<p>van der Weerden, T. J., T. M. Styles, et al. (2017). "Nitrous oxide emissions from cattle urine deposited onto soil supporting a winter forage kale crop." New Zealand Journal of Agricultural Research 60(2): 119-130.</p>
<p>Abstract<br />Wintering cows on forage crops leads to urine being excreted onto wet, compacted soils, which can result in significant emissions of nitrous oxide (N2O). A field trial was conducted to determine the N2O emission factor (EF3; proportion of urine-N lost as N2O-N) for dairy cows wintered on a kale forage crop on a poorly drained soil. Urine was collected from non-lactating dairy cows on a forage kale diet and applied at 550&#8197;kg&#8197;N&#8197;ha&minus;1&nbsp;to artificially compacted soil to simulate trampling and non-compacted soil in a kale field. Cumulative N2O losses over four months were 7.38 and 2.64&#8197;kg N2O-N&#8197;ha&minus;1&nbsp;from urine applied to, respectively, compacted and non-compacted soil. The corresponding EF3&nbsp;values 0.75% and 0.30%, respectively, differed (P&thinsp;=&thinsp;.003) due to compaction. Combining our results with previous studies, where brassica-fed livestock urine was applied to soils supporting a forage brassica crop, suggested a significant relationship between soil water-filled pore space (WFPS) and brassica-derived urine EF3&nbsp;(P&thinsp;=&thinsp;.005).</p>
<p><strong><a href="http://www.tandfonline.com/doi/full/10.1080/00288233.2016.1273838">Read more</a></strong> (external link)</p>