Comparison of nitrate leaching from oats and Italian ryegrass catch crops following simulated winter forage grazing: a field lysimeter study. Issue 3 (3rd July 2017) - Carey, P. L.
ABSTRACT: Intensive winter forage grazing systems have a high risk of environmental impact due to nitrate leaching from urine deposition on cool, wet, fallow soils. We investigated the effect of sowing two catch crops after simulated winter forage grazing on kale to potentially reduce N leaching losses from a winter application of labelled 15 N-urine (350 and 700 kg N ha −1 ) using field lysimeters. The experiment measured the capture of N by the sowing at recommended dates of either oats ( Avena sativa ) or Italian (It.) ryegrass ( Lolium multiflorum ) and the resulting 15 N balance. Results showed that the sowing of an oats catch crop reduced nitrate leaching by 25% over the critical winter–spring drainage period compared with It. ryegrass. Relatively small amounts of the labelled 1 ⁵N-urine (3–4%) were captured in the catch crops of urine treatments so the reduced nitrate leaching under the oats crop was attributed to lower drainage over the period.