The aims of agricultural nitrogen (N) management are to provide sufficient N to plants to maximize crop growth and yield, whilst minimising negative environmental impacts such as nitrous oxide (N2O), a potent greenhouse gas (GHG). The flux of this gas from agricultural soils is correlated to the amount of N fertilizer applied, as well as soil and environmental conditions. Reducing the amount of synthetic fertiliser inputs and promoting the storage of organic carbon through the use of organic soil amendments may be an effective pathway to reduce GHG emissions and improve N use efficiency. A fully randomized block design was established on a black vertosol in a subtropical horticultural cropping system to estimate the efficiency and environmental impact of different types of raw verses composted manure in combination with reduced synthetic fertilizer inputs. The treatments consisted of all combinations of raw and composted cattle feedlot (FM) and chicken manure (CM) with synthetic nitrogen at commercial rates (100%) or reduced rates (100% - N[org amend]). High temporal resolution gas sampling (sub-daily) was conducted using automated gas chambers on the CM treatment and manual gas sampling technique (weekly) on the FM will be used to quantify the N2O dynamic emission. Complementary soil nitrogen data will give a better understanding of the effects of organic amendments in relation to N2O emissions.