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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.

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Background: Soil calcareousness is the major problem in arid and semi arid regions globally since lime induced chlorosis lead to the deficiency of many essential plant nutrients which in turn resulted in reduced growth and yield loss of many crops. To explore the effects of various concentrations of calcium carbonate (CaCO3) on seed germination and seedling growth of groundnut genotypes and to identify CaCO3 stress tolerant and sensitive groundnut genotypes. Methods: The seed germination and seedling growth of ten groundnut genotypes (CO 6, CO 7, TMV 2, TMV 10, TMV 13, TMV 14, VRI 7, VRI 8, ALR 2 and BSR 2) was investigated with CaCO3 concentrations ranging from 1 to 100 mM L-1 for a period of 14 days. Result: The genotypes VRI 8 and TMV 10 showed higher seed germination and seedling growth even at higher CaCO3 concentration (upto 20 mM L-1) and considered as tolerant genotypes. Whereas TMV 2 and VRI 7 exhibited drastic reduction even at 1 mM L-1 and confirms their susceptibility to CaCO3 stress. Higher concentrations of CaCO3 in the growing medium greatly decreased the germination rate, germination index and vitality index but the impact differs with potentials of genotypes studied.

Aims: The present study was conducted to investigate the potentials of amino acids and low molecular weight organic acids, two major components of plant root exudates on phosphorus release from highly calcareous soils. Study Design: Factorial experiment based on completely randomized design was used. Place and Duration of Study: Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India between 21st and 22nd of December 2020. Methodology: An incubation experiment was conducted with two amino acids (glycine and lysine) and four low molecular weight organic acids (citric acid, malic acid, oxalic acid and acetic acid) at seven different concentrations (0, 20, 40, 60, 80 & 100 mM) for assessing their potentials of phosphorus release from highly calcareous soils (>15% free CaCO3). The soils were incubated for a time interval of 5, 10, 20, 30, 60, 120, 240, 960 & 1440 minutes. Available Phosphorus status in the soils treated with both acids were analyzed after the expiry of each incubation time. Results: Organic acids had higher impact on phosphorus release than amino acids. Kinetic data obtained from the experiment were adequately described by Simple elovich (r2 ≥ 0.90, P < .001) and Power function (r2 ≥ 0.80, P < .001) models for both acids. Glycine among amino acids and citric acid among low molecular weight organic acids were highly effective in releasing phosphorus from highly calcareous soils. Conclusion: The experiment concludes that, incubating the highly calcareous soils with 100 mM citric acid for 1440 minutes increased the kinetics of phosphorus release. The Simple elovich model was the best fitted model to explain the phosphorus release from calcareous soils as influenced by amino acids and low molecular weight organic acids.