GLYPHOSATE SORPTION IN SOILS OF DIFFERENT pH AND PHOSPHORUS CONTENT
- 1 April 2001
- journal article
- Published by Ovid Technologies (Wolters Kluwer Health) in Soil Science
- Vol. 166 (4), 230-238
- https://doi.org/10.1097/00010694-200104000-00002
Abstract
The sorption mechanism of glyphosate, one of the most frequently used herbicides in the world, resembles that of phosphate. This study quantifies the variation in glyphosate sorption and desorption to a coarse sandy soil and to a sandy loam soil with varying phosphorus content and pH. Using batch experiments, glyphosate adsorption and desorption isotherms were determined on soil samples taken from long-term field experiments that received different additions of phosphorus and lime during 60-year (coarse sand) and 100-year (sandy loam) periods. Sorption isotherms were non-linear and manifested adsorption desorption non-singularity. The isotherms were best fitted with an extended Freundlich model, which had earlier been shown to describe phosphate sorption data well. The phosphate content in the soils had a significant influence on the sorption of glyphosate. With 0.5 M bicarbonate extractable P (pH 8.5) increasing from 6.2 to 58.7 in the loamy sand and 9.1 to 87.4 in the coarse sand, the extended Freundlich adsorption coefficient (Kf,MF,ads) decreased from 214.7 to 106 and from 154.0 to 83.5, respectively. Liming of the coarse sandy soil resulted in stronger glyphosate sorption because of an increase of reactive amorphous aluminum and iron hydrous oxides with increasing pH values. Glyphosate competes with phosphate for sorption sites, a quality that might result in glyphosate being sorbed more weakly in soils with high phosphorus levels.This publication has 14 references indexed in Scilit:
- [14C]Glyphosate transport in undisturbed topsoil columnsPest Management Science, 2000
- Influence of pH and solution composition on the sorption of glyphosate and prochloraz to a sandy loam soilChemosphere, 1999
- Adsorption of Glyphosate by Humic SubstancesJournal of Agricultural and Food Chemistry, 1996
- Hydrogen‐bonding interactions between the herbicide glyphosate and water‐soluble humic substancesEnvironmental Toxicology and Chemistry, 1994
- Adsorption and desorption of glyphosate in some European soilsJournal of Environmental Science and Health, Part B, 1994
- Sorption of lonisable organic compounds by field soils. Part 2: Cations, bases and zwitterionsPesticide Science, 1991
- Adsorption of glyphosate by soils and clay mineralsJournal of Agricultural and Food Chemistry, 1987
- Adsorption of glyphosate by soilsPesticide Science, 1976
- Adsorption, Mobility, and Microbial Degradation of Glyphosate in the SoilWeed Science, 1975
- Rapid Inactivation of Glyphosate in the SoilWeed Science, 1975