HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) An erratum has been published An erratum has been published Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Scribner, S. L. Articles by Boyd, S. A. Search for Related Content PubMed Articles by Scribner, S. L. Articles by Boyd, S. A. Agricola Articles by Scribner, S. L. Articles by Boyd, S. A.

Desorption and Unavailability of Aged Simazine Residues in Soil from a Continuous Corn Field

Department of Crop and Soil Sciences, Michigan State Univ., Plant and Soil Sciences Bldg., East Lansing, MI 48824

^* Corresponding author.

ABSTRACT

The sorption/desorption behavior of field weathered (aged) simazine (2-chloro-4,6-bis(ethylamino)-s-triazine) residues from a 20-year continuous corn (Zea mays L.) field was compared to that of ¹⁴C-simazine recently added to the same soil. The apparent sorption coefficients of the aged residues determined from 24-h and 48-h desorption experiments were approximately 15 times higher than the sorption coefficients of added simazine. Aged simazine residues were also shown to be biologically unavailable to sugarbeet (Beta vulgaris L.) and to microbial degraders, whereas recently added simazine showed herbicidal damage to sugarbeet and was substantially (ca. 48%) degraded during a 34-d incubation in soil. Apparently, the process of pesticide aging results in simazine residues that are less bioavailable, as shown by their resistance to plant uptake and microbial degradation, and that desorb slowly into soil solution. The concentration of simazine in water from field soil-samples (C) was monitored throughout a growing season, and compared to the equilibrium aqueous phase concentration (C_c) predicted from the laboratory determined sorption coefficient (K_oc of added ¹⁴C-simazine. The fractional equilibrium values (C/C_e.) were approximately 1 at the time of simazine application in May but fell to 0.05 during July and August. These results show that the concentration of simazine in water contacting field soil is likely to be substantially lower than that predicted from laboratory determined sorption coefficients, except immediately following application.