Pesticide influence on soil enzymatic activities

The influence of four pesticides, e.g. glyphosate, paraquat, atrazine, and carbaryl, on the activities of invertase, urease and phosphatase of twenty- two soils, numbered as 1-22, was investigated. Soils displayed a general va riability of enzyme activities with invertase being more abundant than urea se and phosphatase in the order listed. The addition of glyphosate and para quat activated invertase and urease activities in several soils. Increments of invertase activity ranged from a very low increase (+4%) up to +204% in soils 11 and 14, respectively. Smaller increases were measured for urease. A general inhibitory effect (from 5% to 98%) was observed for phosphatase in the presence of glyphosate. The effects of atrazine and carbaryl on the three soil enzymes were evaluated against that exhibited by methanol, the s olvent used for their solubilization. In almost all soils, atrazine further inhibited invertase activity with respect to the inhibitory effect shown b y methanol. By contrast, consistent activation effects (from 61% to 10217%) were measured for urease with methanol alone and/or methanol-pesticide mix tures. Contradictory results were observed with phosphatase. Similarities f ound between the results obtained with enzymes in soils and those measured with synthetic enzyme complexes (e.g. free enzymes and/or clay-, organo-, a nd organo-clay-enzyme complexes) exposed to the same pesticides allowed som e relationships between responses of soil enzymes to pesticides and soil pr operties to be hypothesized. (C) 2001 Elsevier Science Ltd. All rights rese rved.