Stream water quality in intensive cereal cropping catchments with regulated nutrient management

Melland, A. R. and Mellander, P. -E. and Murphy, P. N. C. and Wall, D. P. and Mechan, S. and Shine, O. and Shortle, G. and Jordan, P. (2012) Stream water quality in intensive cereal cropping catchments with regulated nutrient management. Environmental Science and Policy, 24. pp. 58-70. ISSN 1462-9011

Abstract

Regulating farm nutrient management is a European Union policy approach to meet water quality targets. In two intensively cropped catchments (9km2 and 11km2) in Ireland, high resolution monitoring was undertaken over two years to investigate interactions between the regulations and nutrients in streams. In a catchment with predominantly well-drained soils (Arable A) farmed for spring barley, high phosphorus (P) concentrations and turbidity during peak river flows indicated high connectivity of nutrient sources with streams. High baseflow volumes, however, maintained mean stream P concentrations below the environmental quality standard (EQS). Total oxidised nitrogen (TON) concentrations decreased during storms and baseflow concentrations remained relatively stable and below drinking water standards. In a contrasting catchment on moderate to poorly drained soils (Arable B) farmed for winter wheat, dairy and beef, the EQS for P was never met. High baseflow P concentrations during summer were attributed largely to loss of dilution in low discharge rates. Spatial surveys of water quality indicated baseflow P concentrations were influenced by persistent point sources. Baseflow TON concentrations were lower during summer than winter and this was attributed to seasonal disconnection and attenuation of N sources. Average annual streamflow total P loads were higher from Arable B (0.72kgha-1) than from Arable A (0.27kgha-1) whereas TON loads were higher from Arable A (28kgha-1) than from Arable B (17kgha-1). Suspended sediment losses, after a first approximation, were less than 0.18tha-1yr-1. The upper quartile of stream discharge dominated annual loads of P, TON and suspended sediments. Of most concern were stream P concentrations in Arable B and potentially P and N loads from both catchments given both catchments contribute to eutrophic coastal waters. Compliance with farm nutrient management regulations should mitigate persistent agricultural point sources but will not affect non-agricultural point source influences on stream P concentrations. Under current regulations, decreased N surplus at source and subsequent depletion of nitrate from vadose and groundwater stores may decrease TON loads over time.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © 2012 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 02:48
Last Modified: 02 Feb 2017 05:35
Uncontrolled Keywords: catchment hydrology; mitigation measures; nitrate; nitrates directive; phosphorus
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090508 Water Quality Engineering
16 Studies in Human Society > 1605 Policy and Administration > 160507 Environment Policy
07 Agricultural and Veterinary Sciences > 0701 Agriculture, Land and Farm Management > 070101 Agricultural Land Management
Socio-Economic Objective: D Environment > 96 Environment > 9609 Land and Water Management > 960904 Farmland, Arable Cropland and Permanent Cropland Land Management
Identification Number or DOI: 10.1016/j.envsci.2012.06.006
URI: http://eprints.usq.edu.au/id/eprint/25786

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