New Zealand Journal of Agricultural Research abstracts

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The effectiveness of different nitrification inhibitor formulations in limiting nitrate accumulation in a Southland pastoral soil

L. C. Smith

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

R. M. Monaghan

AgResearch
Invermay Agricultural Centre
Private Bag 50 034
Mosgiel, New Zealand

S. F. Ledgard

AgResearch
Ruakura Agricultural Centre
Private Bag 3123
Hamilton, New Zealand

W. D. Catto

Ballance Agri-Nutrients
Private Bag 12 503
Mount Maunganui, New Zealand

Abstract  In pastoral dairy grazing systems, the high localised nitrogen (N) concentration in urine patches has been identified as a major source of nitrate nitrogen (NO₃-N) available for leaching. Our study was initiated to investigate the effectiveness of different formulations of a nitrification inhibitor, dicyandiamide (DCD), in limiting NO₃-N accumulation in a typical Southland pastoral soil. Various formulations of DCD (Super U, DCD-urea granules, DCD in zoelite granules and DCD in solution), both in the presence and absence of artificial urine, were applied to small plots in late October 2003. With the exception of Super U, all the DCD formulations evaluated were effective in limiting the nitrification of ammonium-nitrogen (NH₄-N) to NO₃-N in soil for in excess of 100 days. Thus, applying DCD in a granular form or in conjunction with granular fertiliser can be an effective way to limit NO₃-N build-up in the soil profile. Total pasture production over the duration of the trial was increased by the DCD application in the N-fertilised treatments by between 8 and 21%, but no significant differences in pasture production were noted for treatments that included an application of artificial urine. The DCD application had the added benefit of limiting nitrate accumulation in the herbage to safe levels for ingestion by grazing animals, as well as a trend to increase herbage magnesium (Mg) and calcium (Ca) concentrations, so counteracting the possible detrimental effects of high potassium (K) concentrations where urine had been applied to a Southland pastoral soil.

Keywords  nitrogen; nitrate; urine; nitrification inhibitor; dicyandiamide (DCD); pasture; dairy; urea

A05020; Received 12 May 2005; accepted 31 August 2005; Online publication date 18 October 2005
New Zealand Journal of Agricultural Research, 2005, Vol. 48: 517–529
0028–8233/05/4804–0517 © The Royal Society of New Zealand 2005

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