Abstract: A field plot experiment was set to study the improvement effect of Yishizhuang commercial organic fertilizer on acid soil and the appropriate amount of it on potato. The results showed that the soil fertility was high, and the contribution rate ranged from 62.98% to 89.57%. It was completely feasible to replace part or even all chemical fertilizers with Yishizhuang commercial organic fertilizers.The combined application of the organic fertilizer and the formula fertilizer was better than the simple application of the organic fertilizer. The main performance was that the potato big potato rate was higher and the potato commodity quality and commodity rate were improved correspondingly. The quadratic and cubic regression equations of the amount of organic fertilizer and potato yields fitted by Excel reached extremely significant level. The maximum and optimal usage of the organic fertilizer on potatoes calculated by quadratic regression equation were 9 660 kg/hm² and 7 993 kg/hm², respectively. The highest and the most economic yield of potato were 33 314 kg/hm² and 32 897 kg/hm², respectively. The organic fertilizer had better effect on improving acidified soil. With the increase of the dosage, the soil pH and base saturation increased continuously. Exchangeable basic ions such as potassium, calcium and magnesium increased.However, the contents of exchangeable aluminum and available manganese in soil gradually decreased. It had certain effect on inhibiting the toxicity of aluminum and manganese in soil.

Key words: Yishizhuang, commercial organic fertilizer, potato（Solanum tuberosum L.）, suitable dosage