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

This Article Full Text (PDF) 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 Murray, M. R. Articles by Hall, J. K. Search for Related Content PubMed Articles by Murray, M. R. Articles by Hall, J. K. Agricola Articles by Murray, M. R. Articles by Hall, J. K.

Sorption-Desorption of Dicamba and 3,6-Dichlorosalicylic Acid in Soils

Dep. of Agronomy, 114 Tyson Building, Pennsylvania State Univ., University Park, PA 16802.

^* Corresponding author.

ABSTRACT

Sorption-desorption of the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) and its metabolite 3,6-dichlorosalicylic acid (DCSA) was studied in soils using experimental conditions that modeled selected physical and chemical properties of soils. Changing the soil/solution ratio (1:1 and 1:10) and temperature (15, 25, and 35 °C) of the soil slurry had no significant effect on sorption of dicamba for the soils studied, except for the Elkton (Typic Ochraoquults) Ap where, at a 1:1 soil/solution ratio, Freundlich constants, Kf, of 0.08 and 0.07 were found at 15 and 25 °C, respectively. The DCSA sorbed to all five soils under all experimental conditions with Kf values ranging from 1.23 for the Evesboro soil (Typic Quartzipsamments) to 34.04 for the Hagerstown Bt soil (Typic Hapludalfs). Changing the soil/solution ratio from 1:1 to 1:10 did not significantly change the Kf, except for the Hagerstown Bt, where an increase in Kf value from 27.54 to 29.79 was obtained. Increasing temperature from 15 to 35 °C generally resulted in a decreased Kf value for DCSA. Both dicamba and DCSA showed increased sorption with decreasing equilibrium solution pH. The percent of sorbed DCSA that was desorbed after two washings with deionized water was 28.2% or less for these soils. Dicamba was readily desorbed (79.2%) after two washings from the Elkton soil. Dicamba showed increased sorption when the Hagerstown Ap was saturated with Fe³⁺, but did not show any response to Cu²⁺, Al³⁺, and Ca²⁺ saturations. The DCSA showed increased sorption to all four cation saturations. A complexation bonding mechanism between DCSA and polyvalent surface cations is proposed. For limed agricultural soils, dicamba would be highly mobile in both topsoil and subsoil matrices. Once dicamba degrades to DCSA, however, sorption can be expected to become significant. Under field conditions, DCSA sorption can be expected to increase with soil depth, especially where soil pH and temperature decrease and exposed surface metal groups increase.

Paper no. 7803 in the Journal Series of the Pennsylvania Agric. Exp. Stn., University Park, PA 16802. Supported by funds from the Northeast Pesticide Agricultural Impact Assessment Program (NAPIAP). USDA Res. Grant no. 82-CRSR-2-2057.

Received for publication November 17, 1987.