Abstract: [Objective] To assess the effects of varied harvest periods on agronomic traits and biological yields of two maize varieties, screen the maize varieties suitable for preparing silage in Liangcheng County, Ulanqab City,Inner Mongolia, and determine the best harvest period. [Method] A whole plant silage maize variety Jidong 81 and a grain maize variety Ganyou 702 were used as experimental materials. A total of 11 harvest dates during 5^th September and 5^th October in the year 2019 were set. The plant heights as well as fresh matter yields, dry matter contents and dry matter yields in different parts of the tested maize were monitored and statistically compared. [Result] The plant heights of the two maize varieties increased at first and then stabilized with the extension of the harvest periods. The maximum plant heights were observed on 17^th September in both Jidong 81 and Ganyou 702, which were 3.51 m and 2.94 m, respectively; the average plant height of Jidong 81 was significantly （P<0.05） higher than that of Ganyou 702 during the experimental period. The fresh matter yields of stems and leaves, stalks, ears and whole plant of the two maize varieties increased first and then decreased, their dry matter contents showed an gradually increasing trend, and their dry matter yields increased at first and then stabilized. There was no significant （P>0.05） difference in the whole plant average fresh matter yield between the two maize varieties. Jidong 81 had significantly （P<0.05） lower whole plant average dry matter content and whole plant average dry matter yield in comparison to Ganyou 702. [Conclusion] The best harvest period for the whole plant silage maize variety Jidong 81 was from 23^th to 26^th September, and that of the grain maize variety Ganyou 702 was from 17^th to 20^th September. Under the same planting conditions, Jidong 81 was more suitable to be promoted in this area.

Key words: harvest period, variety, silage maize, agronomic traits, biological yield