Strategies for mitigating N2O and N2 emissions from an intensive sugarcane cropping system
Johannes Friedl, D. Warner, Weijin Wang, David Rowlings, Peter Grace, Clemens Scheer
Abstract
Abstract In sugarcane cropping systems, high rates of N fertiliser are typically applied as sub-surface bands creating localised zones of high mineral N concentrations. This in combination with high levels of crop residue (trash) retention and a warm and humid climate creates conditions that are known to promote soil denitrification, resulting in high emissions of the potent greenhouse gas N 2 O. These losses illustrate inefficient use of N fertilisers but total denitrification losses in the form of N 2 and N 2 O remain largely unknown. We used the 15 N gas flux method to investigate the effect of cane trash removal and the use of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N 2 and N 2 O emissions on a commercial sugarcane farm at Bundaberg, Australia. High gaseous N losses were observed under the standard grower practice where cane trash retention and N fertiliser application (145 kg N ha −1 as urea) resulted in N 2 and N 2 O emissions (36.1 kg N ha −1 ) from the subsurface N fertiliser band, with more than 50% of these losses emitted as N 2 O. Cane trash removal reduced N 2 emission by 34% and N 2 O emission by 51%, but had no effect on the N 2 O/(N 2 + N 2 O) ratio. The use of DMPP lowered N 2 and N 2 O emission by 35% and 98%, respectively, reducing the percentage of these losses (N 2 + N 2 O) emitted as N 2 O to only 4%. We conclude that the use of DMPP is an effective strategy to reduce N losses, minimise N 2 O emissions, while keeping the benefits of cane trash retention in sugarcane cropping systems.