Effect of Fertilization with Sludge-Ash Granulates on the Activity of Selected Soil Enzymes

In the two-factorial vegetation experiment, the activity of dehydrogenase, phosphatase and urease was examined under the influence of the applied sludge-ash granulates produced from waste (sewage sludge, ash, sawdust). The research scheme included a control object, four types of fertilizer granulates, three doses and four dates of enzymatic activity indicators determination. The experiment was established in four replications. The size of granulate doses was determined on the basis of their nitrogen content. Dose I, II and III were: 0.24 g, 0.48 g and 0.72 g N•pot, respectively. The test plant was rapeseed of Larissa cultivar. The sludge-ash granulates were applied to the pots filled with the soil, in accordance with the experimental scheme. The soil samples for chemical analyses were taken from the top layer (0–20 cm) of spring rape cultivation four times: May 16, June 2, July 2 – dates from I to III, respectively, and August 2 after harvest – date IV. In average soil samples, the enzymatic activity of dehydrogenase, urease and phosphatase was determined. The research revealed that the highest increase in enzymatic dehydrogenase activity was obtained after applying granulate B, while phosphatases and urease after the application of granulate D. The smallest increase in dehydrogenase and phosphatase activity was obtained after the application of granulate C. The dose size of the applied granulates and date of uptake had a significant impact on the growth activity of the enzymes studied. The activity of dehydrogenase, phosphatases and urease, depending on the type of applied granulate, dose and date of soil sampling, was on average 7.28%, 30.5% and 7.94% higher, respectively, compared to the control. The correlation coefficient between dehydrogenase activity and urease and phosphatase was positively associated and amounted to r = 0.569 and r = 0.553, respectively. The applied fertilization with sludge-ash granulates A, B, C and D stimulated the increase in dehydrogenase, urease, and phosphatase activities in all fertilizer objects.