The total-N (NT) and organic-C (TOC) concentrations of the soil and organic amendments were measured with a EuroVector automatic microanalyser. The organic matter (OM) content of the soil was determined by multiplying TOC by 1.72 and the OM of organic amendments by ashing at 430 °C. Other parameters determined in the organic materials were water-soluble (1:20, w:v) phenolic substances, by a modified version of the Folin method for chemical quantification (Maestro-Durán et al., 1991), and carbohydrates, by the anthrone method. Ammonium nitrogen (NH4+-N) was extracted with 2 M KCl and determined by a colorimetric method based on Berthelot's reaction. Total P was determined colorimetrically as molybdovanadate phosphoric acid, after nitric-perchloric acid (2:1) digestion. Chemical analyses were done at least in duplicate.