Main content area

Field mobility and persistence of alginate controlled release formulations of atrazine

Johnson, R. M., Pepperman, A. B., Selim, H. M.
Soil science 1998 v.163 no.1 pp. 46
clay soils, atrazine, alginates, encapsulation, leaching, detection, monitoring, enzyme immunoassays, Louisiana
The mobility and persistence of alginate-encapsulated controlled release (CR) formulations of atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine -2,4-diamine] were compared with commercial formulations of atrazine in field studies on a Sharkey clay soil. Commercial and CR formulations were applied at a rate of 2.24 kg active ingredient ha to 30-m plots planted to sugarcane (second stubble). Three replications of each treatment were included in a randomized complete block design. Soil samples were taken at several depths by extraction with methanol, and the atrazine content was determined by enzyme immunoassay (EIA). A subset of the samples was analyzed by a gas chromatograph-electron capture detector (GC-ECD) for comparison purposes. The results indicated that CR formulations provided greater retention of atrazine in the soil surface horizon than was observed for the commercial liquid formulation. Although all formulations exhibited a decrease in surface concentrations by the last sampling period (4.5 months after application), CR formulations were slightly more persistent than the commercial formulation. Neither the commercial nor the controlled release formulation increased the amount of atrazine leached into subsoils. Enzyme immunoassay results correlated well with GC-ECD (r = 0.76***, n = 27; r = 0.85***, n = 26). The EIA method predicted slightly higher atrazine concentrations than the GC method and also gave false-positive results. It was hypothesized that atrazine metabolites were responsible for these effects. The EIA antibody used for this work is known to cross-react with these compounds. Despite the cross-reactivity observations, significant differences were still observed between atrazine formulations and sampling dates.