Under the background of mechanical grain harvesting, the purpose of this study was to determine the accumulated temperature requirements of maize in different planting regions after physiological maturity by dehydration to the suitable harvest date, so as to provide the theoretical guidance for selecting suitable grain harvesting varieties, and rationally arrange agricultural operations and improve mechanical utilization efficiency in each planting region.

From 2014 to 2018, 141 maize varieties with different maturity periods selected to observe the dynamic changes of grain moisture content at typical test points in the northwest maize region (NW), the north maize region (NM) and Huang-huai-hai maize region (HM). Combining with meteorological date, the accumulated temperature requirements of maize field stalk dehydration to 25% and 20% grain moisture content after the physiological maturity were analyzed in different production regions.

The grain moisture content was different at physiological maturity in different production regions. The average grain moisture content was 28.5%, 29.9% and 29.6% in HM, NW and NM, respectively. Correlation analysis showed that there was no significant correlation between the growth period of different varieties and the grain moisture content at physiological maturity. The accumulated temperature of grain moisture content from physiological maturity to 25%, 20% and grain moisture content at physiological maturity were used as indexes. By using the two-way average method, the tested varieties were divided into 4 types, including low accumulated temperature demand and high moisture content (I), high accumulated temperature demand and high moisture content (II), low accumulated temperature demand and low moisture content (III), and high accumulated temperature and low moisture content (IV). For the northwest China, north China and northeast China, III and IV could be selected, but IV varieties needed to reserve enough accumulated temperature to dehydrate in the field. While the summer maize with growing twice a year in the Huanghuaihai region, III varieties could better coordinate the production and allocation of wheat and maize, and make full use of the excess temperature that could be used for grain dehydration.

Because of different dehydrating conditions such as temperature, the days when grain moisture content from physiological maturity to 25%, 20% showed that the northwest maize region was longer than the north maize region and Huang-huai-hai maize region. Grain moisture content and harvest quality can be effectively reduced by selecting the accumulated temperature varieties suitable for different regions and scientifically setting the harvest date.