Herbicidal potential of the allelochemicals from Pennisetum purpureum Schumach. on the seedling growth of Paspalum conjugatum.
Pennisetum purpureum is one of the invasive weeds in Malaysia. This weed possesses secondary metabolites that could play the role of dominating the ecosystem. Their allelochemicals thus, have potential to be used in herbicidal formulations to control weeds. Therefore, a study was carried out on the potential of the herbicidal activity of the "above-ground" parts of P. purpureum in the laboratory and greenhouse using the aqueous extract (@: 0 g/L (control), 20 g/L, 40 g/L, 60 g/L, 80 g/L and 100 g/L) and debris (incorporated into the soil) (@: 0 g/500 g (control), 5 g/500 g, 25 g/500 g and 50 g/500 g (leaf debris/soil)) of P. purpureum. The effects of different concentrations of contaminated soil and the root exudate of P. purpureum on the seedling growth of the weed bioassay species (Paspalum conjugatum) was studied in an experiment using four replications. Results under laboratory conditions showed that the growth of P. conjugatum was inhibited by 100% at the concentrations of 80 g/L and 100 g/L of the aqueous extract of P. purpureum. Besides, the seedling growth of P. conjugatum was inhibited by more than 50% at the concentration of 50 g/500 g (1/10) of the debris of the above-ground parts of P. purpureum to soil, respectively. Moreover the germination and seedling growth of P. conjugatum were also inhibited by more than 50% when planted in 500 g of infested soil and treated with applications of the root exudate of P. purpureum. Results from these studies suggest that P. purpureum has herbicidal activity and the potential to be explored further in the search for allelopathic chemicals.