A field experiment was carried out during Rabi 2017-18 to study the effect of glyphosate on Arbuscular mycorrhizal fungi (AM) activity in sodic soil and Okra (A. esculentus) growth at Anbil Dharmalingam Agricultural College & Research Institute, Tiruchirapalli. Experiment was conducted in Randomized Block Design (RBD) with seven treatments viz., control, AM 100 kg ha-1, glyphosate 12 ml.L-1, AM + different rates of glyphosate @ 6, 12, 18 and 24 ml.L-1 and were replicated thrice. The glyphosate was applied as pre plant herbicide 20 days before sowing and AM bio fertilizer was applied as basal before sowing of A. esculentus. Results showed that the increased rates of glyphosate decreased the root colonization and AM spore was only 19.00 and 20.67 (no/100 g of soil) at flowering and harvest stages respectively in AM fungi plus double dose of glyphosate (24 ml.L-1) applied plot. Significantly higher root colonization and AM spore was recorded by AM alone applied plot and also increased the soil available P status at harvest significantly. The AM application over control increased the colonization percentage as well as spore count (no/100 g of soil) to the tune of 66-69 and 55-59 per cent, respectively and showed that the native AM viability is very low in sodic soil. The higher rates of glyphosate plus AM application reduced the root and leaf efficiency of A. esculentus and also delayed the days to 1st and 50% flowering.
Key words : Abelmoschus esculentus, Glyphosate, AM fungi, Root colonization, Spores, Sodic soil