Assessing the impact of azadirachtin application to soil on urease activity and its kinetic parameters

Abstract

The kinetic parameters of soil urease have attracted considerable attention; however, little information is available on its kinetic parameters and behaviors in response to azadirachtin application to the soil. A short (14-day) field experiment was conducted using Albic Luvisol soil (loam texture; pH 6.70; electrical conductivity 0.81 dS m-1; CaCO3 content 0.04%; total organic carbon 0.99%) as the experimental soil in the Perm region of the Russian Federation to investigate the effects of different azadirachtin application doses on soil urease activity and its kinetic behaviors. The results showed that the highest urease activity was found under high azadirachtin application doses (0.6 L ha-1) compared to the control (0 L ha-1), recommended (0.3 L ha-1), and low (0.15 L ha-1) azadirachtin application doses at all different incubation times (1, 2, 3, 6, and 12 h). Soil urease enzymes exhibited typical Michaelis-Menten kinetic behaviors; high azadirachtin application doses increased the substrate affinity constant (KM) and decreased the maximum reaction rates (Vmax) of soil urease. As compared to the control azadirachtin application dose, the low azadirachtin application dose increased the Vmax of soil urease; however, with low and recommended application doses, the Vmax of soil urease decreased. Overall, in this study, all azadirachtin application doses were effective in influencing the kinetic behavior of urease in Albic Luvisol.