| In order to understand the characteristics of high-yielding population (higher than7500kg-hm"2, hereinafter as HYP) of late-sown wheat in rice-wheat cropping system, with a medium gluten wheat variety Yangmai20as test material, the field experiments were carried out during the two wheat growing seasons from2011to2013. The seeding dates were November20in both growing seasons. The experiments were conducted at different combinations of planting density, nitrogen amount, and the ratio of nitrogen applied before sowing and at tillering, jointing and booting stages. This study investigated the differences in grain yield components and population formation indexes between HYP and middle-high-yield (less than7500kg-hm’2, hereinafter as MHYP). In addition, the characteristics of physiological basis were analyzed. By analyzing and evaluating the effects of different cultivation techniques on wheat quality and economic profit, the best cultivation technology achieving HYP was proposed. This study could provide theoretical and technological supports for high-yield in late-sown wheat after rice. The main results were as follows:1. Of the yield components, the number of spikes is the utmost factor affecting wheat yield. There was significant difference in the number of spikes between HYP and MHYP. However, there were no significant difference in the number of grains per spike and1000-grain-weight between HYP and MHYP. For achieving HYP, the number of spikes, the number of grains per spike, and1000-grain-weight should be kept at540×104～570×104·hm-2,38～42, and36g respectively.2. In the HYP. the number of basic seedlings, the number of stems and tillers at jointing stage, the number of spikes per unit area, and the percentage of ear-bearing stems and tillers were maintained at315×104-hm-2,1200×104·hm-2,540×104～570×104·hm-2,38～42, and45%～48%, respectively. The LAI of HYP at booting stage was7.2-7.5. Besides, the dry matter accumulation amount (DMAA) increased slowly from emergence to jointing, rapidly from jointing to anthesis. Especially, the increment in DMAA after anthesis was kept at a level higher than6000kg·hm-2.3. The nitrogen accumulation in HYP could be expressed with an "S" shaped figure. It accumulated at a low rate from emergence to jointing, rapidly from jointing to anthesis, and slowly again from anthesis and maturity. An appropriate accumulation of nitrogen before anthesis and reasonably high accumulation of nitrogen after anthesis were beneficial to the translocation of photosynthate from vegetative organs to grains. The nitrogen accumulation amount was positively related to grain yield at both anthesis and maturity. The higher the nitrogen accumulation amount, the higher the grain yield was.4. Compared with MHYP, SPAD reading, photosynthetic rate (Pn), and the activities of POD and CAT in flag leaves after anthesis were higher in HYP, but MDA content was lower in HYP. Increased SPAD reading, Pn, and the activities of POD and CAT or decreased MDA content in flag leaves after anthesis prolonged the photosynthetic duration, which promoted grain filling and consequently final grain yield.5. The grain processing quality, flour pasting properties, and the rheological properties of dough were not worsen in the HYP. The content of protein, wet gluten, and starch, dough development time, the stability and farinograph quality number in the HYP were even better than those in the MHYP. These indicated that higher economic profits could be achieved at a relatively low total cost in the HYP.6. To achieve a grain yield higher than7500kg·hm-2in late-sown wheat Yangmai20, planting density, nitrogen amount, and the ratio of nitrogen application at seeding, tillering, jointing, and booting should be maintained at315×104-hm-2,240～270kg·hm-2, and5:1:2:2or3:1:3:3. |
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