Influence of soil water holding and transport capacity on glyphosate dynamics in two agricultural soils from Pampas Region

Water dynamics is one of the most important regulating factors on glyphosate fate in agricultural soils. The objectives of this work were: i- to determine static and dynamic soil physical quality (SPQ) indicators during the crop cycle in two different textured soils from Argentinean Pampas Region, under no tillage (NT) and conventional tillage (CT); ii- to quantify glyphosate accumulation during the crop cycle in two different textured soils of Argentinean Pampas Region under NT and CT; and iii- to determine the relationship between glyphosate accumulation and vertical transport during the crop cycle with the static and dynamic SPQ indicators. Static and dynamic SPQ indicators and Total Extractable Glyphosate (TEG) were determined in a silty loam typic Argiudoll (Pergamino site, PER) and in a sandy loam Entic Haplustoll (Dorila site, DOR) at the beginning and the end of the crop cycle. In general, soils under NT showed higher values of plant available water content (PAWC) and lower values of saturated hydraulic conductivity (K-0) as compared with CT. PER showed higher values of water content at wilting point (theta(wp)), as compared with DOR. High values of theta(wp), along with low values of K-0 were correlated to glyphosate accumulation, especially in the top soil. On the other hand, high values of K-0 may favor vertical transport, as was observed under CT for PER. Our results show that repeated glyphosate application could lead to its accumulation in agricultural soils, depending of the soil type and tillage systems, implying a potential risk of soil pollution.