Effects Of Density On Grain Yield And Important Agronomic Traits Of Spring Wheat Under Northwest Oasis Area

Grain yield was the integrative performance of agronomic traits and physiological traits such as grain filling characte which were spike number per hectare,grain number per spike,thousand grain weight et al.Grain filling character was the important physiological traits affecting grain yield.The central issue of high-yield for wheat cultivation was to harmonize these factors with well development.Three spring wheat cultivar Xihan No.1,Xihan No.2,Xihan No.3 were adopted,Twelve planting densities were designed as following seedlings per spuare meter:20(T1),25(T2),33(T3),50(T4),100(T5),250(T6),300(T7),450 (T8),600(T9),750(T10),900(T11),1050(T12).The paper has studied the effect of planting density on grain yield,agronomic traits,grain filling characters and the relationships between the factors under the north-west oasis ecological condition of spring wheat,.the main results are as follows:1 There were significant difference among treatments on grain yield,thousand grain weight,grain number per spike,spike number per square meter,stem number per square meter,kernel weight per plant,spikes per plant,stems per plant ratio of tillers survived,leaf area index(LAI),biolgical yield per plant,plant height,spike length,spike weight,length of inverted first,third and forth internode,width of inverted first internode.2 The optimum desntity among three varieties was different but contiguous. Grain yield ranged from 2508.08 to 5276.46 kg per hectare of Xihan No.1.A11 had the highest grain yield.The grain yield between A10 and A11 had no significant difference,indicating that the optimum desntity was ranged from 400 to 480 seedling per square meter.Grain yield ranged from 2314.54 to 5493.73 kg per hectare of Xihan No.2.B11 had the highest grain yield.The grain yield among B9,B10 and B11 had no significant difference,indicating that the optimum desntity was ranged from 400 to 570 seedling per square meter.Grain yield ranged from 2956.77 to 5416.96 kg per hectare of Xihan No.3.C10 had the highest grain yield.The grain yield among C9,C10 and C11 had no significant difference,indicating that the optimum desntity was ranged from 350 to 540 seedling per square meter.3 The correlation analysis showed that the relativity among traits were different in different densities treatment among three varieties,the main traits of determining on grain yield were spike number per square meter.Grain yield was possitively correlated with spike number per square meter significantly,negatively correlated to grain number per spike significantly.There was extremely significant correlation between grain yield and thousand grain weight in Xihan No.1 and Xihan No.2, however no significant correlation was found in Xihan No.3.There were significant negative correlation among yield compositions.4 Grain number per spike and thousand grain weight was negatively correlated to density.Thousand grain weight decreasing with density increasing among three varieties was high respectively from T1 to T5,from T1 to T2,from T4 to T5,which was significant difference from other treatments.Grain number per spike decreasing with density increasing among three varieties was high respectively from T1 to T2, T1,T1,which was significant difference from other treatments.Spike number per square meter decreasing with density decreasing among three varieties was high respectively from T10 to T12,from T11 to T12,from T11 to T12,which was significant difference from other treatments.5 Density have significant effect on agronomic traits which had significant or close relationships with wheat 3 yield factor in different wheat varieties,spike length, Spikes per plant,spikes per plant,stems per plant ratio of tillers survived on different varieties exhibited a negativerelationship with planting density.Agronomic traits of single plant of Xihan No.1,Xihan No.2 and Xihan No.3 which decreased with the incrensing of planting density were all the highest levels at low density.However, there was positive correlation between stem number per square meter and density,stem number per square meter which decreased with the decreasing of planting density was the highest levels at high density.6 Growth traits of single plant on different cultivars were found to be affected by planting density.Density have definite influences upon plant height,leave growth indexes(leaf-longth,leaf-width),showing no significant correlation between them. There was a negative correlation between biolgical yield per plant of different cultivars and density,and the former which decreased with the increasing of planting density was the highest levels at low density.Leaf area index(LAI) of different cultivars also had a high level when the density is high.7 The accumulating course of grain dry matter weight had three stages which were gradual increasing period,rapid increasing period and slow increasing period among three varieties.The contribution to grain was the most in the rapid at stage, and the increasing of grain weight occupied 54.36%～67.68%of grain weight at rapid stage.The change of grain dry weight of winter-wheat in the three experiments was that the increasing of grain dry weight displayed the "S" curve of "slow-rapid-slow",and could be fit by the Logistic equation.8 With density increasing,the duration of grain filling(T) was shortened,the average rate of grain filling(R) was reduced,but the time of maximum rate of grain filling(T_MAXR) was similar.9 The relationship between thousand grain weight and grain filling parameters was different under different density treatments among three varieties.The correlation analysis showed that TGW of Xihan No.1 was positive correlated with T,R,maximum rate of grain filling(R_MAX),T_MAXR,the days of grain filling of gradual growth period(T1),the days of grain filling of fast growth period(T2),the days of grain filling of slow growth period(T3),the rate of grain filling of gradual growth period(R1),the rate of grain filling of fast growth period(R2) at 0.01 significant level,nonsignificantly correlated with the rate of grain filling of slow growth period (R3).Effect of T to grain was greater than R,but R was significantly correlated with R_MAX,T_MAXR.The correlation analysis showed that TGW of Xihan No.2 was positive correlated with R_MAX,R,R1,R2 and R3,negatively correlated with T3,T and T2,nonsignificantly correlated with T_MAXR and T1.The correlation analysis showed that TGW of Xihan No.3 was positive correlated with R_MAX,R,T2 and R2,negatively correlated with T1,nonsignificantly correlated with T_MAXR,T3,R1 and R3.