The objective of this experiment was to investigate the role of different N fertilization rates and the use of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP, commercially sold as Entec) in reducing N2O emissions from subtropical maize systems over summer. At the same time, particular attention was given to the yield response shown by the different treatments, in order to evaluate the respective economical sustainability and N2O intensity. The field experiment was set up in Kingaroy ( S-E QLD), on a euchrozems Ferrosol soil, using a randomized complete three-block design (three replicates per treatment). The four treatments encompassed three different fertilization rates and two types of Urea (conventional and DMPP urea): control treatment (L1: 40 kg-N ha-1 -conv. urea), sub-optimal N rate (L2: 100 kg-N ha-1 –conv. urea) and optimal N rate (L3: 160 kg-N ha-1 –conv. urea, L4: 160 kg-N ha-1 –DMPP urea). The N2O emissions were measured from planting (December 20th 2011) to harvest (June 20th 2012) with a fully automated greenhouse gas measuring system. In order to gain optimum understanding of the dynamics influencing greenhouse gas production and release in agricultural soils, the air temperature and the soil moisture inside the measuring chambers were constantly monitored. To compare the "environmental" performances of the four treatments with agronomical sustainability grain yields were also determined.