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TECHNICAL REPORTS

Vadose Zone Processes and Chemical Transport

Evaluation of Cover Crop and Reduced Cultivation for Reducing Nitrate Leaching in Ireland

^a Dep. of Geology, Trinity College Dublin, Dublin 2, Ireland
^b Teagasc, Johnstown Castle, Wexford, Ireland
^c Teagasc, Oak Park, Carlow, Ireland

^* Corresponding author (kirstyhooker{at}hotmail.com).

Received for publication December 19, 2006. Nitrate (NO₃) loss from arable systems to surface and groundwater has attracted considerable attention in recent years in Ireland. Little information exists under Irish conditions, which are wet and temperate, on the effects of winter cover crops and different tillage techniques on NO₃ leaching. This study investigated the efficacy of such practices in reducing NO₃ leaching from a spring barley (Hordeum vulgare L.) system in the Barrow River valley, southeast Ireland. The study compared the effect of two tillage systems (plow-based tillage and noninversion tillage) and two over-winter alternatives (no vegetative cover and a mustard cover crop) on soil solution NO₃ concentrations at 90 cm depth over two winter drainage seasons (2003/04 and 2004/05). Soil samples were taken and analyzed for inorganic N. During both years of the study, the use of a mustard cover crop significantly reduced NO₃ losses for the plowed and reduced cultivation treatments. Mean soil solution NO₃ concentrations were between 38 and 70% lower when a cover crop was used, and total N load lost over the winter was between 18 and 83% lower. Results from this study highlight the importance of drainage volume and winter temperatures on NO₃ concentrations in soil solution and overall N load lost. It is suggested that cover crops will be of particular value in reducing NO₃ loss in temperate regions with mild winters, where winter N mineralization is important and high winter temperatures favor a long growing season.

Abbreviations: CC, cover crop • PL, plow-based tillage • RC, reduced cultivation • TON, total oxidized nitrogen • TIN, total inorganic nitrogen