Abstract: 【Objective】To study the effects of different nitrogen,phosphorus,and potassium fertilizer treatments on apple yield and quality,and to provide references for scientific fertilization in production.【Methods】During the apple germination,flowering,flower bud differentiation,and fruit expanding stages,different NPK fertilizer treatments were set up：S1 treatment（42,13,26 kg/hm²,42,21,41 kg/hm²,19,12,63 kg/hm²,14,4,80 kg/hm²）,S2 treatment（46,8,30 kg/hm²,46,16,45 kg/hm²,23,16,60 kg/hm²,0,8,75 kg/hm²）,and S3 treatment（51,10,22 kg/hm²,42,18,50 kg/hm²,23,9,68 kg/hm²,0,10,80 kg/hm²） with conventional fertilizer as control（CK）. Using 9-year-old apple variety,Ruiyang,as test material,the yield and quality indexes of apples in different treatments were measured.【Results】Compared with CK,the fruit vertical diameter,transverse diameter,single fruit weight,and yield of apple treated with S1,S2,and S3 all showed increasing trend. The yield and commodity rate of apples under S1 treatment increased by 4.0% and 3.8%,respectively,compared with CK. Different fertilizer treatments had most impact on fruit surface color,in terms of apple fruit appearance and quality. In comparison with CK,the fruit surface colour of S1,S2 and S3 treatments all tended to decrease,with the coloring degree（a* value） of S3 treatment increased. The color brightness（L* value） and background color（b * value） of S1 treatment significantly decreased（P<0.05）,although there was no significant difference（P>0.05） in color ratio and fruit shape index compared with CK . The fruit hardness,titratable acid content and solid-acid ratio had greater impact on the internal quality of the fruit. The fruit hardness in different fertilizer treatment had increase trend,with S1 treatment significantly increased（P<0.05） by 9.5% compared with CK. The titratable acid content in S1 treatment significantly decreased（P<0.05） by 25.0%,while the solid-acid ratio significantly increased（P<0.05） by 29.3% compared with CK.【Conclusion】S1 treatment improved apple yield and commodity rate,resulting in better overall quality performance.

Key words: Apple, Nitrogen,phosphorus,and potassium fertilizer, Yield, Quality