DefinePK

Abstract

Field experiments were conducted to study the effect of pesticide applications on soil nitrification dynamics in cotton agroecosystem. The pesticides either alone or in combination mixture were applied according to the normal agricultural application rates in test, farmer with pesticide applications and control without pesticide applications fields. Soil samples were collected before and after two days, following pesticide applications and at sowing, before pesticide application, after all pesticide applications, at harvest and at post harvest time during the crop seasons 1997-1999. Soils were incubated under laboratory conditions using ammonium sulfate as substrate. In 1997 crop season soil samples were incubated for 28 days with a substrate of 144 mgkg -1 soil while in 1998-1999 the incubation period was 14 days with substrate of 212 mgkg -1 soil. The soil samples were analyzed for total NO2 NO3 N content using steam-distillation method. Othofonprox, profenophos cypermethrin and bifenthrin endosulfan inhibited while, endosulfan, imidachloprid, methamidophos, endosulfan alongwith dimethoate, profenophos alphmethrin, chlorpyrifos tralomethrin acetamiprid and cyhalothrin profenophos diafenthiuron stimulated the nitrification. All other pesticidal applications have no effect on this parameter. Samples collected at different intervals of time from all the fields in three years study showed no differences in nitrification from sowing to harvest. The variations observed, in general, being very week and transient and resulting in a recovery of nitrification.