Glyphosate dynamics prediction in a soil under conventional and no-tillage systems during the crop cycle

Abstract

Simulation models are efficient tools to predict the fate of different solutes in agricultural soils. This work aimed to compare measured and predicted glyphosate and AMPA (aminomethyl phosphonic acid; its main metabolite) contents in a soil under no-tillage (NT), and conventional tillage (CT); and to compare the predictions considering constant and time-variable hydraulic properties. Additionally, we evaluated the ability of the model to predict glyphosate and AMPA accumulation during the crop cycle. Hydrus 1-D code was used to predict the glyphosate and AMPA dynamics, considering constant and time-variable hydraulic properties during the studied crop cycle. In general, the prediction of glyphosate and AMPA distribution along the soil profile using HYDRUS 1-D was satisfactory; however, an overestimation of both compounds was observed in the first 0.20 m of the soil probably because of the preferential flow. Additionally, the accumulation process of glyphosate and AMPA in the soil during the crop cycle was underestimated by HYDRUS 1-D, as compared with the observed field data. Simulated data show that higher values of K 0 increase the risk of glyphosate and AMPA vertical transport. The inclusion of temporal variation of hydraulic properties in glyphosate and AMPA simulation did not improve the simulation performance, showing that the model is more sensitive to the parameters related to the solutes. From the obtained results, HYDRUS 1-D code allowed to predict glyphosate and AMPA dynamics reasonably well in agricultural soils of the Argentinean Pampas region and is a potential model to give support in the analysis of the environmental risk of leaching and soil contamination.

Glyphosate and aminomethyphosphonic (AMPA) contents in Brazilian field crops soils

“…The most accepted explanation for soluble glyphosate vertical migration is by preferential solute transport through macropores (Borggaard & Gimsing 2008, Candela et al 2010, Laitinen et al 2006, Soracco et al 2018. Translocation by roots degradation (Laitinen et al 2006), higher hydraulic conductivity (Soracco et al 2018, Villarreal et al 2020) and factors decreasing glyphosate adsorption such as higher soil pH and phosphate content (Borggaard & Gimsing 2008, Okada et al 2016) are other invoked processes enhancing vertical migration of glyphosate. As glyphosate progresses downward into the soil, the bioactivity of microfauna decreases and so does the glyphosate degradation into AMPA (Bento et al 2016, Bergström et al 2011, Cecilia & Maggi 2017.…”