Effect of Different Ratio of N,P and K Fertilizers on Photosynthetic Characteristics of Fuji Apple in South of Xinjiang

Using 15 years Fuji apple in southern Xinjiang as test materials with the second combination design of three-factor five levels,the effect of the different NPK ratio on photosynthetic characteristics of apple was studied.The results showed that SPAD value was positively correlated with the amount of nitrogen and potassium while phosphorus was negatively correlated.The effect of nitrogen was greater than that of potassium.There were synergism effect between nitrogen and phosphorus,nitrogen and potassium and phosphorus and potassium.A dual peak curve presented in Pn diurnal variations of Fuji apple leaves and photosynthesis with midday resting phenomenon.Phosphorus could improve Pn.Appropriate application of NPK fertilizer would improve the apple leaves WUE.