Repeated annual use of the nitrification inhibitor dicyandiamide (DCD) does not alter its effectiveness in reducing N2O emissions from cow urine

Urine deposited by grazing animals in patches is the single largest source of N2O emissions in New Zealand. In recent years, a nitrification inhibitor, dicyandiamide (DCD) has been developed that substantially reduces these emissions. However, uncertainty exists about the sustained effectiveness of repeated use of DCD on reducing N2O emissions from urine patches. The aim of this study was to determine if DCD application for 4 or 5 consecutive yr alters its effectiveness to reduce N2O emissions from cow urine patches (EF3). A second objective was to summarise results of New Zealand studies published in the last decade on effects of DCD to reduce N2O emissions from animal urine. At 'repeated-DCD-use' sites and 'non-DCD' sites in Canterbury and Southland (New Zealand), N2O emissions were measured for 6 mo from three treatments being: Control, Control + DCD, Urine and Urine + DCD. At the Canterbury site, DCD application reduced (P<0.05) EF3 by 61-70%, but had no effect at the Southland site, probably due to extremely wet soil conditions. Results show that after 4 or 5 yr of application, the DCD impact on reducing N2O emissions did not change. This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture Finding a Balance between Food and Emissions. Guest Edited by TA. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. (C) 2011 Published by Elsevier B.V.