Potassium Dynamics and Relationships with Oil Palm Bunch Yields in Ultisols of NIFOR Main Station

Background and Objective: Potassium is the most utilized element by oil palm for bunch production. It is labile and exists in four major forms that are in equilibrium with one another. It is important to know the form of K that correlates more with the bunch yield of oil palm. The objective of the study was to determine the most dynamic form of K that correlates with bunch yields of oil palm in an Ultisol. Materials and Methods: Potassium forms and dynamics and their relationships with fresh fruit bunch yields were studied in soils sampled from profile pits, accurately labelled, processed and analyzed for physical and chemical properties and forms of potassium using standard laboratory methods. Activities of potassium, calcium and magnesium were determined from their respective activity coefficients which in turn were determined from the extended Debye and Huckel equation. Results: The HNO₃ extractable K was the most dynamic form of K and constituted 31.95% of total K reserves bunch weight was significantly and positively correlated with HNO₃ extractable K (difficultly exchangeable K) with r = 0.943, p<0.01), residual K (r = 0.924, p<0.01); potassium activity coefficient (r = 0.834, p<0.01); calcium activity coefficient (r = 0.827, p<0.05) and calcium activity (r = 0.867, p<0.05). Bunch weight also correlated positively and significantly with the number of harvested bunches with (r = 0.902, p<0.05). Conclusion: It highlighted the need to manage the organic matter, nitrogen, potassium and calcium contents of Ultisols under oil palm by deliberate application of empty fruit bunches (EFB) to increase the total K reserve of the soil.