Nonexchangeable Potassium Reserves in an Alfisol in Relation to Potassium Uptake by Potato

The contribution of step-K and constant rate-K (CR-K), non-exchangeable potassium reserves towards potato tuber production and K-uptake was studied in field on Alfisol. At all levels of K tried, there was no change in CR-K, while step-K and equilibrium activity ratio of K(AR_e^K) and threshold level of release of ‘intermediate K’ recorded fall during 75–100 days after planting. The yield and K-uptake by shoots and potato tuber showed a positive response to K application, but due to translocation of K from shoots to tuber displayed contrasting trends of variations at the tuber bulking phase from 75 to 100 DAP.