Available nitrogen and arginine deaminase activity in groundnut (Arachis hypogaea L.) fields after imidacloprid, diazinon, and lindane treatments

Plant available nitrogen and arginine deaminase activities 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 only for the seed treatments. An average half-life (t(1/2)) of diazinon in seed- and soil-treated fields was 29.32 and 34.87 days, respectively. Its residues were detected till 60 days in both seed- and soil-treated fields. Diazinon treatments had shown stimulatory effects on available nitrogen in both types of treatments. However, the increase in arginine deaminase activity was only observed in diazinon soil-treated field. Residues of imidacloprid and lindane were detected in seed-treated fields till 90 and 120 days with an average half-life (t(1/2)) of 40.96 and 53.39 days, respectively. Imidacloprid had stimulatory effects, and lindane had adverse effects on both available nitrogen and arginine deaminase activities.