Effects of Incorporated Corn Residues on Glyphosate Mineralization and Sorption in Soil

In modern agricultural systems employing conservation tillage practices, glyphosate is widely used as a preplant burndown herbicide in a wide range of crops. Conservation tillage systems are characterized by a significant presence of crop residues at the soil surface so that glyphosate is applied to a soil matrix rich in poorly decomposed crop residues. Incorporation of corn residues in the range from 0.5 to 4% caused different effects on mineralization and sorption of [14C]glyphosate in sandy and sandy loam soils. More specifically, low levels of incorporated corn residues did not affect or slightly stimulated herbicide mineralization in the sandy and sandy loam soils, respectively. In the sandy soil, incorporation of the highest level of corn residues (4%) caused a decrease in [14C]glyphosate mineralization. [14C]Glyphosate sorption on both soil types was reduced in samples receiving high amounts of incorporated corn residues. Keywords: Glyphosate; corn residues; herbicide sorption; herbicide mineralization; genetically modified corn