This project aims to maximise nitrogen use efficiency (NUE) in the Australian mango industry. Mangoes are a significant tree crop grown in tropical and subtropical climates of Australia. Nitrogen (N) is essential for mango tree development, fruit production and quality. Presently, only limited data is available for Australian mango growing regions on the relative importance of soil N processes, total N loss from current management practices and profitable use of N in the plant. This research will use stable isotopes to quantify plant N demand, soil supply and current practice N use efficiency (NUE) to develop best management practices for optimising N fertiliser use, including enhanced efficiency fertilisers (EEFs).