Characterisation of potassium in red (alfisols), black (vertisols) and alluvial (inceptisols and entisols) soils of India using electro-ultrafiltration

• Published in: Geoderma 1991, Vol.50 (3), p.185-196
• Main Authors: Dhillon, S.K., Dhillon, K.S.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Soils; Surficial geology
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/0016-7061(91)90033-P

Ten surface samples from eight benchmark soil series representing Alfisol, Vertisol, Inceptisol and Entisol soil orders of India were subjected to electro-ultrafiltration (EUF) analysis. Desorption rate of K was generally dependent on the amount and type of clay minerals present in the soil samples. Over a period of 35 min the greatest amount of K was desorbed from samples of smectitic Vertisols and the smallest from those of illitic Inceptisols and Entisols. Amounts of K desorbed from kaolinitic (Alfisols) and illitic soil samples during the first 10 min (EUF-10K) were significantly correlated with water soluble K ( r=0.98∗∗) and ar o K is an index of immediately available K ( r=0.93∗∗). Potential buffering capacity of smectitic and illitic soil samples was also significantly correlated with EUF-10K ( r=0.85∗∗). Amounts of K extracted over 35 min (EUF-35K) were related with ammonium acetate extractable K (r=0.96∗∗) and the amount of K held on non-specific sites, Δ K 0 (r=0.88∗∗) . The EUF-K quotient, i.e., the ratio of K desorbed between 30 and 35 min at 80°C to K desorbed from 0 to 30 min at 20°C, for different soil samples was in the sequence of generally reported K selectivity trends of their respective dominant clay minerals: illite>smectite>kaolinite. Only in well buffered illitic soil samples, K desorbed during 5 to 10 min (2nd fraction) and 30 to 35 min (7th fraction) were dependent on the K saturation percentage. Potassium buffering power of different soil samples, as indicated by the ratio of the 7th to the 2nd EUF-K fractions, were in the sequence: illitic>smectitic>kaolinitic.