Surveying Thermally-defoliated Cotton Plots with Color-infrared Aerial Photography

Abstract

Thermal defoliation is a nonchemical alternative for terminating cotton (Gossypium hirsutum L.) growth and preparing it for harvest, making the technique ideal for cotton grown in sustainable systems. For large cotton fields, growers need assistance in examining the effectiveness of thermal defoliation because green leaves remaining in the field reduces the price grade of the cotton and increase the time needed to harvest the fields. We qualitatively and quantitatively evaluated aerial color-infrared photographic transparencies of two study sites to determine the feasibility of using color-infrared aerial photography as a tool for surveying cotton plots subjected to thermal defoliation. Treated canopies appeared brown and in mixtures of brown and red tones on the colorinfrared transparencies, leading to their separation from the control plant canopies (appearing in a red color). Quantitative analysis indicated that the green, red, and/or near-infrared light sensitive layers of the film significantly contributed to the color differences observed between the thermally-defoliated plots and the control plots. The results indicate that color-infrared aerial photography has high potential as a tool for assisting growers in surveying thermally-defoliated cotton fields. After visiting suspect areas identified on the photography, producers may opt to reapply the treatment.