Cotton crop maturity: A compendium of measures and predictors

The timing of cotton crop maturity is a major determinant of yield, fiber quality, and net returns. Yet there is surprisingly little consensus on the definition of crop maturity in cotton and no standard method of measuring its timing. This review provides a composite definition of crop maturity consisting of physiological and harvest maturity, plus an agronomic maturity date at which the crop is ready for application of harvest-aid chemicals. Physiological maturity of the whole plant is attained upon maturity of the uppermost (youngest) harvestable boll, which depends on maturity of its seed and fiber. This review describes methods of assessing agronomic and fiber maturity, plus 12 methods of measuring the relative timing of crop maturity at the end of season. The review also describes 10 methods of predicting maturity timing based on morphological features or developmental progress of the crop. These indicators are evaluated in terms of their predictive accuracy, heritability, and data collection requirements as reported in the literature. Predictive accuracy, represented by coefficient of determination of various predictors relative to end-of-season measures, tends to increase as the time of data collection approaches the time of crop maturity. Heritability estimates for maturity timing traits in four studies provide no evidence that end-of-season measures of crop maturity are less heritable than in-season estimators. For crop managers and breeders, the choice of maturity indicator must weigh its utility and accuracy against data collection requirements. In recent years, product-quantity measures have largely given way to time-event measures in which the threshold events correspond to agronomic maturity, such as 60% open bolls, or four nodes above cracked boll. Ultimately, estimation of thermal time elapsed from planting until maturity of the uppermost harvestable boll offers the most direct measure of cotton crop maturity. (C) 2016 Elsevier B.V. All rights reserved.