Evaluating the effects of dicyandiamide (DCD) on nitrogen cycling and dry matter production in a 3-year trial on a dairy pasture in South Otago, New Zealand

Abstract

The nitrification inhibitor dicyandiamide (DCD) has been reported to significantly reduce nitrate (NO À 3 ) leaching and nitrous oxide (N 2 O) emissions under urine patches in New Zealand trial conditions. However, results on the efficacy of DCD for increasing pasture production have been inconclusive. As part of a national series of nitrous oxide mitigation research (NOMR) trials, a 3-year study was conducted at a dairy farm in South Otago to examine the effect of DCD on pasture production and N leaching under mowing and/or (simulated) grazing conditions and on N 2 O losses from dung and urine patches. Over the three trial years, DCD significantly inhibited nitrification in urine-amended soil, reducing peak NO À 3 concentrations in the soil by >50% and the N 2 O emission factor from urine by 33%-72%. Nitrate concentrations in drainage under simulated grazing plots with or without DCD applications were low and consequently no effect of DCD was detected. The N 2 O emissions and N leaching results suggested that high rates of denitrification occurred in the imperfectly draining soil, particularly in years 2 and 3 of the study. DCD significantly increased spring pasture dry matter (DM) yields from urine patches by 9%-21% in all years under mowing, but no significant annual effect on DM response was detected under either mowing or grazing. The observed increases in DM response in the urine patches under mowing were not detectable under the variable pasture responses under true grazing conditions.

Effect of dicyandiamide (DCD) delivery method, application rate, and season on pasture urine patch nitrous oxide emissions

“…2; Table 2). Similar findings on the effectiveness of broadcasting DCD at 10 kg ha −1 for reducing N 2 O emissions have been reported in other studies (e.g., de Klein et al 2011;Luo et al 2013;Cameron et al 2014;de Klein et al 2014;Kim et al 2014;Ledgard et al 2014). Ledgard et al (2008) developed a novel-patented approach to strategic application of DCD to urine patches by directly administering the DCD to animals.…”

“…As discussed earlier, DCD is subject to degradation and leaching from the surface soil where urine has accumulated and N 2 O is being produced, leading to lower efficiency of DCD use (Luo et al 2008;Shepherd et al 2012;Kelliher et al 2014). Compared with the southern part of country, DCD would be less effective in the northern North Island of New Zealand, where the present study was conducted, due to warmer soil temperatures in winter de Klein et al 2014;Kim et al 2014;Ledgard et al 2014), as an increase in soil temperature has been shown to decrease the efficacy of DCD (Puttanna et al 1999). As well, the current study was conducted on a free-draining volcanic soil, which has naturally high rates of nitrification (Sarathchandra 1978) and rainfall/ drainage levels that are generally higher than those in many other dairying regions.…”

“…The efficacy of DCD is influenced by a number of factors, such as temperature, soil type, organic matter content, rainfall, and drainage (Amberger 1989). Studies in New Zealand have shown that broadcast application of DCD to grazed pasture can decrease N 2 O emissions by up to 70 % from urine patches (e.g., Di and Cameron 2005;de Klein et al 2011;Luo et al 2013;Welten et al 2013a;Cameron et al 2014;de Klein et al 2014;Kim et al 2014;Ledgard et al 2014). These studies also suggest that the effect of DCD on N 2 O emissions may also be affected by seasonality due to different amounts of rainfall and soil temperatures.…”

N2O emissions from urine-treated tropical soil: Effects of soil moisture and compaction, urine composition, and dung addition

“…Flux calculations (unit: ng N g − 1 dry soil h − 1 ) were based on the assumption that there was a linear increase in the N 2 O concentration with time in the closed chamber. The procedure followed was the same as in numerous recently published studies (de Klein et al, 2014;Lessa et al, 2014;Martins et al, 2015;Cardoso et al, 2016;Nichols et al, 2016;van der Weerden et al, 2016). The lowest detection limit was found using linear regression (see Parkin et al, 2012), which was compared to the quadratic methods of Hutchinson/Mosier and revised Hutchinson/Mosier.…”

Ammonia and nitrous oxide emission factors for excreta deposited by livestock and land‐applied manure

“…The number of studies quantifying N 2 O emissions from dung treated with nitrification inhibitors is small; however, our analysis of 39 observations suggested a mean reduction of 63% in N 2 O EF for cattle dung. Again, temperature is a key variable, with temperate New Zealand studies showing a reduction (e.g., Cameron et al., 2014; de Klein et al., 2014), whereas Brazilian studies under a subtropical climate showed limited effectiveness (Simon et al., 2018).…”