Effects of Seeding Date and Variety Type on Yield,Growth Stage and Utilization of Temperature and Sunshine in Rice

【Objective】This study was conducted to investigate the effects of seeding date and variety type on yield, growth stage and utilization of temperature and sunshine under the rice-wheat cropping system in midland of Jiangsu Province. The result will provide a theoretical basis for scientific use of the seeding date and adoption of suitable variety types.【Method】With medium-maturing late Japonica rice varieties, early-maturing late Japonica rice varieties, late-maturing medium Japonica rice varieties, medium-maturing medium Japonica rice varieties and late-maturing medium Indica rice varieties as materials, using four seeding dates, a comparative study of seeding date and variety type on yield, growth stage and utilization of temperature and illumination was conducted【.Result】The grian productivity of different variety types showed that late-maturing medium Japonica rice varietiesearly-maturing late Japonica rice varietiesmedium-maturing medium Japonica rice varietieslate-maturing medium Indica rice varietiesmedium-maturing late Japonica rice varieties. With delay of seeding date, the grain yields of the five rice variety types all decreased significantly, but the decrements varied. The yields decreasing range of different variety types showed that medium-maturing late japonica rice varietieslate-maturing medium indica rice varietiesearly-maturing late japonica rice varietieslate-maturing medium japonica rice varietiesmedium-maturing medium japonica rice varieties. With the delay of seeding date, the growth process of all the varieties delayed and the growth stages of all the variety types shortened,the accumulated temperature and illumination hours for growth stages significantly reduced. In the same seeding date, the yield discrepancy among different varieties showed an increasing trend with the delay of seeding date. According to the growth stage,the effect of seeding date on the utilization rate of temperature and light resources of different variety types could be divided into two categories, one was the little influence on the short growth period which were medium-maturing medium japonica rice varieties and late-maturing medium indica rice varieties,the other was the great influence on the long growth period which were late-maturing medium japonica rice varieties, early-maturing late japonica rice varieties and medium-maturing late japonica rice varieties. The suitable variety types were preliminarily regionalized based on the different seeding dates as follows:early-maturing late japonica rice varieties and late-maturing medium japonica rice varieties, medium-maturing medium japonica rice varieties, late-maturing medium indica rice varieties should be adopted in Mid-May; late-maturing medium japonica rice varieties and early-maturing late japonica rice varieties, medium-maturing medium japonica rice varieties, late-maturing medium indica rice varieties should be adopted in late May; late-maturing medium japonica rice varieties and medium-maturing medium japonica rice varieties and early-maturing late japonica rice varieties should be adopted in early June; medium-maturing medium japonica rice varieties should be adopted in mid-June. 【Conclusion】 With the delay of seeding date, the grain yield, days of growth stage and utilization of temperature and illumination of the five rice variety types all decreased. Considering the rice-wheat cropping systems and heat conditions, a preliminary division for adopting suitable variety types of different seeding date was made, in order to provide reference for rice production in large area.