Effects Of Different-growing-stage Shading And Nitrogen Levels On Yield And Quality Formation Of Japonica Super Rice

In order to study the effects of different-growing-stage shading and nitrogen levels on yield and quality formation. Field experiment was conducted with 2 conventional japonica super rice varieties representative in the region of Yangtze River japonica super rice Nanjing 44 and Ningjing 3 under two nitrogen fertilization levels (N10:150 kg ha-1, N20:300 kg ha-1) and three shading treatments (L1:no shading, L2:shading 20 days before heading, L3:shading 20 days after heading) in 2012 and 2013 on the farm of Yangzhou university. The main results were as follows:1. Yield under the same level of nitrogen fertilizer with different light treatment was L1>L3>L2. Compared with L1, L2 not only reduced the effective panicles and grains per panicle, resulting in the decline of total spikelets by 24.81% to 35.63%, but also significantly reduced the tiller number and leaf area index at heading by 2.90%-6.44% and 19.02%-27.17% respectively, causing photosynthetic potential, dry matter accumulation decreased significantly from heading to maturity, and at last the final yield decreased by 27.23%-35.26%. Under L2 condition, with increasing nitrogen level, tiller number and leaf area index at heading increased significantly, resulting in photosynthetic potential, dry matter accumulation increased significantly from heading to maturity, and the ultimately effective panicles, number of grains per panicle, total number of spikelets and the yield improved significantly. Compared with L1, L3 mainly affected photosynthate accumulation from heading to maturity, leading to seed setting rate and grain weight significantly decreased by 1.49%-4.48% and 5.54%-9.17%, and the final yield decreased by 10.91%-18.47%.Under L3 condition, with increasing nitrogen level, photosynthate accumulation from heading to maturity increased significantly, dry matter translocation from stems and leaves to the panicle increased significantly, meanwhile, translocation rate and contribution rate were further improved, and the ultimate yield improved significantly.2. Compared with L1, L2 significantly reduced NPK accumulation from jointing to heading and at whole heading stage, mainly due to the significant decrease of the root oxidation ability of a-NA and root dry weight before heading, resulting in decreased root nutrient uptake capacity and the final yield decreased. L3 significantly reduced NPK accumulation from heading to maturity and at whole maturity stage, mainly due to the significant decrease of the root oxidation ability of a-NA and root dry weight after heading. Although the root was gradual aging with the function declining after heading, resulting in the reduced effect on root system, nutrient absorption and yield in L3 than in L2, the final yield was still lower in L3 than in LI. Under L2 and L3 conditions, with increasing nitrogen level, the root oxidation ability of a-NA and root dry weight increased significantly, resulting in that NPK accumulation increased significantly in various stages from jointing to maturity, then the final yield and nitrogen use efficiency improved significantly.3. Compared with L1, L2 and L3 were all improved the chalky grain rate, chalkiness, protein content and setback, and decreased amylose content, peak viscosity, hot viscosity, cool viscosity, breakdown and consistence, but the influence of L2 on the out quality, cooking and eating quality, nutritional quality, characteristic value of RVA profile were less than L3. Besides, L2 significantly improved brown rice, milled rice and head rice rates, but L3 is the opposite. Under L2 and L3 conditions, with increasing nitrogen level, the brown rice rate, milled rice rate, head rice rate, chalkiness, protein content and setback were increased significantly, and the chalky grain rate, amylose content, peak viscosity, hot viscosity, cool viscosity, breakdown and consistence were decreased significantly.