INFLUENCE OF SOIL MOISTURE AND TEMPERATURE ON PENDIMETHALIN DEGRADATION IN CULTIVATED AND FORESTED LANDS - Carpathian Journal of Earth And Environmental Sciences

Degradation of pendimethalin [N-(1-ethylpropyl)-2, 6-dinitro-3, 4-xylidine] was evaluated under varying environmental conditions by monitoring its residual concentration in soil at weekly interval during an incubation period from 0 to 11 weeks. A factorial arrangement of treatments of two soils differing in land use (cultivated and forested), two moisture regimes (30 and 80 %) and two temperatures (20 and 40°C) were examined. After 11 weeks of incubation, initial concentration of pendimethalin (8.00 μg g^-1 soils) reduced to 2.00 and 1.40 μg g^-1 soil in cultivated and forested lands, respectively. The mean per cent of pendimethalin degraded corresponded to 70.79 and 77.50 in cultivated and forested lands following the order: Forested land > Cultivated land, revealing the impact of land use. It is attributed to more organic C (3.25%) accumulated by regular and long-term addition of litter in soil under forests. Significant relationship (R² = 0.991**- 0.997**) was noticed linking pendimethalin degradation with incubation period. Rate of degradation was rapid at 30 % moisture and 40°C as evidenced by about 6 days advancement in half life (DT50) due better adaptability of microbes to degrade pendimethalin under aerobic (30% moisture) and warmer conditions (40°C) as compared to moist (80 %) and cooler (20°C) conditions.