Effects Of Different Density And Nitrogen Application Rate On Nitrogen Utilization Efficiency And Yield Formation Of Bowl Mechanical-transplanting Rice

In order to investigate the effects of different densities and nitrogen application rates on nitrogen utilization and yield formation of rice transplanted by bowl seedling machine,the experiment was conducted in Jizhai Village,Changji Town,Sansui County,Guizhou Province,from 2017 to 2018 with C Liangyou Huazhan,a hybrid indica rice.Two factors and two levels of split zone design were adopted.Density（D）and nitrogen application rate（N）were set as two factors.The main area was treated by D,and the secondary area was treated by N application rate.There were three D levels of 216,500 holes/ha（33×14cm）,168,400 holes/ha（33×18 cm）,126,300 holes/ha（33×24 cm）and four N levels（0 kg N/ha,75 kg N/ha,150 kg N/ha,225 kg N/ha）.The yield,composition,growth characteristics,photosynthetic characteristics,fluorescence parameters and N utilization of rice transplanted by pot seedling machine were studied.The test results show that:1.Yield and yield components of bowl mechanical-transplanting rice under N application rate and D（1）The effect of N application rate on yield was extremely significant levels.With the continuous increase of N application rate,it increased first and then decreased in the experiment.The highest yield and highest yield were obtained when the N application rate was 150kg/ha.They are 8694.49kg/ha respectively.With the decrease of D,the yield has a certain decreasing trend.The density is the lowest when the density is 12.63 million points/ha,which is 7359.81kg/ha.The difference in the effect of interaction on yield was not significant.The yield was 150 kg/ha and the highest density was 21.65 million points/ha,which was the highest yield of 9572.88 kg/ha.（2）With the increase of N,the number of effective panicles increased gradually,while the change of 1000-grain weight and seed setting rate was not obvious,but it was always the lowest under N4（225kg/ha）treatment.With the decrease of D,the number of effective spikes gradually decreases.The effects of interaction on the number of effective panicles and the total number of grains per panicle reached a very significant level.2.Effects of N application rate and machine insertion D on the growth characteristics of above ground parts of bowl mechanical-transplanting rice（1）N application rate and D had significant effects on plant height,tiller number,leaf area,leaf area index,dry matter accumulation,and crop growth rate.With the increase of N application rate,plant height（booting stage,maturity stage）,leaf area ratio（jointing-heading）,dry matter accumulation（booting stage）showed a trend of increasing gradually,and photosynthetic potential（jointing-booting,booting-heading）,leaf area（booting stage,heading stage）,and leaf area index at booting stage showed opposite trends;with the increase of N application rate,net assimilation rate（jointing-heading）,crop growth rate（booting-mature）,strain The high（jointing stage）and dry matter accumulation（jointing stage,heading stage）increased first and then decreased.With the decrease of D,crop growth rate（transplanting-jointing）,leaf area index（jointing stage,booting stage）,photosynthetic potential（jointing-booting,booting-heading）,number of stems(jointing stage,booting stage,heading during the critical period,the dry matter accumulation and total biomass showed a decreasing trend.With the decrease of D,the leaf area index and plant height（jointing stage,maturity stage）at the heading stage increased first and then decreased.（2）The effect of interaction on leaf area index（booting stage）,leaf area（heading stage）and leaf area ratio（jointing-heading）reached a significant level,while dry matter accumulation（heading stage）and stage dry matter accumulation（jointing-heading,heading-maturity）,crop growth rate（joint-booting,booting-maturity）has reached a significant level.3.Effects of N application rate and machine insertion density on photosynthetic characteristics of leaves in bowl mechanical-transplanting rice（1）With the increase of N application rate,the SPAD value of jointing stage increased first and then decreased,and the booting stage and heading stage showed a trend of increasing gradually.The effect of D on SPAD values is not significant.The effect of interaction on the SPAD value at jointing stage reached a very significant level.（2）With the increase of N application rate,the net photosynthetic rate（Pn）increased in jointing stage and booting stage,stomatal conductance（Gs）and transpiration rate（Tr）increasing both increased at jointing,booting and heading stage.At jointing,booting and heading stage,,intercellular CO₂concentration（Ci）increased first and then decreased during jointing,booting and heading,and water use efficiency（WUE）and photosynthetic nitrogen utilization efficiency（PNUE）showed a downward trend in heading stage.The yield increased first and then decreased.With the decrease of machine insertion D,Pn and Gs increased at the jointing stage,and the booting stage increased first and then decreased,while the Ci increased first and then decreased at jointing and heading stage.However,it showed a downward trend at booting stage;Tr showed an increasing trend at jointing stage,and decreased at booting stage,but decreased first and then increased at heading stage;WUE showed an increasing trend at jointing stage and booting stage;PNUE showed first at booting stage after the increase,the trend is reduced,and the yield is decreasing.N application rate and D interaction reached a very significant level at the booting stage and heading stages of Pn,jointing stage and heading stage Gs,heading stage Tr,and main growth period WUE and PNUE.3.Effects of N application rate and machine insertion D on the accumulation characteristics of rice nutrient in bowl mechanical-transplanting rice（1）With the increase of N application rate,the total nitrogen（nitrogen,phosphorus,potassium）and total potassium accumulation at the heading stage increased first and then decreased,while the nitrogen accumulation at maturity gradually increased..With the decrease of D,total（nitrogen,phosphorus,potassium）,total（nitrogen,phosphorus,potassium）and total（nitrogen,phosphorus,potassium）in the maturity stage gradually increased.The effects of interaction on the total nitrogen and total nitrogen accumulation at the jointing stage were extremely significant,but had a significant effect on the total（phosphorus,potassium）and total potassium accumulation during the jointing stage.（2）With the increase of N application rate,the potassium accumulation in the jointing stage（stem sheath,leaf）and the accumulation of stem and sheath（phosphorus and potassium）in the heading stage increased first and then decreased,while the mature stage（nitrogen and phosphorus）nitrogen accumulation in potassium,mature leaves（phosphorus,nitrogen）,mature leaf nitrogen,and heading stage（leaf and ear）showed a gradual increase.With the decrease of D,stem and sheath（nitrogen,phosphorus,potassium）,heading stage（nitrogen,potassium）,heading stage（nitrogen,phosphorus,potassium）,jointing stage（stem sheath,leaf）phosphorus The accumulation of all the factors showed a gradual decrease,and the accumulation of nitrogen in the stem sheath at the jointing stage increased first and then decreased.The effects of interaction on the nitrogen accumulation in the mature stage（stem sheath,ear）,the nitrogen in the jointing stage,and the accumulation of phosphorus in the heading stage reached a significant level.（3）With the increase of N application rate,the heading-mature nitrogen accumulation decreased gradually,while the jointing-heading phosphorus accumulation increased first and then decreased.With the decrease of D,the accumulation of jointing-heading phosphorus increased first and then decreased.The effects of interaction on nitrogen,phosphorus and potassium（joint-heading,heading-maturation）reached extremely significant levels.4.Effects of N nitrogen application rate and machine insertion D on the fluorescence parameters of flag leaf in bowl mechanical-transplanting rice（1）With the increase of N application rate,the photochemical efficiency（Fv/Fm）,apparent electron transport rate（ETR）,and non-photochemical quenching coefficient（q N）are not obvious,but the maximum fluorescence（Fm）,initial fluorescence（Fo）showed a gradual increase trend;with the decrease of density,Fv/Fm and ETR showed a trend of increasing gradually,q N and Fo showed opposite trends,while Fm showed a trend of increasing first and then decreasing.5.Effect of N application rate and machine insertion D on nitrogen use efficiency of bowl mechanical-transplanting rice（1）With the increase of N application rate,fertilizer-nitrogen recovery efficiency（FRE）,fertilizer-nitrogen agronomic efficiency（FAE）,fertilizer-nitrogen physiological efficiency（FPE）,partial factor productivity of applied nitrogen（PFP）,nitrogen grain production efficiency（NGPE）,nitrogen dry matter production efficiency（NDGPE）showed a gradual decrease trend,while the nitrogen requirement for 100 kg grains showed the opposite trend,and the change of nitrogen harvest index（NHI）was not obvious.With the decrease of D,FAE,FRE,NGPE and NDGPE showed a trend of decreasing gradually,while NRG had a certain increasing trend,and the change rule of NHI was not obvious.The interactions reached a very significant level for rice FPE,FAE,FPE,PFP,NRG,NHI and NDGPE.In this test,the nitrogen fertilizer absorption and utilization rate was 56.85%.7.The performance of rice seedlings and their components,nutrient uptake,above ground growth characteristics,photosynthetic characteristics,fluorescence parameters,nitrogen utilization rate,etc.in the integrated seedling machine,within the treatment range set by this experiment,In this area,rice seedling transplanted rice was treated with D2N3 as suitable machine insertion density and nitrogen application rate.The D and N application rate were 168,400 holes/ha（33×18cm）and 150kg/ha,respectively.The yield of the combination was 9304.05kg/ha.