The application of organic amendments (OA) is a strategy to improve soil fertility and offset the high cost of mineral fertilizers used in agricultural systems. However, information on the interaction of OAs with synthetic fertilizers and the resulting greenhouse gas emissions from these combinations are not well understood for different soil types. A 36 day laboratory incubation experiment (3 compost x 3 N rates) was conducted to quantify soil N2O emissions along with CO2 and mineral N from subtropical soils in Gatton, Australia. Nitrous oxide emissions decreased by 68% and 57% in 60N and 120N treatments respectively with the increase in compost applications rates up to 30 t/ha and 60 t/ha. Adding 60 t/ha compost and 120 kg N/ha is considered as the optimum fertilizer rate to minimize N2O and CO2 emissions from a sub-tropical Vertosol and potentially conserving soil physical, chemical and biological properties for a sustainable crop growth.