Cassava production in Amazonas state deserves to be highlighted due to its great historical, social, and economic importance. Weed competition severely constrains cassava production in Amazonas. The use of cover crops is safe and very efficient at eliminating weeds while keeping the soil covered. The objective of this study was to evaluate physical properties of soil and glyphosate residues in storage roots as a function of the weed management in cassava. The experiment was carried out in a randomized complete block design with five treatments and five repetitions. The treatments were biological control with two species of cover plants (Brachiaria ruziziensis and Mucuna pruriens), chemical control, mechanical control, and treatment with no weed control. The cover crops characteristics evaluated were dry weight, the percentage of cover, and rate of decomposition of plant residues. In the soil, the bulk density and total porosity were determined. The contamination of the storage roots was evaluated based on the analysis of glyphosate residue. Brachiaria ruziziensis presented more dry weight and higher percentage of cover compared with M. pruriens, and both cover crops showed very similar decomposition rates. The physical properties of soil were unaffected by any treatment evaluated. There was no detection of glyphosate and its metabolite, aminomethylphosphonic acid (AMPA), in any treatment evaluated. Chemical control with glyphosate is not able to contaminate cassava storage roots.
The economic potential of guarana relies on the energetic and medicinal properties of its seeds, which can be used to produce soft drinks, sticks, powder, and syrup. Brazil is the only guarana producer on a commercial scale, and the guarana crop system is the main agricultural activity in Maués, Amazonas. Although several types of technology have been developed to reduce costs and increase guarana productivity, the most important optimization of seedling production by cutting still needs to improve the rooting percentage and reduce mortality rates. However, the use of rooting inducers for guarana is still unestablished. Therefore, we evaluated the rooting potential of herbaceous cuttings from three guarana cultivars under different indole-3-butyric acid (IBA) concentrations. We recorded qualitative data from the roots of the cuttings. The IBA doses did not increase the percentage of rooted cuttings; however, they increased the root system quality of the guarana cuttings. We present this rooting method for the guarana plant as the most appropriate and least costly for small producers.