By comparing the effects of different sowing dates on yield of double cropping rice and utilization efficiency of light and heat energy, and analyzing the sensitivity of different varieties to sowing date and light and heat resource efficiency, the best sowing date was investigated, which was conducive to double-cropping rice yield and resource utilization efficiency in Hunan province.

Using the main double-cropping rice varieties approved in Hunan province, the main double-cropping rice producing area, as the test materials, three sowing dates for early and late rice were set up for field experiments from 2018 to 2019. The rice growth period, yield and yield components as well as meteorological data were analyzed to compare the yield and the utilization efficiency of light and heat resources of each variety under different sowing dates.

With the delay of the sowing date, the early and late rice shortened the growth period by shortening the days of the sowing-ear start stage, while the yield of early rice showed an increasing trend. Late-maturing rice responded faster to late sowing than middle-maturing late rice; In 2018, with the delay of sowing date, the heat energy utilization rate of early rice decreased by 2.73% and 4.45% respectively, the light energy utilization rate decreased by 1.28% and -1.77% respectively, the heat energy utilization rate of late rice decreased by -2.64% and 8.15% respectively, and the light energy utilization rate decreased by 2.14% and 13.25% respectively. In 2019, with the postponement of sowing date, the heat energy utilization rate of early rice increased by 0.36% and 10.36% respectively, and the light energy utilization rate increased by 1.53% and 12.52% respectively. The heat energy utilization rate of late rice decreased by -0.72% and 6.09% respectively, and the light energy utilization rate decreased by 0.58% and 6.21% respectively.

The sowing date had a significant impact on the utilization efficiency of light and heat resources of double-cropping rice. It was appropriate to delay the sowing date of early rice and advance the sowing date of late rice to improve the efficiency of light and heat resources. The comprehensive efficiency of the combination of the second sowing date of early rice+the second sowing date of late rice for double cropping rice is higher, and the combination of late-maturing early rice and medium-maturing late rice combination had higher comprehensive efficiency.