Relationship of Some Forms of Potassium with Neutral Normal Ammonium Acetate Extractable K in Mineralogically Different Benchmark Soil Series of India

Loosely held forms of K viz. water soluble, 0,01 M CaCl₂ 0.01 M citric acid, 1.38 N H₂SO₄ and strongly held 6NH₄SO₄, and NaTPB-K were evaluated in twenty-two benchmark soil series in relation to neutral 1N ammonium acetate (NH₄OAc) extractable K, a commonly used measure for assessing the available K in all the soil testing laboratories in India. Smectitic Vertisols and vertic sub-groups showed larger K in all the extractants except in NaTPB, followed by illitic Inceptisols, Alfisols, Entisols and Aridisols and kaolinitic Alfisols and Inceptisols. The NaTPB extractable nonexchangeable form of K was larger in illitic soils as compared to other soils. Except some Alfisols, surface soils had higher K status than subsurface soils. In smectitic and illitic soils NH₄OAc-K showed highly significant correlation with different forms of K except with NaTPB-K in illitic soils, whereas relationships in kaolinitic soils were either poor or nonsignificant.