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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Pearson, R. J. Articles by Comfort, S. D. Search for Related Content PubMed Articles by Pearson, R. J. Articles by Comfort, S. D. Agricola Articles by Pearson, R. J. Articles by Comfort, S. D.

Observed and Simulated Solute Transport Under Varying Water Regimes: II. 2,6-Difluorobenzoic Acid and Dicamba

Dep. of Plant, Soil and Environmental Science, Montana State Univ., Bozeman, MT 59717-0312;

S. D. Comfort

Dep. of Agronomy, Univ. of Nebraska, Lincoln, NE 68583-0915.

^* Corresponding author (usswi{at}msu.oscs.montana.edu).

ABSTRACT

Significant interest in the fate of agrichemicals in soils has prompted the development of several transport simulation models. Our primary objective was to evaluate the simulation model LEACHM for predicting the fate of dicamba (3,6-dichloro-2-methoxybenzoic acid) and a nonreactive tracer, 2,6-difluorobenzoic acid (2,6-DFBA) in fallow and cropped (barley, Hordeum vulgare L.) systems under different water application levels. A field study (1992) was conducted using in situ soil columns on a Borollic Calciorthid (Brocko silt loam, Gallatin Co., MT). Dicamba (¹⁴C-labeled) and 2,6-DFBA were surface applied at rates of 0.26 and 112 kg ha^–1, respectively. Solute concentrations were measured at three depths (0.36, 0.66, and 0.96 m) using porous cup lysimeters for 70 d following chemical application. Time-moment analysis of observed solute breakthrough curves (BTCs) generally showed increasing travel times with increasing soil depth and decreasing water application. Dicamba transport was similar to 2,6-DFBA, with the exception that 40 to 60% of applied dicamba was degraded during transport. The distribution of ¹⁴C remaining in the soil columns showed that the primary degradate of dicamba, 3,6-dichlorosalicylic acid (DCSA), was confined primarily to surface samples (0–0.2 while dicamba was found only at lower depths. This is consistent with a much higher sorption coefficient (K_oc) determined for DCSA relative to dicamba. Comparison of observed and predicted (LEACHM) solute BTCs suggested that preferential solute transport occurred especially under high and medium water regimes. Finally, data from three field seasons at the same site suggest that the timing of chemical application relative to initial soil water content and plant stage, the presence of root channels, and temporal changes in soil hydraulic properties in the absence of tillage may significantly affect the degree of preferential flow and subsequent agreement between predicted and observed BTCs.

Contribution of the Montana Agric. Exp. Stn., Journal no. J-5003.

Received for publication April 10, 1995.

This article has been cited by other articles:

				J.W. Roy, J.C. Hall, G.W. Parkin, C. Wagner-Riddle, and B.S. Clegg Seasonal Leaching and Biodegradation of Dicamba in Turfgrass J. Environ. Qual., July 1, 2001; 30(4): 1360 - 1370. [Abstract] [Full Text] [PDF]