Effects of Nitrogen Application Rate on Photosynthesis Characteristics after Anthesis and High Grain Yield of Winter Wheat

Photosynthetic capacity and dry matter accumulation(DMA) are important traits that influence biological yield and ultimate grain yield in wheat.These traits are quantitatively inherited and are greatly influenced by environment,and about more than 60% of assimilates in grain are derived from post-anthesis assimilates.Nitrogen fertilizer could effectively regulate the accumulation of carbohydrate in wheat(Triticum aestivum L.).Effects of nitrogen(N) application rate on photosynthetic characteristics,DMA after anthesis and grain yield of winter wheat were studied in the field experiment with two type cultivars(Yumai 49 and Lankao Aizao 8) and five N rates(0,90,180,270 and 360 kg N·hm-2) at two sites(Wen county and Lankao county) of Henan province,China in 2007-2008 growing seasons.N was applied according to 5∶5 ratio as basal feitilizer at seeding time and top-dressing at jointing stage.Results indicated that the proper N rates(180~270 kg N·hm-2) could improve leaf's SPAD value and photosynthetic rate after anthesis of both wheat cultivars at two sites,and final grain yield was above 9 000 kg per hactare.In addition,there were differences of the yield components in different N application rates.Comparing with no N treament,N application markedly increased spike numbers with highest values of Yumai 49 with 270 kg N·hm-2 and Lankao Aizao 8 with 180 kg N·hm-2 at two sites.Differences between N application rates of achieving the highest grain yield in both wheat cultuvars also indicated differences of N use efficiency between two genotype cultivars.On the whole,the proper N application with 180~270 kg N·hm-2 according to the 5∶5 ratio at seeding time and jointing stage played an important role in increasing dry matter production after anthesis,spike grain numbers and grain weight,and finally achieved the super high yield of winter wheat at two sites.