Managing Plant Density And Nitrogen Input To Optimise The Lodging Resistance Of Winter Wheat While Maintaining Acceptable Grain Yield

Field experiments were carried out at the experimental station of Guozhai Village,Guoyang Prefecture,Bozhou,Anhui,China during 2014–2015 winter wheat growing seasons.Two winter wheat cultivars(Jimai22 and Shannong15)were used to investigate responses of grain yield and lodging resistance to N input(225 and 300 kg·hm-2)and plant density(120,180,and 240 plants·m-2)treatments.The planting density and amount of nitrogen of winter wheat flowering period,flower after 20 d after anthesis and 30 d stem morphological characteristics and base of the second internode of physiological and biochemical characteristics,and to explore the density and nitrogen fertilizer on winter wheat culm mechanical strength and anti inverted index and yield were investigated.The test results are as follows: 1.Effects of nitrogen application rate and density on the leaf area of flag leafUnder the same nitrogen application rate,the flag leaf area of J22 was not significantly different with the change of density,and showed that the density had no significant effect on the flag leaf area when the same amount of nitrogen applied.In low density and dense conditions,flag leaf,leaf area decreased with the increase of amount of nitrogen decreased significantly,but under the condition of high density the effect of nitrogen application rate on flag leaf area was small.2.Effects of nitrogen fertilizer and density on the net photosynthetic rate of flag leafWith the application rate of nitrogen fertilizer increased from 225 kg·hm-2 to 300 kg·hm-2,photosynthetic rate of low density was significantly increased,but the photosynthetic rate of high density of flag leaf was not significantly difference.With the increase of nitrogen fertilizer used in the fields,photosynthetic rate of flag leaf was significantly increased,but the high density will inhibit this effect.In the early stage of growth,the effect of fertilization for photosynthesis is not obvious.With the increased of fertilization,the photosynthesis was significantly increased in grain filling of wheat.Under the condition of the same amount of nitrogen fertilizer,planting density by 120 to 240 strains·m-2,flag leaf photosynthetic rate significantly decreased,indicating that with the increase of planting density,the net photosynthetic rate of flag leaf was gradually decreasing.3.The effect of nitrogen application rate and density on yield and composition of winter wheatGrain yield increased significantly when plant density increased from 120 to 240 plants· m–2 in both cultivars with low N inputs.Under high N input,significant increases in grain yield were observed from D1 to D2,but no further increases were observed from D2 to D3.The increase in grain yield with optimum plant density was essentially due to the increase in the number of spikes per square meter,which was able to compensate for decreases in kernels per spike and kernel weight.Additionally,under high N input increasing the density of plants above 180 plants· m-2 would not produce an increase in grain yield.In D1 and D2,higher grain yield was observed under high N input primarily because of the increased number of spikes per square meter and kernels per spike.Equal grain yield was observed at D3 under both N input treatments;consequently,the grain yield in D3 under low N input was equivalent to the yield at D2 and D3 under high N input.These results indicated that high plant density under low N input could achieve equal grain yield compared with the same or lower plant density under high N input.4.Effects of nitrogen application rate and density on grain filling potential of winter wheatThe nitrogen fertilizer application rate increased from 225 to 300 kg·hm-2,the grain filling potential of the same planting density significantly decreased,which showed that the increase of nitrogen fertilizer application rate reduced the grain filling potential of J22.Under the same nitrogen application rate,when the planting density was increased from 120 to 240 plants· m–2,the grain filling potential was significantly decreased,which indicated that the increase of the planting density could reduce the filling potential of J22.The grain filling potential was linearly related to the grain weight of wheat.Under this experimental condition,nitrogen fertilizer or increase density,grain weight decreased,because after nitrogen fertilizer increased,while enhance photosynthesis,but increase the cause of the spike grain number after the increase in the amount of nitrogen fertilizer rate exceed the margin of increase photosynthetic rate,decrease assigned to a single grain of photosynthetic product;Increased density causes the decrease of grain weight was increased after the density ontogenesis,leading to a fall in flag leaf photosynthetic rate,resulting in assigned to a single grain of photosynthetic product to decrease.5.Effects of nitrogen and density on the morphology and physiological and biochemical characteristics of stemAlthough grain yield increased through the management of plant density and N input,increases in plant density and N input significantly raised the risk of lodging,mainly by raising plant height,the length of each internode and peduncle and by reducing dry weight;filling degree;diameter;wall thickness;the concentrations of cellulose,lignin,and total soluble sugar;the C/N ratio;which caused the second basal internode's TFS decreased.6.Effects of nitrogen and density on culm lodging resistance indexRaised internode lengths and plant heights resulted in higher CHCG.The correlation analysis indicated that increase in plant density and N input reduced TFS and CLRI,mainly by reducing dry weight;filling degree;diameter;wall thickness;the concentrations of cellulose,lignin,and total soluble sugar;and the C/N ratio of the basal internode.Consequently,CLRI trended to decrease as plant density and N input increased and was highest in D1 under low N input.The increase of planting density conditions,we can reduce the amount of nitrogen to increase lodging resistance index.With higher plant density and low N input,plant height,the length of the base internode,and CHCG were equal to or even lower than values with lower plant densities under high N input.Dry weight;filling degree;diameter;wall thickness;the concentrations of cellulose,lignin,and total soluble sugar;the C/N ratio;and especially TFS and CLRI were equal to or exceeded values under lower plant density and high N input when plant density was higher and N input was low.These results demonstrated that with higher plant density under low N input,lodging resistance could equal or exceed results with lower plant densities and high N input.The reduction in lodging resistance through increasing plant density could be offset by reducing N input while maintaining acceptable grain yield.Therefore,sowing with high plant density under relatively low N input represents a compromise that resulted in both high grain yield and lodging resistance.