Abstract: 【Objective】To analyse the effect of sowing date on the growth and development of grain harvesting spring maize and the matching of heat resources,as well as to clarify the mechanism for achieving the yield increase and heat resources synergy of grain harvesting spring maize by early sowing at appropriate time,provide a theoretical basis for promoting the optimal cultivation of grain harvesting spring maize.【Methods】The late maturing variety ZD 958 was used as the common control. Five grain harvesting spring maize varieties suitable for local planting were selected as the test varieties. The sowing date networking test was carried out in six ecological areas：the east warm and cool dry farming area of Daxing′anling Mountains,the south warm and dry farming area of Daxing′anling Mountains,the warm and hot irrigation area of West Liaohe Plain,the warm and hot irrigation area of northern hills of Yanshan Mountains,the warm and hot irrigation area of Tumechuan Plain,and the warm and hot irrigation area of Hetao Plain in Inner Mongolia. The effects of sowing date on the growth and development,dry matter accumulation and yield formation of grain harvesting spring maize,as well as the relationship between the growth of grain harvesting spring maize and heat factors was analyzed.【Results】Early sowing at appropriate time accelerated the emergence of grain harvesting spring maize,increased the utilization rate of effective accumulated temperature in spring by 1.5 percentage points,prolonged the duration of growth after anthesis by an average of 2 d,increased the distribution of accumulated temperature after anthesis by 1.5% to 3.1%,increased the accumulation of dry matter after anthesis by 3.9%,and increased the dry matter accumulation rate by 9.5%,promoted grain filling,increased the number of grains per ear and 1 000 grain weight,and advanced maturity by 3-5 d. When early sowing at appropriate time,for every 1 ℃ rise in diurnal range the dry matter accumulation rose by 0.4 t/hm². For every 1 ℃ increase in average daily temperature,the average 1 000 grain weight increased by 21.1 g and yield increased by 0.9 t/hm² at the same time.【Conclusion】Early sowing at appropriate time improved the matching and utilization of the diurnal range and dry matter accumulation at flowering and grain stage. With 9.9% yield increase in grain harvesting spring maize,the utilization rate of annual accumulated temperature increased by 1.1 to 2.8 percentage points,resulting in accumulated temperature of 43.7 to 130.9 ℃ for grain dehydration at later stage,achieving high yield,high efficiency and high quality direct grain harvesting.

Key words: Grain harvesting spring maize, Sowing date, Growth and development, Heat