Highest enzymatic activity of observed in which size of soil clay particle
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Enzymatic activity is an important property for soil quality evaluation. Two sequences of experiments were carried out in order to evaluate the enzymatic activity in a soil (Rhodic Eutrudox) amended with cattle manure, earthworm casts, or sewage sludges from the municipalities of Barueri and Franca. The activity of commercial enzymes was measured by microcalorimetry in the same soil samples after sterilization. In the first experiment, the enzyme activities of cellulase, protease, and urease were determined in the soil samples during a three month period. In the second sequence of experiments, the thermal effect of the commercial enzymes cellulase, protease, and urease on sterilized soil samples under the same tretaments was monitored for a period of 46 days. The experimental design was randomized and arranged as factorial scheme in five treatments x seven samplings with five replications. The treatment effects were statistically evaluated by one-way analysis of variance.
Effects of the oil well-drilling fluid additives on soil enzyme activities were studied by Demidienko and Demurdzhan (1988). Twenty inorganic and organic compounds and mixtures used for the preparation of oil well-drilling fluids were added to samples of an uncontaminated common chernozem from the Dnieper-Donets Depression, at a rate of 1% (weight/weight). In comparison with the untreated control samples, each fluid additive exerted a negative or positive effect at least on one of the six enzyme activities studied (invertase; urease; protease; nitrate, nitrite, and hydroxylamine reductase). The majority of the fluid additives decreased invertase, nitrate and hydroxylamine reductase activities and increased the other activities. The increase was most pronounced in the case of urease activity.