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Based on the field trial, by using the quadratic general spinning design, a mathematical model foe grape yield and its constitutive factors is established. Water and fertilizer are considered as the main factors affecting the yield. The characteristics and laws of water—fertilizer interaction for increasing the yield are discussed and the suitable amount of water and fertilizer for a certain yield can be calculated. (1) The coupled zones for optimal supplies of water and fertilizer, for high yield and quality of grape were identified through the established relationships. (2) Field experiment on the coupling effect of water and fertilizer on the grape with drop irritation have been conducted .The result showed that the fertilization had a significant function in bringing water into full play, and the supplemental irrigation had the same function for the fertilizer. With a low irrigation rate, the interaction between water and fertilizer was increased with the increase lf fertilizer rates. However, the reverse was true with a higher rate of irrigation. The supplemental irrigation raised the yields and fertilizer-use-efficiency for the first crop while decreased yield and the efficiency for the second crop. However, as a whole, the fertilizer-use-efficiency was still higher with irrigation no matter what amount of water was used for irrigation. (3) The optimal composite scheme of water and fertilizer for a maimed yield, application of watering was 133.5m3/667m2,N 9.8kg/667m2,P2O5 2.6kg/667m2, K2O 5.4kg/667m2. (4) The optimal composite scheme of water and fertilizer for a maimed the sugar content, application of watering was 123.2m3/667m2,N 6.3kg/667m2,P2O5 1.9kg/667m2, K2O 0.8kg/667m2. (5) The optimal composite scheme of water and fertilizer for a maimed Vc content, application of watering was 138.6m3/667m2,N 8.7kg/667m2,P2O5 4.4kg/667m2, K2O 5.4kg/667m2. (6) The optimal composite scheme of water and fertilizer for a maimed the acid content, application of watering was 123.1m3/667m2,N 10.2kg/667m2,P2O5 3.4kg/667m2, K2O 2.7kg/667m2. (7) The yield of grape to the four factors was in order of N>W>P>K; The sugar content of grape to the four factors was in order of P>N>W>K; The Vc content of grape to the four factors was in order of N=N>K>W; The acid content of grape to four factors was in order of N>K>W>P. (8) In water stress circumstances, the effects of irrigation were extremely remarkable. While the contribution of fertilization relatively less. Consequently, there was no interaction between watering and fertilization. Watering to much could lead to the decrease of yield. The interaction among W-P,W-N combinations was obvious. (9) Irrigation promoted nutrient uptake by grape, the interaction of water fertilizer could improve yield and quality of grape effectively Irrigation increased N,P,K use efficiency. However irrigation could decrease the sugar content of grape, the interaction between water and fertilizer can elimited. this disadvantage. (10) Irrigation and fertilizing too much could decrease the yield and quality of grape and limit water use efficiency.
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