Evaluation of Various Materials for Harvest Preparation and Defoliation in Southeastern Arizona

Abstract

A single defoliation experiment was conducted during the 2004 growing season in an effort to evaluate the effectiveness of commercially available harvest preparation materials in the higher elevation areas of southeastern Arizona. Many growers will not employ a defoliation regime but will let the crop naturally senesce with the cooler temperatures and frost. This evaluation compared a standard treatment of Ginstar with some additional tank mix ethephon based products from DuPont and BASF. These treatments were compared to the common Na chlorate treatment employed by many growers in this region of the state. Treatments included a base rate of 8 oz/acre Ginstar with three different rates of both CottonQuick and Prep. Treatments were applied on 15 October in a randomized complete block design with four replications. Data collected included observations of percent defoliation, percent regrowth control, and percent open boll on two separate dates after treatment (27 October and 4 November). Yield data was also collected at the end of the season by harvesting the center two rows of each plot. Sub samples were collected for fiber quality analysis. Results showed significant differences among treatments with respect to defoliation parameters measured. Treatments including Ginstar and higher rates of both CottonQuick and Prep performed well. The treatment consisting of Na chlorate alone was also effective. The Ginstar + CottonQuick treatment did appear to have a slight advantage in final percent open boll counts. No significant differences among treatments were detected with respect to yield and fiber quality. However, lint yield for the control treatment was lower than the other defoliation treatments. This would indicate that some type of defoliation regime does provide benefit in terms of increased yield.