| Nowadays drought is one of the most important ecological problems in the world,and the most serious stress factors restricting development of agriculture. A betterunderstanding of drought and fertilizer effects on growth and development,physiological characters, grain yield and quality traits of winter wheat is veryimportant to improve both grain yield and quality. To evaluate the effects ofwater-fertilizer coupling on yield formation and grain quality traits of winter wheat,experiment was carried out in rain-sheltered condition with factors of water, nitrogenand phosphorus fertilization in a typical arid climate in middle China for two years.The results were as follows.1. Irrigation had significant effects on the photosynthetic rate, stomatalconductance, transpiration rate in flag leaf and top second leaf in rain-shelteredcondition during the whole growth of wheat (P≤0.05or≤0.01). Photosynthetic ratereached the highest value at irrigation amount of308.5mm in the day of6days afteranthesis (DAA), and at the amount of153.5mm both in13and23DAA. While thephotosynthetic rate in flag leaf decreased sharply during grain filling period. With theincrease of nitrogen application, the photosynthetic rate and stomatal conductance inflag leaf increased and then decreased on6,13,23DAA. N105P42W308.5andN179.2P126W153.5obtained the highest values of photosynthetic traits among allcombinations of treatment. Correlation analysis indicated that, the photosynthetic ratein leaf significant positively correlated with stomatal conductance and transpirationrate (P≤0.01), while significant negatively correlated with intercellular CO2concentration (P≤0.01), implying that decline of photosynthetic rate was mainlycaused by non-stomatal factors.2. The results of two year study indicated that irrigation and nitrogen applicationhad significant effects on grain protein and amino acids contents (P≤0.01) of winterwheat. The interaction of irrigation and nitrogen fertilization also presented significanteffects (P≤0.05or≤0.01). No significant effect of P fertilization on protein and aminoacids contents was observed. Protein and amino acid contents in wheat grainsincreased with increasing nitrogen fertilization rate, but dropped with increasing ofirrigation amount. However, as irrigation amount was above282.0mm, and nitrogenfertilization rate was above179.2kg·hm-2, the changes became not less obvious.Protein content decreased as the nitrogen fertilization rate above179.2kg·hm-2. The trend of ETT/ATT was contrary to that of amino acid content. It indicated that highnitrogen treatment with drought stress went against of the improvement of grainquality. The contents of protein and amino acids in wheat grains reached the highest intreatment of N105P42W127with nitrogen fertilization rate of105kg(N)·hm-2,phosphorus fertilization rate of42kg(P2O5)·hm-2and irrigation amount duringgrowing season of127mm. While ETT/ATT reached the highest in treatment ofN30.8P126W282with nitrogen fertilization rate of30.8kg(N)·hm-2, phosphorusfertilization rate of126kg(P2O5)·hm-2and irrigation amount during growing seasonof282mm. Overall, N179.2P126W282with nitrogen fertilization rate of179.2kg(N)·hm-2, phosphorus fertilization rate of126kg(P2O5)·hm-2and irrigation amountduring growing season of282mm was the best treatment.3. Application of nitrogen and phosphorus had significant effects on starchpasting properties (P≤0.05or P≤0.01) of winter wheat. The main starch viscosityparameters (peak viscosity, through viscosity and final viscosity) were increasedsignificantly when nitrogen application increased from0kg·hm-2to105kg·hm-2. Andthe starch viscosity parameters reached the highest values at the phosphatic amount of168kg·hm-2. No significant effect of irrigation on starch pasting properties wasobserved. But interaction of irrigation×nitrogen had significant effects on someparameters of starch pasting property (P≤0.05or≤0.01). Overall, the combination oftreatments N105P168W217.5, with nitrogen rate of105kg(N)·hm-2, phosphorus rate of168kg(P2O5)·hm-2and irrigation amount of217.5mm, obtained the best starchquality in the experiment. Correlation analysis indicated that, starch viscosityparameters had positive significant correlation with grain yield in crop season of2009～2010,but had not correlation in crop season of2010～2011. And it indicatedthat possibility of improving both grain yield and starch content was exist.4. Irrigation had significant effects on grain yield and its components (P≤0.01) ofwinter wheat. Both the culm population and ear number increased with enhance ofirrigation amount, and reached the highest value at irrigation amount of282.0～308.5mm. Grain number per ear and grain yield reached the highest values atirrigation amount of308.5mm, while thousand kernel weight (TKW) at irrigationamount of282.0mm. The culm population increased with nitrogen applicationimprovement from30.8kg·hm-2to179.2kg·hm-2. Grain yield increased when nitrogen application increased from0kg·hm-2to105kg·hm-2. The treatment of N179.2P126W282obtained the largest culm population, for grain number per ear and grain yield,treatment of N105P42W308.5,and for TKW, N30.8P126W282obtained the highest values,respectively.5. Irrigation had significant effect on grain yield and water utilization efficiencyin rain-sheltered condition during the whole growth of wheat (P≤0.01). The waterutilization efficiency reached the highest value at irrigation amount of308.5mm,lowest at127.0mm. It indicated that irrigation amount was still a limiting factor forincreasing the water utilization efficiency in arid area. The water utilization efficiencyreached the highest at nitrogen rate of210.0kg·hm-2, phosphorus rate of84.0kg·hm-2,while got the lowest value when no nitrogen and phosphorus application. Thecombination of treatments N105P42W308.5obtained the highest value for both grainyield and water utilization efficiency. Grain yield had significant positive correlationwith water utilization efficiency (P≤0.01). So the treatment of higher water utilizationefficiency always had higher grain yield.
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