Cotton growth and yield after seed treatment with mepiquat chloride in the tropical winter season

Abstract

Cottonseed ( Gossypium hirsutum L.) was treated with mepiquat chloride (MC) to examine its potential for the management of vigorous early growth experienced on cotton grown in the tropical winter season. As there is little published research from the field on this topic, we aimed to determine the effect of seed treatment of cotton with MC grown to maturity. In two field experiments over two seasons the seed surface was treated. Seed surface treatment was compared with pre-sowing priming with MC in experiment 2. Lint yields were high, 2059 and 2270 kg/ha averaged over all treatments in experiments 1 and 2. In both experiments, seed surface treatment with 2 g MC/kg reduced ( P < 0.05) plant height for up to 30 days after sowing and there were no significant changes to rate of crop development, time to maturity, lint yield or fibre quality. In experiment 2 treating with MC reduced plant establishment in proportion to the amount of MC applied ( P < 0.01). Pre-sowing priming caused approximately twice the reduction in plant height per gram of MC than surface treatment and significant differences persisted longer, even until maturity using 8 g MC/kg seed. Priming with ≥4 g MC/kg seed had additional effects ( P < 0.05): (1) reduced node development between first square and first flower, (2) delayed the time to first square, first flower and maturity by 4 days, (3) increased production of bolls on monopodial branches, and (4) reduced lint yield compared to the same concentrations applied to the surface. Fewer smaller plants having smaller bolls were implicated in this response. It was concluded that the relative benefit of seed treatment with MC at the concentrations and methods that did not reduce lint yield appears questionable as height reductions per gram of MC/ha were less than measured at this location with the same amount applied as a foliar spray.