Response of soil microbiota to the addition of 3 , 3 ′ - diaminobenzidine

3,3′-Diaminobenzidine was applied at doses of 5, 10, 25, and 50 mg kg−1 of soil and their effects were evaluated on indigenous soil microbial communities (viable aerobic bacteria, fungal populations, aerobic N2-fixing bacteria, denitrifying, and nitrifying bacteria), and soil enzymatic activities (acid and alkaline phosphatases, arylsulfatase, and dehydrogenase). At doses of 5 or 10 mg kg−1, 3,3′-diaminobenzidine increased the numbers of culturable soil bacteria, including Azotobacter spp., nitrifying and denitrifying bacteria. Higher doses (25–50 mg kg−1) enhanced growth of aerobic nitrogen fixers too, but negatively affected denitrifying and nitrifying bacterial groups, altering the natural balance of populations involved in N cycling. Fungi were not strongly affected by any doses tested. All enzymatic activities in soil were enhanced by application of 3,3′-diaminobenzidine. © 2003 Elsevier Science B.V. All rights reserved.