MODEL ANALYSIS OF TEMPERATURE AND SOLAR-RADIATION LIMITATIONS TO MAIZE POTENTIAL PRODUCTIVITY IN A COOL CLIMATE

In cool-temperate climates, potential maize grain yields are variable and often small. Low temperature prolongs growth duration, reduces cro p growth rate, and increases the risk of frost terminating grain filli ng prematurely. The objectives of this study were (1) to assess the pe rformance of a radiation- and temperature-driven maize simulation mode l in a cool-temperate climate and (2) to modify the model to allow the effects of temperature and solar radiation on growth and yield to be simulated in both warm and cool climates. Modifications to the model t o improve simulation in the cool climate included a changed phenology response to low temperature, a reduction in radiation-use efficiency a nd rate of harvest index increase at low temperature, and an increased time lag between silking and the start of grain growth at low tempera ture. The modified model gave good agreement between observed independ ent datasets and simulated values of grain and total biomass yield in tropical, subtropical and cool-temperate locations; root mean square d eviations of the comparisons averaged across all locations were about 12% of the mean values. Thus the utility of the model has been enhance d for a wider range of climates. The study also showed that the conclu sion from previous analyses with the model in warm climates that the h ighest potential maize yields occur at locations with a combination of high incident radiation, low temperature and long growth duration may not be valid if mean temperature during growth is less than ca. 18 de grees C, However, this condition would only occur in cool-temperate cl imates.