Effects Of Topdressing Nitrogen Amount On Yield And Quality And Physiology Of Different Gluten Type Wheat Cultivars

The experiment was carried at the Beijing Experimental Base of Institute of Crop Sciences,Chinese Academy of Agricultural Sciences in 2016-2017.The two factor randomized block design was adopted to study the effects of Nitrogen Topdressing on yield,quality and physiological indexes of different gluten type wheat cultivars.The tested materials were strong gluten cultivars:Gaoyou 2018,Shiluan 02-1;medium gluten cultivars:Zhongmai 8 and Zhongmai 175;weak gluten cultivars:Yangmai 22 and Yangmai 15.The main results of the experiment are as follows:(1)With the development of the growth process,the plant height of all wheat cultivars showed a trend of gradual increase.The plant height,spike length and seed setting spikelet number are significantly increased with the increase of nitrogen topdressing amount within the scope of 75-135 kg·hm-2 at the jointing stage and the highest level is 135 kg hm-2.The number of infertile spikelets was significantly reduced,and the lowest level is 135 kg hm-2.The population total stem number of all cultivars showed a trend of increased first and then decreased.Appropriate application of nitrogen fertilizer can increase the population total stem number,reduce the ineffective tillering,and improve the population quality after jointing,the best topdressing nitrogen treatment was 135 kg·hm-2.The effect of topdressing on the total stem number was obviously different because of different varieties,which show that the strong gluten wheat was the most affected,followed by the medium gluten wheat,and the weak gluten wheat was the least affected.The increasing topdressing nitrogen at jointing stage could slow down the decline rate of leaf area index in the late growth stage,and the most significant effect of nitrogen is 135 kg hm’2,with strong gluten wheat(24%)<medium gluten wheat(26%)<weak gluten wheat(48%).(2)There were significant difference in dry matter accumulation and distribution of different gluten wheat cultivars and main organs of wheat.With the increase of topdressing nitrogen,the dry matter accumulation of different cultivars showed increasing trend at the flowering stage.The total dry matter accumulation of strong gluten wheat was higher than that of medium gluten wheat and weak gluten wheat.Comparing the accumulation of dry matter in major organs,the dry matter accumulation in stems and spikes was higher of strong gluten wheat and higher in the leaves of medium gluten wheat.With the increase of topdressing nitrogen,the dry matter accumulation and distribution ratio of wheat organs increased significantly,which showed stem>leaf and spike,and the highest nitrogen treatment was 135 kg hm’2,which was significantly higher than other nitrogen treatments.The ratio of dry matter accumulation in grain of strong gluten wheat was significantly higher than that of medium and weak gluten wheat at mature stage;the dry matter of glume + cob was significantly lower than that of medium and weak gluten wheat;the increase of topdressing nitrogen also increased the dry matter accumulation,distribution ratio,and total dry matter accumulation of organs at the mature stage of wheat cultivars,was the highest with topdressing nitrogen of 135 kg·hm-2.(3)Increasing nitrogen topdressing had an elevation effect on the content of chlorophyll a and b in wheat flag leaf,and was more conducive to the formation of chlorophyll b.The effect was most obvious when nitrogen topdressing amount was 135 kg·hm-2.In this experimental conditions,the net photosynthetic rate,stomatal conductance,transpiration rate and leaf temperature of the flag leaves of the wheat cultivars increased gradually with the increase of nitrogen topdressing,and the growth rate also gradually increased,with nitrogen topdressing 135 kg·hm-2 was the highest.The intercellular CO2 concentration of the flag leaves gradually decreased with the increase of nitrogen topdressing,and all cultivars showed basically the same trends.(4)All wheat cultivars showed the highest activity of nitrate reductase in flag leaves at flowering stage and gradually decreased with the development of grain after flowering.In the range of 75-135 kg·hm-2,the NR activity of the flag leaves of all types wheat increased with the increase of the amount of nitrogen topdressing,and the highest rate of nitrogen topdressing of 135 kg hm-2.With the increase of nitrogen,the accumulation of nitrogen in the vegetative organs,the accumulation of nitrogen in grains,the amount of nitrogen transferred from the vegetative organs to grains,and the contribution rate to the grains all showed increasing trend at the flowering and maturing stages,the highest amount of nitrogen was 135 kg hm-2.However,the amplitude of increasing in nitrogen assimilation after anthesis decreased.(5)The grain yield and protein yield were higher in medium and strong gluten wheat,which was significantly higher than weak gluten wheat.In the range of 75-135 kg·hm-2,the grain yield,spike number,grain number per spike,grain weight per spike,protein yield,and biological yield of all cultivars increased significantly with increasing nitrogen topdressing,and the treatment of 135 kg·hm-2 is the highest.(6)As the amount of topdressing nitrogen increased,the test weight and the flour yeild decreased significantly,but the grain hardness increased significantly;the grain albumin,globulin,gliadin and glutenin content and total protein content of all wheat cultivars increased in which gliadin and gluten increase more than albumin and globulin;The effects of topdressing nitrogen on the sedimentation value,wet gluten,water absorption,development time,stable time and farinograph quality number showed a same law in three types of wheat cultivars,which expressed those both increased with the increase of nitrogen topdressing,and the softening degree decreased with the increase of nitrogen topdressing.For medium and strong gluten wheat,the quality characters were the best when the nitrogen topdressing amount was 135 kg·hm-2,while the weak gluten wheat was suitable for the nitrogen topdressing amount of 75 kg·hm-2.The increase of nitrogen application was not conducive to improving the processing quality of weak gluten wheat.Above all,in this experiment,topdressing nitrogen fertilizer at the jointing stage is beneficial to optimize the agronomic characters of wheat,construct a reasonable polulation,improve the chlorophyll content of the flag leaves,improve the photosynthetic performance and promote the plants’ absorption and accumulation of nitrogen.The agronomic characters,yield components,photosynthetic physiology and processing quality of the three gluten type wheat cultivars were greatly affected by the topdressing nitrogen content.Strong gluten and middle gluten can obtained the best yield and best quality when the nitrogen topdressing is 135 kg·hm-2;but for weak gluten wheat,the yield is the highest with nitrogen of 135 kg·hm-2,while the processing quality is appropriate with nitrogen of 75 kg·hm-2.So,we still needs to choose a reasonable cultivation plan between yield and quality according to the purpose of production,the synergy between the two remains to be further studied.