EFFECT OF DRYING ON EXCHANGEABLE POTASSIUM OF ONTARIO SOILS AND THE RELATION OF EXCHANGEABLE POTASSIUM TO CROP YIELD

Abstract

Exchangeable potassium in field moist, air-dry and oven-dry samples of surface soil of 15 soil types was extracted with 0.1 N ammonium acetate. It was found that, if the per cent potassium saturation of the cation exchange capacity was 1.11 ± 0.12, no change in the amount of exchangeable potassium occurred during drying of the soil. Above this equilibrium per cent potassium saturation, the exchangeable potassium was decreased by drying, and below this per cent saturation exchangeable potassium was increased by drying.The degree of correlation of exchangeable potassium at each of the different soil moisture contents with yields, i.e. Log (100 – % yield), of wheat, oats, and corn in the field was not affected by the drying treatment. Moreover, the exchangeable potassium level accounted for a relatively small part of the yield variability of these crops. For potatoes, however, there was a highly significant correlation between exchangeable potassium at each soil moisture content and yield, i.e. Log (100 – % yield) and the correlation coefficient was highest for the oven-dried soil.The degree of correlation between per cent potassium saturation at the different soil moisture contents with crop yield was not significant for any of the four crops.