Glyphosate herbicide affects belowground interactions between earthworms and symbiotic mycorrhizal fungi in a model ecosystem

Abstract

Herbicides containing glyphosate are widely used in agriculture and private gardens, however, surprisingly little is known on potential side effects on non-target soil organisms. In a greenhouse experiment with white clover we investigated, to what extent a globally-used glyphosate herbicide affects interactions between essential soil organisms such as earthworms and arbuscular mycorrhizal fungi (AMF). We found that herbicides significantly decreased root mycorrhization, soil AMF spore biomass, vesicles and propagules. Herbicide application and earthworms increased soil hyphal biomass and tended to reduce soil water infiltration after a simulated heavy rainfall. Herbicide application in interaction with AMF led to slightly heavier but less active earthworms. Leaching of glyphosate after a simulated rainfall was substantial and altered by earthworms and AMF. These sizeable changes provide impetus for more general attention to side-effects of glyphosate-based herbicides on key soil organisms and their associated ecosystem services.

Effect of conventional and organic orchard floor management practices on arbuscular mycorrhizal fungi in a ‘Cripp’s Pink’/M7 apple orchard soil

“…Negative effects of glyphosate, supportive of the findings in the present study, have been recently reported by Druille et al (2013) and Zaller et al (2014). Causes of negative effects may be direct, i.e., damage to the external hyphae and/or AM spores, or indirect, as where root exudate production is reduced by the herbicideinduced death of targeted host plants, as in T1 and T2 at Elgin, where the tree rows were kept mainly weed-free with glyphosate.…”

Anecic earthworms (Lumbricus terrestris) alleviate negative effects of extreme rainfall events on soil and plants in field mesocosms

“…It should be noted, however, that water infiltration is highly heterogeneous in space (Hassler et al 2014), and that the experiment was performed in intact soil, rather than in a homogenised substrate. Water infiltration may indeed be unpredictable even under highly controlled conditions: for instance, in a greenhouse experiment that simulated a heavy rainfall event similar to ours (40 mm), anecic earthworms increased water infiltration (Zaller et al 2011), but the effect was not repeatable in a subsequent experiment with similar methodology (Zaller et al 2014).…”

Short-term transport of glyphosate with erosion in Chinese loess soil — A flume experiment

“…With the increased use of glyphosate-based herbicides, the occurrence of glyphosate and its metabolite AMPA derived from intensive agriculture triggers great attention being paid on the risks of glyphosate in environment (Qiu et al, 2013;Zaller et al, 2014). In highly erodible land, together with runoff and suspended load, glyphosate and AMPA, supposedly, are transported, deposited, and probably accumulated in nearby areas (Ulén et al, 2014).…”

“…The repetitive use of glyphosate-based herbicides in the field, however, increases the possibility of glyphosate occurrence in, and threat to, soil, plants, surface/ground water (Borggaard and Gimsing, 2008), and animals (Lanctot et al, 2013;Muangphra et al, 2014;Yadav et al, 2013;Zaller et al, 2014). Meanwhile, the risk is particularly high when applied pesticide on bare soil directly before and after sowing.…”