Germination of weeds and species grown and submitted to the growing of sunn hemp and its extract

Sunn hemp (Crotalaria juncea L.) is a tropical legume that could be an important summer cover crop, it has the potential for suppressing both crops and weeds. The objective of this study was to evaluate the allelopathic effect of sunn hemp in different spacing intervals and densities, in the germination of corn, beans, rice, soybeans and weeds. The study was conducted in Cáceres/MT and Paraguaçu Paulista/SP. Sunn hemp was planted to obtain matter for the extraction of allele chemical compounds and the suppressive effect from growing sunn hemp on the weeds on the crops in the field. The corn, bean, rice, soybean and bitter grass seeds were the bio-indicators. There were two spacing intervals (0.25 m and 0.50 m) and three densities (25, 40 and 50 plants m-1) evaluated the sunn hemp height, density, dry weight of weeds (g/m2) and the germination and root length of the planted specie seedlings. The reduction of sunn hemp plant spacing reduces the growth of weeds in the field that directly interfere in the germination and growth of seedlings. The crops display different sensitivity to the concentration of sunn hemp extracts, bean extract displays the greatest sensitivity to the extract, even at the lowest concentration, when compared to corn and rice, as it also affects the root. No significant interference was present in soybean extracts. Bitter grass has reduced germination from the extracts and increased numbers of abnormal plants.