Air-drying pretreatment effect on soil enzymatic activity

Air-drying of soil samples is a common practice for all-purpose soil testing. However, it may cause the cessation of microbial activity changing the biochemical attributes. For this reason, field-moist samples are commonly used in the assessment of the enzyme activity in soils. This practice may, therefore, discourage the use of enzymes in soil quality evaluations. This study evaluated the effects of air-drying on cellulase, arylsulfatase and acid phosphatase activities in soil; the hypothesis was that the activities of these enzymes determined in air-dried soil samples are similar to those obtained at field-moist samples. Soil samples were collected (0-10 cm) in a long-term experiment that received two rates (10 and 20 t/ha) of sewage sludge and mineral fertilizer and was cropped with maize. Collected soil samples were split into two groups. In the first one, the enzymes were determined at field-moist samples, while in the second one, the samples were air-dried before enzymatic analyses. Acid phosphatase was significantly affected by air-drying while the arylsulfatase activity hardly changed. The results showed that the enzymes determined in air-dried soil samples hold the capacity to identify different organic management and can, potentially, be used as soil quality indicators.