Physicochemical properties and enzymatic activity of sulfur-acidified horticultural soil

This experiment was performed under laboratory conditions in three replicat ions. Three types of horticultural soil were put in plastic pots using 200 dm(3) per pot. Prior to filling the pots, the soils were carefully mixed wi th dusty elementary sulfur at 0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 g.dM(-3) and incubated for three months at 18-20 degreesC, maintaining moisture at 60% o f capillary water holding capacity. After 90 days the samples were taken fo r the determination of active acidity in H2O, hydrolytic acidity (H) and to tal of bases (S). Based on the results of the assay, the total exchange cap acity (T) and degree of base saturation (V) were computed from the formulas : T = S + H and V = S.T-1.100. In addition, the activity of dehydrogenases, urease and acid and alkaline phosphatase was determined. Elementary sulfur was found to have an effect on physicochemical and bioche mical properties of horticultural soil. The highest rate of sulfur reduced pH (in H2O) from 6.7 to 3.9, the total of exchange bases by 3-fold, the tot al exchange capacity by 1.2-fold and the degree of base saturation by 2.4-f old. It also depressed the activity of dehydrogenases by 12.6-fold, urease by 74.1-fold, acid phosphatase by 1.8-fold and alkaline phosphatase by 4.1- fold. Sulfur applied at 5 g.dm(-3) increased hydrolytic acidity by 9-fold.