Plant Available Phosphorus and Total Phosphorus as Affected by Diazinon, Imidacloprid and Lindane Treatments in Groundnut Field

Plant available phosphorus and total phosphorus were determined in insecticide-treated groundnut (Arachis hypogaea L.) fields between July and November for three consecutive years (1997–1999). Diazinon was applied for both seed-and soil-treatments. However, imidacloprid and lindane were used for the seed treatments. An average half-life (t_½) of diazinon in seed- and soil-treated fields was 29.3 and 34.9 days, respectively. Its residues were detected till 60 days in both cases. In diazinon seed-treated field, available phosphorus more or less not affected; while, total phosphorus decreased and increased alternatively between 15 and 120 days. However, diazinon soil treatment indicated significant decrease in available phosphorus with more or less similar alternative changes in totot phosphorus. Imidacloprid and lindane persisted tiil 90 and 120 days with avveage half-lives (t_½) of 40.9 and 53.3 days, respectively. In imidacloprid seed-treated field, available phosphorus increased significantly from 30 to 90 days; whereas, no effect on total phosphorus was found. However, lindane seed treatment indicated significant increases in avaiiable phosphorus and decreases in total phosphorus during 30 to 120 days.