Impact of Acephate and Buprofezin on Soil Urease

Abstract

Urease catalyzes the hydrolysis of urea into carbon dioxide and ammonia. In soil, it exists as an intracellular or extracellular enzyme. It has been found that urease activity in soil is often correlated with the soil microbial activities. Urease of microbial origin plays an important role in nitrogen transformation in soils. Like other soil enzymes, urease is also substantially affected by the application of pesticides. The present chapter provides the nontarget effects of acephate and buprofezin towards soil urease activity. The data obtained from laboratory experiments revealed that the activity of urease was adversely affected by acephate. Even though the enzyme activity was stimulated by 40% at 2.5 μg g⁻¹ of acephate, there was a gradual decline with increasing concentrations of acephate. On the other hand, buprofezin, even at 7.5 μg g⁻¹ soil did not affect urease activity in soil. Repeated applications of buprofezin resulted in 30–50% reduction in the enzyme activity. In all, urease was more sensitive to acepahte than buprofezin. In NPK-amended soils, the enzyme activities were adversely affected after two applications of the insecticides. Acephate and buprofezin, in combination at equal concentrations of 2.5 or 5 μg g⁻¹, caused either an additive or synergistic effect on urease activity. But, antagonistic effects were observed at higher levels of 7.5 and 10 μg g⁻¹ soil. Moreover, the activity of urease was adversely affected by the combination of the two insecticides in soil samples amended with N-P-K.