The CCCINDVI and the MTCI were therefore chosen to build the confusion matrix for the AS zone as well as harvested yield (Table 4). The CCCINDVI was classified Class 1 (low index value) 4 times for the 30 N and 0 for the other 2 N treatments, but 2 times was classified as Class 2 (medium index value) while it should have been in Class 1. Its overall accuracy was 71 % (Table 4). The MTCI had confounding effects between Class 1 and 2 for estimating 30 N, and Class 2 and 3 for 70 N and had an overall accuracy of 50 %. Grain yield response to N fertilizer can be also used as a proxy for crop response to N fertilization, and its overall accuracy was 65 % with the response for each class being very close to the normalized CCCINDVI response (Table 4).