Impact of dicyandiamide application on nitrous oxide emissions from urine patches in northern Victoria, Australia

Animal production systems in Australia are a significant contributor to nitrous oxide (N2O) emissions from soil, with the Australian Greenhouse Gas Inventory attributing similar to 25% of the N2O emissions from agricultural soils to animal production. Recent studies in New Zealand using dicyandiamide (DCD) in association with the application of urine to pastoral soil have reported reductions in N2O emission of up to 78% and reduced nitrate leaching of up to 45%. As such, the application of DCD to grazed pastures offers potential to reduce emissions resulting directly from animal production. This study was conducted on a border-check irrigated perennial pasture used for dairy production in northern Victoria. Automated enclosure chambers were linked to a fourier transformed infrared spectrometer to determine N2O emissions. The three treatmentswere a control, dairy cow urine (1000 kg N/ha) and dairy cow urine (1000 kg N/ha) with DCD included (10 kg/ha). The treatments were applied in mid-spring (15 September 2005) and again in mid-summer (25 January 2006) to a new area of pasture with N2O emissions measured for 120 and 70 days, respectively. Soil temperature and soil water content were monitored continuously. Soil inorganic-N was measured (0-100 mm) every 7 to 14 days for up to 120 days. Application of DCD reduced N2O emissions from a urine patch by 47% when applied in mid-spring and 27% when applied in mid-summer. The impact of the application of DCD on emissions from single urine patches lasted for similar to 50 days in mid-spring and 25 days in mid-summer. These reductions are lower than those reported in New Zealand studies and are likely to be related to soil conditions, principally temperature. The surface application of DCD has potential to reduce emissions from urine patches in northern Victoria; however, the effects are likely to be short-lived given the soil temperatures and high clay content typical of many Australian soils. More research is required to examine emission reduction options that are cost effective for animal production systems.