Nitrogen fertiliser use is essential for adequate food production, but the low efficiency of use results in significant emissions of the potent greenhouse gas nitrous oxide, as well as other forms of nitrogen pollution. Enhanced efficiency fertilisers (EEFs) have shown promise for improving nitrogen use efficiency. However, the effect of EEFs depends on complex interactions with plant growth, soil conditions, water management and climate.
This project focused on the interactions of EEFs with the soil-plant-atmosphere system and nutrient cycles.
Researchers investigated the fate of nitrogen in EEFs amended with urease and nitrification inhibitors. The studies were largely laboratory based, so that conditions known to influence how the inhibitors work (temperature, moisture) could be controlled across a range of soil types collected from locations around Australia. Three nitrification inhibitors (DCD, DMPP and Nitrapyrin) were tested with nine soils from sugarcane or grain growing regions, pasture systems, or pasture converted to cropping systems.
One field trial was conducted on ryegrass pasture in south west Victoria to identify all potential losses of nitrogen from different EEFs applied over an eight month period. It compared nitrous oxide and nitrate emissions from the use of nitrification or urease inhibitor-coated fertilisers, a fine particle spray application of urea and a liquid application of urea ammonium nitrate.
In the laboratory studies, DCD and DMPP reduced nitrate production by up to 80% and nitrous oxide emissions by 8–83% across all soils, with greater reductions at lower soil temperatures.
The field experiment showed that DCD and DMPP-coated fertilisers resulted in reduced nitrous oxide emissions and that urease inhibitor-coated fertiliser resulted in reduced ammonia loss in both autumn and spring. Climatic conditions - namely soil moisture and rainfall - were highly influential on the level of ammonia loss. Application of a urease inhibitor (Agrotain) reduced ammonia loss under both situations by between 40 and 70%. Using nitrification inhibitors reduced the amount of nitrate found in the soil and reduced nitrous oxide emissions to varying degrees over the time of study. The greatest reductions occurred in spring when emissions from untreated fertiliser were higher.
The results showed that targeting inhibitor use to particular times of the year increased the benefit gained from paying the premium for inhibitor-coated fertilisers.
The project demonstrated that nitrification inhibitors can reduce nitrous oxide emission from agricultural soils but also that further work is required to determine the main drivers controlling their performance, and to assess where they are likely to work best and why.
This project was part of the national Nitrous Oxide Research Program, funded by the Australian Government Department of Agriculture, Fisheries and Forestry under its Australia’s Farming Future Climate Change Research Program.
|Nitrous oxide publications||A bibliographic survey of research publications produced by PICCC's nitrous oxide projects.|