REMOTE SENSING OF BARLEY STRESSED WITH CO2 AND HERBICIDE

Stress cause crops to grow at less than their full potential and can cause reduction in yield; this is as a result of threats emanating from the causative factor(s) known as stressors. Field experiments were conducted in 2010 to compare the effects of two stress-inducing agents on the spectral reflectance of barley: (1) High concentration of Carbon dioxide in soil and (2) four different levels of concentration of herbicide application. Carbon dioxide concentrations up to 80% in soil were applied to experimental plots as part of a study of the potential effects of leakage from carbon capture and storage. In a separate set of plots, glyphogan herbicide (Makhteshim Agan, UK) containing 360g l -1 of glyphosate was applied at four different levels of concentration, at the rate of 0.15 , 0.3 , 0.6 and 1.2 l ha -1 in 200 l ha -1 of water. These rates are equivalent to 5, 10, 20 and 40% of the usual lethal dose for barley crop, diluted to give the normal rate of spray coverage. Thus 0.1, 0.2, 0.4, and 0.8 ml Glophogan in 80 ml of water was sprayed evenly over each of the four plots treatment levels. This was designed to provide a range of levels of stress to the barley crop. Plant stress effects were detected by spectral scanning between 350 and 2500 nm with an ASD Fieldspec FR spectroradiometer (ASD, Boulder, USA). Canopy reflectance spectra were used to locate the position and height of the inflection point of the red edge by derivative analysis and to investigate other peaks that may indicate stress in plants. Measurements of soil gas concentration, and chlorophyll content were carried out at various stages of the crop development to determine any variations as the experiments progressed.