The interaction between potassium and magnesium red yellow podzolic soils with laterite and its effect on nutrition of coconut palms

Abstract

The interaction between plant available potassium and magnesium in highly leached red yellow podzolic soild with laterite in southern coastal area of Sri Lanka and its effect on coconut palm was studies in a 3*2K*Mg factorial experiment that consisted of 3 levels of potassium and 2 levels of magnesium fertilizer application to coconut palms in plots. Five years after continuation of treatment application, soil samples were taken from top soils (0-20 cm) and sub soils (20-40cm) at monthly intervals for 10 months and analyzed for exchangeable potassium and magnesium (1M ammonium acetate extraction at pH 7.0) and water soluble potassium and magnesium (1:10soil/water ratio). Leaf samples taken from the 14 frond at bimonthly intervals were analyzed for potassium and magnesiu.. The results showed that the application of potassium fertilizer decreased the quantity of both exchangeable and water extractable magnesium and magnesium fertilizer decreased the quantity of exchangeable potassium in soils. The mutual decreasing effect on the exchangeable fraction of each nutrient is attributed to low cation exchange capacity and base saturation of the soils. The close association of the coconut leaf nutrient contents with soil nutrient status implies that poor chemical characteristics of red yellow podzolic soils bring about imbalance of potassium and magnesium nutrition in coconut palms.