The use of glyphosate-based herbicides (GBHs) in industrial agriculture has intensified in the past decades, causing a growing concern about the occurrence and spatial distribution of glyphosate and its principal metabolite, aminomethylphosphonic acid (AMPA), in the environment. In 2014, glyphosate and AMPA content was measured in 45 soils from the St. Lawrence Lowlands (Quebec, Canada) before seeding and at harvest in soybean field crops using various weed management practices with or without GBH applications. At the same time, a recent history of agricultural practices and soil conditions was compiled for the sampled sites. The results of the study show that 91% of the samples contained detectable amount of either glyphosate or AMPA, with maximum values of 0.47 mg·kg−1 and 1.16 mg·kg−1 for glyphosate and AMPA, respectively. Surprisingly, detectable amounts of AMPA were measured in fields not treated with GBHs in 2014, whereas traces of both glyphosate and AMPA were detected in organic field crops, highlighting the potential spreading and/or persistence of both compounds in the environment. Glyphosate content was significantly higher in clay soils rich in exchangeable cations, such as Mg2+, K+ and Ca2+, which can contribute to the retention of glyphosate in soil via complexation processes.
Riparian buffer strips (RBS) are encouraged to control agricultural diffuse pollution. In Quebec Province, Canada, a policy promotes 3-m-wide RBS. Abiding farmers minimally maintain herbaceous vegetation, but nutrient retention efficiency could be improved with woody biomass. This work aimed to assess if fast-growing willows (Salix miyabeana Seemen 'SX64') could reduce nutrient loads to a stream, in addition to yielding biomass. Triplicate treatments of two Salix stem densities and a herbaceous control plot were monitored from 2011 to 2013 in a randomized block design on agricultural fields of the St. Lawrence Lowlands with sandy loam (Saint-Roch-de-l'Achigan [SR]) and organicrich (Boisbriand [BB]) soils. Runoff, interstitial water, and water from the saturated zone were sampled 16 (SR) and 14 (BB) times to quantify nutrient buffering (NO 3 − , NH 4 + , P, and K). Sampling campaigns followed (i) snowmelt or ³15-mm natural precipitation events after (ii) fertilization and (iii) glyphosatebased herbicide applications. Concentration reduction before and after the RBS was highest for nitrates (77-81% in runoff at BB, 92-98% at 35-to 70-cm depth at SR) just after fertilization, when edge-of-field concentrations peaked. Total P removal was observed in runoff after fertilization at SR, and K removal was punctually witnessed at BB. Riparian buffer strips were inefficient for NH 4 and dissolved P removal, and RBS effluents exceeded aquatic life protection standards. Salix plantations, irrespective of stem density, were not more efficient than herbaceous RBS. This shows that without fertilizer input reductions, narrow RBS are insufficient to protect streams from excess nutrients in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] crops.
Glyphosate-based herbicide (GBH)
applications were reported to
induce physiological damages to glyphosate-resistant (GR) soybean,
which were mainly attributed to aminomethylphosphonic acid (AMPA).
In order to study glyphosate and AMPA dynamics in plants and associated
phytotoxic effects, a greenhouse experiment was set where GR soybeans
were exposed to GBH (0.7 to 4.5 kg glyphosate ha–1) and sampled over time (2, 7, 14, and 28 days after treatment (DAT)).
Hydrogen peroxide content increased 2 DAT, while a decrease was observed
for the effective quantum yield (2, 7, 14 DAT), stomatal conductance
(2 DAT), and biomass (14 DAT). Glyphosate content was higher in leaves,
followed by stems, and then roots. AMPA content tended to increase
with time, especially in roots, and the amount of AMPA in roots was
negatively correlated to mostly all phytotoxicity indicators. This
finding is important since AMPA residues are measured in agricultural
soils several months after GBH applications, which could impact productivity
in GR crops.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.