Herbicides use in crop production: An analysis of cost-benefit, non-target toxicities and environmental risks

Under intensive agriculture, weeds cause heavy losses in crop yield and quality. The existing manual method of weed control is no longer sustainable because of paucity of labours, higher wage, and huge drudgery. Herbicide is an easier, more efficacious, and economical tool for weed control in crops and un-cropped situations. However, the consequences of herbicide use, concerning non-target toxicities, and the evolution of herbicide-resistant weeds have drawn the attention of world communities. Therefore, in this review, we attempt to highlight the potential benefits vis-à-vis harmful consequences of herbicides in diversified crop ecologies across the world. Herbicide use resulted in weed control efficiency of 52-96% in different agro-ecologies. Besides, it could increase grain yield of different arable crops by 19-372% with an additional economic benefit of US$ 305 - US$ 867 over unweeded control. Chemical weed management resulted in gain in net returns by 4-12% over manual weeding (∼two hand weedings) and by 7-247% over the weed-free check in different countries. The majority of herbicides used at recommended doses in crops did not show any direct and/or residual toxicity on soil micro-organisms in agro-ecologies. Environmental conditions may change pesticide impacts on non-target micro-organisms. Over-reliance on herbicides and injudicious use at higher rates may lead to a fragile ecosystem, but judicious use can stimulate productivity, profitability and livelihood security. Hence, integrated weed management (IWM) that can restrict weed populations below threshold level, reduce environmental foot-print, increase cropping system sustainability, and reduce selection pressure for weed resistance to herbicides has been suggested.