Effects Of Nitrogen Postponing On Group Quality And Nitrogen Utilization In Different Genotypes Of Indica Hybrid Rice

Four different genotypes of indica hybrid rice Ⅱ you498(Al), Fyou498(A2). Rong18you188(A3), Chuanxiang9838(A4) were used as test materials in this experiment. Four different nitrogen applications with different ratio of base-tiller nitrogen fertilizer and earing fertilizer B1(10:0), B2(7:3) and B3(5:5) were designed under the same amount of nitrogen(180kg hm-2) was studied in2011. One treatment without nitrogen was set as control group(CK). The effects of nitrogen postponing on tiller dynamic, canopy structure, plant morphology, stem character, dry matter accumulation, yield, nitrogen assimilation and utilization were studied to research the response of different genotypes of indica hybrid rice to different nitrogen application, find out the best genotype of indica hybrid rice which has higher nitrogen utilization, and provide the theoretical basis for production. The main results of this experiment were showed as follows:1. Improving the ratio of nitrogen postpoing controled the development of tillers efficiently, decreased the number of ineffective tillers, enhanced the percentage of bearing tiller; improved canopy structure, increased the length of flag leaf, but had small affection on the length of upper second and third leaf to the first, width of upper three leaves; increased light trasmittance and the area of sword leaf, decreased LAD of upper layer in rice group. The nitrogen application with highest ratio of postponing B3(5:5) had the highest percentage of bearing tiller, and area of sword leaf in canopy, but had small LAD in upper-layer of rice group, which increased its light transmittance. Different genotypes had different response to nitrogen postponing, nitrogen postponing could increase area of sword leaf of Ⅱyou498and Fyou498without increasing the angle of upper three leaves to stem. Rongl8you188and Chuanxiang9838had significant increase in the angle of upper two leaves to stem, led to the loose of plant type and leaf, which affected the acception from light in lower layer.2. Nitrogen postponing improved the character of rice stem. Increasing the ratio of nitrogen postponing increased the internode roughness, thickness and circularity of basal internode were increased, and decreased the length of basal internode which could improve the ability of lodging-resistant. The internode length under spike and the height of spike were increased with increased ratio of nitrogen postponing which could improve the mophology of plant, increase the amount of illumilation. The length of basal three internodes were decreased as the increase of nitrogen postponing ratio in II you498. The internode length of Fyou498had various reponse to nitrogen postponing, the basal third internode was longest when no nitrogen was applied, but shortest with the application of basal fertilizer:earing fertilizer5:5; the basal two internodes were shortest in the treatment without nitrogen application. The internode length had different response to nitrogen postponing, but all of them had shortest length in the treatment with no nitrogen, the fourth and fifth internode had shorter length in the treatment of basal fertilizer:earing fertilizer=5:5compared with other nitrogen application.3. Nitrogen postponing improved the pattern of dry matter accumulation. Increasing the ratio of nitrogen postponing could increase the amount of dry matter accumulation in later growth stages, improve the proportion of spike in mature stage, increase the output rate and transport rate in leaf and stem. Except the B4(0:0), rice plant had the highest dry matter accumulation amount, spike dry matter proportion, output rate and transport rate of leaf and stem in the nitrogen application of B3(5:5). Different genotypes of rice showed different response to different nitrogen applications in dry matter accumulation. Rongl8youl88had the highest dry matter accumulation amount and spike proportion in mature stage, Ⅱ you498had the highest output rate and transport rate in stem, Chuanxiang9838had the highest output rate and transport rate in leaf.4. Nitrogen postponing increased nitrogen accumulation after heading stage, transport rate and transport amount in stem and leaf, nitrogen partial factor productivity, rate of nitrogen abortion and utilization, decreased nitrogen proportion in spike, nitrogen dry matter productivity, nitrogen rice productivity, nitrogen harvest index and nitrogen physiological utilization. Different genotypes of rice showed different reponse to different nitrogen application in nitrogen accumulation and abbortion. Fyou498had the highest nitrogen accumulation, physiological utilization, the rate of abortion and utilization. Chuanxiang9838had the highest nitrogen proportion in spike, nitrogen transport rate and transport amount in leaf, nitrogen rice productivity.Ⅱ498had the highest transport rate and amount in stem, nitrogen partial productivity and nitrogen harvest index.5. Nitrogen postponing improved the yield of rice, but had different effects on different yield components. Spike length, number of effective spike and grain number per panicle were increased when the ratio of nitrogen postponing was increased, but1000-grain weight, setting percentage, filling rate and filling degree were decreased. Ⅱ you498had the highest setting percentage, filling rate and filling degree. Fyou498had the highest spike length, grain number per panicle. Chuanxiang9838had the highest1000-grain weigth and number of effective spike.To sum up, in this experiment, increasing the ratio of nitrogen postponing could improve group quality, increase nitrogen utilization in some extend, increase yield with a certain amount of nitrogen application(180kg hm-2). When the application was basal fertilizer:earing fertilizer5:5, rice had appropriate group quality, less ineffective tillers, more effective tillers, higher percentage of bearing tiller; feasible canopy structure, higher light transmittance in top, bigger sword leaf area, stronger ability of lodging-resistance, which provide a guarantee for maintaining high photosynthetic efficiency after heading stage. It improved dry matter accumulation of spike and whole plant, and promoted the transportation of matter after heading stage effectively, improved number of panicle and storage capacity, so that high yield was obtained. Higher nitrogen postponing ratio could improve nitrogen accunulation amount, nitrogen proportion in spike. Taking all the index and the response of different genotypes of rice to different nitrogen application into consideration, Ⅱyou498had appropriate group quality and canopy struture, strong ability of lodging-resistance which could help itself get high yield.