Auxin injury on cotton, II: Effects on yield components

Abstract

Auxin-tolerant cotton (Gossypium hirsutum, L.) cultivars are the latest tools producers use to combat herbicide-resistant weed species during the growing season. The widespread implementation of auxin-tolerant crops has led to an increase in in-season applications of auxins. Auxin drift has subsequently become a more prominent issue in the agricultural industry and causes producers to shift management tactics. Yield partitioning research based on auxin application timing has been conducted, but more information is needed concerning application rate and the interaction between application rate and timing. Experiments were conducted from 2019 to 2021 in Grand Junction, TN, to determine the effects of synthetic auxin exposure on boll positioning, development, and production. Applications of 2,4-dichlorophenoxyacetic acid (2,4-D) or dicamba were made to cotton cultivars of the opposite technology at either matchhead square or 2 weeks after first bloom (FB + 2WK). Nontreated experimental plots were also included. More severe impacts on overall lint yield, yield partitioning, and yield components were observed following exposure to 2,4-D than dicamba. Application rate and timing also impacted yield components and partitioning. Exposure to 2,4-D during vegetative growth caused increased partitioning to vegetative and aborted fruiting positions but decreased partitioning to position 1, zone 2 (nodes 9 through 12), and zone 3 (nodes 13 and above) as application rate increased. Exposure to these rates at FB + 2WK did not impact yield partitioning. Environmental conditions following applications of 2,4-D or dicamba play an important role in the recovery and growth of cotton and subsequent yield penalties.