Potash need assessment and use experience in Khyber Pakhtunkhwa (KP)

After nitrogen and phosphorus, potassium is the third major plant nutrient which is becoming deficient in the soils of Khyber Pakhunkhwa Province of Pakistan. Responses of various crops to potash application and soil analysis results of various areas of KP clearly indicated deficiencies of potash. In a survey of nutrient status of different districts of KP, twenty one percent of the soil samples analyzed were deficient in K, while 50 percent were marginal. However, major areas of K deficiency are observed in Malakand agency, Swat, and Mansehra districts. A recent survey of orchard soils (citrus, apple, and peaches) showed that 9% soils were deficient in K while 47% were marginal. Usually the addition of K increased the yields giving higher value cost ratios (VCRs) and crop response ratios especially for cereal crops under irrigated conditions. Balanced application of NPK and Zn produced significantly higher yields of wheat on eroded lands in Swat and Rod-Kohi soils in D.I. Khan. The available data showed that, complex fertilizers proved better than straight fertilizers. As regards muriate of potash (MOP) vs sulfate of potash (SOP), the superiority of one over the other depends upon the type of soil and climatic conditions, and the crop. In D.I. Khan SOP proved better for rice, and equally effective for wheat and maize. On the other hand, MOP improved the quality of wheat regarding protein content as well as the uptake of K by maize and wheat, however, increased the chloride content of soil. In Peshawar and Swat, both the sources were found equally effective as regards yield without any accumulation of chloride by MOP at Tarnab but its application increased chloride content significantly at the depths of 31-60 and 61-90 cm in Swat district. Use of potash needs to be promoted as it is very important for improving the quality of crop products. As regards source of K, SOP should be preferred for sulfur loving and quality crops, low rainfall areas and heavy textured soils. Use of the source of K should be site and crop specific. Future strategies for promotion of K should include research on K-fixing capacity and clay mineralogical investigation of benchmark soil series important for agriculture purposes, application of K on the basis of crop requirement and fixing capacity of soil, mapping of K in addition to other nutrients in different areas of KP.