Mepiquat chloride applications across two nitrogen rates in a conservation tillage cotton system

Authors: Balkcom, Kipling; MONKS, C. DALE - North Carolina State University; BROWN, STEVE - Auburn University

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2022
Publication Date: 6/1/2022
Citation: Balkcom, K.S., Monks, C., Brown, S.M. 2022. Mepiquat chloride applications across two nitrogen rates in a conservation tillage cotton system. Journal of Cotton Science. 26:1-13.

Interpretive Summary: A plant growth regulator is a management tool to limit excessive cotton vegetative growth, but over-application can sometimes decrease yield. In addition, information on how different application strategies perform in a conservation system is limited. An ARS scientist in Auburn, AL in conjunction with scientists from North Carolina State Univ. and Auburn Univ. compared how different plant growth regulator strategies affected plant growth and yield across two N rates in a conservation tillage system. The greatest N rate increased plant heights two out of three years, but the most effective strategy to control plant height varied across growing seasons. No clear application strategy was identified that consistently minimized height to node ratios. Whole plant biomass was reduced only reduced one site-year out of five with mepiquat chloride. Yield responses to mepiquat chloride also varied across growing seasons and ranged from a 16% yield decrease to a 9% yield increase. Different weather conditions for each growing season likely produced inconsistent cotton yield responses to mepiquat chloride. Although variable, our results suggest that cotton growers using conservation systems can expect similar performance from mepiquat chloride applications compared to cotton grown in conventional systems.

Technical Abstract: In cotton production, a plant growth regulator is a management tool to limit excessive cotton (Gossypium hirsutum L.) vegetative growth, but over-application can promote early cut-out and sometimes decrease yield. Specific information on how different plant growth regulator application strategies perform in a conservation system is limited. Our objective was to compare how different plant growth regulator strategies affected plant growth and yield across two N rates in a conservation tillage system during the 2006 to 2008 growing seasons in Alabama. Treatments were arranged in a randomized complete block design with a split-plot treatment restriction and four replications across five site-years. Main plots were two N rates (101 and 134 kg N/ha), and subplots were six mepiquat chloride application strategies. The 134 kg N/ha rate increased plant heights two out of three years, but the most effective strategy to control plant height varied across growing seasons. No clear application strategy was identified that consistently minimized height to node ratios. Whole plant biomass was reduced by mepiquat chloride applications, but only for one site-year out of five. Yield responses to mepiquat chloride were inconsistent across growing seasons and varied from a 16% yield decrease to a 9% yield increase. Variable environmental conditions occurred across growing seasons that likely resulted in inconsistent cotton yield responses to mepiquat chloride applications. Although variable, our results suggest that cotton, grown in a conservation system, responded comparably to mepiquat chloride applications in conventional systems. Specific environmental conditions during each growing season likely affected mepiquat chloride efficacy.