The impact of aqueous and N-hexane extracts of three Fabaceae species on seed germination and seedling growth of some broadleaved weed species

Weed infestation is a persistent problem for centuries and continues to be major yield reducing issue in modern agriculture. Chemical weed control through herbicides results in numerous ecological, environmental, and health-related issues. Moreover, numerous herbicides have evolved resistance against available herbicides. Plant extracts are regarded as an alternative to herbicides and a good weed management option. The use of plant extracts is environmentally safe and could solve the problem of herbicide resistance. Therefore, laboratory and wire house experiments were conducted to evaluate the phytotoxic potential of three Fabaceae species, i.e.,Cassia occidentalisL. (Coffee senna),Sesbania sesban(L.) Merr. (Common sesban) andMelilotus albaMedik. (White sweetclover) against seed germination and seedling growth of some broadleaved weed species. Firstly, N-hexane and aqueous extracts of these species were assessed for their phytotoxic effect against lettuce (Lactuca sativaL.). The extracts found more potent were further tested against germination and seedling growth of four broadleaved weed species, i.e.,Parthenium hysterophorusL. (Santa-Maria),Trianthema portulacastrumL. (Pigweed),Melilotus indicaL (Indian sweetclover). andRumex dentatusL. (Toothed dock) in Petri dish and pot experiments. Aqueous extracts of all species were more toxic than their N-hexane forms for seed germination and seedling growth of lettuce; therefore, aqueous extracts were assessed for their phytotoxic potential against four broadleaved weed species. Aqueous extracts of all species proved phytotoxic againstT.portulacastrum,P.hysterophorus,M.indicaandR.dentatusand retarder their germination by 57, 90, 100 and 58%, respectively. Nevertheless, foliar spray ofC.occidentalisextract was the most effective againstT.portulacastrumas it reduced its dry biomass by 72%, whileM.albawas effective againstP.hysterophorus,R.dentatusandM.indicaand reduced their dry biomass by 55, 68 and 81%, respectively. It is concluded that aqueous extracts ofM.alba,S.sesbanandC.occidentaliscould be used to retard seed germination ofT.portulacastrum,P.hysterophorus,M.indicaandR.dentatus. Similarly, aqueous extracts ofC.occidentaliscan be used to suppress dry biomass ofT.portulacastrum, and those ofM.albaagainstP.hysterophorus,R.dentatus. However, use of these extracts needs their thorough testing under field conditions.