MINIMUM EXCHANGEABLE POTASSIUM IN MOLLISO LS OF THE ARGENTINE PAMPAS

Plants can take up only a fraction of exchangeable potassium (K. int) available in the soil (NH4OAc, 1N, pH 7 method). A percentage of this value remains constant and is named minimum exchangeable potassium. Th e objective of this experiment was discover the amount of minimum exch angeable potassium in Argentinian Pampas Mollisols, by means of intens ive cropping experiment carried out in the Greenlouse. Each soil was s eed, and Rye-grass was harvested 6 times. The lapse of time between em ergence and harvest was 30 days. Different soil series have different minimum K. int values wich are related to clay content, with a regress ion coefficient of r = 0.85.