Abstract: 【Objective】 To clarify the effects of different nitrogen and potassium ratios on potato root correlation index during tuber bulking period and yieid under the condition of high ridge drip irrigation in semi-arid area,then the suitable nitrogen and potassium combinations condition for root growth and yield increase of potato were screened.【Methods】 The root activity,total root absorption area,root morphological indexes,commercial potato rate and yield of potato were analyzed under 9 treatments field test with different nitrogen and potassium ratios at the Wuchuan drought planting experimental station.【Results】 The root activity and total root absorption area of potato with N₁₂K₁₅ were the highest and significant differences（P<0.05） compared with other treatments（except N₁₂K₁₈ treatment on root activity）. The root length,root surface area and root tips number were highest when root diameter range from 0-0.5 mm,accounting for 35.7%-47.3% of the total root length,57.7%-71.4% of the root surface area,and 89.7%-94.6% of the total root tips number. Root volume of potato elevated with increase of root diameter when the root diameter was higher than 4.5 mm root volume reached 51.6%-56.0% which was the highest. Root top ratio by N₁₂K₁₅ treatment was the highest（0.67）. N₁₂K₁₅ treatment also had the highest number of commodity potato,total weight of commodity potato,commodity potato rate and yield among all treatments. The N₆K₁₅ and N₆K₁₈ treatments were effectively improved number of commodity potato,total weight of commodity potato,commodity potato rate and yield than N₆K₁₂ treatment,number of commodity potato reached 6.5%-29.9%,total weight of commodity potato increased 10.7%-32.2%,yield increased 14.2%-30.1%.【Conclusion】 The effect of N₁₂K₁₅ treatment on potato root growth and yield increase was more significant at the Wuchuan drought planting experimental station.

Key words: Potato, Nitrogen and potassium ratios, Root growth, Yield