Title: EXCHANGEABLE AND WATER-SOLUBLE POTASSIUM IN SOILS AND DEGREE OF SATURATION IN RELATION TO TOMATO YIELDS
Abstract: In 33 field trials on soils varying in texture from sandy loam to clay loam in Prince Edward County, Ontario, exchangeable potassium, per cent potassium saturation, and water-soluble potassium were significantly correlated with yield response of tomatoes to potassium fertilizer on the sandy loam soils, but there was no correlation within the loam and clay loam groups. The mean c 1 value in the modified Mitscherlich equation relating exchangeable potassium to yield response within the sandy loam group was 0.00555 and the coefficient of variation was 19.8 per cent. The corresponding coefficients for c 1 values based on per cent potassium saturation and water-soluble potassium were of greater magnitude. The amounts of potassium soluble in boiling 1 N HNO 3 were not related to yield response.Exchangeable potassium and the non-exchangeable form soluble in boiling 1 N HNO 3 increased, whereas water-soluble potassium decreased with increasing clay content of the samples. Water-soluble potassium was significantly correlated with per cent potassium saturation within the sandy loam and loam groups.