Trials were conducted at 16 locations in 1991 to evaluate effects of cotton defoliation treatments on cotton quality as measured by the HVI classification system. Defoliation treatments compared were DROPP^®, DROPP tank-mixed with other competitive commercial defoliants, and a competitive defoliant or mixtures of competitive products. Treatments were compared side by side applied to cotton in blocks large enough to provide at least one module of harvested cotton per treatment. At the gin, two samples were taken from each module; one after ginning but prior to lint cleaning, and another following lint cleaning. Samples were assessed for quality with the HVI system as well as traditional classing.

Preliminary results of quality measurements show close association of cotton defoliation by treatments with HVI measured trash content in samples taken after ginning but prior to lint cleaning. Highest defoliation and lowest trash content prior to lint cleaning were with the DROPP tank mix treatment, with lower defoliation and higher trash content for the competitive treatment and the DROPP alone treatment. Lint cleaning effectively lowered trash content of all treatments to equal and acceptable levels.

As might be expected, defoliation treatments did not affect micronaire, staple length, fiber strength or length uniformity.

Differences among treatments were found in HVI color grade of samples taken after lint cleaning. A higher percentage of samples with better color grades was recorded with the DROPP tank mix treatment compared to the other two treatments. The DROPP tank mix treatment had the highest percentage of samples in grade 21 (strict middling) and lowest percentage in grade 41 (low middling). The same trend, although not as strong, was shown with samples from the DROPP alone treatment.most samples from treatments with competitive products were grade 31 (middling) with low percentages of grade 21 and grade 41.