| The deepening control continental river irrigated area and protects ecological and environmental understanding with implement "western China development" stratagem, so it is an urgent requirement to returning cultivated land to forests or pastures in some regions. The problem of how to scientifically utilization for limited water resources and melioration ecological and environmental continually are urgent requirement to important project currently. Alfalfa (Medicago sativa L.) is commonly called "kings of forage crop", with high adaptable, developed roots and high yield. Alfalfa is commonly known not only as a high quality forage crop, but also a plant can amelioration soil and control winds and sand. Thus, the problem of scientifically utilization for water resources and protect ecological environment in this region has become very important operation significance through research on the relationship between the biological specificity of alfalfa and water utilization. The research was tested in Hexi Corridor Zhangye area. Three irrigation treatments (W1, W2 and W3) were arranged in different rectangular plots. The effect of water consumption on leaf area index (LAI), height, dry matter, underground biomass and nutrient component and so on morphological characteristics of alfalfa were conducted in this paper. Some databases were analyzed by variance analysis. At the same time, the water consumption and water-consuming law of alfalfa were discussed.The effect of irrigation on morphological characteristics of alfalfa in Northwest Continental River irrigated area was considerable. The results showed that:1. The effect of irrigation on the aboveground biomass is considerable. In the florescence, there is significance divergence between handle W2 and handle W1, W3. The aboveground biomass is marked divergence between handle W1 and W2 during the period of seeding. The aboveground biomass of W1 is the highest during the growth season in Hexi Corridor. But the WUE in handle W2 is more economic than the others. Water use efficiency was improved in W2 with lower irrigation than W1. Thus, the handle W2 is one of the irrigation means which can be popularized befittingly in local alfalfa planting.2. Most of the alfalfa root system are distribute at the surface soil from 0cm to 50cm.There is different effect on the root system of alfalfa with different water treatment: In W1, the root system is living mainly in surface layer; in W3, the length of alfalfa root system is more big than that of W1 and W2, but the diameter is relatively small in W2, alfalfa have reached more underground biomass.3. The LAI of alfalfa is enhanced with water content lower limit of soil add. The LAI of alfalfa alter with a parabola curve during the whole growth season. The LAI of alfalfa reach the climax at florescence and then fall down before bifurcation stage. At the same time, the LAI of W2 is greater than that of W1 and W3.4. During the whole growth season, the height of alfalfa in W3 is the lowest. It is nearly equal that the height of alfalfa in W2 and W1 during the florescence and the period of seeding. The growth velocity of alfalfa is great difference in earlier days because of the water lower limit, but isn't divergence at the later stage. 5. The effect of water handles on the nutrition composition of alfalfa isn't divergent. Alfalfa in W1 has more protein than that of W2, but the divergence is not marked. In the same water treatment, the content of protein and fat decrease with the delay of bear stage, yet the content of fiber increase.6. The effect is prominent on the content of Pro of alfalfa with different water treatment. There is more Pro of alfalfa leaf accumulated in W3 than that of W2 and W3. As far as the given alfalfa plant concerns, the content of Pro is the highest in upper leaf and the inflorescence is least. The effect on the content of Pro can be ignored in W1, because the water content of alfalfa is very tall.7. The relativity with the accumulation amount of dry matter of alfalfa and water co...
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