Nitrogen (N) plays a key role in the growth and development of a cotton plant and the timing of N fertiliser application has a critical effect on yield. In the Australian cotton industry, N fertiliser is typically applied at a uniform rate across a field at a high enough rate to ensure N is not limiting at any area of the field and this practice is not necessarily cost effective. This project investigates the use of vegetation indices (VIs) derived from multispectral imagery from planes and satellites to estimate plant nitrogen status to facilitate variable rate fertiliser application and for predicting lint yield at time of harvest.