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Subject: Agricultural Chemicals × Author: Pal, Suman Lata × End date: 2018 × Start date: 2010 ×
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    ThesisItemOpen Access
    Persistence/issipation, adsorption-desorption and leaching behaviour of ethofumesate and oryzalin herbicides in soil and water
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2012-08) Pal, Suman Lata; Sand, N.K.
    Herbicides are indispensable for sustained agricultural production, but due to their hazardous after effects on human beings, wild life and environment, it is mandatory to evaluate their residues. The investigation was undertaken to develop simple method for extraction and analysis of persistence, adsorption-desorption and leaching studies of two herbicides ethofumesate and oryzalin in soil, water. Ethofumesate [(±)2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methane-sulfonate] member of Benzofuron used as pre - and/or post-emergence in sugar beet and other beet crops, turf, graminaceous plants, broad leaf plants, weeds of sugar beet meadow, greensward meadow and other meadows such as rye grass and the other pasture grasses. Oryzalin [3,5-dinitro-N4,N4-dipropylsulfanilamide] belongs to Dinitroaniline herbicide family has broad spectrum of activity against annual grasses, broadleaf weeds, woody shrubs and wines in grapes, berries and orchard crops, including both fruits and nuts. In the present study, tap water and soils (silt clay loam and sandy loam) samples randomly drawn at different soil depth were characterized for general physicochemical properties. UV-Vis spectroscopy revealed λmax of herbicides as 280 nm which was used for the detection in HPLC. The limit of detection of ethofumesate and oryzalin in soil and water were 0.02 μg g-1 or ml and 0.01 μg g-1 or ml respectively. During experiment, extraction of herbicide from soil was done with acetone: methanol (5:1 v/v), 5% sodium chloride, n-hexane and dichloromethane. In case of water, partitioning was performed with dichloromethane. The HPLC conditions during analysis was ODS-2 (C-18 column), mobile phase with composition methanol: water (70:30 v/v) and flow rate of mobile phase was 1ml min-1. Ethofumesate and oryzalin often both have a “biphasic” breakdown pattern in soil follow first order kinetics. The half life (t1/2) values for ethofumesate were found for initial and later both phases were 12.70 & 51.88 days and 15.12 & 55.72 days at recommended and double recommended dose in sandy loam soil whereas, in silty clay loam soil 9.49 & 64.02 days at recommended dose and 11.53 & 68.39 days at double recommended dose. On the other hand the half-lives of oryzalin for both phases were 6.50 & 39.08 days and 6.60 & 42.38 days at recommended and double recommended dose in sandy loam soil whereas, in silty clay loam soil were 5.56 & 51.00 days at recommended dose and 6.006 & 56.78 days at double recommended dose respectively. No detectable residue (< 0.02 μg g-1 for ethofumesate and 0.01 μg g-1 for oryzalin) of oryzalin and ethofumesate were found on 150th and 170th day of application in silty clay soil, 120th and 150th day of application in silty clay soil and 120th and 90th day of application in water respectively at both doses. While, the degradation pattern of both herbicides followed monophasic first order kinetics in water. In water the half-lives of ethofumesate were found to be 34.59 and 37.15 days whereas, for oryzalin 42.99 and 48.53 days at both doses recommended and double recommended dose respectively. Adsorption was highest in case of higher concentration on both soils and adsorption increases as concentration increases. The percent adsorption was higher in silty clay loam soil than sandy loam soil due to presence of higher organic content in silty clay loam soil. The adsorption of oryzalin was higher than ethofumesate in both soils. In the presence of organic matter the adsorption increased as concentration increases. So, organic matter may be used to decrease the mobility of ethofumesate and oryzalin in soil. The ethofumesate and oryzalin herbicide’s adsorption-desorption data described well to Langmuir, Freundlich and Temkin isotherms, respectively. However, the fit to Freundlich adsorption model was greater than that of Langmuir or Temkin on the basis of values of regression coefficient. Leaching study of ethofumesate and oryzalin were performed in silty clay loam soil and sandy loam soil at recommended dose. The residues of herbicides were found to be beyond 0-20 cm and 0-10 cm of soil depth, and showing less mobility in both types of soil. But in presence of organic amendments such as vermicompost and FYM (Farm Yard Manure) greatly enhanced the adsorption capacity of herbicides in soil depths in soil columns.