Effects Of Nitrogen Fertilizer And Density On Stem Lodging Related Traits And Yield Of Wheat

Lodging is one of the significant causes of wheat yield and quality reduction.Increasing planting density is an important cultivation technique to increase wheat yield by increasing spike numbers and increasing nitrogen application rate is an important cultivation technique to increase wheat yield by increasing spike grain weight.However,this can easily lead to poor stem quality and lodging phenomenon.The occurrence of lodging severely restricted the increase of wheat yield.Therefore,lodging resistant variety SN23（Shannong 23）and lodging sensitive variety SN16（Shannong 16）were used as test materials.Three nitrogen fertilizer levels:120 kg ha^-1,N1,240 kg ha^-1,N2,360 kg ha^-1,N3 and four density levels:75×10~4plants ha^-1,D1,225×10~4plants ha^-1,D2,375×10~4plants ha^-1,D3,525×10~4plants ha^-1,D4were set to study the relationship between cell wall components and stem breaking strength,and the effects of nitrogen application rate and planting density on lodging resistance of wheat stem.The effects of nitrogen application rate and planting density on lodging resistance of wheat stem were discussed in terms of morphological characteristics of different internodes,accumulation of cell wall components and lignin synthesis pathway.The main results of this test are as follows:1.Effects of nitrogen fertilizer and density on yield,dry matter accumulation and redistribution of wheatOptimized the amount of nitrogen application and planting density could improve the dry matter accumulation and yield of wheat population.Compared with other treatments,SN23had the highest yield under N2D3 treatment;SN16 had the highest yield under N2D2treatment.Under the condition of high nitrogen and high density,1000-grain weight and grain number per spike were lower,while under the condition of low nitrogen and low density,grain number per spike was lower,so it was difficult to achieve wheat yield increase.With the increase of nitrogen input,the accumulation of dry matter in wheat plant and the transfer of dry matter to grains increased,which could achieve yield increase.Increasing planting density reduced the accumulation of dry matter and the transfer of dry matter to grains,which was not conducive to yield increase.2.Effects of nitrogen fertilizer and density on morphological characteristics and breaking etrength of stem at different internodesOptimized the amount of nitrogen application and planting density could enhance stem quality and lodging resistance of wheat.Compared with other treatments,N2D1 treatment had higher stem quality and better lodging resistance.Under the condition of dense planting,the change of basal internode length was the most obvious.Compared with N1,the basal internode（I1+I2）increased by 23.05%,and the upper internode（I3+I4+I5）increased by7.69%under N3 treatment.Compared with D1,the basal internode（I1+I2）increased by51.70%,and the upper internode（I3+I4+I5）increased by 19.50%under D4 treatment.Under the condition of low density,the internode length,stem diameter,wall thickness and stem break resistance were all higher.Increasing planting density resulted in the decrease of internode plumpness,stem diameter,wall thickness and stem break resistance.Low nitrogen（N1）and excessive nitrogen（N3）were not conducive to the improvement of stem length,stem thickness,wall thickness and stem break resistance.3.Effects of nitrogen fertilizer and density on accumulation of different internode cell wall componentsOptimized the amount of nitrogen application and planting density could promote the accumulation of cellulose,hemicellulose,lignin and S and G monomers in wheat stems,reduce the accumulation of H monomers and enhance the lodging resistance of wheat stems.Compared with other treatments,the contents of cellulose,hemicellulose,lignin,S and G in wheat stem under N2D1 treatment were higher,while the content of H monomer was lower.Under the condition of low density（D1）,the contents of cellulose,hemicellulose,lignin and S and G monomer in each internode increased,while the content of H monomer decreased,and lodging resistance of stem increased.Under the condition of medium and high density（D2,D3,D4）,the contents of cellulose,hemicellulose,lignin and S and G monomers in each internode decreased,and the content of H monomer increased,which was not conducive to the improvement of lodging resistance of wheat stem.