Nanoemulsion Formulation of Mustard Seed Meal for Weed Suppression with Minimal Environmental Impact

Weed infestation, particularly by Phalaris minor (little seed canary grass), poses a major challenge to wheat (Triticum aestivum) production and has led to repeated reliance on synthetic herbicides, raising concerns related to environmental safety and human health. Consequently, there is a growing need for sustainable and eco-friendly alternatives that selectively suppress weeds without compromising crop growth. In this study, a nanoemulsion (NEm) of mustard (Brassica juncea) seed meal was developed and evaluated as a targeted bioherbicidal formulation with improved environmental compatibility. The optimized NEm exhibited uniform nanoscale particle size and enhanced physicochemical stability while maintaining stable isothiocyanate (ITC) content over 30 days of storage. Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) confirmed the chemical integrity and nanoscale morphology of the formulation. The stability studied showed that NEms remained stable under thermal and mechanical stress and across wide range of dilution conditions. Germination and physiological assays demonstrated effective suppression of both resistant and susceptible biotypes of P. minor, accompanied by enhanced seed imbibition and membrane leakage, while T. aestivum germination remained unaffected. Environmental fate studies indicated rapid degradation of the NEm in soil, with transient effects on soil dehydrogenase activity. Furthermore, germination and early seedling growth of Oryza sativa, Vigna radiata and Zea mays were not adversely affected, confirming safety for succeeding crops. Overall, the mustard seed meal based NEm represents a promising plant-derived, eco-friendly herbicidal formulation that combines effective weed control with environmental safety and sustainability.