Sugarcane for Bioethanol: Soil and Environmental Issues

Cultivation of sugarcane for bioethanol is increasing and the area under sugarcane is expanding. Much of the sugar for bioethanol comes from large plantations where it is grown with relatively high inputs. Sugarcane puts a high demands on the soil because of the use of heavy machinery and because large amounts of nutrients are removed with the harvest; biocides and inorganic fertilizers introduce risks of groundwater contamination, eutrophication of surface waters, soil pollution, and acidification. This chapter reviews the effect of commercial sugarcane production on soil chemical, physical, and biological properties using data from the main producing areas. Although variation is considerable, soil organic C decreased in most soils under sugarcane and, also, soil acidification is common as a result of the use of N fertilizers. Increased bulk densities, lower water infiltration rates, and lower aggregate stability occur in mechanized systems. There is some evidence for high leaching losses of fertilizer nutrients as well as herbicides and pesticides; eutrophication of surface waters occurs in high-input systems. Soil erosion is a problem on newly planted land in many parts of the world. Trash or green harvesting overcomes many of the problems. It is concluded that sugarcane cultivation can substantially contribute to the supply of renewable energy, but that improved crop husbandry and precision farming principles are needed to sustain and improve the resource base on which production depends