Effects Of Nitrogen Fertilizer And Chemical Control On Lodging,Radiation,Heat And Water Utilization Efficiency And Yield Of Maize Under High Density

Increasing planting density is an effective measure to improve maize yield.However,high planting density may cause lodging and reduce the radiation,heat and water utilization efficiency,which leading to the yield reduction.Therefore,we study the effects of nitrogen fertilizer and chemical regulation on lodging and yield formation of maize under high-density cultivation,in order to provide theoretical basis for high-yield and high-efficiency cultivation of maize under high planting density.The experiment was carried out in 2017 and 2018 at experimental station of Northeast Agricultural University,used Longyu 365 as the experimental material,with three nitrogen levels of 100,200 and 300 kg·ha^-1?N100,N200 and N300?at high planting density(90000 plants·ha^-1),and applied chemical control?Yuhuangjin,30%amine fresh ester·ethyl hydroxide?at seven-leaf stage.We studied the effects of nitrogen fertilizer and chemical controlon the lodging resistance,canopy photosynthesis,grain filling,radiation,heat and water utilization efficiency and yield.Due to the good repeatability of the experiment in two years,this study analyzed the data in 2017.The results of the study show that:1.With the increase of nitrogen fertilizer,plant height and internode length increased,stem diameter increased and then decreased,ABA content in basal internode decreased,IAA,GA and ZR content increased,cellulose,hemicellulose,lignin,lignin synthesis related enzyme activity,bending strength and puncture strength gradually decreased,and lodging rate increased.Chemical control significantly reduced plant height,shortened the basal internode length,increased stem diameter,increased basal internode ABA content,reduced internode IAA,GA and ZR content,increased stem cellulose,hemicellulose,lignin,lignin synthesis related enzyme activity,bending strength and puncture strength,and effectively reduced lodging rate.2.Under the nitrogen application rate of 200 kg·ha^-1,the number,diameter,angle,volume and dry weight of roots,root bleeding sap and its components reached the maximum value.At the same time,chemical control significantly increased the number,diameter,angle,volume and dry weight of brace roots,and increased the volume of root bleeding sap,and Ser of mineral nutrition and amino acid.The yield was positively correlated with root bleeding sap and its components.The treatment of 200 kg·ha^-1 nitrogen application and chemical control is conducive to improving the brace root morphology and root bleeding sap characteristics,and plays an important role in improving the yield.3.With the increase of nitrogen fertilizer,the light transmittance of canopy decreased gradually.Under the nitrogen application of 200 kg·ha^-1,the mean leaf angle,LAI,SPAD value,and activity of Ru BP carboxylase,PEP carboxylase,NR and GS were the highest.At the same time,chemical control increased the mean leaf angle,canopy transmittance and LAI in the later growth stage,and significantly increased the SPAD value,and activity of Ru BP carboxylase,PEP carboxylase,NR and GS.Correlation analysis showed that the yield was positively correlated with SPAD value,and activity of photosynthetic related key enzyme and nitrogen metabolism enzyme.The treatment of 200 kg·ha^-1 nitrogen application and chemical control improved the canopy structure,photosynthesis and nitrogen metabolism,and provide a basis for yield improvement.4.The the content of IAA,GA,CTK and ABA,and the maximum grain-filling rate and the mean grain-filling rate reached the maximum value under the nitrogen application of 200 kg·ha^-1.The chemical control increased the hormone content of the grain,reduced the T_max,and increased V_max and V_m.Correlation analysis showed that IAA,CTK,GA and ABA contents were positively correlated with grain filling rate,while yield was positively correlated with maximum and mean grain-filling rate.The treatment of 200 kg·ha^-1 nitrogen application and chemical control was beneficial to the improvement of hormone content in grain and grain filling rate.5.With the increase of nitrogen fertilizer,the radiation,heat and water utilization efficiency increased and then decreased.Chemical control significantly improved the radiation,heat and water utilization efficiency.Under the treatment of 200 kg·ha^-1 nitrogen application and chemical control,radiation,heat and water utilization efficiency reached the maximum value.6.With the increase of nitrogen fertilizer,the bald length of ear decreased.Meanwhile,chemical control significantly increased the ear width and grains number per row,and significantly reduced the bald length.Under the treatment of 200 kg·ha^-1 nitrogen application and chemical control,the bald length was the shortest,the ear width,grains number per ear,1000-grain weight and yield reached the maximum value,and the maximum yield was 12646 kg·ha^-1.