3.6. Relationship between potato uptake K and tuber yield
A significant relationship between total uptake K by potato plant and total tuber yield existed (Fig. 6). Fertilizer K can be recommended by the regression equation based on this relationship. Fertilizer recommendation needs to consider soil K input/output balance. Fertilizer K rate based on K removal depends on soil K level and objectives. If you want to maintain the soil K level the amount of fertilizer K recommended should be the same as amount of K removal by potato plants. If the soil has sufficient K level and want to mine soil K resource then fertilizer K rate can be the difference between K removal and indigenous K supply (IKS), which will gradually mine the soil K sources. If soil has insufficient K supply the rate of recommended fertilizer K should be more than the amount of K removal for building up soil K fertility.