452-20 Predicting Variations in the Glyphosate Sorption Coefficient Across Two Loamy Agricultural Fields.

Poster Number 1523

See more from this Division: SSSA Division: Soil Physics
See more from this Session: General Environmental Soil Physics and Hydrology: II
Wednesday, November 5, 2014
Long Beach Convention Center, Exhibit Hall ABC
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Trine Norgaard1, Marcos Paradelo2, Per Moldrup Sr.3, Ty Paul Ferre4, Inoka Damayanthi Kumari Kahawaththa Gamage2 and Lis W. de Jonge1, (1)Department of Agroecology, Aarhus University, Tjele, Denmark
(2)Aarhus University, Tjele, Denmark
(3)Aalborg Univ Sohngaardsholmsvej 57 D-building, Aalborg University, Aalborg, Denmark
(4)University of Arizona, Tucson, AZ
Poster Presentation
  • Poster Long Beach.pdf (1.7 MB)
  • Its efficiency has made glyphosate one of the most frequently used herbicides worldwide, but continuous detections of glyphosate and its metabolite (AMPA) in groundwater call for improved understandings and solutions. The risk for glyphosate groundwater contamination is strongly influenced by glyphosate sorption. Texture, organic matter content, solution pH, ionic strength, soil mineralogy, and phosphorus content may among other things all affect glyphosate sorption characteristics, and across fields-scale areas these parameters may be highly variable. Predictive models are needed to assess the spatial variability of the glyphosate sorption coefficient Kd.

    Sampling of 110 soil samples was carried out in 15 m x 15 m grids on two loamy, agricultural fields in Silstrup (clay content: 0.14 - 0.19 kg kg-1) and Estrup (clay content: 0.06 - 0.14 kg kg-1), Denmark. Soil texture, organic carbon, soil pH and electrical conductivity, oxalate-extractable aluminum (Alox), iron (Feox) and phosphorus (Pox), Olsen-phosphorus (Olsen-P) and glyphosate Kd were determined on all soil samples. In Silstrup and Estrup Kd varied from 344-667 L kg-1 and 161-535 L kg-1, respectively. The higher Kd in Silstrup was likely caused by higher contents of clay and Feox due to glyphosates sorption affinity to soil minerals. In single linear correlations, Kd for Silstrup showed the best, negative correlation with Olsen-P (R2=0.20) and next best, positive correlation with clay (R2=0.19), whereas for Estrup Kd showed the best, positive correlation with Feox (R2=0.73) and clay (R2=0.52).

    Multiple linear regressions were carried out to obtain the best-four set of parameters to explain the variations in Kd. For Silstrup the best-four set consisted of the parameters clay, EC, silt and sand (R2=0.37), and for Estrup the best-four set included clay, pH, Feox and Olsen-P (R2=0.87).  A best common subset representing the same best-four set of parameters for both fields comprised clay, pH, Feox, and Olsen-P (R2=0.59) - the same best-four set as for Estrup separately.

    See more from this Division: SSSA Division: Soil Physics
    See more from this Session: General Environmental Soil Physics and Hydrology: II