Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: MAINTAINING SOIL RESOURCES FOR EFFECTIVE CONSERVATION AND HERBICIDE MANAGEMENT IN MID-SOUTH CROP PRODUCTION

Location: Crop Production Systems Research Unit

Title: Enhanced Degradation and Soil Depth Effects on the Fate of Atrazine and Major Metabolites in Colorado and Mississippi Soils

Authors
item Krutz, Larry
item SHANER, DALE
item Zablotowicz, Robert

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2010
Publication Date: May 25, 2010
Citation: Krutz, L.J., Shaner, D.L., Zablotowicz, R.M. 2010. Enhanced Degradation and Soil Depth Effects on the Fate of Atrazine and Major Metabolites in Colorado and Mississippi Soils. Journal of Environmental Quality, 39:1369-1377.

Interpretive Summary: This study was conducted to compare degradation of the herbicide atrazine in soil collected from different depths and herbicide use histories. Pooled across depth, 50% of applied atrazine remained in soil 2 months after application when there was no prior exposure history; conversely, less than 50% of the herbicide remained after six days in soils with a prior exposure history. Results from this study will allow USEPA and USDA-ARS modelers to more accurately predict the herbicide’s off-site movement and subsequent environmental impact on surface and ground water quality.

Technical Abstract: This report’s aim is to inform modelers of the differences in atrazine fate between s-triazine-adapted and non-adapted soils as a function of depth in the profile, and to recommend input values for pesticide process sub-modules. The specific objectives of this study were to estimate the atrazine-mineralizing bacterial population (AMBP), cumulative atrazine mineralization, atrazine persistence and metabolite [desethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA)] formation/dissipation in CO and MS s-triazine-adapted and non-adapted soils at three depths (0- to 5-cm, 5- to 15-cm, and 15- to 30-cm). Regardless of depth, the AMBP and cumulative atrazine mineralization was at least 4.9- fold higher in s-triazine-adapted than non-adapted soils. Atrazine half-life (T½) values pooled over non-adapted soils and depths approximated historic estimates, T1/2 = 61 d. Atrazine persistence in all depths of s-triazine-adapted soils, however, was at least 4-fold lower than that of the non-adapted soil. Atrazine metabolite concentrations were typically lower in s-triazine-adapted than non-adapted soil after 35 d of incubation, regardless of depth. Results indicate (i) accurate modeling of atrazine fate and transport will require modelers to discriminate between s-triazine-adapted and non-adapted soils; ii) an atrazine half-life of 6 d is advised for s-triazine-adapted soils, while a half-life of 60 d is recommended for non-adapted soils; iii) best estimates for DEA, DIA, and HA half-life values in non-adapted soils is 52 d, 36 d, and 60 d, respectively. Conversely, the recommended half-life for DEA, DIA, and HA in s-triazine-adapted soils is 10 d, 8 d, and 6 d, respectively; iv) the default maximum half-life factor, i.e., the multiple of the near-surface half-life that the half-life reaches at 100 cm, of 10 is accurate for non-adapted soils, but it is likely that the value must be set greater than 10 for s-triazine-adapted soils; and v) a reasonable estimate for amount of atrazine degraded to DEA, DIA, and HA in non-adapted soils is 10%, 72%, and 18%, respectively; conversely, the recommended estimate for s-triazine-adapted soils is 71% for HA, 23% for DEA, and 6% for DIA. Future field-scale modeling efforts, however, are required to verify these predictions.

Last Modified: 7/25/2014
Footer Content Back to Top of Page