Potencial alelopático de Bixa orellana L. sobre sementes de Bidens pilosa L. e Raphanus sativus L.

Abstract

Increase in agricultural production in consequence of food demand requires an increase in synthetic products to control pests, diseases and weeds that negatively affect production. This practice has generated discussions amongst environmentalists, researchers and the general population about the problems these pesticides can cause to humans and the environment. Thus, organic products gained market due to their quality and absence of such chemicals. In this context, allelopathy has become a valuable tool to control weeds in these production systems, considering that these are natural compounds, safe for humans and that help minimizing environmental contamination. For this research, aqueous extracts of annatto seeds (Bixa orellana) not ground and ground with different extraction times (0, 24 and 48 h) to evaluate their allelopathic potential to control the weeds Bidens pilosa and Raphanus sativus. The experiment consisted of four treatments in four different extract concentrations (1.25%, 2.5%, 5% and 10%) and control group. Statistical design was factorial with two levels and data collected were submitted to ANOVA and means compared using Scott-Knott test (p < 0.05). Parameters evaluated were related to seed germination and seedling initial development. Extraction time 24 h for not ground and ground annatto seeds presented higher allelopathic effects for B. pilosa, affecting seed germination percentage and speed, and emergence index, dry matter, and shoot and radicle length. On the other hand, the same extraction time for not ground and ground annato seeds resulted in stimulation for R. sativus. , observed allelopathic effects were of stimulation. Thus, it is possible to infer that aqueous extracts of annato seeds, ground and not ground, may be a viable option to substitute synthetic products to control B. pilosa in organic crop production systems.