ABSTRACT
Tolerance of Roundup Ready cotton to multiple applications of Roundup Ultra was evaluated at an on-farm site in Horry County, SC, in 1999. Paymaster 1220BR cotton was planted May 22, 1999. Plots were 4 rows, 30 feet long, and were arranged in a randomized complete block design with 6 replications. Treflan (trifluralin) was applied preplant-incorporated @ 1.5 pt/ac, and Cotoran (fluometuron) was applied preemergence @ 1.5 qt/ac to the entire test area. The test was maintained weed-free. Roundup Ultra treatments evaluated were none, 1.5 qt/ac applied postemergence (POST) when cotton seedlings were in the 2-leaf stage, 1.5 qt/ac applied POST at the 4-leaf stage, 1.5 qt/ac applied POST at the 4-leaf stage followed by (fb) 1.5 qt/ac POST-directed at the 8-leaf stage, 1.5 qt/ac applied POST at the 2-leaf stage fb 1.5 qt/ac POST at the 4-leaf stage fb 1.5 qt/ac applied POST-directed at the 6-leaf stage fb1.5 qt/ac applied POST-directed at the 8-leaf stage, and 2 qt/ac applied POST at the 4-leaf stage fb 2 qt/ac POST-directed at the 8-leaf stage. Twenty plants/plot were plant-mapped August 15, 1999. The center two rows of each plot were harvested with a spindle-picker in mid-November.
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