Enzyme Activities as Indicators of Soil Quality: Response to Intensive Soybean and Rice Crops

Abstract

Soil enzyme activities are often used as indicators of soil contamination. The responses of the activities of specific soil enzymes, dehydrogenase, acid phosphatase, β-glucosidase, carboxylesterase, and urease to different land uses (soybean and rice crops, and a reference site) were analyzed. Changes in activity at the start and end of each crop cycle were quantified. In general, the catalytic activity of all enzymes was lower in both crops than in the reference site. Regarding the soybean crop, all the enzyme activities decreased at the start of the crop cycle (27.5–53%, with respect to reference site values), whereas only acid phosphatase, β-glucosidase and carboxylesterase were lower at the end of the cycle (70.3%, 29.44%, and 45.79%; respectively). In the rice crop, dehydrogenase, acid phosphatase, and β-glucosidase activities were lower at the start of the cycle (27.88%, 50.32%, and 23.21%; respectively), with respect to reference site. However, the enzyme activity was lower at the end of the cycle compared to the reference site (dehydrogenase 20.47%, acid phosphatase 72.72%, β-glucosidase 57.77%, carboxylesterase 27.59%), except for urease activity. Current results suggested that the use of enzyme activities as indicators of soil quality is a viable approach to assess the pesticide impact in agricultural soils of Argentina.