| Corn is in our country and even the world’s largest food crops,and is suitable for planting corn yield efficiency together with nitrogen is an effective way to study different corn varieties increase,decreases the nitrogen response,clear biological built corn individuals,groups,source-sink relations,the yield and nutrient use efficiency,analysis under the condition of nitrogen nutrition physiological characteristics,for resolving the high-efficient and high-yield corn planting,achieve corn yield efficiency coordination is of great significance.The study was carried out in field for two years,In 2017,three corn varieties(zhenghong 6,zhongyu 3 and zhengdan 958,respectively,were set as ZH6,ZY3,ZD958),five densities(5.25,6.00,6.75,7.50 and 8.25×10~4plants/hm~2,respectively,were set as D5.25,D6,D6.75,D7.5 and D8.25),and two nitrogen levels(200 and 250 kg N/hm~2,respectively,N200 and N250).In 2018,2 corn varieties(ZY3,ZD958),4 planting densities(4.50,6.00,7.50 and 9.00×10~4plants/hm~2)and 4 nitrogen levels(0,120,180 and 240 kg N/hm~2,N0,N120,N180and N240)were set.The effects of different corn cultivars-density-nitrogen interactions on the agronomic behavior,biological construction,source-reservoir relationship,yield,nutrient uptake and utilization,and soil organic carbon,nitrogen and microbial characteristics of corn were studied.The main results were as follows:(1)Corn plant height,ear height,stem diameter are red in varieties were characterized by ZH6>ZY3>ZD958 alone,with the increase of planting density,increase corn plant height,ear position high,stem diameter decreases,and corn harvest folding rate,lodging rate increase,particularly in the density of high nitrogen treatment,discount rate and lodging rate increased significantly,nitrogen coordination with density can be adjusted by corn plant height,ear height and stem diameter,the relationship between the lodging to control the inverted folding of the corn.Both the leaf area per plant and the leaf area index of corn were as follows:ZY3>ZH6>ZD958.With the increase of planting density,the leaf area per plant decreased,the leaf area index of corn population increased,the photosynthetic potential of corn population increased,the SPAD value of ear leaf decreased,and the net assimilation rate showed no significant difference.When the nitrogen content exceeds the range of 180～200 kg/hm~2,the leaf area per plant and leaf area index of corn population decrease,the SPAD value of ear leaf increases with the increase of nitrogen content,and the proportion of dead leaves under nitrogen application is significantly lower than that under no nitrogen application,from the silking stage to20 days after the silking stage,there was no significant difference between the group photosynthetic potential and net assimilation rate in 2017 in the treatment of nitrogen consumption.In 2018,the annual average value reached a maximum at 180 kg/hm~2(N180),and when the nitrogen consumption exceeded 180 kg/hm~2,it presented a downward trend.(2)The dry matter quality of a single plant and the dry matter quality of a population in corn varieties showed as follows:ZY3>ZH6>ZD958 in harvest period,with the increase of planting density,the dry matter quality of a single plant decreased,while the dry matter quality of a population increased.Largest dry matter accumulation rate in the performance of the varieties of ZY3>ZD958>ZH6,density increase,the largest dry matter accumulation rate,the accumulation of dry matter distribution ratio drop before silking stage,dry matter accumulation after silking stage allocation proportion increases,leaf and stem sheath dry matter transfer traffic volume presents the increasing trend,leaf and stem sheath transport rate and the contribution rate of seed,no obvious regularity,at harvest time,the change order of dry matter distribution ratio of each part was:grain>stem>leaf>cob>bract>leaf sheath.Nitrogen application can increase the dry matter mass of corn per plant,population dry matter mass and the maximum accumulation rate of dry matter.When the nitrogen content exceeds the range of 180～200 kg/hm~2,it shows a decreasing trend,and the effect of nitrogen application on dry matter distribution is not significant.(3)Dense planting can significantly increase the rate of empty stem,inverted stem and lodging,and reduce the double-panicle rate,nitrogen application can increase the rate of double panicle and reduce the rate of empty stem,but increase the probability of inverted and lodging.Similarly,dense planting would lead to worse ear traits,decreased ear length and ear thickness,and increased bald tip length.Nitrogen application would improve ear traits.Different corn varieties have different yield performance,In 2017,the grain yield per plant was ZD958 and ZY3 significantly higher than ZH6,in 2018,ZY3 was significantly higher than ZD958,the grain yield per plant decreased with the increase of planting density,and the grain yield per plant decreased with the nitrogen consumption over the range of 180-200 kg/hm~2;The population grain yield in each variety was as follows:ZH6>ZY3>ZD958 in 2017,ZY3<ZD958 in 2018,in 2017,the average population grain yield under N200treatment was 8.32%higher than that under N250 treatment,and the yield of ZD958,ZY3 and ZH6 was the highest under the density of 7.50,6.75 and 7.50×10~4plants/hm~2under the nitrogen consumption condition of 250 kg/hm~2,nitrogen dosage increase,in 2018 the average group reduced grain yield increase after the first,biggest production in 180 kg/hm~2,yield was 17.24%higher than that of the implementation,N0,N120,N180 treatment with ZY3 next ZD958 respectively under the density of7.50,6.00×10~4plants/hm~2 yield is the largest,dosage of nitrogen under the condition of 240 kg/hm~2 can support 9.00×10~4plants/hm~2 corn population with high density,grain yield not to drop,increase close the nitrogen potential in oil production increase can give full play to the group and realize the nitrogen supply and demand balance between plants,the purpose of production.(4)With the advance of the growth period,the nitrogen content of the corn stem,leaf and leaf sheath decreased,and the nitrogen accumulation of the population increased with the advance of the growth period,and reached the maximum value at the harvest period,the accumulation of nitrogen in different parts of the harvest period was as follows:grain>stem>leaf>rachis,sheath>bract.With the increase of planting density,the nitrogen content in all parts of corn decreased significantly,while the population nitrogen accumulation increased significantly,in 2017 and 2018,the population nitrogen accumulation reached its maximum value under D8.25 and D9.00respectively.In 2017,the nitrogen accumulation under N200 treatment was significantly higher than that under N250 treatment,and in 2018,the nitrogen application treatment was significantly higher than that under no nitrogen application treatment.Nitrogen transfer traffic volume reduced with the increase of density increased after the first,2017,2018 annual has a maximum value under D7.50treatment,nitrogen dosage increased,nitrogen transfer capacity,transport rate and contribution rate of grain in 2017 showed N250 treatment is higher than the N200treatment,in 2018 n turn traffic and transport rate and the contribution rate of grain showed the trend of increased after the first drop,when more than 180 kg/hm~2nitrogen rates begin to decline.Density increase nitrogen partial productivity increased significantly,2017,2018 annual has a maximum value under D7.50treatment,nitrogen use efficiency and nitrogen fertilizer utilization rate of agronomy,when more than 200 kg/hm~2 nitrogen rates,nitrogen partial productivity,nitrogen use efficiency decline in 2017,2018,nitrogen partial productivity,nitrogen use efficiency and nitrogen fertilizer utilization rate of agronomy reduced with the increase of dosage of nitrogen increased after the first,in the N120 respectively,N180,N180treatment has a maximum value.(5)With the increase of nitrogen content,total nitrogen content,microbial biomass carbon and nitrogen in 0-20 cm soil first increased and then decreased,all of which reached their maximum value under N180 treatment.Soil nitrate nitrogen showed a trend of increasing all the time,and soil ammonium nitrogen showed opposite performance with soil nitrate nitrogen.The activity of sucrase,alkaline phosphatase and urease in 0-20 cm soil was consistent.With the increase of nitrogen content,it increased significantly and began to decline when it exceeded 180 kg/hm~2,while catalase activity showed a downward trend when it exceeded 120 kg/hm~2.The appropriate nitrogen content could significantly improve the total nitrogen content,microbial carbon nitrogen and soil enzyme activity.In conclusion,in hilly corn area in the middle of Sichuan Province,the suitable planting density was increased and the yield was increased significantly.The nitrogen consumption was within the range of 180～200 kg/hm~2,which realized the coordinated improvement of corn yield and efficiency,and significantly improved the soil total nitrogen content,microbial carbon,nitrogen and soil enzyme activity.Based on various indexes of agronomic traits,bioconstruction,yield,nutrient uptake and utilization,soil organic carbon,nitrogen and microbial characteristics of corn,the suitable planting density of national tested corn variety ZD95 and Sichuan main corn varieties ZY3 and ZH6 was 7.50×10~4plants/hm~2,6.75-7.50×10~4×10~4plants/hm~2and 7.50×10~4plants/hm~2,and the suitable nitrogen consumption was 180-200kg/hm~2. |
