title: Soil carbon, nitrogen and phosphorus changes under sugarcane expansion in Brazil.
abstract: Historical data of land use change (LUC) indicated that the sugarcane expansion has mainly displaced pasture areas in Central-Southern Brazil, globally the largest producer, and that those pastures were prior established over native forests in the Cerrado biome. We sampled 3 chronosequences of land use comprising native vegetation (NV), pasture (PA), and sugarcane crop (SC) in the sugarcane expansion region to assess the effects of LUC on soil carbon, nitrogen, and labile phosphorus pools. Thirty years after conversion of NV to PA, we found significant losses of original soil organic matter (SOM) from NV, while insufficient new organic matter was introduced from tropical grasses into soil to offset the losses, reflecting in a net C emission of 0.4 Mg ha(-1)yr(-1). These findings added to decreases in (15)N signal indicated that labile portions of SOM are preserved under PA. Afterwards, in the firsts five years after LUC from PA to SC, sparse variations were found in SOM levels. After more than 20 years of sugarcane crop, however, there were losses of 40 and 35% of C and N stocks, respectively, resulting in a rate of C emission of 1.3 Mg ha(-1)yr(-1) totally caused by the respiration of SOM from C4-cycle plants. In addition, conversion of pastures to sugarcane mostly increased (15)N signal, indicating an accumulation of more recalcitrant SOM under sugarcane. The microbe- and plant-available P showed site-specific responses to LUC as a function of different P-input managements, with the biological pool mostly accounting for more than 50% of the labile P in both anthropic land uses. With the projections of 6.4 Mha of land required by 2021 for sugarcane expansion in Brazil to achieve ethanol's demand, this explanatory approach to the responses of SOM to LUC will contribute for an accurate assessment of the CO₂ balance of sugarcane ethanol.
authors: Center for Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário 303, 13416-000 Piracicaba, SP, Brazil. Electronic address: andrefranco@usp.br.
authors: André L C
authors: AL
authors: Franco
authors: Center for Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário 303, 13416-000 Piracicaba, SP, Brazil.
authors: Maurício R
authors: MR
authors: Cherubin
authors: Department of Soil Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Av. Pádua Dias 11, 13418-900 Piracicaba, SP, Brazil.
authors: Paulo S
authors: PS
authors: Pavinato
authors: Department of Soil Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Av. Pádua Dias 11, 13418-900 Piracicaba, SP, Brazil.
authors: Carlos E P
authors: CE
authors: Cerri
authors: Department of Environmental Systems Science, ETH Zurich, Tannenstrasse 1, 8092 Zurich, Switzerland.
authors: Johan
authors: J
authors: Six
authors: Shell Technology Centre Houston, 3333 Highway 6 South, Houston, TX 77082, USA.
authors: Christian A
authors: CA
authors: Davies
authors: Center for Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário 303, 13416-000 Piracicaba, SP, Brazil.
authors: Carlos C
authors: CC
authors: Cerri
mesh_terms: D000383:Agriculture; D001938:Brazil; D002244:Carbon / Q000032:analysis*; D018556:Crops, Agricultural / Q000254:growth & development; D017753:Ecosystem; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D031786:Saccharum / Q000254:growth & development*; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
keywords: Bioenergy; Environmental sustainability; Land use change; Soil organic matter