Srivastava, AnjanaMonika2019-04-222019-04-222018-12http://krishikosh.egranth.ac.in/handle/1/5810100770Penoxsulam is a post-emergence, triazolopyrimidinesulfonamide group of herbicide,used to control broadleaf and sedges weeds in rice crop. Thedissipation, persistence and leaching behavior of this herbicidewas investigated under laboratory conditions. Dissipation study of penoxsulam was performed in two soil samples at two concentrations i.e. 0.5 and 1.0 μg g-1 under non flooded conditions (20% moisture regime)and 1.0 and 2.0 μg g-1 under flooded conditions (submerged conditions). Penoxsulam was extracted by two methods (simplified QuEChERSmethod as well as long traditional method).The analysis of the herbicide was done by high performance liquid chromatography (HPLC). The average recoveries of penoxsulam in soil ranged between 88.4 and 89.6%at lower application (0.5 μg g-1) rate and 93.6 and 95.5% at higher application (1.0 μg g-1) rate. Penoxsulam residues declined consistently with time in both the type of soils under both the conditions. At lower application rate (0.5 μg g-1) penoxsulam declined continuously persisting up till 21st day with dissipation up to 75.0% and 72.3% in the two soil samples while at higher application rate (1.0 μg g-1) it persisted up till 30th day dissipating up to 73.4% and 74.5% in the two soil samples under non flooded conditions. However, under flooded conditions the herbicide declined slowly persisting up to 30th day with dissipationup to 80.6% and 77.2% in the soil samples at lower application rate (1.0 μg g-1) and at higher application rate (2.0 μg g-1) it persisted up to 60th day with dissipation up to81.6% and 80.0% in the soil samples.Penoxsulamwas not detectable(ND) i.e. < 0.004 μg g-1 on 30thand 60thday of herbicide’s application in both the type of soils at lower and higher application rates respectively under non flooded conditions whereas, underflooded conditions it was ND on 60th and 90th day of application.Dissipation of penoxsulam occurred in a single phase with the persistence data fitting well with the first-order kinetics. The half-life of penoxsulam was 3.48 and 3.57 d at lowerapplication rate in the two soils and 4.10 and 4.17 d in both the type of soils at higher application rateunder non flooded conditions.Under flooded conditions the t1/2 values in both the soil samples were 5.50 and 6.93 d at lowerapplication rate and 10.0 and 10.19 at higherapplication rate. Penoxsulam does not persist for long time at lower concentration but is more persistent at higher concentration in both the subtropical soil under both the conditions. The degradation products and metabolites of penoxsulam were identified by LC MS/MS analysis. Leaching experiment of penoxsulam was also conducted in two soils at two application rates (0.5 and 1.0 μg g-1)via batch method. The presence of penoxsulam was very low in the first and third leachate but it was determined in high amount in the second leachate, which was collected after 72 hours of leaching initiation. The residues of penoxsulam in leachate of acidic soil were slightly lower than that of neutral soil probably because of higher stability of the herbicide at low pH.ennullThesis