The aim of the project is twofold: to draw up a nitrogen budget for cotton under various conditions that are known to affect the crop's response to nitrogen; and to continue to develop the SJRATAC fruit model, in particular by refining the cotton nitrogen sub-model. The value to the industry will be to improve the efficiently of nitrogen fertilisation and pest management. Cotton growers apply between 100 and 200 kg/ha of fertiliser nitrogen to the crop, costing the industry as a whole approximately $15 million annually. At best only 50% of the nitrogen applied is taken up by the crop. Study in more detail of the fate of all nitrogen applied to the crop, and the factors affecting it, is a vital step towards improving the efficiency of nitrogen fertilisation. Incorporation of nitrogen in the SIRATAC fruit model with strengthen the application of SJRA TAC pest management to situations where nitrogen is limiting, and will be a step towards using the SIRATAC model for nitrogen management