Abstract:The experiments of potassium nutrition in papaya （Carica papaya L.） showed that leaf blight was caused by available potassium deficiency in soil where papaya was planted. Application of potassium fertilizer could effectively control such disease and get higher yield. In the roots, stems, leaves and petioles of papaya with leaf blight which was caused by potassium deficiency, the contents of magnesium were obviously increased, indicating the antagonistic effect between the two elements in papaya plants.