Fate of 2,4‐D Iso‐octyl Ester after Application to a Wheat Field

Abstract

Dissipation of iso‐octyl ester of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and its acid metabolite in air, crop, and soil components were measured in a wheat (Triticum aestivum L.) field during and following application. Drift losses during application were only 0.2% of the amount applied. Air samples, collected at six heights ranging from 30 to 200 cm above the crop canopy during the first 7 d after application showed distinct ester gradients in the air, with concentration highest in the samples closest to the crop canopy. The highest concentration was measured during the afternoon of day 1 when 1604 ng m−3 were recorded 30 cm above the crop canopy. The vertical flux of the ester showed distinct diurnal variations with maxima reached in the early afternoon of day 1 and 2, followed by a rapid decline of the ester flux thereafter, corresponding with the depletion of the ester from the crop canopy. The total or cumulative vapor losses of the iso‐octyl ester over the 5‐d sampling period were estimated to be 93.5 g ha−1 or 20.8% of the amount applied. The crop canopy intercepted 52% of the applied ester and acted as the major source of vapor losses. The magnitude of vapor activity was controlled primarily by the atmospheric stability and air temperature following application. On entry into the crop, the ester was hydrolyzed to the acid metabolite, which reached its maximum level on day 3. There appeared to be a rapid initial metabolism of the acid followed by a slow decline. Ester losses from the soil surface occurred only when the soil surface was moist, i.e., after a rainfall event or in the early hours of the morning following the deposition of dew. In addition, both the hydrolysis of the ester and the subsequent degradation of its acid metabolite in the soil were dependent on the availability of surface soil moisture. No detectable 2,4‐D remained in the soil after 34 d.

Metribuzin residues in lentil following postemergence application

“…Field-applied herbicides have been shown to persist as plant surface deposits for as long as 14 d after application (Grover et al 1994), however, such deposits generally dissipated rapidly during the first 3 to 5 d (Grover et al 1985(Grover et al , 1994Smith et al 1986;Cessna 1993). Although, in these studies, uptake by the crop accounted for some of this dissipation, weather conditions during the first few days after herbicide application can also influence losses through volatilization (Grover et al 1985(Grover et al , 1994, photodegradation (Cessna and Muir 1991) and rainfall washoff (Behrens and Elakkad 1981;Anderson and Arnold 1985).…”

“…Although, in these studies, uptake by the crop accounted for some of this dissipation, weather conditions during the first few days after herbicide application can also influence losses through volatilization (Grover et al 1985(Grover et al , 1994, photodegradation (Cessna and Muir 1991) and rainfall washoff (Behrens and Elakkad 1981;Anderson and Arnold 1985).…”

Bulk Deposition of Pesticides in a Canadian City: Part 1. Glyphosate and Other Agricultural Pesticides

“…This included herbicides fenoxaprop and glufosinate that are among the most widely applied pesticides in Manitoba (Table 2). Pesticide residues become airborne through application drift, volatilization from plant, land and water surfaces, or by being attached to winderoded soil (Grover et al 1985;Coupe et al, 2000;Larney et al, 1999). Both fenoxaprop and glufosinate are rapidly degraded in Prairie and other soils (Smith 1985, Smith 1988, Smith and Belyk 1989, Xiaoxu et al 2011, Sing et al 2013) and hence post-volatilization losses and their attachment to wind-eroded soil are expected to be limited.…”

Residues of 2,4-D and Picloram in Aspen Poplar and Soil After Application With a Roller

“…The extract residue was transferred to a Florisil Milled poplar tissue (10 g of leaves, twigs, stems clean-up column (Grover et al 1985) with two or roors) and 110 mL of 0. I N NaOH solution con-1.5-mL hexane rinses of the 25-mL round bottom tained in a 25tl-ml-Erlenmeyer f'lask were heated f'lask.…”