Efficacy of herbicides on weed control, rhizospheric micro-organisms, soil properties and leaf qualities in tea plantation

Field trials were conducted in Tarai region of Jalpaiguri, West Bengal, India (26°88 N latitude; 88°32 E longitude, and 122 m above mean sea level) under natural weed infestations in tea garden during 2017 and 2018 to evaluate the efficacy of herbicides on weed flora, non-target soil organisms, leaf quality and productivity of tea (var. TV-23). The pattern of nutrient uptake and soil physicochemicals properties were also itemized. The treatments were comprised of three doses of glufosinate ammonium 13.5% SL (0.27, 0.34, 0.45 kg/ha), glyphosate 41% SL (1.23 kg/ha), paraquat dichloride 24% SL (0.60 kg/ha) and weedy check within a randomized complete block design, replicated four times. The results revealed that glufosinate ammonium at 0.45 kg/ha was the most efficient against grassy and broad-leaf weeds with higher weed control efficiency (> 90%) and total green leaf yield (3.0 t/ha and 2.96 t/ha). Herbicides did not show any phytotoxicity symptoms on the matured tea plants throughout the observation period. An initial detrimental effect on rhizospheric micro-flora (total bacteria, fungi, and actinomycetes) was imposed by residual toxicity of herbicides but at later stage, no harmful effects were observed. Maximum nutrients uptake and soil available nutrients were determined under the higher dose of glufosinate ammonium. Tea leaf quality did not significantly influence by weed management practices. Based on overall performance, the glufosinate ammonium 0.45 kg/ha may be considered as the best substitute for others post-emergent herbicide against the complex weed floras in tea garden.