European Journal of Soil Science, February 2011, 62, 23–28 doi: 10.1111/j.1365-2389.2010.01315.x Effect of sugarcane harvesting systems on soil carbon stocks in Brazil: an examination of existing data C. C. Cerri a , M. V. Galdos a , S. M. F. Maia a , M. Bernoux b , B. J. Feigl a , D. Powlson c & C. E. P. Cerri d a Centro de Energia Nuclear na Agricultura (CENA/USP), Universidade de Sao Paulo, Av. Centenario 303, CEP. 13400-970, Piracicaba, Brazil, b Institut de Recherche pour le D´ eveloppement (IRD), UMR Eco&Sols (Inra, IRD, SupAgro), 2 place Viala – Bat. 12, 34060 Montpellier Cedex 1, France, c Rothamsted Research, Soil Science Department, Harpenden, AL5 2JQ, UK, and d Escola Superior de Agricultura Luiz de Queiroz (ESALQ/USP), Universidade de Sao Paulo, Av. Padua Dias 11, CEP. 13418-900, Piracicaba, Brazil Summary Agricultural management practices that promote net carbon (C) accumulation in the soil have been considered as an important potential mitigation option to combat global warming. The change in the sugarcane harvesting system, to one which incorporates C into the soil from crop residues, is the focus of this work. The main objective was to assess and discuss the changes in soil organic C stocks caused by the conversion of burnt to unburnt sugarcane harvesting systems in Brazil, when considering the main soils and climates associated with this crop. For this purpose, a dataset was obtained from a literature review of soils under sugarcane in Brazil. Although not necessarily from experimental studies, only paired comparisons were examined, and for each site the dominant soil type, topography and climate were similar. The results show a mean annual C accumulation rate of 1.5 Mg ha −1 year −1 for the surface to 30-cm depth (0.73 and 2.04 Mg ha −1 year −1 for sandy and clay soils, respectively) caused by the conversion from a burnt to an unburnt sugarcane harvesting system. The findings suggest that soil should be included in future studies related to life cycle assessment and C footprint of Brazilian sugarcane ethanol. Introduction Sugarcane (Saccharum officinarum L.), a crop originating from New Guinea, was one of the first tropical crops to be adapted to large-scale farming. Sugarcane is a C4 plant that is highly efficient in turning solar radiation into biomass. It is a perennial crop that is harvested on an approximately annual cycle, with up to six cycles before replanting. Sugarcane is currently produced commercially in over 70 countries, with nearly 22 million ha harvested annually, mostly between the 35 N and 35 S latitudes. Brazil is currently the largest producer of sugarcane, being responsible for one-third of that harvested in the world (FAO- STAT, 2009), with an area of 7 million ha (CONAB, 2009). A large part (85%) of the sugarcane cropped in the country is concentrated in the south-central region, where S˜ ao Paulo state is the main producer, with close to two-thirds of the Brazilian cropped area of 3.8 million ha. In the traditional sugarcane production system, burning residues has been a common practice in order to facilitate the manual Correspondence: M. V. Galdos. E-mail: mvgaldos@gmail.com Received 27 November 2009; revised version accepted 18 May 2010 harvest and transport operations. After burning, the partially burned tops are separated from the stalks and left on the field. The burning of sugarcane biomass before harvest represents 11% of all harvested residues burnt annually in the world (IPCC, 1995). The above-ground biomass is composed of approximately 60–80% stalks, and the rest are leaves and tops. According to field experiments with controlled pre-harvest fires, 70–95% of the dry matter of leaves and tops is lost with pre-harvest burning of sugarcane (Mitchell et al., 2000). Part of the charcoal produced during the burning events is carried by air currents, reaching the surrounding areas. As well as the nuisance of charcoal deposition in residential areas, there is evidence of a link between sugarcane residue burning and respiratory diseases affecting the population living in areas close to the sites of production (Canc ¸ado et al., 2006). The release of <4 μm silica minerals found within ash and aerosols produced by burning sugarcane can cause respiratory diseases (Le Blond et al., 2008). In addition to direct human health effects, there are envi- ronmental impacts related to burning sugarcane residues. For example, large concentrations of dissolved organic carbon (C) in the atmosphere have been measured in sugarcane production regions (Coelho et al., 2008). Crutzen & Andreae (1990) have © 2010 The Authors Journal compilation © 2010 British Society of Soil Science 23