6Chaudhary R A, Akram M, Gill K H, et al. Zinc requirement of potato crop in the Punjab Pakistan [J]. Journal of Soil Science, 2001, 19 (1-2): 81-83.
7Trehan S P, Claassen N. Potassium uptake kinetics of potato, wheat and sugar beet plants as affected by the K nutritional status [J]. Indian Journal of Plant Physiology, 2001, 6 (1): 14-18.