The effect of time of winter urine deposition on mineral nitrogen leaching and implications for grazed forage crops

Time of urine application on mineral N (Nmin) leaching from a pumice soil was tested. Artificial urine (600 kg N ha −1 ) was applied in early June or late July to small plots after removing a kale/swede crop or to ryegrass/white clover. Mineral N leached in the first winter (measured by porous cups, 600 mm deep) was similar under pasture or ex-forage crop: 185 vs. 60 kg N ha −1 for June or July urine, with 170-300 kg N ha −1 remaining in the soil (0-600 mm) at the end of drainage. Additionally, 54-118 kg N ha −1 leached in the second winter. In total, later application decreased Nmin leaching by 35-40%. Application of the process inhibitor dicyandiamide increased soil Nmin levels in the post forage crop site for the early urine application but had no effect in the late-applied urine treatment. There was no significant effect on N leaching.