Plant growth regulation: a method for fine-tuning mepiquat chloride rates in cotton1
ABSTRACT Plant growth regulator management has been a challenge for cotton growers, due to the increased weather instability and the adoption of early cultivars, in off-season crops. This study aimed at proposing a new method, called Crop Growth Rate, to define mepiquat chloride rates in cotton crops, as well as to compare it with traditional management practices. Except for micronaire, there was no difference in cotton growth parameters, neither in yield nor fiber quality, between the new method and the traditional one. The mepiquat chloride rates were, on average, 24 % higher and 43 % lower in late and early maturity cultivars, respectively, for the new method. The number of bolls in plants treated with mepiquat chloride was lower than in non-treated plants, for the IMA5672B2RF and IMA5675B2RF cultivars, but a higher average weight of bolls was observed for these genotypes. The new method is efficient in defining the plant growth regulator rate to avoid an excessive growth and results in less mepiquat chloride applied to early cycle cultivars, preserving lint yield and fiber quality.