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Desorption of cations from scottish soils by electro‐ultrafiltration
Author(s) -
Sinclair Alex H.
Publication year - 1980
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740310604
Subject(s) - chemistry , loam , soil water , potassium , desorption , ultrafiltration (renal) , saturation (graph theory) , extraction (chemistry) , magnesium , sodium , aqueous solution , environmental chemistry , analytical chemistry (journal) , chromatography , adsorption , soil science , environmental science , mathematics , organic chemistry , combinatorics
Soil cations were desorbed by electro‐ultrafiltration (EUF), i.e. by applying an external electric field to aqueous suspensions, and collecting the cations by ultrafiltration. Three different field strengths were used to obtain several cation fractions in a single extraction run lasting 35 min. Potassium desorbed in 10 min (K 10 ) was closely correlated with the equilibrium activity ratio (AR 0 ) of soil K measured in 0.01M CaCl 2 , for all but the sandy loam soils, while that desorbed in 35 min (K 35 ) was less than the exchangeable K, but correlated closely with it. EUF values compared favourably with other soil K parameters, determined by conventional methods, for predicting uptake of K by rye‐grass from ten soils during intensive cropping in the glasshouse. Sodium desorbed in 35 min (Na 35 ) approximated to the exchangeable Na, although most of it was desorbed in the first 15 min. Na 10 and Na 35 accounted for about 56% of the variation in Na uptake by ryegrass at the first cut, and 68% of the variation in the cumulative uptake at the sixth cut. Between 9–24% of the exchangeable calcium was desorbed in 35 min, and magnesium desorbed was closely correlated with both the Mg concentration of the soil saturation extract and the exchangeable Mg. EUF extraction of Mg is less satisfactory than for K, Na and Ca owing to the precipitation of Mg(OH) 2 on the cathode filter.