3. The neutralizing substances incorporated into soil had a more positive effect on counts of microorganisms than on the enzymatic activity of soil. All the applied substances affected positively the counts of actinomyces and copiotrophic bacteria as compared with the control. With respect to fungi, they presented a positive response only in soil previously cropped with yellow lupine and enriched with charcoal and loam. In general, the neutralizing substances added to soil had a positive effect on the activity of acid phosphatase and urease. As for alkaline phosphatase, the neutralizing substances had a negative influence on the activity of this enzyme.