Abstract:

In order to reveal the influence mechanism of sowing date adjustment on crop yield formation, a field experiment was conducted to adjust the sowing date of the same variety of summer maize from 2019 to 2021 at Hebei Gucheng Agricultural Meteorology National Observation and Research Station in Northern north China, which was set up in four sowing date, as 10 d early sowing, 10 d late sowing, 20 d late sowing and control. By monitoring the growth period changes, plant dry matter accumulation, leaf photosynthetic characteristics and grain filling characteristics, and sampling at maturity to determine the yield components, the results showed that:the sowing date of summer maize was appropriate to be advanced,the seedling stage,ear stage and the whole growth period were extended,especially,the duration of effective filling was extended with the advance of sowing date.The effective grain filling duration days were extended by 4.7 days for every 10 days ahead of the sowing date.The average filling rate of winter wheat was 4.04% higher on the sowing date was advanced by 10 days, compared with the sowing date was deferred by 10 or 20 days and the control.Grain filling accumulation increased,and 100-grain weight increased by 5.459 g.The main yield components of summer maize,such as grain number per ear,grain weight per ear and 100-grain weight showed significant differences during sowing,and increased with the sowing date.The theoretical yield increased by 1 395.4 kg/ha with 10 days ahead of the sowing date during the experimental period from June 8 to July 8.The average net photosynthetic rate(Pn)of leaves in the critical development period of summer maize increased by 0.764 μmol/(m²·s)with every 10 days ahead of sowing date,and the average Pn of sowing date 10 days earlier was increased by 7.31% compared with the control and late sowing 10 and 20 days.With the increase of photosynthetic rate,dry matter production,accumulation and transfer to grain were increased,and the grain weight per ear and 100-grain weight increased by an average of 24.01% and 18.00%,respectively,compared to the control and late sowing 10 and 20 days.Advancing sowing date resulted in low plant height,strong stems,lodging resistance,large individual green leaf area,high leaf area index(LAI),and high leaf photosynthesis ability,above-ground dry matter allocation rate at maturity stage every 10 days in advance of sowing date:grain weight improved by 2.26%,the source—pool distribution of dry matter between plant vegetative organ and ear changed,ear weight per ear,100-grain weight and grain yield increased.The research showed that the double cropping area of winter wheat—summer maize in north China could effectively improve the yield per unit area by making full use of the heat resources increased by climate warming,reasonably allocating stubble,sowing summer maize early at the appropriate time,and extending the development period and grain filling time.

Key words: Summer maize, Northern north China, Sowing date, Growth characteristics, Yield-increasing effect