| Grain yield was the integrative performance of agronomic traits and physiological traits which were spike number per hectare, grain number per spike, thousand grain weight et al. The central issue of high-yield for wheat cultivation was to harmonize these factors with well development. The paper has studied the effect of irrigation, fertilizer, planting density and sowing date on grain yield, agronomic traits, physiological traits and the relationships between the factors under the north-west oasis ecological condition of winter wheat. the main results are as follows:1. Five water treatments were designed with equal quantity-unequal times and equal times-unequal quantity at jointing(J), heading(H) and grain filling(G) based on 1800 m3·hm-2 water irrigated in winter. The irrigation quota were J1650 (m3·hm-2, W1), J1200 +H1050(m3·hm-2, W2), J1050+H1050+F1050(m3·hm-2, W3), J750+H750+F750 (m3·hm-2, W4), J1050 +H750+F450(m3·hm-2, W5). The results showed that grain yield ranged from 4674.65 kg·hm-2 to 6296.52 kg·hm-2 and W3 had the highest grain yield, but WUE could be enhanced by water saving. There were significant difference among the grain yield, grain number per spike, thousand grain weight, leaf area index(LAI), water use efficiency (WUE ) and leaf relative water content(RWC). The grain yield of W3 was 18.69%,17.62%,0.91% and 34.98% higher than W1,W2,W4 and W5 respectively. The grain yield among W1,W2,W3 and W4 had no significant difference, indicating that there had not yield reduction with 600 m3·hm-2~1500 m3·hm-2 water saving. W4 had the highest WUE which increased respectively by 16.98%, 14.09%, 12.70% and 34.94% as compared to W1, W2, W3 and W5.Under the conditions of conventional irrigation, six planting densities were designed as following seedlings per hectare: 450×104 (T1), 525×104(T2), 600×104(T3), 675×104(T4), 750×104(T5), 900×104(T6). The results indicated that grain yield ranged from 6369.04 kg·hm-2 to 8649.87 kg·hm-2. T4 had the highest grain yield which was24.23%, 11.32%, 8.92%, 23.59% and 20.87% higher than T1, T2, T3, T5 and T6 respectively. There were significant difference among treatments on grain yield per area, spike number per hectare, grain number per spike, thousand grain weight, spikes per plant, stems per plant, leaf area index(LAI), plant height, water use efficiency(WUE) and the canopy apparent photosynthesis rate(CAP). The spike number per hectare should kept at 974×104 to 1016×104 spikes and that grain yield can achieved from 7770 kg ? hm-2 to 8650kg ? hm-2 of winter wheat at Hexi Corridor. There were five topdressing treatments at the jointing stage as following pure N and P2O5 per hectare F1(N0P0), F2(N0P60), F3 (N60P0), F4 (N60P60) and F5(N135P120)under the same base fertilizer with pure N165kg?hm-2and P2O5105 kg·hm-2. The results showed that grain yield ranged from 6753.38 kg·hm-2 to 8206.48 kg·hm-2 kg·hm-2, F5 had the highest grain yield which was 21.52%,15.60%,7.35% and 6.77% respectively higher than F1, F2, F3 and F4. There were significant difference among grain yield, WUE, thousand grain weight and LAI.There were six sowing date which were 17/9 (S1), 19/9 (S2), 24/9 (S3), 29/9 (S4), 4/10(S5) and 15/10 (S6). The results show that grain yield ranged from 5467.05 kg·hm-2 to 8337.45 kg·hm-2 , S1 had the highest grain yield which was 15.32%,20.69%,34.49%,56.08% and 52.50% respectively higher than S2, S3, S4, S5 and S6. There were significant difference among grain yield, spike number per hectare, WUE, biology yield, spike length, seeding number per hectare and LAI. The grain yield among S1, S2and S3 had no significant difference, therefore the appropriate growing time should keep from 17/9 to 24/9 for winter wheat at Hexi oasis and sowed early can enhance grain yield.2. The correlation analysis showed that the relativity among traits were different and the traits of determining yield were different in the experiments of irrigation, planting density, fertilizer and sowing date. The main traits of determining on grain yield were thousand grain weight and grain number per spike in the experiment of irrigation, that was spike number per hectare in the experiment of planting density and sowing date, and that was thousand grain weight in the experiment of fertilizer.Grain yield was possitively correlated with thousand grain weight (r=0.99**) and grain number per spike (0.87*), however no significant correlation was found between grain yield and spike number per hectare in the experiment of irrigation. Among the yield components only thousand grain weight and grain number per spike had significant correlation each other. So under this irrigation condition, both of them were promoted together at the same time.There was extremely significant correlation between grain yield and spike number per hectare (r=0.89**, r=0.94**) in the experiment of planting density and sowing date. However no significant correlation was found between the grain yield and kernel number per spike or thousand grain weight. The spike number per hectare, grain number per spike and thousand grain weight had also no significant correlations each other. A significant correlation existed between grain yield and thousand grain weight (r=0.88*) in the experiment of fertilize but no significant correlation was found between the grain yield and kernel number per spike or spike number per hectare. The spike number per hectare, grain number per spike and thousand grain weights had also no significant correlations each other.There was extremely significant correlation between WUE and grain yield in the experiment of irrigation, fertilizer, planting density and sowing date (r=0.87* ~ 0.99**), which indicated that obtaining high grain yield and WUE were realized.As one of population index, LAI showed a single-peak curve in the whole growth duration in the experiments of water, planting density, fertilizer and sowing date treatments. The peak value of LAI appeared at heading stage in the experiment of irrigation but which appeared at anthesis in the experiments of planting density, fertilizer and sowing date. In the experiment of irrigation W1 and W2 had bigger variation coeffecient (CV) than others. It indicated that water deficit expedite the leaf senescence. Grain yield had no significant correlation with LAI at all growth stages or the mean value of measured times during the whole growth stages in the experiment of irrigation. Grain yield only had significant correlation with LAI of early and middle grain filling stage in the experiment of planting density, and that is anthesis, early , middle grain filling stage and the mean value of all measured times in the experiment of fertilizer, and that is all growths stage and the mean value of all measured times in the experiment of sowing date.3. There were significant difference among the photosynthetic rate (Pn), transpiration rate (Tr) and stomata conductance (Gs) in the experiments of irrigation, planting density, fertilizer and sowing date. The high peak value of Pn, Tr and Gs appeared at different growth stage and the difference of them were changed with the different experiment. The peak value of Pn appeared at heading stage , Tr appeared at early grain filling stage in the treatments of irrigation, planting density and fertilizer. However the high peak value of Gs appeared at different stage in the different of experiments. The difference among Pn, Tr and Gs during the whole growth stage for W1and W2 were bigger than W3, W4 and W5 in the experiment of irrigation. The difference of Tr and Gs were bigger than Pn in the experiments of planting density, fertilizer and sowing date.4. The correlation coefficient between grain yield, agronomic traits and physiological traits (Pn, Tr, Gs, et al.) were changed with the difference of experiment and measured date. Grain yield had significant correlation with Pn (r=0.92**) of anthesis but had negative correlation with the mean value of Pn (r=-0.89*) for all measured times in the experiment of irrigation. There were no significant correlation was found between the grain yield and Pn at other measured times during the whole growth stages. Meanwhile Grain yield had no significant correlation with Pn of any measured times and the mean value of all measured times during the whole growth stages in the experiments of planting density and fertilizer. Grain yield had negative correlation with Pn of heading stage in the experiment of sowing date; There was no significant correlation between grain yield and Tr of any measured times and the mean value of all measured times during the whole growth stages in the experment of irrigation, planting density, fertilizer and sowing date; Grain yield had significant correlation with the mean value of Gs in the experment of irrigation, but had no significant correlation with Gs of any measured times and the mean value of all measured times during the whole growth stages in the experments of planting density, fertilizer and sowing date.Plant height, spike length, grain number per spike, thousand grain weight and biology yield had significant correlation with Pn, Tr or Gs in some growth stage in the different experiment.5. The correlation among the physiological indexes was changed with different experiments. There were no significant correlation between the mean values of Pn, Tr or Gs in the experiment of irrigation. Pn had significant correlation with Tr or Gs at early grain filling stage. However there was no significant correlation between Pn and Tr or Gs at heading stage and anthesis. Gs and Tr had significant correlation in whole growth duration respectively. It indicated that stomata opening plays an important role on adjustment of transpiration; Leaf relative water content (RWC) had significant correlation with Pn at heading stage(r=0.94), but had no significant correlation with Tr and Gs at any measured time during whole growth stages.Although the average value of Pn, Tr and Gs across whole growing season were highly positively correlated, their correlation coefficient at different growth stage still had considerable difference in the experiment of the density and fertilizer.There was no significant correlation between Pn and Gs or Tr, but Gs had significant correlation with Tr at jointing and heading stages in the treatment of sowing date.
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