Proximal sensing and vegetation indices for site-specific evaluation on an irrigated crop tomato

Abstract

The present paper deals with proximal sensing technique applied to a drip irrigated tomato field. The aim of this "on farm" research was the evaluation of three Vegetation indices, WI (Water index) WI/NDVI and TSAVI (Transformed Soil Adjusted Vegetation Index), to analyze the correlation among VIs and tomato yield, to assess the spatial variability of a tomato crop, and finally to identify homogeneous crop area. Until 90 days after transplanting, tomato field was almost uniform, either at a visual assessment or according to spectroradiometric readings. At the end of the vegetative growth stage (from 90 days after transplanting), a spot crop area showed increasing soil moisture conditions due to soil topography. In this spot area, plants first yellowed and after started dying. Among indices, TSAVI appeared the most effective to detect excess soil water conditions, infect at 105 DAT TSAVI index was highly significant correlated to tomato yield, demonstrating to be a good index for early detecting excess crop water status. This study reinforce the possibility of detecting plant water stress by spectroradiometric measurements at field scale (ground-based measurements) and at territorial level.