Nutrient Losses to Water & Atmosphere

The core focus of the Nutrient Losses to Water & Atmosphere team is developing management practices and technologies for New Zealand farms for minimising transfers of nitrogen, phosphorus, sediment and faecal micro-organisms from soil to water and nitrous oxide emissions to air.

Currently, the two key components of the environmental footprint of New Zealand farms are ‘non-point source pollution’ for our waterways and greenhouse gas (GHG) emissions to air.

“Non-point source pollution” is increasingly recognised as an important causal factor contributing to the deterioration of water quality in many parts of the country.  In sensitive catchments these pollutants can seriously compromise many of the important community values that New Zealanders have identified as being important to them e.g. healthy trout fisheries, good stream and river habitat values, safe for swimming or drinking, aesthetically pleasing, etc.

As a signatory to the Kyoto protocol, New Zealand also has an obligation to reduce its GHG emissions to 1990 levels on average over the 2008-2012 period. Agricultural emissions contribute about 50% to New Zealand total emissions, of which 2/3 as methane from animals and 1/3 as nitrous oxide (N2O) from soil. Our team’s GHG research focuses on N2O emissions from soil and storage of carbon in pastoral soils.

Whilst there are no magical “silver bullets” on the horizon for reducing nutrient losses to water and air, research has identified a number of important management practices and technologies that can significantly reduce farming’s footprint on water quality and N2O emissions.

One set of technologies developed to conserve soil N or increase the efficiency of N supply to plants is the application to soils of nitrification inhibitors such as dicyandiamide (DCD).  These chemicals slow or “inhibit” the conversion of nitrogen (N) from the relatively immobile ammonium (NH4) form to the mobile nitrate (NO3) form. As NO3 can be lost from soil to both water (nitrate leaching) and air (N2O emissions), inhibiting the formation of NO3 is a win-win option reducing N losses to water as well as air.

Because water quality or GHG issues and policy frameworks are discussed and developed at a community or national level, but mitigation actions usually take place at a farm level, the research teams have an important role in informing individuals and communities of the effects of farming activities on the wider environment. This role of translator between individuals and communities is becoming increasingly important as:

• the pastoral industries increasingly recognise the off-site impacts of their farming operations, and
• the wider community deliberates the environmental and economic trade-offs associated with the on-going intensification of farming and the costs of implementing good environmental practices.

Staff are based at the Invermay Agriculture Centre (Mosgiel), Woodlands Farm (Southland) and the Lincoln Research Centre.