F. Noorbakhsh, S. Hajrasuliha, G. Emtiazy,
Volume 5, Issue 3 (10-2001)
Abstract
The urease enzyme plays an important role in the efficient use of urea fertilizer and some environmental risk assessment. Urease activities in 20 different soil samples of arid to semi-arid regions of Isfahan Province were determined and their correlations with some soil physical, chemical and biological characteristics were studied. Urease activities range from 5.3 to 79.2 µg NH4
+ g
-1 soil 2hr
-1.
Results indicated that soil organic carbon was significantly correlated with urease activity (r=0.899***). None of sand, silt and clay percentages were significantly correlated with urease activity. Total nitrogen was significantly correlated with urease activity (r=0.797***). Electrical conductivity of saturated paste extracts were also negatively correlated (r=-0.499*) but sodium adsorption ratio (SAR), pH, equivalent calcium carbonate and cation exchange capacity failed to be correlated significantly with urease activity. No significant correlations were found between urease activity and total bacteria (on nutrient agar) or total fungi (on potato dextrose agar), but the bacteria that could colonize urea-agar media were significantly correlated with urease activity (r=0.47*). Multiple stepwise regression analysis showed that organic carbon accounted for most of the variation in urease activity.
H. Dehghan-Menshadi, M. A. Bahmanyar, S. Salek Gilani, A. Lakzian,
Volume 16, Issue 60 (7-2012)
Abstract
Biological indicators are considered soil quality elements, due to their dependence on soil organisms. In order to investigate The effect of compost and vermicompost enriched by chemical fertilizers and manure on soil organic carbon, microbial respiration, and enzymes activity in basil plant's rhizosphere, a field experiment was conducted as a split-plot design with randomized complete blocks and three replications in 2006. The main plot involved six levels of fertilizer including: 20 and 40 tons of compost enriched, 20 and 40 tons of vermicompost enriched per hectare, chemical fertilizer and control without fertilizer and sub-plot, and period of application (two, three and four years). The results showed that application of compost and vermicompost at all levels increased soil organic carbon (OC) and soil microbial respiration, microbial biomass and urease activity compared to the controls (p<0.05), but increasing trend among the treatments was not similar. The maximum amounts of OC, soil microbial respiration and enzyme activity were observed in 40 tons of vermicompost enriched with chemical fertilizer ha-1 with four years of application. In high levels of compost application, the urease activity was decreased.
