Abstract
Current increases in producing considerable amount of organic matter such as, sewage sludge has resulted in their application on agricultural lands. Soil biological and biochemical properties are influenced by organic matter application. The effect of nitrogen and phosphorus enriched sewage sludge on urease activity was investigated in this study. Different rates of sewage sludge (0, 200 and 350 t ha-1) were enriched using nitrogen (0, 170 and 250 kg ha-1 in the form of urea) and phosphorus (0 and 150 kg ha-1 in the form of potassium phosphate) fertilizers. This experiment was performed using a factorial model in completely randomized design. Prepared soil samples were incubated at 25 o C and 70% of water holding capacity. Urease activity was measured colorimetrically. The results showed that application of sewage sludge and nitrogen fertilizer increased urease activity markedly within the first 15 days of incubation, although its activity dropped down sharply by the end of the experiment. Also, the results of phosphorus application showed a decrease in enzyme activity. In conclusion increasing time decreased the available substrate for enzyme activity and resulted in the reduction of enzyme activity reduction.
F.V. Kakhki, G. Haghnia, A. Lakzian . (2008) Effect of enriched sewage sludge on soil urease activity , The Journal Soil & Environment , Volume 27, Issue 2.
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