SURVEYING THERMALLY-DEFOLIATED COTTON PLOTS WITH COLOR-INFRARED AERIAL PHOTOGRAPHY

Authors: Fletcher, Reginald; Showler, Allan; Funk, Paul

Submitted to: Crop Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2007
Publication Date: 6/25/2007
Citation: Fletcher, R.S., Showler, A., Funk, P.A. 2007. Surveying thermally-defoliated cotton plots with color-infrared aerial photography. Crop Management [online]. Available: http://www.plantmanagementnetwork.org/cm/research/2007/thermal.

Interpretive Summary: Cotton producers need assistance in examining the effectiveness of thermal defoliation within fields. Cotton harvested from areas where leaf kill was incomplete may receive lower price grades because chlorophyll in green leaves rubs against the cotton fibers during harvest, staining the fibers and reducing the price grade. ARS scientists evaluated color-infrared aerial photography as a tool for surveying cotton plots subjected to thermal defoliation. Plants responding to the treatment and areas that needed further treatment were readily located on the color-infrared aerial photographs. These results indicate that color-infrared aerial photography can provide the information that growers need for surveying cotton fields subjected to thermal defoliation. Growers may opt to reapply the treatment to areas not responding to the first treatment.

Technical Abstract: Producers can use heated air (thermal defoliation) as a nonchemical alternative for terminating cotton (Gossypium hirsutum L.) growth and for preparing it for harvest, making this technique ideal for cotton grown in sustainable systems. For large cotton fields, growers need assistance in examining the effectiveness of the thermal defoliation. Cotton harvested from areas where appropriate leaf kill did not occur may receive lower price grades because chlorophyll in green leaves rubs against the cotton fibers during harvest, which stains the fibers and thus reduces the price grade. We qualitatively and quantitatively evaluated color-infrared aerial photography as a tool for surveying cotton plots subjected to thermal defoliation. Treated canopies appeared brown on digitized (scanned) color-infrared positive transparencies, causing them to be easily separated from nontreated canopies. The green, red, and/or near-infrared light sensitive layers of the film contributed to the significant differences (t-test; P < 0.05) observed between treated and nontreated canopies, with the red light sensitive layer being most responsive to the treatment. These results indicate that color-infrared aerial photography can provide the information that growers need for examining thermally defoliated cotton fields. Growers may opt to reapply the treatment to areas not responding to the first treatment.