Allelopathic Effects of Digitaria sanguinalis (L.) Scop. and Biden pilosa L. Extracts on Pisum sativum L. and Lactuca sativa L.

The allelopathic effect, which either inhibits or stimulates the development and growth of surrounding plants (crops or weeds) via the production of secondary metabolites, is a crucial challenge for crop selection. This study examined the effects of Digitaria sanguinalis and Bidens pilosa, two locally prevalent weeds, on the seed germination and seedling growth of two main agricultural crops (Pea and Lettuce) were investigated. To assess the effects of D. sanguinalis and B.pilosa leaf aqueous extracts in the laboratory, three different concentrations (2, 5, and 7%) were used. The leaf extract of B. pilosa significantly reduced germination rates and inhibited seedling growth in both crops, whereas D. sanguinalis increased germination and seedling growth in Pea but reduced them in lettuce. Furthermore, the highest inhibitory effects were detected in lettuce at all concentrations (2, 5, and 7%), whereas a stimulatory effect was noticed in pea at 2 and 5% concentrations, but inhibitory effects were observed at higher concentrations (7%). It was concluded that the B. pilosa aqueous leaf extracts were more deleterious than D. sanguinalis extracts on the germination and growth of the tested crops. The potential damage and allelopathic effects of the aforementioned weeds should be considered during crop production.