Linkage between glyphosate adsorption/desorption and mineralization in Central European agricultural soils

The pesticides bioavailability in soil is primarily governed by sorption behaviors of soil. This study aimed to study adsorption, desorption, and bioavailability of glyphosate in agricultural soils and to find relationships to its mineralization. We examined 21 soil samples from Germany and Slovenia, varied widely in soil texture (8 – 86% sand), soil organic matter (1.2 – 4.5%), pH (5.0 – 7.1), exchangeable ions (7.5 – 32.9 mmolc 100 g-1) parameters. A batch experiment based on OECD guideline 106 was utilized to assess adsorption/desorption characteristics in soil of the herbicide glyphosate. Experimental results indicated that glyphosate was strongly adsorbed (77 and 100%) at Kelheim and Brezje soils, and weakly desorbed (5.7 and 49.0 %) at Brezje and Skrinjar soils, respectively. A significant variance in glyphosate mineralization was observed across different soils. Among evaluated parameters, exchangeable acidity was found to be the primary factor influencing adsorption and desorption of glyphosate, revealing a significant negative correlation at p<0.0001. Additionally, a statistically significant relationship (R2 = 0.5299 at p=0.0002) was obtained between adsorption/desorption and mineralization in soils of glyphosate herbicide. The study revealed that adsorption/desorption of glyphosate is heavily influenced by exchangeable acidity, and the mineralization of glyphosate is closely tied to a soil's capacity for glyphosate adsorption/desorption.