Plantas de cobertura no manejo sustentável das infestantes e na produtividade do guaranazeiro (Paullinia cupana var. sorbilis (Mart.) Ducke)

Abstract

Guarana represents one of the main economic potentialities among the main crops in the state of Amazonas due to the high concentration of caffeine present in its seeds. However, the climatic conditions in Amazonas favor the appearance of pests, diseases and the growth of weed, contributing to the competition with guarana plants. In the case of weed, depending on the size of the area under cultivation, the producer can use herbicides more frequently to weed control. In sustainable agroecosystems, cover crops can be great allies in crop management, contributing to improve the agricultural production and promoting benefits such as nutrient and organic matter replacement in the soil and suppressing weed. Therefore, the objective of this study was to evaluate the effect of cover crops (Brachiaria ruziziensis, Canavalia ensiformis and Mucuna deeringiana) on soil, weed suppression and guarana productivity. After the installation of the experiment were evaluated: floristic composition of weed, biomass production of cover crops, percentage of soil cover, decomposition rates of vegetal residues produced by cover crops, chemical analysis of dry matter of cover crops, nutritional analysis of guarana leaves, caffeine content in guarana seeds and guarana productivity. The data were submitted to analysis of variance and the F test was applied at 5% of probability, using the statistical computer program ASSISTAT version 7.7. Digitaria horizontalis was the most important weed, suppressed only by the B. ruziziensis, this cover crop suppressed 100% of the weed in guarana crop, presenting excellent soil cover and high biomass production. The highest dry matter yield, nitrogen and potassium levels were observed in M. deeringiana. The highest amounts of calcium, magnesium and phosphorus were found in C. ensiformis. Brachiaria ruziziensis presented the highest dry matter decomposition rate. In the first year, the highest rates of potassium release occurred in C. ensiformis, and of nitrogen and calcium in B. ruziziensis. In the second year, C. ensiformis presented the highest rates of nitrogen and potassium release. The types of weed management influenced the nitrogen, potassium and calcium levels in guarana leaves, however, did not affect the guarana productivity. Canavalia ensiformis increased the caffeine concentration in guarana seeds.