Pasture dry matter responses to the use of a nitrification inhibitor: a national series of New Zealand farm trials

Abstract

The use of nitrification inhibitors has become increasingly common on dairy farms in NZ since 2004, ostensibly to reduce nitrogen (N) loss from nitrate leaching and nitrous oxide emissions. A potential benefit of this reduction in N loss, however, is an increase in dry matter (DM) production. Pasture response data were collated from a national series of farm trials conducted in 132 paddocks on 37 farms in the North Island (NI) and South Island (SI) of New Zealand where paddocks were randomly split into two halves with one half treated with the nitrification inhibitor eco-n TM . Measurements conforming to a strict protocol were made using pasture plate meters. There was a highly significant overall DM response to inhibitor use of 19% across all trials (14% NI, 21% SI) although full-year responses were more variable between NI regions (4Á27%) than SI regions (12Á31%). Generally, DM responses were greater than those demonstrated by previous small-scale experimental trials and this may indicate the influence of a farmÁsystem effect. Several reasons are speculated for this effect but further research is required to identify the factors involved.

The effects of nitrification inhibitors on pasture production

“…The effects of DCD on pasture production, as measured in the large-plot trials discussed above, are not as large as those reported by Carey et al (2012). Furthermore, these results do not require the explanation offered by those authors of a 'farmÁsystem effect'.…”

“…The response to eco-n TM relative to the control was 3.1% (NS) when pasture production was assessed using the traditional cage/mowing technique and 15.3% when pasture production was assessed using a plate meter. Thus, it appears that pasture plate meters introduce a bias sufficient to explain the difference between the large average response of 19% reported by Carey et al (2012) and the balance of the evidence summarised above.…”

“…Dear Sir, Carey et al (2012) reported results from a series of trials conducted on 37 farms throughout New Zealand measuring the effects of the nitrification inhibitor eco-n TM on pasture production. Paddocks (137) were split in half.…”

“…Furthermore, these results do not require the explanation offered by those authors of a 'farmÁsystem effect'. This leads to the suggestion that the large-pasture responses reported by Carey et al (2012) may be an artefact of the methodology used. This is supported by results reported by Hanly et al (2007), who measured the effects of eco-n TM under grazing over 2 years in large plots (150 m)15 m; three replicates of two treatments) using the traditional exclusion cage/mowing technique and using a plate meter (C-Dax).…”

Influence of enhanced efficiency fertilisation techniques on nitrous oxide emissions and productivity response from urea in a temperate Australian ryegrass pasture

“…This indicates that the dominant loss pathways will differ between systems, years and seasons. A synopsis of pasture trials conducted on 132 paddocks in 37 farms across New Zealand found overall biomass benefits from the use of a nitrification inhibitor (DCD) (19% increase), with variation around this dependent upon the region (Carey et al 2012). The authors of the New Zealand study point out that this benefit is greater than reported on previous individual small plot studies (Carey et al 2012).…”