Abstract: In order to explore the effects of nitrogen and potassium combined application on the growth and yield of sweet potato [Ipomoea batatas (L.) Lam.] under shading conditions, the long-vine variety G8017 and the short-vine variety G8507 were used as materials, and four nitrogen and potassium ratios were set up [CK: blank control; C1: low nitrogen and low potassium (urea 75 kg/hm² + potassium sulfate 150 kg/hm²); C2: high nitrogen and low potassium (urea 300 kg/hm² + potassium sulfate 150 kg/hm²); C3: high nitrogen and high potassium (urea 300 kg/hm² + potassium sulfate 600 kg/hm²)]. The pot experiment was carried out under 50% shading environment, and the agronomic traits, photosynthetic characteristics and yield were measured. The results showed that C2 significantly promoted the increase of vine length. C3 showed the best performance in stem diameter, branch number, root dry weight and yield, and effecitively increased chlorophyll content, net photosynthetic rate and antioxidant enzyme activity. Correlation analysis showed that the root yield of the two varieties was significantly positively correlated with the number of branches, stem diameter, dry matter weight above ground and dry matter weight of tubers, and negatively correlated with vine length and T/R(the ratio of shoot dry weight to root dry weight). In summary, C3 (high nitrogen and high potassium) was a suitable fertilization strategy for sweet potato cultivation under moderate shading conditions.

Key words: sweet potato[Ipomoea batatas (L.) Lam.], shading, nitrogen-potassium ratio, photosynthetic characteristics, yield