“…Particularly for leguminous plants, nitrogen fixing may be severely affected by Al toxicity in subsoil (Silva and Sodek, 1997). These consequences, taken together, may decrease carbon sequestration and biomass formation, which is the key for nutrient recycling in soil (Alcântara et al, 2000), physical protection of soil against high temperatures (Oliveira et al, 2002) and erosion (Nascimento and Lombardi Neto, 1999), weed control (Severino and Christoffoleti, 2001), nitrogen incorporation (Debarba and Amado, 1997) and addition of organic carbon to soil (Testa et al, 1992). Recently there has been great interest in tropical leguminous plants, because of the increased adoption of green manuring in Brazilian cerrados (savannah) (Amado et al, 1999) and fruitproducing regions, for example in citrus orchards (Silva et al, 2002b) as a result of the necessity of a stable and sustainable production.…”