Combined Effect Of Nitrogen Level And Seeding Rate On Nitrogen Concentration,Population And Grain Yield In Different Winter Wheat Cultivars

Two winter wheat cultivars,Yumai 49-198?multi-spike?and Zhoumai 16?large-spike type?were used to investigate the effects of nitrogen level and seeding rate on dry matter accumulation,translocation and grain yield in two genotypes of winter wheat,and find a balance between nitrogen level and seeding rate for high yield and high efficiency in wheat.The experiment was set as a split-plot design of three nitrogen levels: N1(0 kg·hm^-2),N2(180 kg·hm^-2),N3(360kg·hm^-2),four seeding rates: D1(75 kg·hm^-2),D2(150 kg·hm^-2),D3(225 kg·hm^-2),D4(300 kg·hm^-2).The main results was showed as following: 1.The effects of ineraction between different nitrogen level and seeding rate onpopulation dynamic of wheat.There was a significant differences between nitrogen application amount and seeding rate on wheat population.Along with the increasing of seedinging rate,the total stem number increased significantly under the same nitrogen rate.Wheat stems number was significantly lower in the control than that in the N fertilization treatment with no difference among nitrogen treatment in the equal seeding rate.Ear-bearing percentage?ETP?of tillers had a reducing trend with the crease of N fertilizer rate and seeding tare.The ETP of YM49-198 was higher than ZM16.The highest ETP was D1N1 and D2N2 at the year of 2014-2015 and at the year of 2015-2016,respectively.2.Effect of nitrogen supply on dry matter accumulation and transport in wheat with different plant populations.Wheat dry matter accumulation quantity was presented as a tendency to increase during the whole period.The dry matter from jointing to flowering had the highest ratio,which from flowing to harvest came second.Nitrogen application and seeding rate improved wheat dry matter accumulation from flowering to harvest,but it did not increase from jointing to flowering.The dry matter accumulation of YM49-198 of treatment D3N3 were highest in two years and dry matter accumulation of ZM16 of treatment D4N3?2014-2015?and D3N3?2015-2016?were highest.When the seeding rate higher than the D3 processing,there was no significant difference between N2 and N3.Dry matter accumulation of YM49-198 was obvious greater than ZM16 because of the advantage of ear-bearing.The distribution law in each organ of material in harvest was followed by: grain>stems>cob,glume>leaves.Nitrogen application improved dry matter accumulation in each organ.When the seeding rate lower than the D3 processing,grain yield increased with the increase of N application rate,and when seeding rate was higher than D4,yield was increasedfirstly and then dropped with the increase of the application rate.At the same N application rate,dry matter accumulation of stems,leaves and cob,glume increased with the seeding rate increasing.With the increase of sowing rate,the proportion of dry matter distribution in leaves and cob,glume increased at maturity,while the ratio of dry matter distribution of grain and stem and sheath was decreased.For translocationcharacteristics,translocation amount of wheat,transport rate and its contribution to grains of wheat at pre-anthesis was higher than other seeding rateunder the seeding rate of D1,whereas the dry matter accumulation and its contribution to grains after anthesis was lower than others.At the same seeding rate,the increase of N application rate could improved transport rate at pre-anthsis and dry matter accumulation after anthesis,with the decrease of its contribution to grains.3.Effect of nitrogen supply on accumulation,distribution and reutilization of nitrogen in wheat with different plant populations.Accumulation of nitrogen in wheat increased along with the increase of N application rate.There was nosignificant difference among different seeding rate of N accumulation at N1.With nitrogen addition increasing from N2 to N3,accumulation of nitrogen increased with the seeding rate.Translocation and distribution of nitrogen was affected by N application level and seeding rate.N translocation of different plant organs at pre-anthsis under N application of N1 was fllowed by: leaves>stems>cob,glumewhile stems>leaves>cob,glume was founded at N application of N2 and N3.Nitrogen translocation of different plant organs increased with N application level.Nitrogen concentration of two genotype wheat increased significantly with the increase of nitrogen level,and decreased with the increase of seeding rate.Plant organs nitrogen concentration and nitrogen level were positively correlated at flowering and maturity.Organ nitrogen concentration increased with seeding rate decreased at N1.Organ nitrogen concentrationincreased first and then decreasedwith the increase of seeding rate at N2 and N3.Compared with flowering stage,the leaf nitrogen concentration decreased at maturity.The effects of nitrogen application were significant when the sowing rate was low?D1 and D2?.When the sowing rate increased to D4,the effect of nitrogen rate on nitrogen concentration was reduced,which was not conducive to the increase of organsnitrogen concentration.Soil nitrate accumulation was first decreased and then increased in various soli layers.In the soil nitrogen balance system,the quantity of nitrogen surplus in the soil of YM49-198 at N1,N2,N3 reached-48 kg·hm^-2,-9 kg·hm^-2,111kg·hm^-2;the nitrogen surplus of ZM16 reached-103 kg·hm^-2,-7kg·hm^-2,118kg·hm^-2.The quantity of nitrogen surplus decreased by 40.9-44.7% when seeding rate increased from D1 to D4 at N3.The decrease in soil N loss in erosion was due to crop absorbing of soil N with seeding quantity increased.4.Effect of nitrogen supply on grain yield and its composition in wheat with different plant populations.In the same seeding rate,there was no difference of grain yield at D2,D3 and D4,the grain yield at D1 was lower than them.There was no difference in D3N2,D3N3,D4N2,D4N3 of yield.Panicle number increased and 1000 kernel weight decreased with N application or seeding rate raised;grains per par increased with nitrogen level,but decreased with seeding rate.The nutrient uptake and dry matter accumulation of wheat at different yield levels were analyzed by using the results of different nitrogenous combinations.The results showed thathe largest wheat population reached 1170-1250×10⁴·hm^-2 and panicle number reached 620-680×10⁴·hm^-2 could reached high yield(8.5 t·hm^-2).The plant N content should be 2.82 mg·kg^-1 at regreening stage and 1.13 mg·kg^-1 at harvest.Dry matter accumulation and N accumulation should reached 17-20 t·hm^-2 and 260-280 kg·hm^-2.The results showed that the seeding rate was 190-200 kg·hm^-2 and appropriate fertilization amount was 220-250 kg·hm^-2 of YM49-198,and the seeding rate was 210-230 kg·hm^-2 and appropriate fertilization amount was 210-270 kg·hm^-2 of ZM16 by curve fitting based on yield,seeding rate and N application.