Leaf Emergence and Leaf Duration Related to Thermal Time Calculations in Ceres-Maize
- Tom Hodges and
- David W. Evans
In the CERES-Maize model, maize (Zeta mays L.) leaf initiation and appearance are modeled using thermal time derived from air temperature. Prior to the elevation of the culm apex, soil temperature, which is calculated by the model from air temperature, is used to calculate thermal time. No provision is made for response differences in leaf appearance rate due to cultivar or daylength. This research compares predicted with actual leaf development for up to 10 hybrids in five experiments for 4 yr. It also compares calculated versus measured soil temperatures in 1 yr. Thermal time requirements for appearance of leaf tips and collars and for duration of leaf expansion were determined using thermal time equations from the CERES-Maize model. Thermal time values per leaf were stable within experiments, but varied substantially among years and hybrids. Although the CERES-Maize model predicts leaf tip appearance moderately well, the rate of leaf development appears to differ among hybrids and may be sensitive to daylength and temperature extremes that are not considered by the model. Improvements are also needed in the model prediction of soil temperature.
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