Evaluation of a Ground-Based Sensing System for Wheat Performance Under Water-Limited Conditions.

Field phenotyping has been increasingly important for identifying abiotic stress tolerance in major crops. Remote sensing tools may provide a quick way to evaluate plant performance under stress conditions. The objective of this study was to evaluate a ground based plant health sensing system (PHS) for measuring plant height and spectral reflectance in wheat under drought condition. The PHS consisted of a multi-spectral optical sensor for measuring spectral reflectance of a plant canopy, an ultrasonic sensor for measuring plant height, a GPS system, and a data acquisition and processing unit. The system was calibrated and installed on a tractor. Twenty winter wheat genotypes were planted under dryland and irrigated conditions in the second week of October 2012 at Bushland, Texas. The experimental design was randomized complete block with three replications. Data on plant height and spectral reflectance; blue, green, red and near-infrared, were collected twice from dryland plots (186 and 214 days after planting, DAP), and once from irrigated plots (208 DAP). After height and reflectance measurements, aboveground biomass (ABM) was determined by destructive sampling from a 0.5 m inner row. There were significant differences among the wheat genotypes for plant height and normalized difference vegetative index (NDVI) irrespective of growing conditions. Under dryland condition, a significant linear relationship was detected between ABM and plant height; and between ABM and NDVI. However, the relationship was not evident between these variables under irrigated condition. The lack of relationship could be due to freeze damage in irrigated wheat. Nevertheless, the initial data from this study showed that PHS may be used for rapid measurement of plant height and spectral reflectance; and to predict wheat aboveground biomass under stress condition.