Mepiquat Chloride and Irrigation versus Cotton Growth and Development

Abstract

AbstractCotton (Gossypium hirsutum L.) produces excessive vegetative growth when grown under optimum water and nutrient conditions. The plant growth regulator Mepiquat Chloride (MC); 1,l‐dimethyl piperidinium chloride reduces vegetative growth and can promote early maturity. Its effect on yield has been inconsistent, with some researchers showing an increase while others have indicated a decrease. This variation in yield has often been attributed to environmental factors and variations in water and fertilizer inputs. This study examined the effect of MC on cotton growth, under varying irrigation treatments, to determine if soil moisture interacts with MC. The experiment was conducted in 1987 with two cotton cultivars, Stoneville 825 (‘ST825’) and Deltapine 20 (‘DP20’), grown in pots, with five irrigation treatments [1.2,1.0,0.8,0.6, and 0.4 times previous day's pan evaporation (PE)] each with and without MC applied. Mepiquat Chloride reduced plant height, number of main stem nodes, and internodal length. The effect on boll numbers was mixed between cultivars. In some instances under the same irrigation treatment (1.2 PE), the number of bolls was higher in ST825 with MC applied than with control while in DP20 the control treatment had the higher number of bolls. Mepiquat chloride's effectiveness on vegetative growth tended to decrease as the number of days after application increased. Differences in response within irrigation treatments was attributable to MC. Differences in response between irrigation treatments with MC applied was attributable to irrigation and cultivar differences and not to interaction between soil moisture and MC.