, D.
van Leeuwen, J.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Journal of Environmental Quality, 2005; 34(6):2118-2128
Statement of Responsibility
J. W. Cox, J. Varcoe, D. J. Chittleborough and J. van Leeuwen
Conference Name
Abstract
Received for publication January 15, 2005. Concentrations of phosphorus (P) in runoff from agricultural catchments in southern Australia are high and well above national and international limits. Phosphorus was found to exit two subcatchments of 3.6 and 4.2 ha in the Adelaide hills via both overland flow and interflow. The subcatchments had texture-contrast soils with high inputs of superphosphate and were openly grazed by cattle all year. Interflow at the boundary of the B and C soil horizons accounted for as much as half the total water flow that was measured (overland flow, A–B interflow, and B–C interflow). The average flow-weighted concentration of total P within overland flow was as high as 0.25 mg L–1, and 0.05 mg L–1 in B–C interflow. In most years P loss was in the dissolved (<0.45 µm) form. In some years, interflow was the major pathway for P loss off these catchments. The B–C interflow cannot be discounted when searching for management options to reduce P loss from texture-contrast soils to waterways. Preliminary laboratory experiments showed promise that gypsum could modify agricultural soils and reduce the concentrations of P (and dissolved organic C) in runoff before it enters public water supply reservoirs. In this study, gypsum, applied at a rate of 15 Mg ha–1 to the 4.2-ha subcatchment, substantially modified the soil chemistry, and thereby soil structure. The size and stability of structural aggregates increased markedly and this change affected not only the A but also the upper B horizons, to a profile depth of approximately 50 cm. However, the impact of these physicochemical changes on P concentrations in runoff was not marked. Average profile P concentrations were only slightly lower in the runoff from the subcatchment following treatment. The high subsoil macroporosity of the gypsum-treated subcatchment caused an increase in the proportion of runoff by interflow.
School/Discipline
Dissertation Note
Provenance
Description
Copyright © 2005 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
Access Status
Rights
Copyright status unknown