Decreasing Nitrous Oxide Emissions In High Rainfall Cropping Systems. Hamilton, Victoria, 2009 - 2012 [Theme 1: Inhibitors for reducing emissions]

Brief description

Cropping is expanding in the southern high rainfall zone and it is important that we provide farmers with management options that minimise greenhouse gas emissions without reducing productivity. An increasing proportion of land in the high rainfall zone is being converted from pasture to cropping, but the process of changing land use can have significant ramifications for greenhouse gas emissions. Nitrous oxide emissions in excess of 3kg nitrogen/hectare/year (equivalent to 1460kg of carbon dioxide) have previously been measured at Hamilton, when a high fertility legume dominant pasture was converted to a cereal crop. The purpose of this project is to test management and mitigation options that could reduce the nitrous oxide emissions that are released during such a landuse change. We are testing the effect of soil tillage and also a chemical that inhibits the bacteria involved in the soil nitrogen cycle. Nitrous oxide emissions from conventionally cultivated soil are being monitored compared to direct drilling of the crop. The application of a nitrification inhibitor (dicyandiamide - DCD) is also being trialled. DCD temporarily disrupts the process by which microbes convert ammonium to nitrate, slowing the production of nitrate and reducing nitrous oxide emissions from the soil. Automatic gas collection chambers connected to a tuneable diode laser are used to measure nitrous oxide release from the soil. The chambers close 16 times throughout the day for 30 minute intervals to collect nitrous oxide gas. Carbon dioxide levels are also measured within the chambers while remote sensors log soil moisture and temperature. The chambers are moved to different locations within 12 trial plots to minimise any interference to the natural pattern of crop growth. A comprehensive dataset will be developed for input into a national greenhouse gas model and for use in producing scientific publications that will contribute to the Australian National Greenhouse Gas Inventory.