Alelopatia da casca de café, implicações ambientais e valorização do resíduo a partir da compostagem

Abstract

Coffee growing generates coffee skin (CS) in great amounts. The accumulation of these residues forms a dead covering on the soil with allelopathic potential. Allelopathy is the inhibition or stimulation of neighboring plants growth that have this potential. Before this effect, CS is used in the control of invader plants in different cultivations. When it comes to great amounts used for this purpose, researches are incipient as for the resulting environmental impacts. This study aims to survey environmental impacts generated by its disposal, as well as to propose an alternative method for the residue disposal. To know the volume generated and the CS destination, data was surveyed by means of the cooperatives that benefit coffee in the State of Paraná. This study showed that the State generates approximately 144 thousand tons and the biggest part is destined to agriculture. The research was accomplished in two phases: the first one on the Field and the second one in laboratory and in area destined to composting. The first one was made in coffee cultivation, made available by Cooperativa Agroindustrial Consolata (Copacol), where data and samples were collected from the vegetation and soil. Vegetation was qualitatively and quantitatively analyzed. For quali-quantitatively analysis of vegetation, 4 areas of 100 m2 were used with and without influence of residue. From each area, 10 parcels of 10 m2 were selected for the fitossociological survey. In the parcels the data was surveyed for analysis of the following parameters: density, frequency, biodiversity and similarity among areas. The following was used to determine the species: specialized bibliography, identification keys, consultation of experts and comparison with the collection of Municipal Botanic Museum of Curitiba. 34 species were determined, belonging to 31 kinds and 16 families, being Asteraceae family the most representative (27%). The areas 1 and 2 showed more similarity in relation to the others. The soil samples were submitted to routine physical chemical analysis for the pH, organic carbon, phosphor, potassium, calcium and magnesium, acidity, aluminum and mesh determination. Areas 3 and 4 showed different conditions, mainly related to acidity and phosphor. Phytochemical characterization was made and it pointed to fixed acids, alkaloids, amino groups, coumarins, steroids, glycosyl flavones and tannin as the main classes of present substances. The second phase was led in laboratory and in area destined to composting. On this phase, tests with Cucumis sativus were made by means of biotests with extracts of CS at 0, 5, 10, 15 and 20%, with ten repetitions for each treatment. The extract stimulated the biomass of C. sativus, as its biggest concentration. Allelopathy biotests were made on Petri plaques with C. sativus seeds and extracts at 25, 50, 75 and 100%, with 6 repetitions of each. There was inhibition of radicle development in every treatment with coffee skin. CS composting and poultry litter (PL) were accomplished and biotests with CS and PL compound with 0, 15, 45 and 60 days. Composting can help in the reduction of polluting potential of CS and PL, for the biotests showed improvement of the compounds with the increase of the composting period, being the best results with the 60-day compound.