| Abstract: | Total K, Na, Ca and Mg in the sand, silt and clay of six British and four Malayan soils and the proportions released to H+-resins in 1 h, 3, 10, 23 and 43 days were measured. The clays contained and released to the resins more K and Mg than coarser fractions. The release was continuous except from the acid Malayan soils which stopped releasing K after 3 days. More Mg was released to the resins than K, although no non-exchangeable Mg but much non-exchangeable K was released to ryegrass grown in the soils (after liming). This suggests that H+-resins caused structural decomposition of the clay minerals which, together with the anomolous K release from acid soils, would limit their usefulness for measuring soil cations available to crops. |
