AGROCLIMATIC BASIS OF OPTIMUM SEEDING TIME OF CROPS

In this article the theoretical method to determine the optimum seeding time of wheat and maize is established.For wheat,it is based on the close relationship between accumulated temperature and number of leaves on the main stalk as well as number of stalks per plant of wheat,and for maize,based on the climatic potential productivity model of maize.Using these models,we found that the optimum seeding time should be,for winter wheat,decided by accumulated temperature from seeding date to the beginning of dormancy,and for maize,postponed for about 30 days for medium variety and about 50 days for early variety in contrast with traditional seeding time.Besides,through analysing climatic data the agroclimatic pattern of optimum seeding time for both crops in Beijing area has been found as well.