Influence of arbuscular mycorrhizal fungi on glyphosate dissipation rate in okra cultivated sodic soil of Tamil Nadu

Abstract

Aim: To elucidate the influence of non target Arbuscular Mycorrhizal (AM) fungi on glyphosate dissipation in okra cultivated sodic soil of Tamil Nadu. Methodology: A field experiment was carried out during Rabi 2017-18 to study the interactive effect of glyphosate and Arbuscular mycorrhizal fungi (AM) on glyphosate dissipation in sodic soil from okra (A. esculentus) grown field. Experiment was laid adopting Randomized Block Design (RBD) with different rates of glyphosate and with and without AM fungi. Glyphosate was applied as pre-plant herbicide 20 days before sowing, and AM biofertilizer was applied as basal before sowing of okra. Soil samples were collected from the field at different time interval after glyphosate application and analysed for glyphosate and Amino Methyl Phosphonic Acid (AMPA) residues. Results: Glyphosate persistence decreased with time and degraded with the mean half-life ranging from 5.09 to 10.35 days by following first order reaction kinetics. AMPA was witnessed from day 1 and increased up to 15th day and followed first order reaction kinetics dissipation with the mean half-life of 8.62 to 13.06 days. Glyphosate and AMPA residues were recorded below detection limit (0.01 mg kg-1) on 45th and 60th days, respectively, in soil. Interpretation: The higher rates of glyphosate showed enhanced persistence of glyphosate and its metabolite AMPA in soil, hence application of AM fungi 100 kg ha-1 with lower glyphosate rate of 6 ml/L can be recommended for okra cultivated sodic soil with the safer waiting period of after 45 days harvest.

Dynamics of Glyphosate and Aminomethylphosphonic Acid in Soil Under Conventional and Conservation Tillage

“…The dissipation of glyphosate and the formation/dissipation of AMPA in the no-till system must therefore be evaluated and compared with that in conventional agriculture to determine whether and to what extent the altered soil properties affect their persistence. Glyphosate dissipation and AMPA formation/ dissipation in agricultural soils have been extensively evaluated both in laboratory (Gimsing et al 2004b;Accinelli et al 2005;Prata et al 2005;Stenrød et al 2006;Weaver et al 2007;Simonsen et al 2008;Zablotowicz et al 2009;Lancaster et al 2010;Aslam et al 2015;Cassigneul et al 2016;Bento et al 2016;Góngora-Echeverría et al 2019;Okada et al 2019) and field studies (Mamy et al 2008;Syan et al 2014;Bandana et al 2015;Yang et al 2015;Guijarro et al 2018;Bento et al 2019;Brindhavani et al 2020). Among the above-cited papers, the studies of Aslam et al (2015) and Bento et al (2019) regarded non-tilled soils exclusively.…”

Herbicides and nutrients interaction on earthworm activity in tomato cultivated soil and toxicity appraisal

“…Then, it dried to a moist level, re-dissolved in acetonitrile and analysed in high-performance liquid chromatography (HPLC). Glyphosate was extracted and analysed, as detailed by Brindhavani et al (2020), using HPLC. The extraction and detection method was validated by performing recovery studies before analysing unknown samples, as described by Janaki et al (2016) for bensulfuron methyl.…”