Abstract: To reveal the impacts of sowing date on growth stage, grain dehydration process, dry matter accumulation and yield of summer maize, an experiment with three sowing dates was conducted at the agrometeorological experimental station of Taian in Shandong province in 2014 and 2015, in which the summer maize variety of Jundan 29 was used. The three sowing dates were June 5 (denoted as M−10), June 15 (denoted as M) and June 25 (denoted as M+10). The results showed that under the delay of sowing date (M+10), the duration of the summer maize at the whole growth period was shortened. Among them, the duration change from tasseling to maturity period was the largest, which was 7−10 days shorter than that of M and M+10. The water content and dry matter accumulation in kernels in summer maize of M−10 were higher than those of M+10. The grain dehydration rate of early sowing before physiological maturity was slower than that of late sowing, while that of early sowing after physiological maturity was faster than that of late sowing. The yield and yield structure factors of summer maize were significantly affected by different sowing dates under different meteorological conditions. Compared with the normal sowing date (June 15) of local summer maize, early sowing date (M−10) could increase the 100-grain weight and harvest index of summer maize, and reduce the bald point ratio. Compared with late sowing date (June 25), the grains per spike of summer maize under early sowing was significantly increased by 4.5% (2014) and 7.8% (2015) respectively. The 100-grain weight under early sowing was significantly increased by 12.3% (2014) and 16.8% (2015), and the bare tip ratio was significantly decreased by 21.4% (2014) and 12.5% (2015). It could be seen that the later the sowing date, the lower the yield. As a result, summer maize of Jundan 29 could be sown appropriately early in Huanghuaihai plain. Later sowing might easily lead to the delay of growth period and the occurrence of low temperature, which seriously affected the yield.

Key words: Summer maize, Sowing date, Dry matter accumulation, Grain dehydration process, Yield