Effect of potassium fertilization on storage root number, yield, and appearance quality of sweet potato (Ipomoea batatas L.) oleh Ben-kui Liu, Bing-jie Xv, Cheng-cheng Si, Wen-qing Shi, Guo-zheng Ding, Li-xue Tang, Ming Xv, Chun-yv Shi, Hong-jvan Liu