title: Effects of phosphate on the adsorption of glyphosate on three different types of Chinese soils.
abstract: Glyphosate (GPS) is a non-selective, post-mergence herbicide that is widely used throughout the world. Due to the similar molecular structures of glyphosate and phosphate, adsorption of glyphosate on soil is easily affected by coexisting phosphate, especially when phosphate is applied at a significant rate in farmland. This paper studied the effects of phosphate on the adsorption of glyphosate on three different types of Chinese soils including two variable charge soils and one permanent charge soil. The results indicated that Freundlich equations used to simulate glyphosate adsorption isotherms gave high correlation coefficients (0.990-0.998) with K values of 2751, 2451 and 166 for the zhuanhong soil(ZH soil, Laterite), red soil(RS, Udic Ferrisol) and Wushan paddy soil (WS soil, Anthrosol), respectively. The more the soil iron and aluminum oxides and clay contained, the more glyphosate adsorbed. The presence of phosphate significantly decreased the adsorption of glyphosate to the soils by competing with glyphosate for adsorption sites of soils. Meanwhile, the effects of phosphate on adsorption of glyphosate on the two variable charge soils were more significant than that on the permanent charge soil. When phosphate and glyphosate were added in the soils in different orders, the adsorption quantities of glyphosate on the soils were different, which followed GPS-soil > GPS-P-soil = GPS-soil-P > P-soil-GPS, meaning a complex interaction occurred among glyphosate, phosphate and the soils.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Yu-Jun
authors.initials: YJ
authors.lastname: Wang
authors.forename: Dong-mei
authors.initials: DM
authors.lastname: Zhou
authors.forename: Rui-juan
authors.initials: RJ
authors.lastname: Sun
mesh_terms: D000327:Adsorption; D002681:China; D002851:Chromatography, High Pressure Liquid; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000737:chemistry*; D012987:Soil / Q000032:analysis*; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D010710:Phosphates; D012987:Soil; D000097797:Glyphosate