Bioativiade de Crambe abyssinica Hochst (CRAMBE) sobre Euphorbia heterophylla L. (LEITEIRO), Bidens pilosa L. (PICÃO-PRETO) e Glycine max (L.) Merril (SOJA)

Abstract

The use of biomass from plants that take part of crop rotation system can become an alternative to reduce the use of herbicides in controlling weeds. So, the objective of this trial was to evaluate plant growth, yield and quality of soybeans seeds cropped under fallow (without straw) and three periods (88, 52 and 25 days) of straw permanence of crambe on soil (Paper 1); to evaluate the effect of crambe dry biomass, equivalent to 0, 4; 10; 16; 22 and 28 t ha-1 on emergence and development of weeds such as wild poinsettia and hairy beggartick species (Paper 2); and to identify secondary compounds of crambe as well as evaluate the bioactivity of hexane extracts, ethyl and methanol acetate on seeds germination and growth of tomato, wild poinsettia,hairy beggartick, and soybeans seedlings (Paper 3). The results have stated that crambe straw did not show negative effects on growth and development of soybean plants. In addition, there was an increased yield for soybeans crop when straw remained 88 days on soil, prior to sowing, which did not interfere negatively on seeds quality. It was observed that weed seeds presented an impaired emergency when exposed to crambe biomass. Wild poinsettia growth did not change with different amounts of biomass. However, hairy beggartick plants had a linear growth decrease when the amount of biomass in crambe increased on soil. It was also observed that each solvent extracted different compounds in a phytochemical screening. Flavonoids were also found out only by ethyl acetate extract and saponin was obtained only by methanol extract. There was high allelopathic effect of extracts concerning hexane, ethyl acetate and methanol of crambe on tomato as a bio-indicator species. The hexane extracts and ethyl acetate also showed inhibitory effect on hairy beggarticks weed and did not have negative effects on soybeans. Finally, this information can contribute to future researches about bioactive compounds isolation in crambe and use them as a possible bio-herbicide alternative to control weeds. Further studies are indicated to isolate and identify possible active molecules present in the extracts. It is also recommended the use of crambe in crop rotation with soybeans as an alternative to reduce emergence of weeds such as wild poinsettia and hairy beggartick.