Allelopathy defines the production of specific biomolecules (allelochemical) by a plant that can induce positive or negative impacts on another culture. The crop of castor beans (Ricinus communis L.) is being economically valued and receiving attention, mainly by the biodiesel production, castor oil and animal feeding. In this study, the allelopathic effect of aqueous extract from fresh leaves of castor beans (Ricinus communis L.) applied to the beginning stage of soy (Glycine max L.) and of safflower (Carthamus tinctorius L.) was investigated. An experimental was setup with five blocks and four replications, considering that each block refers to a concentration of extract of castor beans fresh leaf (0, 25, 50, 75 and 100%); the one without castor beans leaves was taken as 'witness'. The statistic treatment was done using analysis of variance (ANOVA) and Tukey test with an error rate of 5%. The result showed evidences that there are allelopathic effects among the extract of castor beans fresh leaf and the beginning stage of soy and safflower only in the root part of the seedling.

Allelopathy is a natural botanical effect in which certain crops release inhibitory substances which affect growth and development of other crops to the environment. The ability of plants to exhibit allelopathy vary among species. In Brazil, the allelopathic studies are restricted to common plants, such as corn, soy, wheat, and safflower. Given these factors, there are still many cultures as Ilex paraguariensis that are forgotten, even though, they play an important role in the regional cultivation. The aim of this study was to evaluate the effect of cold water extract of I. paraguensis leaves on germination rates, seeds early growth and speed of germination of Carthamus tinctorius L. sprayed with aqueous extract of mate. The extract production process consists in grinding mate leaves along with cold water and then filtering it to remove the particles. Concentrations of 0 (control), 25, 50, 75 and 100% of the extract were used to induce the treatment, considering 200 g of extracted adult fresh leaves per liter of cold water. The seeds were planted in individual tubes containing specific soil for cultivation and they were all sprayed manually every 3 days using the volume of 500 ml in appropriate concentrations. The experimental design was completely randomized as it follows: 5 treatments, 4 repetitions, and 1 safflower genotype. To carry out the analysis, the emergency data were collected until the thirtieth day. Considering the statistical analysis, there was no change resulting in allelopathic effect in the following rates: germination rate, first germination counting, average time of germination and percentage of germination, stem diameter, root length, and leaf dry mass, but it was observed that in the concentration T3 (50%), there was a significant increase in safflower growth in the following characteristics: leaf fresh mass, root fresh mass, leaf length, leaf area, and root dry mass.