The trial reported here investigated the effect of applying dicyandiamide (DCD) in a granular form on N 2 O 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 N 2 O emissions were made at frequent intervals following treatment application using a standardised soil cover technique. Large variability in N 2 O 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 N 2 O 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 N 2 O emissions occur during the times when nitrification inhibitor application is recommended, granular zeolite/DCD reduced annual N 2 O emission from grazed pastures by 30-45%.

The OVERSEER nutrient budget model is a farm-scale nutrient reporting and greenhouse gas (GHG) emission accounting tool used extensively throughout New Zealand (NZ) by farmers, farm consultants and fertiliser representatives. The model is increasingly being used as a tool for implementing regional council resource management requirements to limit nitrogen (N) and phosphorus losses to waterways. NZ’s main dairy company, Fonterra, also requires dairy farmers to have a nutrient budget as part of the national Clean Streams Accord. This means that a high proportion of NZ farmers can obtain reports of their on-farm GHG emission profile. The GHG emission model is based on models and algorithms used for the NZ GHG national inventory, modified to include a wide range of on-farm management practices. The model estimates methane, nitrous oxide and carbon dioxide (CO2) emissions, and presents the results as CO2 equivalents. This paper describes the model and the benefits of combining nutrients budgets and GHG emissions into a single model. It also demonstrates the effects of management practices on a range of outputs, including N leaching and GHG emissions.