Effects of seeding date on yield, growth period and utilization of temperature and sunshine of mechanical transplanting rice in different ecological regions

Abstract: This study was conducted to investigate the effects of seeding date and variety type on yield, growth period and utilization of temperature and sunshine under the rice-wheat cropping system in different ecological regions of Henan Province. Taking conventional medium-maturing medium Japonica rice variety, conventional and hybrid late-maturing medium Japonica rice varieties, conventional early-maturing late Japonica rice variety and hybrid late-maturing medium indica rice variety as experimental materials, high-yield cultivation method of mechanization planting of carpet seedlings was used in three different sites, i.e. Luoshan rice-growing district along the Huai River in,southern Henan Province, Xincai in central Henan Province and Yuanyang rice-growing district along the Yellow River in northern Henan Province. The effects of different seeding dates on yield, growth period and utilization of temperature and sunshine of mechanized planting rice were comparatively analyzed. Within the set range of seeding date in the experiment, except that the yields of conventional medium-maturing medium Japonica rice variety were highest for Luoshan and Xincai in the second sowing period (On May 16) and for Yuanyang in the first sowing period (On May 11), the yields of conventional and hybrid late-maturing medium Japonica rice varieties, conventional early-maturing late Japonica rice variety and hybrid late-maturing medium indica rice variety were all highest in the first seeding period (On May 11) for every site, and it showed a trend of gradual decline along with the seeding date delaying（P＜0.01）, but significance differences were all different among different variety types and sites. With the delaying of seeding date, yield differences among variety types gradually increased in the same site（P＜0.01）, of which grain yield of hybrid late-maturing medium Japonica rice variety was the highest in every site, and was significantly higher than other variety types in each period. With the delaying of seeding date, the periods of jointing, heading and maturity of all varieties were correspondingly delayed, and whole growth period, and its accumulated temperature, sunshine hours and utilization rate of TPS all showed a significant decreasing trend (P<0.01). And the reduction of growth period along with the delaying of seeding date, was mainly in vegetative growth phase, i.e. from seeding to jointing stages. Therefore, under the condition of rice-wheat cropping system with mechanical planting in Henan Province, the preferred variety that was firstly chosen should be hybird and conventional late-maturing medium Japonica rice varieties in southern Henan, and the variety that was secondly chosen should be conventional early-maturing late Japonica rice variety, and their suitable seeding dates were all from May 11 to May 25. In the northern Henan, the preferred varieties should be the conventional late-maturing medium Japonica rice variety and medium-maturing medium Japonica rice variety, followed by conventional late-maturing medium Japonica rice variety, and their suitable seeding dates were all from May 11 to May 21. The result will provide a reference for the scientific division and the distribution of different rice variety types under mechanical high-yield cultivation and the choosing of its possible seeding date in different ecological areas in Henan Province.