Modelling soil phosphorus decline: expectations of Water Framework Directive policies

Schulte, R. P. O. and Melland, A. R. and Fenton, O. and Herlihy, M. and Richards, K. and Jordan, P. (2010) Modelling soil phosphorus decline: expectations of Water Framework Directive policies. Environmental Science and Policy, 13 (6). pp. 472-484. ISSN 1462-9011


Depletion of plant-available soil phosphorus (P) from excessive to agronomically optimum levels is a measure being implemented in Ireland to reduce the risk of diffuse P transfer from land to water. Within the Nitrates and Water Framework Directive regulations the policy tool is designed to help achieve good status by 2015 in water bodies at risk from eutrophication. To guide expectation, this study used soil plot data from eight common soil associations to develop a model of Soil Test P (STP) (Morgan's extract) decline following periods of zero P amendment. This was used to predict the time required to move from excessive (Index 4) to the upper boundary of the optimum (Index 3) soil P concentration range. The relative P balance (P balance: Total soil P) best described an exponential decline (R 2=63%) of STP according to a backwards step-wise regression of a range of soil parameters. Using annual field P balance scenarios (-30kgPha -1, -15kgPha -1, -7kgPha -1), average time to the optimum soil P boundary condition was estimated from a range of realistic Total P and STP starting points. For worst case scenarios of high Total P and STP starting points, average time to the boundary was estimated at 7-15 years depending on the field P balance. However, uncertainty analysis of the regression parameter showed that variation can be from 3 to >20 years. Combined with variation in how soil P source changes translate to resulting P delivery to water bodies, water policy regulators are advised to note this inherent uncertainty from P source to receptor with regard to expectations of Water Framework Directive water quality targets and deadlines.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © 2010 Elsevier Ltd. 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: 18 Aug 2014 04:30
Last Modified: 25 Aug 2014 05:32
Uncontrolled Keywords: phosphorus; soil; Water Framework Directive
Fields of Research : 05 Environmental Sciences > 0503 Soil Sciences > 050304 Soil Chemistry (excl. Carbon Sequestration Science)
16 Studies in Human Society > 1605 Policy and Administration > 160507 Environment Policy
05 Environmental Sciences > 0503 Soil Sciences > 050302 Land Capability and Soil Degradation
Socio-Economic Objective: D Environment > 96 Environment > 9609 Land and Water Management > 960905 Farmland, Arable Cropland and Permanent Cropland Water Management
Identification Number or DOI: 10.1016/j.envsci.2010.06.002

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