Potassium uptake and storage in oil palm organs: the role of chlorine and the influence of soil characteristics in the Magdalena valley, Colombia

Potassium is the main nutrient in oil palm nutrition. On oil palm estates, potassium fertilization is usually adjusted based on leaflet K content. However, in the Magdalena river valley in Colombia where the soils are deficient in Cl, KCl has always caused a drop in leaflet K content, sometimes to deficiency levels, yet yields remain high. To elucidate this paradox, we conducted a multi-annual trial on 11-year-old oil palms by comparing unfertilized plots and plots receiving KCl or NaCl. We analysed the physico-chemical characteristics of the soils and the K, Ca, Mg, Na, and Cl contents of different organs: leaflets, rachises, petioles, stems, roots, and fresh fruit bunches. Our results showed that Cl stimulated the uptake of K, Ca, and Mg cations in aerial parts and that K was primarily stored in the stem (72% of the K in aerial vegetative organs). Our results also showed that the soils were rich in K easily accessible to the crop, a fact that conventional extraction of exchangeable cations did not reveal, and that the richness was probably of volcanic origin. Lastly, analysis of rachis K content was seen to be a good potential indicator of K taken up by the plant, and could thus replace leaflets for monitoring potassium fertilization in oil palm plantations.