Impacts of fertilisers and legumes on N2O and CO2 emissions from soils in subtropical agricultural systems: A simulation study

There is increasing focus on greenhouse gas emissions from agricultural systems. One suggested method for increasing the sequestration of carbon (C) within agricultural soils is to increase crop productivity and therefore C input into the soil. However, if enhanced production is achieved via nitrogenous fertilisers, there is a potential tradeoff between decreased C emissions and increased nitrous oxide (N2O) emissions due to the increased soil C and nitrogen (N). An alternative is to incorporate leguminous crops into cereal cropping rotations to provide a biological source of N. However, the likely production of N2O from N released during the decomposition of leguminous residues is unknown as is the impact on C input into the soil when some cereal crops are replaced with grain legumes. Consequently, an analysis of the likely impacts has been undertaken for a subtropical dryland cropping system in Queensland, Australia where soil, climate and management are conducive to denitrification losses.