New Zealand Journal of Agricultural Research abstracts

Effect of dicyandiamide applied in a granular form on nitrous oxide emissions from a grazed dairy pasture in Southland, New Zealand

L. C. Smith

AgResearch
Woodlands Research Station
RD 1
Invercargill 9871, New Zealand
chris.smith@agresearch.co.nz

C. A. M. de Klein

AgResearch
Invermay Agricultural Centre
Private Bag 50034
Mosgiel 9053, New Zealand

W. D. Catto

Ballance Agri-Nutrients
Private Bag 12503
Mount Maunganui
Tauranga 3143, New Zealand

Abstract The trial reported here investigated the effect of applying dicyandiamide (DCD) in a granular form on N₂O emissions in a grazed pasture system over 2 years. In 2004, treatments of urea or urea + zeolite-DCD were applied randomly to pairs of plots following grazing in late autumn. Both treatments received urea at a rate of 50 kg N ha^–1, while the latter treatment also included an application of granular zeolite/DCD at 42 kg ha^–1 (DCn™: 10 kg ha^–1 DCD). In 2005, the same treatments were applied following grazing in early and late autumn and early spring. Measurements of N₂O emissions were made at frequent intervals following treatment application using a standardised soil cover technique. Large variability in N₂O emissions and soil mineral N levels were measured, due to the variable nature of urine N return by grazing animals. Nevertheless, the results clearly showed that the granular zeolite/DCD significantly reduced N₂O emissions from grazed pasture from 1.0 to 0.3 kg N ha^–1, 3.7 to 0.7 kg N ha^–1 and 2.9 to 0.3 kg N ha^–1 for the three measurement periods. This equates to reductions of between 75 and 90% over a 2- to 3-month measurement period. Based on these results, and the assumption that 40–50% of annual N₂O emissions occur during the times when nitrification inhibitor application is recommended, granular zeolite/DCD reduced annual N₂O emission from grazed pastures by 30–45%.

Keywords dicyandiamide; grazed dairy pasture; nitrification inhibitors; nitrous oxide; mitigation options

A07021; Online publication date 30 September 2008
Received 23 March 2007; accepted 5 September 2008

New Zealand Journal of Agricultural Research, 2008, Vol. 51:387–396
0028–8233/08/5104–0387 © The Royal Society of New Zealand 2008

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