Studies On Reasonable Use Of Variety Types Of Rice In Lixia River Valleys

A comparative experiment was carried out with different variety types of rice under different seeding date during year2011—2012in Jiangyan District, Taizhou City. The experiment was selected suitable variety types for local in the rice-wheat cropping system. Systematic comparative studies on growth stage and utilization of temperature and sunshine, yield and yield components, characteristics of photosynthetic and matter production, rice quality were conducted to clarity the difference in population productivity and ecophysiological of different variety types under different seeding date, in order to provide theoretical and practical basis for scientific selection and rational layout of different seeding date for different cultivation methods and its supporting variety types. The main result of study was as following:(1) The production of different variety types showed:late-maturing medium japonica rice> early-maturing late japonica rice> medium-maturing medium japonica rice> late-maturing medium indica rice> medium-maturing late japonica rice. With the 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 the different variety types showed:medium-maturing late japonica rice> late-maturing medium indica rice> early-maturing late japonica rice> late-maturing medium japonica rice> medium-maturing medium japonica rice. With the delay of seeding date, the growth process of all the variety types delayed and the growth stages of all the variety types shortened, the accumulated temperature and sunshine hours for growth stages significantly reduced. In the same seeding date, the yield discrepancy among different variety types showed an increasing trend with the delay of seeding date. According to the growth stage, the effect of seeding date on the ultilization rate of temperature and light resources of different variety types could be divided into two categories, one was the little influence to the short growth period which were medium-maturing medium japonica rice and late-maturing medium indica rice, the other was the great influence to the long growth period which were late-maturing medium japonica rice, early-maturing late japonica rice and medium-maturing late japonica rice. The suitable variety types were preliminarily regionalized based on the different seeding dates as follows:early-maturing late japonica rice and late-maturing medium japonica rice, medium-maturing medium japonica rice, late-maturing medium indica rice should be adopted in Mid-May; late-maturing medium japonica rice and early-maturing late japonica rice, medium-maturing medium japonica rice, late-maturing medium indica rice should be adopted in late May; late-maturing medium japonica rice and medium-maturing medium japonica rice, early-maturing late japonica rice should be adopted in early June; medium-maturing medium japonica rice should be adopted in Mid-June.(2)①Along with the delayed seeding date, dry matter weight of single stem and population at jointing showed a upward trend while at booting, heading, waxy stages and maturity both showed a downward trend.②Along with the delayed seeding date, the dry matter accumulation and proportion of dry matter accumulation from seeding to jointing increased, but from jointing to heading and from heading to maturity decreased.③With the growing process, leaf weight per stem and sheath weight per stem decreased, stem weight per stem firstly increased and then decreased, and panicle weight per stem increased. Along with the delayed seeding date, leaf weight per stem was decreased at booting and heading, increased at waxy stage and maturity; stem weight per stem and panicle weight per stem decreased significantly or very significantly at all stages; sheath weight per stem decreased significantly or very significantly at booting, heading and waxy stage and increased at maturity.④With the growing process, the proportion of leaf, stem, sheath and panicle in the later growth period had the same changes as the dry matter weight. Along with the delayed seeding date, the trend in the ratio of leaf and panicle were the same as leaf weight per stem and panicle weight per stem, while the ratio of stem and sheath were different. The ratio of stem decreased at booting and heading, increased at waxy stage and decreased at maturity; the ratio of sheath decreased at booting and heading, increased at waxy stage and maturity.⑤Along with the delayed seeding date, the exportation, export rate and transformation rate of leaf, stem and sheath decreased significantly or very significantly.⑥Along with the delayed seeding date, the leaf area index of all the variety types had a little decreased at jointing; decreased significantly or very significantly at heading, waxy stages and maturity. The photosynthetic potential from seeding to jointing, jointing to heading, heading to maturity and the whole growth period decreased significantly or very significantly.⑦Along with the delayed seeding date, the crop growth rate from seeding to jointing increased; decreased from jointing to heading and heading to maturity. The net assimilation rate of all the variety types from seeding to jointing increased and from jointing to heading decreased, the net assimilation rate of Yujing6increased from heading to maturity while Wuyunjing24, Nanjing44, Liangyou838were decreased.(3) Along with the delayed seeding date, the milling quality and appearance quality of medium-maturing medium japonica rice and late-maturing medium japonica rice became better while the cooking and eating quality and nutrient quality became worse; the appearance quality and nutrient quality of early-maturing late japonica rice became better while the milling quality, cooking and eating quality became worse; the milling quality, appearance quality, cooking and eating quality and nutrient quality of late-maturing medium indica rice became worse. Therefore, the rice should be seeded as early as the time for harvesting the previous crop in the rice-wheat cropping system, allows to improve cooking and eating quality, effects of seeding date on milling quality, appearance quality and nutrient quality were different because of variety types.