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 Williams, C. F. Articles by Gish, T. J. Search for Related Content PubMed Articles by Williams, C. F. Articles by Gish, T. J. GeoRef GeoRef Citation Agricola Articles by Williams, C. F. Articles by Gish, T. J.

Release Rate and Leaching of Starch-Encapsulated Atrazine in a Calcareous Soil

Dep. of Soil and Environmental Sciences, Univ. of California, Riverside, CA 92521

S. D. Nelson

Dep. of Agronomy and Horticulture, Brigham Young Univ., Provo, UT 84602

T. J. Gish

USDA-ARS Hydrology Lab., Beltsville, MD 20705

^* Corresponding author (williamc{at}mail.ucr.edu).

ABSTRACT

Starch encapsulation (SE) has been proposed as a mechanism for minimizing the impact of atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] on the environment. A two-part study was conducted to evaluate: (i) atrazine release rate as a function of starch granule size, temperature, and water potential; and (ii) to compare the leaching of SE atrazine with the leaching of a commercial formulation in a calcareous soil. Atrazine release-rates from the starch granules were determined as a function of three granule sizes (1.40-0.85, 0.85-0.43, and <0.43 mm) at five temperatures (4, 10, 20, 25, and 35°C), and five matric potentials (0, –0.1, –0.5, –1.0, and –1.5 MPa). Atrazine release-rates from the starch granules increased with decreasing granule size, increasing temperature, and increasing water potential. To evaluate leaching as a function of atrazine formulation, each starch-encapsulated granule size, commercial formulation, and control treatment was replicated six times in irrigated soil columns (0.188 m² x 0.25 m). A pulse of bromide (10.7 kg Br^- ha^-1) and atrazine (1.7 kg ha^-1) were coapplied to the soil columns and effluent concentrations monitored. Irrigation events of 55 mm in 5 h were applied through drip emitters at 10-d intervals for 120 d for a total application of 11.5 pore volumes. Averaged bromide breakthrough curves for each soil column treatment were similar, which indicated that differences in the averaged atrazine mobilities were a result of formulation and not of heterogeneity in the soil matrix. Starch-encapsulated atrazine leaching decreased with increasing granule size; however, all SE formulations were less mobile than the commercial formulation. After 11.5 pore volumes and 120 d, >52% of the commercial atrazine had leached through the soil columns, compared with <38% for the smallest starch granule size and 11% for the largest granule. Starch-encapsulated formulations may be an effective tool for reducing pesticide leaching in calcareous soils.

Received for publication February 12, 1998.