Efeito alelopático do óleo essencial de Cymbopogon nardus e extrato de Annona muricata na germinação de Bidens pilosa e Megathyrsus maximus

The objective of this work was to verify the allelopathic effect of the essential oil of citronella (Cymbopogon nardus) and soursop leaf extract (Annona muricata) on the germination of beggartick’s (Bidens pilosa) and Guinea grass’ seeds (Megathyrsus maximus). The treatments were: citronella essential oil at the following concentrations: 0.25, 0.5, 1.0 and 1.5 mL/L (v/v) and aqueous soursop extracts at concentrations of 25, 50, 75 and 100% (v / v), and a control group of distilled water. The experimental design was completely randomized, and the statistical analysis were ran with a Regression in Analysis of Variance. The parameters evaluated were: relative germination frequency, percentage of germination, average germination time, average germination speed and germination speed index. The results showed that citronella oil was effective in all concentrations: the higher the concentration, the higher was the effect on beggartick and Guinea grass seed germination. The highest concentrations of soursop extract interfered in the all the parameters of beggartick as well as in Guinea grass.