Phosphate fertilizer impacts on glyphosate sorption by soil

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dc.contributor.authorMunira, Sirajum
dc.contributor.authorFarenhorst, Annemieke
dc.contributor.authorFlaten, Don
dc.contributor.authorGrant, Cynthia
dc.date.accessioned2016-10-04T20:51:12Z
dc.date.available2016-10-04T20:51:12Z
dc.date.issued2016-05
dc.description.abstractThis research examined the impact of field-aged phosphate and cadmium (Cd) concentrations, and fresh phosphate co-applications, on glyphosate sorption by soil. Soil samples were collected in 2013 from research plots that had received, from 2002 to 2009, annual applications of mono ammonium phosphate (MAP) at 20, 40 and 80 kg P ha-1 and from products containing 0.4, 70 or 210 mg Cd kg-1 as an impurity. A series of batch equilibrium experiments were carried out to quantify the glyphosate sorption distribution constant, Kd. Extractable Cd concentrations in soil had no significant effect on glyphosate sorption. Glyphosate Kd values significantly decreased with increasing Olsen-P concentrations in soil, regardless of the pH conditions studied. Experiments repeated with a commercially available glyphosate formulation showed statistically similar results as the experiments performed with analytical-grade glyphosate. Co-applications of MAP with glyphosate also reduced the available sorption sites to retain glyphosate, but less so when soils already contain large amounts of phosphate. Glyphosate Kd values in soils ranged from 173 to 939 L kg-1 under very strong to strongly acidic condition but the Kd was always < 100 L kg-1 under moderately acidic to slightly alkaline conditions. The highest Olsen-P concentrations in soil reduced Kd values by 25-44% relative to control soils suggesting that, under moderately acidic to slightly alkaline conditions, glyphosate may become mobile by water in soils with high phosphate levels. Otherwise, glyphosate residues in agricultural soils are more likely to be transported off-site by wind and water-eroded sediments than by leaching or runoff.en_US
dc.description.sponsorshipThe authors would like to acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC) for providing funds for the research, and the University of Manitoba Graduate Fellowship (UMGF), Manitoba Graduate Scholarship (MGS) for stipend to Sirajum Muniraen_US
dc.identifier.citationMunira, S., Farenhorst, A., Flaten, D., Grant, C. (2016). Phosphate fertilizer impacts on glyphosate sorption by soil. Chemosphere. 153: 471-477.en_US
dc.identifier.urihttp://hdl.handle.net/1993/31877
dc.publisherElsevieren_US
dc.rightsopen accessen_US
dc.subjectGlyphosateen_US
dc.subjectBatch equilibrium experimenten_US
dc.subjectSorption distribution constanten_US
dc.subjectMono ammonium phosphateen_US
dc.subjectCadmiumen_US
dc.subjectCompetitive effecten_US
dc.titlePhosphate fertilizer impacts on glyphosate sorption by soilen_US
dc.typeArticleen_US
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