Evolution of kernels moisture content and physiological maturity determination of corn (Zea mays L.)

In northern environments, corn (Zea mays L.) grain yield and quality depends heavily on reaching physiological maturity before the first fall killing frost. Unlike other cultivated plant species, corn physiological maturity is not easily described by visual criteria. Several methods, such as observing the milk line progression and the black layer formation, have been used to determine corn physiological maturity. However, their use in performance trials that include a large number of entries is not practical. Monitoring the decrease in kernel moisture content could be an alternative in evaluating maturity in corn. A 3-yr study was conducted (1) to determine through a linear regression analysis the relationship between kernel moisture content and Julian days during the late August to late September sampling period and (2) to predict from these linear regressions the maturity of commercial hybrids commonly planted in the Saint-Lawrence River Valley area (2300 to 2900 Corn Heat Units). Ninety-nine percent of the linear regression coefficients obtained in the analysis were greater than 0,800 (n = 1169) and black layer formation coincided with kernel moisture contents ranging from 32 to 35%. It is concluded that sampling every 15 d can accurately determine physiological maturity as defined by the 32 and 35% kernel moisture content thresholds.