Avaliação do resíduo alcalino do refino de bauxita como condicionador de solos e do estabelecimento de dendê nos tanques de estocagem / Evaluation of red mud as soil conditioner and of the oil palm in stock tanks vegetated with leguminous trees

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The production of aluminum and alumina generates a great amount of red mud, which is harmful to the environment mainly for its high pH, electric conductivity and concentration of sodium, which restrict plant growth. However, there are some indications that it may be used as a conditioner for acid sandy soils. This work tested a red mud from an alumina production plant by Alumar- São Luís MA, Brazil as soil conditioner for two acid soil types: sandy and clay soils) and the growth of oil palm hybrids (E. guinensis x E. oleifera) grown in red mud deposition tank vegetated with leguminous trees for 8 years. The red mud was characterized in relation to its physical, chemical and microbial characteristics and tested in two types of soils, a Planossolo and an Argissolo and two bioindicators plants, the grass Brachiaria brizantha and common bean (Phaseolus vulgaris). Bean plants were harvested and brachiaria received a first cut 50 days after planting. A second and third cut were performed in brachiaria 70 and 140 days after the first one. Plant biomass was dried until constant weight and analysed for nutrient content. Number of sprouts of grass was counted at the third harvest. The evaluation of oil palm growth on red mud included eight hybrids between Elaeis oleifera x Elaeis guiinensis from Embrapa Amazônia Ocidental. breeding program (C2501, C2301, C2328, C3701, C2801, C7201, RUC13 and RUC 87) 12 months after transplanted to a red mud tank vegetated for 8 years with a mixture of nodulated leguminous trees. Diameter at the base of the plants, top diameter, number of leaves, plant height, diazotrophic bacteria, mycorrhizal fungi and nutrient contents were studied on the oil palm plants. Soil fauna and nutrient availability were evaluated in soils under oil palm and in an area with native species nearby the tanks. The addition of small amounts of red mud to the soils increased soil pH. Addition of red mud decreased plant growth in both soils tested with more deleterious effect on bean than on the grass. However the addition of 5 Mg ha-1 of red mud in the sandy acid soil increased the grass biomass at the last harvest in relation to the control. The evaluation of the oil palm in the tanks indicated that hybrid RUC 87 and C7201 presented larger diameter at soil level, plant height and number of leaves. All cultivars and hybrids showed large population of diazotrophic bacteria in their leaves and mycorhizal infection on roots. Similar richness and density of soil fauna was observed in the red mud below the oil palm to that observed in a soil collect in a secondary forest nearby indicating that the vegetation with leguminous trees is returning the ecological processes toward a sustainable system.

ASSUNTO(S)

leguminosas arbóreas fitotecnia recovery of degraded land recuperação de áreas degradadas mining mineração leguminous trees

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