A field study to evaluate leaching of aldicarb, metolachlor, and bromide in a sandy loam soil

• Published in: Journal of environmental quality Vol. 22; no. 3; pp. 562 - 577
• Main Authors: Smith, C.N, Parrish, R.S
• Format: Journal Article
• Language: English
• Published: American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America 01.07.1993
• Subjects: ALDICARB; ALDICARBE; application technology; ARACHIS HYPOGAEA; bromides; BROMURE; BROMUROS; CARACT MORFOLOGICAS DEL SUELO; emulsifiable concentrates; FORMULACIONES; FORMULATION; Georgia; GEORGIA (EUA); GEORGIE (EU); GRANULE; granules; GRANULOS; half life; labeling techniques; leaching; LESSIVAGE DU SOL; LIXIVIACION; metolachlor; METOLACHLORE; METOLACLORO; MOUVEMENT DE L'EAU DANS LE SOL; MOVIMIENTO DEL AGUA EN EL SUELO; PROFONDEUR; PROFUNDIDAD; sandy loam soils; saturated conditions; soil depth; spatial variation; TECHNIQUE DES TRACEURS; TECNICAS DE TRAZADORES; TIPOS TEXTURALES DE SUELOS; TRAIT MORPHOLOGIQUE DU SOL; TYPE DE SOL TEXTURAL; Georgia
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq1993.00472425002200030022x

Transport and transformation of pesticides used in agricultural situations are subject to vailability from several sources that are impossible to simulate in laboratory settings. This study was conducted to characterize pesticide leaching behavior under conventional croping conditions and to determine the impacts of related sources of vailability. An agricultural field site (Ardilia fine sandy loam, Clarendon loamy sand, Tifton loamy sand, and Lucy loamy sand) located within the Dougherty Plain region of southwest Georgia was used to study pesticide movement in unsaturated and saturated soil zones from 1984 through 1988. A granular formulation of aldicarb [2-methyl-2 - (methylthio) propionaldehyde O-(methylcarbamoyl) oxime], an emulsifiable concentrate of metolachlor [2-chloro-N-(2-ethyl-6-methyl-phenyl)-N-(2-metboxy-1-methyl ethyl) acetamide], and a bromide (Br-) tracer were applied on peanut (Arachis hypogea L.) crops under modified conventional tillage practices. Postapplication vertical movement was monitored for periods of up to 111 d for pesticides and 1307 d for Br-. Application distributions for aldicarb showed measured coefficients of variation ranging from 42 to 72, and for metolachlor from 23 to 44. Spatial variability analyses indicated the existence of small-scale correlation for both pesticides upon initial application, and some large-scale trending was observed for metolachlor. Field-based transformation rates of aldicarb were up to three times higher than laboratory-based values. There was no evidence of migration of any of the pesticides into the saturated zone during the study, although Br- was observed at less than 1 mg kg(-1) in well-water samples. Aldicarb degraded almost completely within d each year, and it was not observed below 1.2 m. Metolachlor profiles always showed concentrations decreasing with increasing depth, and there was no significant movement below 0.3 m. Bromide was observed in soil samples as deep as 3 m only on the 1307th d, a