Herbicide effect on weed control, soil health parameters and yield of Egyptian clover (Trifolium alexandrinum L.)

Abstract Weeds are the major pests of forage production in India. An herbicide program is necessary for effective weed control in Egyptian clover (Trifolium alexandrinum L.). The study was conducted in 2013 and 2014 (two years) with an aim to evaluate the response of Egyptian clover and weeds to different herbicides that were being used in various cropping systems in Uttar Pradesh, India. Weed density and biomass, phytotoxicity of herbicides on crop, chlorophyll and carotenoid content in crop samples, root nodulation, soil dehydrogenase activity, soil microbial activity and herbicides effect on dry fodder yield were evaluated. Seventeen (three grasses, and 14 broadleaves) different weed species were observed in this study. Anagallis arvensis L., Cichorium intybus L., Cynodon dactylon (L.) Pers., Dactyloctenium aegyptium (L.) Wild. and Phalaris minor Retz. were the dominant weed species during the crop season. Among herbicides, Alachlor PRE and Imazethapyr PRE decreased grass weeds by 72% and 75% respectively, compared to weedy check, with no injury to crop at 25 days after sowing (DAS). However, alachlor PRE has controlled 64% more broadleaf weeds compared to Imazethapyr. At 50 DAS, imazethapyr POST, alachlor PRE fb quizalofop-ethyl POST provided excellent control of weeds, and resulted in yield equivalent to non-treated weed free check. Further, alachlor (PRE) fb quizalofop-ethyl (POST) and imazethapyr (POST) were selective herbicides on Egyptian clover (very slight to slight injury), recorded greatest nodule number (23–38 plant−1) and soil microbial community compared to other herbicide treatments. For grass weeds, propaquizafop provided effective control but had phytotoxic effect on the crop. In current scenario, where alachlor has been banned, application of either imazethapyr PRE/POST or imazethapyr PRE fb quizalofop-ethyl POST could be the potential herbicide options for control of weeds and obtaining higher yield of Egyptian clover.