| Under the field conditions, effects of different nitrogen application periods on growth and decline of population, photosynthesis characteristics, dynamics of panicle and floret development, carbon and nitrogen metabolism, matter accumulation and translocation, grain yield and yield components, and main quality indices were studied, during 2008 to 2010, taking two spike-type cultivars (LKAZ 8 and YM 49-198) as experimental material, under the total pure N 240kg/hm2 in Zhengzhou city and 180kg/hm2 in Lankao county. With the total basal N fertilizer dressing and four applying nitrogen periods were included in this experiment, the nitrogen topdressing stages were in returning green stage and post returning green stage 10d, 20d, 30d, with nitrogen fertilization base 50% and topdressing 50%, respectively. The main results were as follow:1. Effects of different nitrogen application periods on growth and decline of population and photosynthesis characteristics of winter wheat. The experiment result showed that the ratio of forming spike from the tillers was increased with two winter wheat cultivars under topdressing nitrogen in suitable period at appropriate rate. And the LAI in the treatments of delaying dressing nitrogen was raised in the two cultivars, among them, the improvement among treatments was expressed obviously in the treatment of T2 in Zhengzhou and the treatment of T3 in dressing pure nitrogen rate of 180kg/hm2. Moreover, the response of nitrogen was different between varieties to nitrogen application period. At the same time, the value of SPAD in flag leaf was kept highness in the treatment of T3 during grain filling, and which increased photosynthetic rate of flag leaf in post-anthesis of wheat. The results indicated that nitrogen nutrient in middle of growth with wheat could be ensured, photosynthetic ability was highly kept, photosynthetic time was postponed, under the application nitrogen period in suitable time. And then much more materials of photosynthetic assimilation was applied in grain filling of wheat, would provide adequacy material sources for grain forming and filling.2. Effects of different nitrogen application periods on dynamics of panicle and floret development of winter wheat. The test results showed that young panicle development was delayed in two spike-type cultivars under dressing nitrogen delayed to a certain extent. And the floret differentiation and development of every floret locations in the third and ninth spikelet were more fast in the former of post-jointing stage 21d in nitrogen topdressing treatments, and developing were relatively slower in post-jointing stage 28d in treatment that of top dressed nitrogen in post-returning stage 20d(T3), in LKAZ 8 during two experimental sites. But the floret development, that in every floret locations of different spikelets, obviously slowed in post-jointing stage 28d in treatment that of topdressing with nitrogen in post-returning stage 30d(T4) with YM 49-198 in Zhengzhou. The experiment results indicated that the nutrient demand in floret could be met in floret development phase under the condition of right stage dressing nitrogen, then properly delayed floret development in every floret locations of different spikelets. Moreover, the floret differentiation could be promoted under the proper dressing nitrogen stage. Compared to control, the number of well floret in treatment of T3 was significantly or highly significant higher than control in two cultivars. And the results showed that differentiation of well floret was promoted, number of fertile floret was increased, under the proper stage with dressing nitrogen. And also which would provide a basis of grain number increased.3. Effects of different nitrogen application periods on enzymatic activities of carbon and nitrogen metabolism of winter wheat. Under this experiment condition, the value of SPS, SS, NR, GS activity of flag leaf in post-anthesis showed a single peak curve in two cultivars, clearly showing an inflexion time slightly after anthesis 10~15d. And the activities of carbon and nitrogen metabolism enzymes in flag leaf with two cultivars were improved under delaying nitrogen with topdressing in grain filling. Meanwhile, the activities value of SPS, GS in superior grains and inferior grains showed the downtrend from post-anthesis 5d, in which the value of SPS activity in superior grains with LKAZ 8 and YM 49-198 was lower at 2.69% and 11.08% compared to inferior grains. In addition, the activity value of GS in grains with YM 49-198 was obviously higher that of LKAZ 8 in grain filling prometaphase(post-anthesis 5~15d), and compared with control, the value of GS activity in grains, included superior and inferior grains, was obviously expressed higher than the treatments of T3 and T4. And the value of SS activity in grains expressed differently, which always maintained a higher level before post-anthesis 20d, then began falling. And also the value of SS activity in grains under topdressing with nitrogen was apparently higher than control. These results indicated that the enzymes activities of carbon and nitrogen metabolism would be enhanced in treatments of delaying nitrogen application with two wheat cultivars.4. Effects of different nitrogen application periods on carbon and nitrogen metabolism and matter accumulation and translocation of winter wheat. The test results showed that the soluble sugar content and sucrose sugar content of flag leaf were obviously improved in the treatment of T3 with two cultivars. But which expressed variously in grains. Compared with control, the soluble sugar content in grains were all increased in treatments of top dressed nitrogen, and sucrose sugar content in grains was increased in the treatment of T3, which showed highness at 19.36% and 31.28% in two cultivars, respectively. Simultaneously, dry matter accumulation amount after anthesis was highly on the treatment of T3, which expressed outstanding under the condition of applying pure N 180kg/hm2. Moreover, Contribution rate of nitrogen translocation to grain nitrogen accumulation maintained about 80% in two cultivars. However, the overall translocation amount and ratio of pre-anthesis stored nitrogen in leaf were higher than other organs. And nitrogen stored amount in organs after anthesis were improved in the treatment of top dressed nitrogen to some extent, in which grain nitrogen content in maturity were increased. These results also indicated that, under the condition of proper applying nitrogen stage, the soluble and sucrose sugar content in grain and flag leaf were improved in grain filling, and dry matter accumulation content was increased after anthesis, and carbon and nitrogen translocation content was also improved in every organs, and finally the dry matter accumulation content in grains was increased at maturity.5. Effects of different nitrogen application periods on grain yield and yield components of winter wheat. The research results showed that grain yields of two cultivars were improved in the treatment of delaying nitrogen application, which expressed highly in treatments of T3 and T4. And analysis of variance indicated that the difference among treatments of T3 and T4 and control reached at the 0.01% significant level. The grain yield with LKAZ 8 duration post-returning 20~30d top dressed nitrogen were higher with 12.84% and 14.27% than control in Zhengzhou and Lankao, respectively. But the same as YM 49-198, which were higher with 8.51% and 13.50% than control, respectively. And then analysis of composite factors of yield, there were no significantly differences among treatments in spike number, except the treatment of T2 and T3 having 0.01% significantly difference with YM 49-198 in Zhengzhou. There were 0.05% or 0.01% significantly differences among treatments of top dressed nitrogen and control in grain number per spike and 1000-grain weight with two cultivars, and in which the treatment of T3 were higher than others, which had 0.01% and 0.05% significant differences. The result indicated that grain number per spike and 1000-grain weight were main impact factors through delaying nitrogen application to improve grain yield, under the condition of this research. 6. Effects of different nitrogen application periods on main quality traits of winter wheat. The results showed that grain protein content showed a high-low-high change. Compared with the check, grain protein content were improved distinctly in the treatment of T3 and T4. There were having 0.01% or 0.05% significantly differences in amylase starch content, amylopectin starch content and total starch content between the treatment of T3 and others. And the PV, TV, FV, BD and SB of flour with two cultivars were improved in the treatments of delaying nitrogen application stage, especially on the treatment of top dressed nitrogen in post-returning stage 20d. Compared with check, the water absorption, development time, stability time and degree of softening of flour with two cultivars were increased under the treatments of delaying dressing nitrogen, under which the farinograph quality index of flour was improved together, and increased by 1.19%~18.06% and 0.76%~13.79% with the two cultivars, respectively. There also were increased in area, resistance, extensibility and maximum resistance of flour in LKAZ 8 under the treatments of delaying dressing nitrogen, to a certain degree, there were improved in extensibility and maximum resistance of flour in YM 49-198, which showed 0.01% and 0.05% significant differences. These indicated that would be improving processing and edible quality of wheat under the condition of delaying dressing nitrogen.In view of the research situations above, duration the wheat production, under the condition of middle and high yielding fertility of land,applying N 180~240kg/hm2, 5:5 proportion of nitrogen application at base and post-returning periods 20~30d (from pistil-stamen primordium differentiation stage to pistil concave differentiation stage), could improve photosynthesis rate, the enzymes activities of carbon and nitrogen metabolism and matter accumulation translocation, and increase grain number of seed setting, 1000-grain weight and grain yield, and improve the main quality parameters, in the two spike-type cultivars of wheat, then would have played a active role in increasing yield and improving quality of wheat. |
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