INFLUENCE OF SOIL INGESTION BY EARTHWORMS ON THE AVAILABILITY OF POTASSIUM IN SOIL - AN INCUBATION EXPERIMENT

An incubation experiment was conducted to study the changes that occur in the K status of soil due to earthworm activity. Samples of Tokomaru silt loam soil were inoculated with the common pasture earthworm species Aporrectodea caliginosa and incubated for 21 days. Aliquots of moist soil were analyzed for exchangeable K by leaching with neutral molar ammonium acetate at 1 : 50 soil solution ratio. Extraction with boiling 1 M nitric acid at 1 : 100 soil solution ratio for 20 min was used to determine available non-exchangeable K. The results indicated that the exchangeable K content increased significantly due to earthworm activity but nitric acid-extractable K did not change significantly. It is inferred that earthworms increase the availability of K by shifting the equilibrium among the forms of K from relatively unavailable forms to more available forms in the soil chosen for the study.