The use of a nitrification inhibitor (DCnâ„¢) to reduce nitrate leaching under a winter-grazed forage crop in the Central Plateau

Abstract

Grazing of brassica winter forage crops returns large amounts of excreted nitrogen (N) back to the paddock during winter when risk of leaching is high. This experiment measured nitrate-N leaching below 60 cm of 132 and 173 kg N/ha following June grazing by dairy cows of swede/kale crops in 2008 and 2009. Application of DCD immediately after grazing plus 6 weeks later decreased leaching by 20-27% (significant at P<0.05). The retained N was measurable in the soil (0-60 cm) at the end of drainage. We conclude that: grazing of winter forage crops can leach large amounts of N; DCD is one tool to decrease leaching; retained N needs to be utilised by the following crop or pasture and represents a valuable resource on the farm. Key words: Winter forage, nitrogen, leaching, DCD