Dissipation of pendimethalin in the soil of field pea (Pisum sativum L.) and detection of terminal residues in plants

Dissipation of pendimethalin in the soil of field peas (Pisum sativum L.) at 0 to 110 days, and terminal residues in green and mature pea were studied under field conditions. Pendimethalin was applied as pre-emergence herbicide at 750, to 185 g a.i. ha^?1 in winter, in field peas. Dissipation of pendimethalin in the soil at 0 to 110 days followed first-order kinetics showing a half-life of 19.83 days averaged over all doses. Low pendimethalin residues were found in mature pea grain (0.004, 0.003, <0.001 μg g^?1), and straw (0.007, 0.002, <0.001 μg g^?1) at 750, 350 and 185 g a.i. ha^?1 treatments, respectively. The study indicated that residues of pendimethalin in green and mature pea were within the prescribed MRL limits.     

Determination of imazosulfuron persistence in rice crop and soil

Imazosulfuron is a new post-emergence sulfonylurea herbicide. It is highly active at low application rates to control annual and perennial broad-leaf weeds and sedges in rice. There is increasing concerned about the persistence of pesticide residues in soils, crop produce and subsequent contamination of groundwater. Thus persistence of imazosulfuron residues under field condition was evaluated. Imazosulfuron was applied at 30, 40, 50 and 60 a. i. g ha ⁻¹ rates, 4 days after transplanting of rice as post-emergence herbicide. Soil and plant samples treated with imazosulfuron were collected at 60, 90 and 120 days after herbicide application and analyzed for residues. Rice grains and straw samples were sampled at harvest (120 days). Residues of imazosulfuron in soil were not found after 90 and 120 DAS (days after spraying). Rice grains contained 0.006, 0.009 μg g⁻¹ residues at 50 and 60 g ha ⁻¹ application rates. 0.009 and 0.039 μg g⁻¹ residues of imazosulfuron were detected at 50 and 60 g/ha rates respectively in rice straw. Residues of imazosulfuron were not detected applied at 30 and 40 g ha⁻¹ in rice grains and straw, respectively and can be safely applied to the transplanted rice.     

Persistence of oxyfluorfen in soil and detection of its residues in rice crop

Oxyfluorfen is a post-emergence herbicide used for control of annual and perennial broad-leaf weeds and sedges in rice. There is increasing concern about persistence of pesticide residues in soils, agricultural products and sub-sequent contamination of ground water through runoff, leaching and drift. Thus, persistence of oxyfluorfen was evaluated under field conditions in a rice cropping system. Oxyfluorfen was sprayed at 240 and 500 g ai ha^?1 application rates to the rice crop as post-emergence herbicide. Paddy grains, straw and soil samples were collected at harvest and analyzed for oxyfluorfen residues by HPLC. Straw samples contained 0.01 and 0.03 µg g^?1 oxyfluorfen residues at 240 and 500 g ha^?1 concentrations, respectively. In the soil, 0.028 and 0.03 µg g^?1 of oxyfluorfen residues were detected when applied at 240 and 500 g ai ha^?1, respectively. However, in rice grains, 0.018 and 0.106 µg g^?1 of oxyfluorfen residues were found in 240 and 500 g ai ha^?1 treated plots. In light of the potential adverse effects of oxyfluorfen, it is important to determine herbicide levels in these crops.