Abstract:
Potential environmental pollutants such as herbicides, may affect soilfauna andflora and microbial activity, depending upon their quantity andfrequency o f application. Therefore, the current study was undertaken to assess the effect o f two herbicides, propanil and glyphosate, on soil microbial activity, as measured by carbon mineralization. Propanil was added at the rate o f 0.0224 (recommended rate), 0.224 and 2.24 pg/g soil and the corresponding rates o f glyphosate were 0.3546 (recommended rate), 3.546, and 35.46 pg/g soil. A Completely Randomized Design (CRD) was used fo r the experiment with four replicates. Carbon mineralization was determined at 1, 3, 5, 7, 10, 14, 21, and 35 days after propanil and glyphosate application and a further reading was taken at 56 days after glyphosate application, considering their half life. Carbon mineralization decreased significantly (P < 0.05) by both herbicides during the early stages o f incubation period. The initial reductions were higher (81% and 47% fo r propanil and glyphosate at the rate o f 2.24 and 35.46 pg/g soil respectively) with the increasing concentrations. Carbon mineralization was increased after 5 days (propanil) and 10 days (glyphosate). The reduction o f carbon mineralization was higher in propanil compared to glyphosate treatments, indicating that propanil was more toxic than glyphosate. However, no significant changes occurred, fo r both herbicides at recommended rates (0.0224 and 0.3546 pg/g soil fo r propanil and glyphosate respectively). Therefore, recommended application rate o f both propanil and glyphosate to red yellow podzolic soils could be recommended, without affecting the microbial activity.
