Potencial de revegetação de solo degradado pela mineração de ferro utilizando leguminosas arbóreas e resíduo de carcinicultura.

Abstract

The addition of organic residues is among the alternatives to rehabilitate degraded lands, aiming to improve the structure as well as the nutrients availability of mining spoils. In the Ceará State, the organic residue from shrimp farms (carcinicultura) deserves attention because it contains relevant amount of nutrients and organic matter. The aim of this study was to test the hypothesis that residue from shrimp farms improves the development of leguminous trees as well as the degraded land. In the initial phase of this study both geochemical and physical-chemical characterization of the organic residue were done aiming to identify the presence of pirite, and the potential risk of acidification. One experiment was set up under controled conditions, in the experimental design of randomized blocks in a factorial scheme 5x3, with four replications. The treatments were five rates of organic residue from shrimp farms (0; 2; 4; 8; 12 Mg ha-1) and three leguminous trees species: Sabiá (Mimosa caesalpiniaefolia Benth), Leucena (Leucaena leucocephala) and Jurema Preta (Mimosa hostilis). Three months after addition of the organic residue were evaluated the growth of leguminous trees, the fitomass, as well as the nutrients accumulation in the above ground, and bellow ground parts of the plants. The availability of nutrients in the substrate also was evaluated. The results of the geochemical analysis showed low amount of pirite, and consequently the low risk of acidification by the use of organic residue from shrimp farms. After a period of three months was observed that leguminous trees presented positive answer to rates of organic residue. The species that presented higher growth and fitomass production were Mimosa caesalpiniaefolia and Mimosa hostilis, presenting also the higher nutrients accumulation. The effects of the organic residue in the soil were: increase in soil eletric conductivity, and pH. The conclusion is that the organic residue from shrimp farms improved the growth and development of leguminous trees in the present study, and it did not damage soil chemical and physical attributes, allowing higher availability of nutrients to favour plant growth in degraded land.