| In recent years,with an increasing grain yield of winter wheat,nitrogen fertilizers have increased which was seriously affected the ecological environment.The experiment was conducted during 2014-2015 growing season at the Agronomy Experimental Station?36°09?N,117°09?E?of Shandong Agricultural University in Tai?an,Shandong Province,China.This experiment was completely randomized block with two planting patterns and three nitrogen rates,to explore by optimizing the crop population structure,canopy photosynthetic active radiation?PAR?,leaf physiological characteristics,dry matter to achieve stable grain yield with reducing nitrogen and improve ecological environment.The winter wheat?Jimai 22?field experiment was conducted in Tai'an,Shandong Province.In this experiment,the main plots were“20+40”cm furrow planting?F?and uniform planting?U?,and the subplots were fertilized with nitrogen at 0 kg ha-1?N0?,112.5 kg ha-1?N1?,225.0 kg ha-1?N2?with three replicates.The results showed that planting pattern and nitrogen rates had significant effects on the crop population structure,canopy PAR,leaf physiological characteristics,dry matter and yield.The results were showed as following:1 Dynamics population developmentThe stem tillers numbers of F planting pattern was larger in the whole growing stage,and fell slowly in the late period;the stem tillers numbers of U planting pattern was larger in early period,then fell rapidly.The overall numbers population of U was smaller than that of F.F could improve leaf area index?LAI?than U.On the later period,such as the filling stage,mature stage,F could slow down the reduction of LAI and maintain higher photosynthetic area.Therefore,it is helpful to construct reasonable population structure of winter wheat and improve the relationship between individual and the group;at the same time,it also benefit to improve LAI.The stem tillers numbers and LAI of winter wheat increased with increased nitrogen rate,but growth gradually weakened.Planting patterns significantly influenced LAI throughout the whole growth period.In addition to the heading stage,planting pattern×nitrogen rate interaction had significant effect on stem tillers number and LAI?P<0.05?.2 Canopy photosynthetic active radiationFurrow planting pattern change the vertical structure of crop,which results in changing the distribution of light in the population.Therefore,F could obviously improve the canopy PAR interception ratio and decreased canopy PAR penetration ratio.The order of total PAR interception ratio and reflection ratio were both showed that F>U.Contrastly,the order of penetration was showed that F<U.F planting pattern could increase the canopy PAR interception ratio,and reduce the loss of light-leaking by changing the surface morphology;meanwhile,ridge can play while edge effect to capture more light.Therefore,F planting pattern could increase yield.PAR interception ratio increased with increased nitrogen rate.But with the further increased nitrogen rate,the potential of PAR interception ratio was decreasing;there was no significant difference between N1 and N2.Effect of planting pattern on PAR interception ratio was more than that of nitrogen rate,but the effect of nitrogen rate had shorted the gap between two planting patterns.PAR penetration ratio was decreased with increased nitrogen rate,which could helpful to reduce the invalid loss of moisture.Different height levels of PAR interception ratio of F were showed“upper-weak and down-strong”to“upper-strong and down-weak”trend during growing stage and U planting patterns were showed"upper-weak and down-strong"trend.With increased nitrogen rates,this trend became slow.Nitrogen rates had significantly influenced on PAR interception ratio of 0-40 cm?except maturity stage?and>40 cm.Effects of planting pattern were greater than that of nitrogen rate.The change diurnal PAR interception ratio at heading stage and filling stage were presented that F>U.There were obvious advantages at 12:00 and 16:00 of F planting pattern.That means of F planting pattern could sufficiently capture light,laying a foundation for improving the photosynthetic performance.The diurnal average of PAR intercept ratio increased with the increased nitrogen rate,which was characterized by N2>N1>N0.The most significant effect of nitrogen rate was at 12:00.3 Photosynthetic physiological characteristicsF planting pattern could improve chloroplast fluorescence parameters of Fv/Fo.The means of F planting pattern had high potential photosynthetic activity,which was helpful to improve photosynthetic activity and maintain high photosynthetic rate?Pn?.Thus it is help to increse the yield.The values of Fv/Fo increased with the increased nitrogen rate.Effect of nitrogen rate was shorted the gap between the two planting patterns.Planting pattern×nitrogen rate interaction had significantly influenced Fv/Fo at maturity stage?P<0.05?.The numerical minimum of Fm/Fv was presented under N0 condition,but there was no significant difference between N1 and N2 conditions?P>0.05?.F planting pattern could make the content of chlorophyll index?CCI?to maintain a higher level in the whole growth stage,and fell slowly in later period which was helpful to delay the leaf senescence and maintain photosynthetic capacity to increase yield.CCI increased significantly with the increased nitrogen rate.Effect of nitrogen rates was lager than that of planting patterns.The change trend of Pn and CCI were consistent.F planting pattern could improve the Pn during the whole growth stage and Pn at later period.F planting pattern could effectively delay to reduce the Pn during maturity stage,which maybe conducive to the formation of grain.With the increased nitrogen rates,Pn increased,but there was no significant difference between N1 and N2 conditions?P>0.05?.Under F planting pattern,appropriate to reduce nitrogen rate was benefit to maintain higher diurnal average of Pn.The diurnal variation of F planting pattern had obvious advantages at 10:00 and 16:00 in heading stage and filling stage.Intercellular CO2 concentration?Ci?,transpiration rate?Tr?and Cond of F planting pattern were higher than that of U within the entire growth period.All traits increased with the increased nitrogen rates,but there was no significant difference between N1 and N2 which was helpful to stable the values of all traits at later period?P>0.05?.Under nitrogen rate of 112.5 kg ha-1,the photosynthetic indexes of F planting pattern had obvious advantages.4 Dry matter accumulation and distributionTotal dry matter accumulation of winter wheat was showed an increasing trend.F planting pattern not only significantly increased the amount of dry matter,but the allocation amounts of leaf and spike were large.That means F planting pattern could improve photosynthetic area and take advantages to the grain formation.Nitrogen rate application significantly affected stem,leaf,spike,total dry matter weight of winter wheat.With the increase of nitrogen rate,dry matter of organs of winter wheat increased gradually.Under the condition of N1,F planting pattern had the best obvious advantage.The growth of net assimilation rate?NAR?of F planting pattern was bigger during the whole period,which was helpful to accumulate dry matter at later period.With the increase of nitrogen rates,NAR was declined.At heading stage,F and U planting patterns had obtained the maximum of dry matter under the N1 condition.5 The relationship between yield and photosynthetic factorsF planting pattern was conducive to improve spikes,plant height,spike length,spikelet number,sterile spikelet number and harvest index?P<0.05?.Thousand grain weights,grain yield,radiation energy utilization of F planting pattern had no significant difference with U planting pattern,but relatively increasing?P>0.05?.With the increased amount of nitrogen rates,the grain yield,stem and leaf dry matters,harvest index,radiation energy utilization and spikes were significantly increased.Effects of nitrogen rates on grain yield,harvest index and radiation energy utilization were obviously higher than those of planting patterns.Nitrogen rates had no significantly influence on the grain,thousand grain weights,spike length,sterile spikelet number?P>0.05?.Effects of nitrogen rates on stem and leaf dry matters and plant height were obviously smaller than those of planting patterns.Comprehensively,F planting pattern×112.5 kg ha-1 interaction can significantly increase spike length and effective spikelet number by reducing the invalid spikelet number to reduce nitrogen production.Pn,LAI,CCI had significantly positive correlation with the grain yield.PAR capture ratio was positively related with grain yield without significance.There was significantly positive correlation between LAI and CCI,PAR capture ratio.The CCI had significantly positive related with PAR capture ratio.The order of impacting on the yield was showed that Pn>CCI>LAI>PAR capture ratio.Photosynthesis indexes?except PAR capture ratio?and the interaction between photosynthetic factors?except the Pn and PAR capture ratio,Pn and LAI interactions?had significantly affected the yield of winter wheat.The photosynthesis indexes had a certain role to improve the grain yield.6 Nitrogen utilizationThe effects of different planting patterns and nitrogen rates on nitrogen accumulation and absorption of winter wheat had a certain difference.Nitrogen accumulation in different organs of F planting pattern were higher than that of U planting pattern at flowering stage and maturity stage.Nitrogen distribution of stems was highest at flowering stage;nitrogen distribution proportion of grain was highest at maturity stage.Grain production efficiency?GE?and nitrogen harvest index?NHI?were 22.5%,1.5%less than that of U planting pattern,respectively.Grain nitrogen accumulation and plant nitrogen accumulation increased with the increased nitrogen rates.Nitrogen use efficiency and NHI were attained the maximum at N0condition,meanwhile,partial factor productivity,agriculture use efficiency and physiological efficiency had significant advantages at N1 condition.Grain yield of F planting pattern under 112.5 kg ha-1 condition had no significant difference with U planting pattern under 225.0 kg ha-1 of winter wheat?P>0.05?.Therefore,"20+40"cm furrow rowing planting pattern combined with 112.5 kg ha-1 nitrogen rate could achieve stable grain yield of winter wheat and improve the ecological environment by optimizing the population structure and photosynthetic property under this experimental condition. |
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