Effects Of Different Planting Densities And Nitrogen Topdressing On Growing Development,yield And Quality Of Winter Wheat

Wheat is the main crop in most parts of northern China,which is widely planted.Ensuring its high and stable yield and high quality has become the basic requirement of wheat production at present.According to basic cultivation measures such as planting density,managing nitrogen fertilizer,matching with fine wheat varieties,which are important means to achieve high-efficiency and high-quality production.This experiment whose controlling factors are the planting density and the amount of topdressing nitrogen fertilizer in spring,using 2-factor split plot design researches the effects of interaction on grain yield,quality and physiological indices of two winter wheat cultivars,Xinong 20 and Xinong 805.The test results are as follows:1.Topdressing of nitrogen 27.8～55.7 kg·ha^-1 pure N in spring combined with 150kg·ha^-1 seeding rate is beneficial to the improvement and maintenance of chlorophyll levels of Xinong 20 and Xinong 805.The Pn of Xinong 20 increased with the increase of density,and the highest was under the condition of 187.5 kg·ha^-1.At the same time,topdressing 27.8kg·ha^-1 pure N was applied,and the two treatments were used for the flag leaf of the filling stage.On the basis of this,increasing the nitrogen application rate will reduce the net photosynthetic rate.Pn of Xinong 805 is different from Xinong 20 in response to density and nitrogen recovery treatment.The net photosynthetic rate on that seeding rate is 112.5 kg·ha^-1and without nitrogen application the is the highest.,and the Gs and Tr of both varieties changed synchronously with Pn.The single stem dry matter of Xinong 20 showed the highest level in the middle and late growth stage under the seeding rate of 112.5 kg·ha^-1and topdressing 55.7 kg·ha^-1 pure N.Xinong 805 was similar,topdressing 55.7 kg·ha^-1 pure N showed the highest single stem dry matter quality level at the same density.2.The maximum grain filling rate V_max,grain filling average rate Vand fast increasing period average filling rate V_s of Xinong 20 decreased with the increase of density,but the corresponding rapid growth period T_k was prolonged.The difference between the maximum rate occurrence time T_v is not obvious;the combination of D2(seeding rate 150 kg·ha^-1)and N2(topdressing 55.7 kg·ha^-1 pure N)under the interaction condition prolongs the rapid increase period T_k The effect is more significant;the grouting characteristics of the varieties are quite different.The filling rate of Xinong 805 is higher than that of Xinong 20,but the duration of the fast increasing period is correspondingly shorter,in D2(seeding rate 150kg·ha^-1)and N3(topdressing 83.5 kg·ha^-1 pure N),the duration of the fast increase period was significantly prolonged,which was conducive to grouting.3.Xinong 20 has higher total nitrogen content in mature soil under D2N3(seeding rate150 kg·ha^-1,topdressing 83.5 kg·ha^-1 pure N),but it is treated compared with N3 treatment at other densities.The vegetative organs have small residual nitrogen and high total nitrogen content,which facilitates the transport of nitrogen to the grain.Xinong 805 had the highest nitrogen content in D1N2(seeding rate 112.5 kg·ha^-1,topdressing 55.7 kg·ha^-1 pure N),and the nitrogen residue in soil and vegetative organs was higher,indicating that the medium density was low.The horizontal nitrogen scavenging rate can increase the nitrogen utilization efficiency of the grain.The nitrogen production efficiency of the two varieties showed high density efficiency and high nitrogen inefficiency.This rule also indicates that the overall nitrogen application level of this experiment is high,which can be appropriately reduced in actual production.4.After the middle stage of grain filling,the plant height of Xinong 20 was the highest in D3N3(seeding rate 187.5 kg·ha^-1,topdressing 83.5 kg·ha^-1 pure N),and the plant height of Xinong 805 under the treatment of this experiment.The variation law is similar to that of Xinong 20.In D3N2(seeding rate 187.5 kg·ha^-1 and topdressing 55.7 kg·ha^-1 pure N),the highest plant height level was observed.The difference in plant height between the treatments in the early stage was not significant,indicating the use and seeding rate of nitrogen fertilizer can be appropriately reduced to achieve the purpose of controlling plant height and reducing lodging.The flag leaf area of Xinong 20 and Xinong 805 began to decrease after the booting stage.The medium density planting with a certain amount of topdressing nitrogen fertilizer will slow down the flag leaf area,indicating that the flag leaf is in this condition.The speed of aging is delayed,so as to extend the functional time of the leaves and ensure the continuous photosynthesis of the flowers.The results are consistent with the changes of SPAD values and grouting characteristics in this study.5.Xinong 20 has the highest actual harvest yield in D3N2(seeding rate 187.5 kg·ha^-1,topdressing 55.7 kg·ha^-1 pure N),and the ear treated under N3(topdressing 83.5 kg·ha^-1 pure N)The number of grains was significantly higher than that without nitrogen recovery,and the increase of density and the increase of nitrogen uptake decreased the 1000-grain weight,indicating that in this experiment,the increase in effective panicle number is still the key to the increase of Xinong 20 yield;The yield of Xinong 805 in D1N3(seeding rate 112.5kg·ha^-1 and t topdressing 83.5 kg·ha^-1 pure N)was the highest under harvest,and the yield increased first and then decreased with the increase of density.The number of spikes and spikes increased with the increase of nitrogen uptake.The variation of grain number and1000-grain weight is similar to that of Xinong 20.6.Density treatment has no significant effect on the quality indexes of Xinong 20 and Xinong 805.Different nitrogen dressings have significant effects on the wet gluten content,ductility and maximum tensile resistance of Xinong 20,within a certain range.The increase of nitrogen content in the above will reduce the above three indicators.Under the highest density and nitrogen-matching conditions,the quality indicators of Xinong 20 are mostly the lowest level in the experimental design.The protein content and wet gluten content of Xinong 805 were the highest under N1(topdressing 83.5 kg·ha^-1 pure N),indicating that a small amount of nitrogen in spring could increase the protein and wet gluten content of Xinong 805.The difference in quality indicators between varieties is generally greater than the difference between treatments.