Fractionation of extractable aluminium and biomass production in an acid soil treated with calcareous amendments

A Typic Palexerult in the "raña" formations of the northern plateau in the province of León (Spain) was subjected to acidity correction field tests over a period of three years. The experimental crop was a local rye variety (Secale cereale L. var. Petkus) and the amendments included gypsum, dolomite, limestone and sugar foam waste, all at a 6000 kg ha�1 rate as CaCO3. General analyses were integrated with specific tests for soluble and easily exchangeable Al forms (Al-CaCl2) in addition to KCl, BaCl2 and CuCl2 extracted Al; adsorbed Al (NH4AcO) and amorphous Al. Two types of multiple linear regression models (OLS) for production each year were established; some encompassed all studied variables and others the six Al forms only. As shown here, Al-KCl, Al-CaCl2, base saturation and exchangeable Ca were the individual variables most strongly correlated with production, with R2=0.865, within the topmost 12 cm of the soil layer receiving the calcareous amendments. A principal component analysis exposed a substantial share of pH-dependent charge in organic matter on the cation exchange capacity of the soil