Synthetic herbicides have had both direct and indirect negative effects on biological organisms as well as on human health. Thus, non-synthetic herbicides for weed control are needed in both organic and traditional agriculture. Natural products such as vinegar and detergents are increasingly popular in treating crop disease as
well as controlling insects and weeds. Therefore, the objective of this research was to determine the herbicidal efficacy of various natural products using different application methods. Various natural products were applied to grass and broadleaf weeds at 1%, 3%, 5% and 10% concentrations to test their herbicidal efficacy and two plants extracts were also used as adjuvants. In addition, the inhibitory effects of
selected brown rice vinegar and EM powder soap on grass and broadleaf weeds were
compared to the inhibitory effects of other vinegars and EM powder soaps. Of the nine various natural products tested, brown rice vinegar and EM powder soap at 5% concentrations were the only applications to completely control grass and broadleaf weeds in Petri dish bioassays. In greenhouse conditions, the shoot fresh weight of Eclipta prostrata, Solanum nigrum, Persicaria hydropier, and Portulaca oleracea was completely inhibited when soil applications of EM powder soap at 10% concentrations were used. EM powder soap was more effective in controlling grass and broadleaf weeds than brown rice vinegar. In addition, brown rice vinegar and EM powder soap did not appear to persist long-term in soil. Moreover, two-time application methods were more effective in controlling all weed species than one- time application methods. However, no synergism effects were observed when brown rice vinegar and EM powder soap were combined other natural products. In addition, brown rice vinegar and EM powder soap did not show adjuvant effects when
combined with plant extracts which can sometimes create better contact with or penetration of the weeds. Thus, brown rice vinegar and EM powder soap could be applied in-row, either single or combined, in order to control weeds growing alongside transplanted vegetable crops.