EXTRACTION OF NONEXCHANGEABLE POTASSIUM FROM SOILS IN GALICIA

We compare the action of 4 extractants which some authors report as being capable of extracting the non-exchangeable K of soils. The extractants used were: boiling 1 M HNO3, Na-TPB, H2SO4 and EUF II. There were large differences between the quantities of K extracted by H2SO4 and EUF II and those extracted by HNO3 and Na-TPB. The best correlations were between EUF II and H2SO4, and HNO3 and Na-TPB. It was inferred that H2SO4 and EUF II do not extract the non-exchangeable K, whereas 1 M HNO3 and Na-TPB do, though HNO3 also extracts part of the mineral K in some cases.