关键词: 稻茬小麦, 氮效率, 物质生产, 衰老

Abstract: 【Objective】This study investigated the post-anthesis characteristics of wheat population in rice-wheat rotation system under high nitrogen utilization efficiency condition. 【Method】 From 2010 to 2012, using wheat variety Yangmai 20 as material, the field experiments were conducted as split-plot design which included 16 combinations of two applications of nitrogen amount (210.0 kg·hm^-2 and 262.5 kg·hm^-2), two nitrogen applied ratios of basis﹕tillering﹕elongation﹕booting (3﹕1﹕3﹕3 and 5﹕1﹕2﹕2), and four nitrogen topdressing stages (flag leaf stage, booting stage, heading stage and anthesis). In the rice-wheat rotation system, wheat populations at different nitrogen utilization rate (NUR) levels were established by agronomic management. The differences of grain yield, matter production, nitrogen absorption, and flag leaves senescence characteristics after anthesis among different NUR level populations were analyzed, respectively.【Result】The range of NUR in different populations was 31.18%-72.23%. Grain yield of NUR≥60% population (NUR-H) was more than 8 500 kg·hm^-2, which was 6.84% higher than NUR 40%-60% population (NUR-M) and was 21.6% higher than NUR≤40% population (NUR-L). There were significant differences among the three populations. NUR was significantly positively correlated with grain yield. And different NUR populations were not distinct in dry matter accumulation amount and nitrogen accumulation amount before the stage of anthesis. With NUR improvement, dry matter accumulation amount after anthesis and at maturity, plant nitrogen content at anthesis, and population nitrogen accumulation amount at maturity increased, which were more than 6 000 kg·hm^-2, 17 500 kg·hm^-2, 1.50% and 215 kg·hm^-2 in NUR≥60% population, respectively. Moreover, along with NUR increasement, decay of population photosynthetic area after anthesis gradually postponed, and net assimilation further increased, as well as flag leaves photosynthetic capacity and anti-oxidant ability after anthesis enhanced, which more obviously performed during the middle and late phase of grain filling. Therefore, photosynthetic material production capacity after anthesis was improved. Decay of leaf area, photosynthetic potential and net assimilation after anthesis in NUR≥60% population was about 0.14 LAI·d^-1, 105×10⁴ m²·d·hm^-2 and 9.50 g·m^-2·d^-1, respectively. In summary, grain yield and NUR were relatively high in the treatment of early topdressing panicle fertilizer (flag leaf stage or booting stage) under the condition of appropriate postponing nitrogen application (nitrogen applied ratios= 3﹕1﹕3﹕3). Rather, yield improvement of high nitrogen application (262.5 kg·hm^-2) was not obvious, and NUR even was quite low. The grain yield was more than 9 000 kg·hm^-2 in experiments carried in two years, and NUR was the highest under the treatment of applied nitrogen amount 210.0 kg·hm^-2, nitrogen applied ratios of basis﹕tillering﹕elongation﹕booting= 3﹕1﹕3﹕3 and topdressed nitrogen at flag leaf stage.【Conclusion】Under high nitrogen utilization efficiency condition, plant nitrogen nutrition level was high during the middle and late phases of plant growth and development, nitrogen absorption and accumulation amount increased in wheat following rice, which was better to improve transportation of nitrogen to grain. Additionally, the process of photosynthetic area decay and leaves senescence was postponed during the late phase, and photosynthetic material production capacity was improved, which could be the reason of simultaneous improvement in NUR and grain yield.

Key words: wheat following rice, nitrogen efficiency, matter production, senescence