Liming effects on soil exchangeable and soil solution cations of 4 soil types in north-eastern Victoria
The effects of lime additions on exchangeable and soil solution cations of four soil types in north-eastern Victoria are discussed. Liming significantly (P < 0.05) reduced the concentration of exchangeable (1 M KCl), extractable (0.01 M CaCl2), soil solution total and monomeric aluminium. Raising the soil pHCa to 4.8 decreased Ale, concentrations below 1 mg kg-1, Al saturation % of the effective cation exchange capacity below 5 and AlTot below 5 PM; and raising the soil pHCa to 5.8 decreased MnCa concentrations below 10 mg kg-1 and AlTot below 2�m on the four soil types used in this study. Grain yield responses were best described by the sum of the activities of the Al monomers. Where organic C was present, responses could also be attributed to the complexing of monomeric Al. Grain yield responses could not always be reliably predicted by the Al saturation % of the effective cation exchange capacity. Liming significantly (P < 0.05) increased the concentration of Ca in the ECEC, but the Ca activity was not well correlated with lime response for all sites. The In ratio of aCa2+/�aAl- mono shows promise in predicting negative responses to lime applications (with values > 6) where soil pHCa is less than 5. The combination of Ca activity and the sum of the activity of the Al monomers, together with organic C content, may provide a better description of the responsiveness of acid soils to lime applications.