This research paper attempts to show efficient use of spectral similarity measures to check desired growth of the crops by comparing farmer's field crops spectra with test field crops spectra of same development stage. Optimum amount of nitrogen (as fertiliser) and water applied increase the NIR reflectance. Dissimilarity in vegetation vigour, resulting from variation in nitrogen and water applied, are easily located when NIR imagery or data are used. Stress is shown by progressive decrease in

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... IR reflectance. The study is carried out for three different crops and field spectra collected from farmers' field were compared with test fields at IARI, New Delhi. Spectral Information Divergence is used as spectral similarity measure and close match between farmer's and test field spectra has been found for four levels of nitrogen and water applied to chickpea, sorghum and wheat crops. Similarity of spectra from farmer's fields with test fields is mapped by SID measure equivalent to coefficient of correlation and average SID measure equivalent to co-efficient of correlation for chickpea was 0.997, for sorghum was 0.996 and for wheat was 0.994. SID similarity among spectra from farmer's fields with spectra from test fields, if crops were water stressed: 0.997 for chickpea, 0.996 for sorghum and 0.991 for wheat. SID similarity among spectra of farmer's and test fields, if crops were Nitrogen stressed: 0.997 for chickpea, 0.994 for sorghum and 0.997 for wheat.