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A field micro-plot experiment with nitrogen isotope (15 N) labelling was performed to study the impacts of the timing of aside-dressed Napplication on urea-15 N in amaize-soil system. The treatment...

Nitrous oxide (N2O) emissions (EN2O) from drained peat soils used for pastoral agriculture have not been measured throughout the year in New Zealand. In response to this research gap, EN2O was measured fortnightly for 1 year in the Waikato region in a plot that was not grazed or nitrogen (N) fertilised. The time series was variable, the frequency distribution skewed and the fortnightly means correlated. To account for these factors, the data were loge transformed and an order 2 autoregressive model used to estimate a mean EN2O of 4.3 g N ha−1 d−1 and 95% confidence limits of 0.6–29.1 g N ha−1 d−1. There was a statistically significant, inverse relationship between EN2O and the depth to groundwater. In winter, when rainfall totalled 393 mm, EN2O and soil N content were significantly greater under a rain shelter designed to minimise N loss by leaching, than in an uncovered plot.

Potential losses of nitrogen (N) from land application of effluents include ammonia (NH3) and nitrous oxide (N2O) emissions. In this review paper, the extent of the NH3 and N2O losses resulting from application of effluents to pastoral soils is assessed. Nitrogen losses, as NH3 and N2O, from applied effluent to pastoral soil ranged from 1%–66% and

Mowing and grazing studies over 3 years were used to examine the effects of application of the nitrification inhibitor dicyandiamide (DCD) on pasture production, soil nitrogen (N) transformations, nitrous oxide (N2O) emissions and nitrate leaching from dairy pastures in the Waikato region (northern North Island) of New Zealand. In all cases, DCD inhibited nitrification and reduced the amount of nitrate production. Emissions of N2O from pastoral soil receiving cow urine in autumn were reduced by 18%–71% due to DCD application. Lysimeter studies showed a decrease in nitrate leaching from urine due to DCD by up to 74%, but it was dependent on timing and frequency of DCD application. DCD applications between April and June were most effective for reducing nitrate leaching, but timing of applications needs to account for the temperature profile effects on DCD longevity in soil and three applications may be necessary to achieve greatest benefits. In the mowing trial in one year there was a 4% (P < 0.05) increas...

Animal urine has been identified as the main source of nitrate leaching from grazed pastures. The nitrification inhibitor dicyandiamide (DCD) can potentially reduce nitrate leaching losses and increase pasture utilisation of nitrogen (N) from urine. A mowing trial was established on a sandy loam (Typic Orthic Allophanic) soil in the Waikato region to examine the effect of liquid and granular forms of DCD, applied in May at rates of 0, 7, 14 and 28 kg ha‐1, on the fate of urea applied at 600 kg N ha‐1 in artificial urine. The DCD treatments increased pasture production over 211 days by an average of 15% (P < 0.001) and there was no significant effect of rate or form of DCD. Soil sampling 76 days after treatment application showed greater amounts of ammonium remaining in the top 450 mm of soil in the DCD treatments (average ammonium‐N for all DCD treatments of 93 kg N ha‐1 compared with 43 kg N ha‐1 for the urine‐only treatment). Total inorganic N in the top 600 mm of soil at the final (118 day) sa...

The use of nitrogen (N) fertiliser has been identified as a possible important source of nitrous oxide (N2O) from pastoral soils, and urea is the main form of N fertiliser used in New Zealand. The aim of this study was to examine the effects of urea application on N2O emissions from pastoral soil. A closed soil chamber technique was used to measure the N2O emissions from a pasture which received either 0 (control) or 50 kg N ha–1 (as urea) per application during different seasons between 2003 and 2005. Overall, urea fertiliser application generally increased N2O fluxes above control levels for up to 30 days, but the duration for which N2O levels were elevated depended on the season. These increases in the N2O fluxes were largely caused by a combination of changes in the soil mineral N level due to urea application, and moisture content of soil in different seasons. Nitrous oxide emissions were higher during the winter and spring measurement periods when the soil water‐filled pore space (WFPS) was...