| The experiment was conducted with two common cultivars, Jimai22(high tilleringcapability) and Tainong18(low tillering capability) in2011-2013wheat growing season inYangzhuang village, Yanzhou, Shangdong. Considering the different tillering capacities, plantdensities of120,180, and240plants m–2were used for cultivar J22, while plant densities of135,270, and405plants m–2were utilized for T18. The N fertilization treatment was appliedat three levels using urea, i.e., no fertilization N (N0),180kg ha–1of N (N180, therecommended N input), and240kg ha–1of N (N240; local farmer’s fertilizer applicationamount). Since the plant density differed between cultivars, the field experiment was designedspecifically for each cultivar, which was established as a split-plot design of three replicateswith N input as the main plots and plant density as the subplot.15N-microplot experiment wasalso included in each plot. The results were as follows:1The effects of different plant density and nitrogen level on grain yield formation inwheat1.1The effects of different plant density and nitrogen level on dry matter accumulationAt the same nitrogen level, the dry matter at maturity was significantly increased withthe increasing plant density, with the increasing plant density, the dry matter accumulationduring the seeding–before winter, before winter-jointing, anthesis-maturity stage weresignificantly increased, the dry matter accumulation ratio during the seeding–before winterand before winter-jointing stage were significantly increased, the dry matter accumulationratio during the jointing-anthesis stage were significantly decreased; At the same plant density,the dry matter at maturity was significantly increased with the increasing nitrogen level, withthe increasing nitrogen level, the dry matter accumulation during the seeding–before winter,before winter-jointing, jointing-anthesis, anthesis-maturity stage were significantly increased,the dry matter accumulation ratio during the anthesis-maturity stage were significantlyincreased. 1.2The effects of different plant density and nitrogen level on grain yieldThe effects of N input, plant density, and all two-way interactions were significant ongrain yield for the two cultivars. An N input of0and180kg ha–1, no significant difference ofHI was observed among the plant density treatment, biomass and grain yield significantlyincreased with the increasing plant density. An N input of240kg ha–1, biomass significantlyincreased with the increasing plant density, no significant difference of grain yield wasobserved between the middle plant density and high plant density treatment, which aresignificantly higher than that of the low plant density.1.3The effects of different plant density and nitrogen level on grain filling parametersindexAn no N input, no significant difference of Tmax, D,T1,T2andT3were observed betweenthe plant density treatments, Wmax, GRmax and the mean grain filling rate showed adecreased trend and the grain weight at maturity significantly decreased with the increasingplant density. An N input of180kg ha–1, no significant difference of D and T1were observedbetween the plant density treatments, Tmax, T2andT3significantly increased, Wmax, GRmaxand the mean grain filling rate showed a decreased trend and the grain weight at maturitysignificantly decreased with the increasing plant density. An N input of240kg ha–1, Tmax,D,T1,T2andT3were all significantly increased, Wmax, GRmax and the mean grain filling rateshowed a decreased trend and the grain weight at maturity significantly decreased with theincreasing plant density.T18had a higher the mean grain filling rate compared to J22.1.4The effects of different plant density and nitrogen level on dry matter translocationAn no N input, both the translocation amount of dry matter stored in vegetative organsbefore anthesis and the dry matter accumulation amount after anthesis increased with theincreasing plant density, no significant difference of the translocation ratio and its contributionto grain of dry matter stored in vegetative organs before anthesis was observed among theplant density treatment. An N input of180kg ha–1, both the translocation amount of dry matterstored in vegetative organs before anthesis and the dry matter accumulation amount afteranthesis increased with the increasing plant density, the translocation ratio of dry matterstored in vegetative organs before anthesis was decreased with increasing plant density. An Ninput of240kg ha–1, the dry matter accumulation amount after anthesis was significantlyincreased with increasing plant density, the translocation amount of dry matter stored invegetative organs before anthesis was increased first and then decreased,the translocationratio of dry matter stored in vegetative organs before anthesis and its contribution to grainswere all decreased with increasing plant density. At the same plant density, the dry matter accumulation amount after anthesis and contribution to grain was significantly increased withthe increasing nitrogen level, the translocation amount and ratio of dry matter stored invegetative organs before anthesis and its contribution to grain were all decreased.2The effects of different plant density and nitrogen level on nitrogen uptake efficiency(UPE)2.1The effects of different plant density and nitrogen level on nitrogen accumulationAt the same nitrogen level, the nitrogen accumulation amount at maturity wassignificantly increased with the increasing plant density, with the increasing plant density, thenitrogen accumulation amount and ratio during the seeding–before winter, beforewinter-jointing, anthesis-maturity stage were significantly increased; At the same plant density,the nitrogen accumulation amount was significantly increased with the increasing nitrogenlevel, with the increasing nitrogen level, the the nitrogen accumulation amount during theseeding–before winter, before winter-jointing, jointing-anthesis, anthesis-maturity stage wereall significantly increased, the nitrogen accumulation ratio during the anthesis-maturity stagewere significantly increased.2.2The effects of different plant density and nitrogen level on nitrogen uptake efficiency(UPE)At the same nitrogen level, UPE was significantly increased with the increasing plantdensity, at the same plant density, UPE was significantly decreased with the increasing plantdensity, the interaction between N input and plant density was manifested at a highest UPEwith a combination of low N input and high plant density.2.3The effects of different plant density and nitrogen level on nitrogen uptake fromdifferent soil layerMean total15N uptake amount at depths0.2,0.6and1.0m were significantly decreasedwith the increasing depth of15N labeling. At the same nitrogen level, total15N uptake amountat depths0.2,0.6and1.0m were significantly increased with the increasing plant density, theabsolute amount and relative proportion of increased15N uptake increased with increasinglabeled depth. At the same plant density,15N uptake amount at depths0.2m and0.6m of Ninput of180kg ha–1were significantly lowerer than240kg ha–1,5N uptake amount at depths1.0m of N input of180kg ha–1were significantly higher than240kg ha–1. AGN was positivelyrelated with15N uptake amount at depths0.2and0.6m, UPE was positively related with15Nuptake amount at depths1.0m.3The effects of different plant density and nitrogen level on nitrogen utilizationefficiency (UTE) 3.1The effects of different plant density and nitrogen level on nitrogen utilizationefficiency (UTE)An N input of0and180kg ha–1, no significant difference of UTE was observed amongthe plant density treatment, An N input of240kg ha–1, no significant difference of UTE wasobserved between the low plant density and middle plant density treatment, which aresignificantly higher than that of the high plant density.3.2The effects of different plant density and nitrogen level on nitrogen harvest index(NHI) and grain nitrogen concentration (GNC)UTE could be calculated based on the ratio of the NHI to the GNC. An N input of0and180kg ha–1, no significant difference of NHI and GNC were observed among the plantdensity treatment, An N input of240kg ha–1, no significant difference of NHI was observedbetween the low plant density and middle plant density treatment, which are significantlyhigher than that of the high plant density. no significant difference of GNC was observedbetween the low plant density and middle plant density treatment, which are significantlylower than that of the high plant density.3.3The effects of different plant density and nitrogen level on nitrogen translocation inwheatAn no N input and N input of180kg ha–1, both the translocation amount of nitrogenstored in vegetative organs before anthesis and the nitrogen accumulation amount afteranthesis increased with the increasing plant density, no significant difference of thetranslocation ratio and its contribution to grain of nitrogen stored in vegetative organs beforeanthesis was observed among the plant density treatment. An N input of240kg g ha–1, themiddle plant density treatment increased the translocation amount of nitrogen stored invegetative organs before anthesis and the nitrogen accumulation amount after anthesis, but nosiginificant difference of the translocation ratio and its contribution to grain of nitrogen storedin vegetative organs before anthesis was observed, compared to the low plant densitytreatment. The high plant density treatment increased the the nitrogen accumulation amountafter anthesis, decreased the the translocation ratio and its contribution to grain of nitrogenstored in vegetative organs before anthesis, no siginificant difference of the amount ofnitrogen stored in vegetative organs before anthesis was observed,compared to the middleplant density treatment.At the same plant density, the translocation amount of nitrogen stored in vegetativeorgans before anthesis and nitrogen accumulation amount after anthesis was significantly increased with the increasing nitrogen level, the translocation ratio of nitrogen stored invegetative organs before anthesis and its contribution to grain were all decreased.4The effects of different plant density and nitrogen level on nitrogen use efficiency(NUE)An N input of0and180kg ha–1, NUE increased significantly with the increasing plantdensity, An N input of240kg ha–1, no significant difference was observed between the highplant density and middle plant density treatment, which are significantly higher than that ofthe low plant density.5The effects of different plant density and nitrogen level on NO3-N and soil nitrogenblanceAt the same plant density, soil NO3-N accumulation in0-200cm soil layer are increasedwith the increase of nitrogen level, which was presented as N240>N180>N0. the residualNmin and nitrogen apparent loss are increased significantly.At the same plant density, soilNO3-N accumulation in0-200cm soil layer are decreased with the increase of plant density,which was presented as low plant densty>middle plant density>high plant density,the residualNmin and nitrogen apparent loss are decreased significantly with the increasing plant density．In the2011-2012year, compared with soil NO3-N accumulation before sowing, at no Ninput, NO3-N accumulation of0-200cm soil layer at maturity of all the plant densitytreatments significantly increased, An N input of180kg ha–1, NO3-N accumulation of0-40cmsoil layer at maturity of all the plant density treatments significantly increased, no significantdifference of NO3-N accumulation of40-120cm soil layer at maturity of all the plant densitytreatments was observed, NO3-N accumulation of120-200cm soil layer at maturity of all theplant density treatments significantly decreased, An N input of240kg ha–1, NO3-Naccumulation of0-40cm and80-100cm soil layer at maturity of all the plant densitytreatments significantly increased, no significant difference of NO3-N accumulation of40-60cm soil layer at maturity of all the plant density treatments was observed, NO3-Naccumulation of100-200cm soil layer at maturity of all the plant density treatmentssignificantly decreased. |
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