Recent advances in mitigation methods for herbicide residues in the soil

In modern agriculture, with more emphasis on high input systems and the widespread application of herbicides has indubitably improved the crop production but has also resulted in inadvertent harm to the ecosystem. The increased awareness towards the adverse effects of herbicide residues on human health and environment resulted in a significant shift towards the mitigation strategies of herbicide residues in the soil as well as in the plants. Several approaches have been found to be utilized for mitigation of herbicide residues in the soil. The hazards from herbicide residues in the soil can be reduced by using low dosage chemicals, tillage operations, crop rotation, using proper nozzle and spraying technique and by using granular, foam, gel and encapsulated materials. Site specific application using variable rate applicator, enhancement of herbicide degradation through bio-stimulation, use of non-phytotoxic oil, adjuvants, surfactants, adsorbents, protectants, antidotes, safeners, biochar, etc. are various other effective ways for mitigation of herbicide residues in the soil. Biochar as an amendment to agricultural soils has been found to increase the bioavailable water, builds soil organic matter, enhances nutrient cycling, lowers bulk density, and can provide shelter for beneficial soil microorganisms. Biochar prevents the mobilization of herbicide residues in soil due to its sorption property and hence helps the crop to escape toxicity. Carbon based nano-absorbents such as carbon nanotubes (CNTs) represents a new class of nanomaterial and has been shown to have good potential in removal of various types of herbicide residues in the soil. Graphene is another carbon nanomaterial that has tremendous potential in water purification as well as in various fields due to its unique physical and chemical properties. Nanocrystalline metal oxides such as ferric oxides, manganese oxides, aluminium oxides, titanium oxides, magnesium oxides and cerium oxides are highly effective adsorbents for a broad range of herbicides. These nanocrystalline metal oxides do not only adsorb but also actually annihilate many chemical hazards by converting them to much safer by-products. The amalgamation of bioaugmentation and bio-stimulation along with organic matter addition might be a promising technology for biodegradation of herbicides in soil.