Determination of Plant Water Stress Using Spectral Reflectance Measurements in Watermelon (Citrullus vulgaris)

Abstract

This study determined water stress for the watermelon (Citrullus vulgaris cv. Crimson Sweet) using remotely-sensed spectral indices. The experiment was conducted in the field during the 2008 growing season in a semi-arid region located in western Turkey. The six spectral indices used were the (1) Optimized Soil Adjusted Vegetation Index (OSAVI), (2) Simple Rate Index (SR), (3) Normalized Difference Vegetation Index (NDVI), (4) Green Normalized Difference Vegetation Index (GNDVI), (5) Water Band Index (WBI) and the (6) Infrared-Red Index (IR-RED). Tests were conducted under varying irrigation applications including 0, 20, 40, 60, 80 and 100 of field capacity and through varying development periods. The four development periods were: (1) flowering (2) fruit growth and (3) ripening and harvest. The experimental results demonstrated that spectral indices have good potential to estimate water stress for watermelon in semi-arid regions. Regression models were obtained between spectral indices and yield at different growth periods. The highest R was found in the 2