Estimation of canopy cover, leaf area index and leaf nitrogen content in sugar beet using digital photography

In this study, digital photography was used to estimate canopy cover, leaf area index and nitrogen uptake by sugar beet (Beta vulgaris L.). For doing this, Pars cultivar was sown in a silty clay loam soil for two years, 2012-14. Irrigation treatments included 100 and 50% of irrigation requirement and nitrogen treatments in four levels including 0, 60, 120 and 180 kg N ha-1. Photos were taken during the growing season using Canon digital camera. Main bands of red, green, and blue (RGB) were extracted from photos using ILWIS software and different combinations of the main bands were prepared. Then, correlation of the obtained combinations with the absorbed N was determined. Results showed a high correlation (0.84) between GMR index (green band minus red band) and the absorbed N. Canopy cover was estimated using MATLAB software and its correlation with the GMR index was 0.78. Extinction coefficient was estimated to be 0.49 for the initial period of sugar beet growth.