Fate of the herbicides glyphosate, glufosinate‐ammonium, phenmedipham, ethofumesate and metamitron in two Finnish arable soils

Abstract

The fate of five herbicides (glyphosate, glufosinate-ammonium, phenmedipham, ethofumesate and metamitron) was studied in two Finnish sugar beet fields for 26 months. Soil types were sandy loam and clay. Two different herbicide-tolerant sugar beet cultivars and three different herbicide application schedules were used. Meteorological data were collected throughout the study and soil properties were thoroughly analysed. An extensive data set of herbicide residue concentrations in soil was collected. Five different soil depths were sampled. The study was carried out using common Finnish agricultural practices and represents typical sugar beet cultivation conditions in Finland. The overall observed order of persistence was ethofumesate > glyphosate > phenmedipham > metamitron > glufosinate-ammonium. Only ethofumesate and glyphosate persisted until the subsequent spring. Seasonal variation in herbicide dissipation was very high and dissipation ceased almost completely during winter. During the 2 year experiment no indication of potential groundwater pollution risk was obtained, but herbicides may cause surface water pollution.

Distribution of glyphosate and aminomethylphosphonic acid (AMPA) in agricultural topsoils of the European Union

“…Second, it is well-known that glyphosate and AMPA strongly adsorb and accumulate in the top centimeter(s) of soils (Laitinen et al, 2006;Okada et al, 2016;Yang et al, 2015). As glyphosate and AMPA contents determined in this study are average values for entire topsoil layers up to 15/20 cm depth (a consequence of using topsoil samples from an already established survey), actual contents in the surface layer could be higher than the determined average, implying that the presented potential erosion-driven transport rates of glyphosate and AMPA could be underestimated.…”

“…Here GlyBH are usually applied one (cereals and oilseeds) to three times a year (orchard crops and vines), at recommended rates between 0.72 and 2.88 kg glyphosate ha −1 per treatment, and at a maximum annual application rate of 4.32 kg glyphosate ha −1 (EFSA, 2013(EFSA, , 2015. Numerous laboratory and field studies have been performed to investigate glyphosate and/or AMPA behavior in more detail, especially their transport to the aquatic environment (Al-Rajab and Hakami, 2014;Borggaard and Gimsing, 2008;Daouk et al, 2013;Laitinen et al, 2006Laitinen et al, , 2009 indicating some recognition and concern that these substances can move towards surface waters. At the same time, glyphosate and AMPA are only sporadically detected in deep groundwater systems and at low concentrations (Battaglin et al, 2014;Horth, 2012;Poiger et al, 2017) indicating that the leaching of these compounds is generally unlikely and probably negligible.…”

“…In fact, despite some recent studies on the distribution of glyphosate and AMPA in soils from Argentina (e.g., Aparicio et al, 2013;Lupi et al, 2015;Primost et al, 2017), U.S.A. (e.g., Battaglin et al, 2014;Scribner et al, 2007) or Australia (e.g., Todorovic et al, 2013), in Europe, where the approval for GlyBH use will be decided by the end of 2017, information on occurrence and levels of these substances in soil is still very limited and out of date (Grunewald et al, 2001;Laitinen et al, 2006Laitinen et al, , 2007Laitinen et al, , 2009. The European long term use of GlyBH, as the most sold herbicide in Europe, urgently require monitoring of residues in agricultural soils.…”

Soil and Environmental Health after Twenty Years of Intensive Use of Glyphosate

“…13 Although glyphosate use has increased nearly 15-fold since 1996 14 when glyphosate-resistant GE crops were first introduced, it is only within the last 5 to 10years that assessment of its detrimental effects on soil and environmental health have become the focus of intensive research efforts. Recent findings that glyphosate tends to accumulate and persist in restricted zones of soils and sediments and in rhizospheres [5][6][7]11,12 emphasizes the need to evaluate environmental effects within these specific microhabitats relative to more traditional investigations of such chemicals amended in "bulk" or root-free homogenous soils and expressing concentrations on a "furrow-slice" basis (i.e., using 908,000kg of soil per ha). For a full understanding of effects of potential glyphosate accumulation in soils, long-term studies on persistence are needed on sites receiving annual application and on those that are no longer under GE cropping systems to determine the extent of any carryover of residual glyphosate and AMPA.…”

“…4 Based on a limited number of studies available, glyphosate residues detected in soils of crop production fields range from 25 to 1000μg kg -1 soil. [5][6][7] Concentrations exceeding 1000μg kg -1 of soil have been detected in silt loam soils of northeast Missouri U.S.A. more than one year after the last application (Kremer, unpublished data). As frequency of glyphosate application increases during the crop season and with annual use, residual concentration likely builds up and persists in soils because about 5% of the applied dose reaches the target weed while the remaining amount contacts the soil surface or is released by roots of plants intercepting the glyphosate, and from vegetative residues treated plants during decomposition.…”