title: Polynomial response of 2,4-D mineralization to temperature in soils at varying soil moisture contents, slope positions and depths.
abstract: The herbicide 2,4-D [2,4-(dichlorophenoxy) acetic acid] is a widely used broadleaf control agent in cereal production systems. Although 2,4-D soil-residual activity (half-lives) are typically less than 10 days, this herbicide also has as a short-term leaching potential due to its relatively weak retention by soil constituents. Herbicide residual effects and leaching are influenced by environmental variables such as soil moisture and temperature. The objective of this study was to determine impacts of these environmental variables on the magnitude and extent of 2,4-D mineralization in a cultivated undulating Manitoba prairie landscape. Microcosm incubation experiments were utilized to assess 2,4-D half-lives and total mineralization using a 4 × 4 × 3 × 2 factorial design (with soil temperature at 4 levels: 5, 10, 20 and 40°C; soil moisture at 4 levels: 60, 85, 110, 135 % of field capacity; slope position at 3 levels: upper-, mid- and lower-slopes; and soil depth at 2 levels: 0-5 cm and 5-15 cm). Half-lives (t(½)) varied from 3 days to 51 days with the total 2,4-D mineralization (M(T)) ranging from 5.8 to 50.9 %. The four-way interaction (temperature × moisture × slope × depth) significantly (p < 0.001) influenced both t(½) and M(T). Second-order polynomial equations best described the relations of temperature with t(½) and M(T) as was expected from a biological system. However, the interaction and variability of t(½) and M(T) among different temperatures, soil moistures, slope positions, and soil depth combinations indicates that the complex nature of these interacting factors should be considered when applying 2,4-D in agricultural fields and in utilizing these parameters in pesticide fate models.
authors.affiliation: Department of Soil Science, University of Manitoba, Winnipeg, Canada. wilsonj@cc.umanitoba.ca
authors.forename: Janna L
authors.initials: JL
authors.lastname: Shymko
authors.forename: Annemieke
authors.initials: A
authors.lastname: Farenhorst
authors.forename: Francis
authors.initials: F
authors.lastname: Zvomuya
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis / Q000737:chemistry*; D000327:Adsorption; D004784:Environmental Monitoring; D006207:Half-Life; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D006813:Humidity; D008350:Manitoba; D012987:Soil / Q000032:analysis / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis* / Q000378:metabolism*; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D015084:2,4-Dichlorophenoxyacetic Acid