Effects Of Direct-seeding Date On Yield Formation And Rice Quality

The experiments were conducted in Changshu institude of agriculture science, Jiangsu Province at Taihu region in 2012-2013, use the conventional japonica rice and japonica hybrid rice four varieties of two types as test materials in the rice-wheat cropping system, systematic comparative studies on growth stage and utilization of temperature and illumination, yield, characteristics of photosynthetic and matter production and rice quality. In order to produce high quality and high yield for the direct sowing rice at Taihu region and rational utilization of natural resources efficiently to provide theoretical and practical basis. The main results are as follows:(1) Sowing have a greater impact on the utilization of temperature and illumination, along with the delayed sowing date, the date of jointing, heading and maturity of all varieties were corresponding delayed, growth stages significantly reduced that growth stages reduced about 0.5 days when the sowing date delayed one day. Growth stages reduced with the delayed sowing date because of the vegetative growth period and the vegetative and reproductive growth period reduced which in range of 3 to 14 days, the reproductive growth period was relatively stable which in range of 0 to 1 days. Four varieties accumulated temperature and illumination hours of growth stages of all varieties reduced significantly or very significantly, which because of the accumulated temperature and illumination hours before heading, especially before jointing, the difference was very significant. In the same sowing, accumulated temperature of japonica hybrid rice were more than japonica rice, while the illumination were no obvious rule. Along with the delayed sowing date, the utilization of temperature and illumination of four varieties were reduced. The number of days from sowing to jointing and growth stages increased linearly with the increase of accumulated temperature and decreased linearly with the increase of illumination hours; the number of days from jointing to heading and from heading to maturity were no significant relationship between accumulated temperature and illumination.(2) Four varieties are safe to mature at five seeding, along with the delayed sowing date, the yields of direct seeding rice reduced very significantly, the changing degree was different that japonica hybrid rice higher than japonica rice. The changing degree of yield components along with the delayed sowing date was different, the per panicle and the total number of spikelets were large amplitude with the delayed sowing date, while the panicles, setting rate,1000-grain weight were smaller amplitude. The per panicle and the total number of spikelets were the important reasons for the significantly reduced of the yield.(3) In terms of characteristics of photosynthetic and matter production, the spike rate of directed seeding rice was reduced, in the jointing stage the leaf area index was increased significantly or very significantly with the delayed sowing date, while in the heading stage and maturity stage the leaf area index was reduced significantly or very significantly with the delayed sowing date; the photosynthetic potential reduced significantly or very significantly from Jointing to heading and from heading to maturity with the delayed sowing date; the dry matter was reduced significantly or very significantly in the jointing stage, heading stage and maturity stage with the delayed sowing date; the accumulation of dry matter reduced significantly or very significantly from Jointing to heading and from heading to maturity with the delayed sowing date; the crop growth rate and the net assimilation rate increased significantly or very significantly in the jointing stage, while reduced significantly or very significantly in the heading stage and maturity stage with the delayed sowing date.(4) Along with the delayed sowing date, the yields of direct seeding rice reduced significantly, the changing degree of yield components along with the delayed sowing date was different, the main reasons for the significantly reduced of the yield were per panicle and the total number of spikelets. The main quality traits of directed seeding rice change different with different sowing date, The processing quality(brown rice rate, Rice rate, milled rice) of directed seeding rice were upward with the delayed sowing date, while the appearance quality(chalkiness rate, chalkiness) and the nutritional quality(amylose content, protein, gel consistency) of directed seeding rice were drop with the delayed sowing date. Cooking and eating quality of directed seeding rice were drop with the delayed sowing date.