Abstract

Cassiterite mining has caused critical damages to the environment with respect to soil degradation and water pollution. In a greenhouse experiment two leguminous species, jack-bean (Canavalia ensiformis) and pigeon-pea (Cajanus cajan), were grown using cassiterite mine spoil as substrate, in the presence of rhizobia and with or without mycorrhizal fungi, and the substrate was amended or not with organic compost and thermo-phosphate, to evaluate the potential development of these plants to grow on this substrate. Shoot height and shoot dry weight, nitrogen and phosphorus shoot contents, root nodule numbers and their dry weight were determined. Amendment with organic compost was important for all observed parameters in both species, but jack-bean had greater shoot N contents and biomass and less mycorrhizal dependence, when comparing with pigeon-pea. However, it was verified that efficiently nodulated plants, as pigeon-pea, can be fundamental for soil reclamation, by reducing the need for fertilizers and by stimulating the biological activity in soil. In our study the utilization of organic compost was crucial for plant growth, while thermophosphate was not always essential, especially in the presence of mycorrhiza. However, the mycorrhizae were essential, at least for pigeon-pea.

Key words: Cassiterite mine spoil, Canavalia ensiformis, Cajanus cajan, amazon region.