Persistence of Butachlor in Soils under Different Moisture Regimes

Persistence of butachlor was studied at two levels (2.5 & 5.0 mg kg⁻¹ soil) of application in three different soils (Hiriyur, Mandya and Mudigere) of Karnataka under three moisture regimes (air dry, field capacity and submergence). The persistence of butaehlor indicated a close correspondence to the first order exponential degradation kinetics in soils and mainly influenced by soil organic matter and moisture. Faster disappearance was noticed under field capacity followed by submergence and air dry conditions in all soils. Half-lives of butachlor under air dry, field capacity and submergence ranged from 52.40 to 59.57, 12.35 to 20.58 and 28.48 to 39.20 days at 5 mg kg⁻¹ application, respectively. The disappearance of butachlor in soils under field capacity was found to follow two different phases of disappearance and both the phases were described by first order degradation kinetics. The disappearance of butachlor was higher in nonsterile soils than in sterile soils under both field capacity and submerged conditions indicating the major pathways of degradation to be microbial. The disappearance of butachlor in all three soils was rapid under field capacity than under submergence even with the addition of farm yard manure and paddy straw as organic amendments.