Effect of salicylic acid on protease and urease activity in soils under Norway spruce pure stands

This study tested the hypothesis that soil protease and urease activity is inhibited by salicylic acid. This was tested in soils from spruce monocultures of different ages and treated by different forest management methods at the Rajec-Němcice Ecosystem Station. Surface organic H-horizons from three study plots were sampled: a mature spruce monoculture of 105 years and two young spruce monocultures of 33 years, one of which was thinned from above and the other thinned from below. Statistically significant differences between the measured values confirm that young stands are sensitive to the presence of 2-hydroxybenzoic acid as a phytotoxic substance. The results of this study do not conclusively show whether the effect of salicylic acid on protease activity inhibition increases when the protease activity itself is high. The impact of salicylic acid on soil urease activity was not clearly evident either.