Abstract
Excessive vegetative growth of cotton occurs under favourable growing conditions and this contributes to yield losses. Low concentrations of mepiquat chloride (1, 1-dimethylpiperidinium chloride) were applied to vigorous, growing cotton by means of two or more sprays at different time intervals. Application of 6, 3–12, 5 g a.i. ha−1 at 14-day intervals limited the growth rate of the main stem in cotton to 8–9 cm per 100 degree days (DD) and reduced plant height by 13–18%. Continuous, but controlled growth is essential to maintain high yield. In four trials, seed cotton yields averaged 3 900 kg ha−1 and were not affected by the various mepiquat chloride treatments. Under conditions of luxurious growth (>10 cm per 100 DD), the yield at first picking increased by between 20 and 26%, and total yield by 5%. It is necessary that intervals between supplementary applications of mepiquat chloride be adjusted according to the expected growth rate.