Early flower bud loss and mepiquat chloride effects on cotton yield distribution

Abscission or abortion of the initial cotton (Gossypium hirsutum L.) flow e r buds or bells increases the importance of retaining fruit on adjacent Or subsequent fruiting positions. Use of the plant growth regulator mepiquat c hloride (MC) (N, N dimethylpiperidinium chloride) improves boll retention o n lower reproductive branches (sympodia), reduces vegetative growth, and in some cases reduces upper sympodial productivity. Our objective was to dete rmine the effect of doses and application timings of MC and different level s of early newer bud removal on within-plant yield distribution. Zero or an average of two or four flower buds located at first positions on lower sym podia were removed from each plant prior to MC applications at two field lo cations in 1992. This bud loss resulted in higher retention at second posit ions on lower sympodia and on slightly higher sympodia. Two biweekly doses of 24.5 g ha(-1) of MC applied at early bloom: also enhanced compensation a nd yield on lower sympodial second positions. Primarily at one location, fo ur weekly MC doses of 12.25 g ha(-1) each beginning when buds were 1 cm lon g resulted in increased monopodial branch yield when there was moderate ear ly bud loss. Depending on field location, one or the other of the MC treatm ents reduced the number of fruiting positions and yield on higher; sympodia when fruit retention on lower sympodia was high. Loss of early buds, which resulted in small increases in vegetative growth, ameliorated this effect. The biological responses produced by early bud loss and MC treatments inte racted positively. After early bud loss, plants treated with MC generally i mproved compensation on lower sympodia without negative effects on upper sy mpodia.