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To meet the growing demand for bioenergy such as ethanol, the area cultivated with sugarcane has expanded, especially in areas currently occupied by extensive pastures with low productivity. However, land-use change (LUC) from pasture to sugarcane implies changes in soil structure and variations in organic matter (SOM) stored in the soil. This study aimed to quantify the impact of LUC on organic matter fractions – particulate organic matter (POM) and mineral-associated organic matter (MAOM) – in soils with contrasting textures, and to explore the correlations between possible alterations in soil aggregation and the effects on carbon (C) stocks and SOM fractions. The study was conducted in two areas in Central-Southern Brazil, one with clayey soil and the other with sandy soil. In each area, a LUC chronosequence was evaluated: native vegetation (NV), pasture (PA), short-term sugarcane (SC1), the area analyzed during the sugarcane plant cycle; long-term sugarcane (SC2), area analyzed during the ratoon sugarcane cycle. In each use, undisturbed and disturbed samples were collected and macroaggregates and microaggregates were obtained by wet sieving and soil samples. In these samples, the physical fractionation of the SOM and the calculation of the C contained in each fraction of the SOM and C total stock of each use were performed. The conversion of NV to PA increased C stocks by more than 50 %, mainly in the MAOM fraction, and maintenance of macroaggregates (more than 80 %) in sandy site; and reduction of C stocks by more than 30 %, mainly MAOM in the clayey area. These benefits acquired from grazing on sandy area were lost with the expansion of sugarcane, a reduction of more than 20 % in macroagregation and C stocks. The sugarcane expansion into pasture with clayey site resulted in C accumulation (more than 2 Mg C ha-1 yr-1) and recovery of stocks on a SC2 basis. Expanding sugarcane areas into low-productivity pasture areas can be considered a sustainable strategy, especially in clayey soils, in which multiple gains occur through C sequestration and improved soil quality, as well as the reduction of CO2 emissions through the diversification of the energy matrix with the production of ethanol.

Submitted by RICARDO DE OLIVEIRA BORDONAL null (rbordonal@yahoo.com.br) on 2016-02-23T22:00:45Z No. of bitstreams: 1 Tese_Ricardo_De_Oliveira_Bordonal_2016.pdf: 3586706 bytes, checksum: 108f9c1e18a486f990bdf2e4f666bec9 (MD5) Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-02-25T16:25:11Z (GMT) No. of bitstreams: 1 bordonal_ro_dr_jabo_par.pdf: 939929 bytes, checksum: dd8229e3cd3d43c5cb50a21e7c12980b (MD5) Made available in DSpace on 2016-02-25T16:25:11Z (GMT). No. of bitstreams: 1 bordonal_ro_dr_jabo_par.pdf: 939929 bytes, checksum: dd8229e3cd3d43c5cb50a21e7c12980b (MD5) Previous issue date: 2016-02-03 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A substituição dos combustíveis fósseis pelo etanol de cana-de-açúcar visando à redução das emissões de gases de efeito estufa (GEE) tem sido recentemente questionada devido às possíveis emissões decorrentes da mudança do uso da terra (MUT). Este trabalho se baseou no inventário de GEE do cultivo e da MUT associada à expansão da cana-de-açúcar no centro-sul do Brasil, com a finalidade de estimar o impacto dessa expansão no balanço de GEE, incluindo as emissões e remoções devido à MUT. Objetivou-se também, por meio de experimento de campo, avaliar as mudanças na quantidade e qualidade do carbono (C) do solo após a conversão de diferentes agrossistemas (café, citros, cultura anual e pastagem) para cana-de-açúcar no sudeste do Brasil. As estimativas apontam que o cultivo da cana-de-açúcar e sua expansão durante 2006-2011 no centro-sul do Brasil resultaram no balanço acumulado total de GEE de 217,1 Tg CO2eq em 2030, incluindo as emissões das atividades de cultivo e as emissões/remoções associadas à MUT. As estimativas indicam que a expansão dos canaviais contribuiu para atenuar parte das emissões de GEE da fase de produção agrícola. Do mesmo modo, o uso de etanol em substituição aos combustíveis fósseis poderia facilmente compensar esse déficit de C. Os resultados das avaliações de campo apontam que a conversão de café para cana-de-açúcar resultou na depleção dos estoques de C do solo de 21,5% (26.8 Mg C ha-1) e 23,6% (34.9 Mg C ha-1) na camada de 0-100 cm ao longo dos períodos de 3 e 4 anos após a MUT, respectivamente. As conversões de pastagem e cultura anual para cana-de-açúcar não apresentaram diferenças significativas na camada de 0-100 cm. Entretanto, apenas a transição de pastagem para cana apresentou diferenças significativas na camada de 0-20 cm, resultando na depleção dos estoques de C do solo de 43,9% (13.3 Mg C ha-1) durante 8 anos após a conversão. Com relação à qualidade do C do solo, a técnica de espectroscopia de fluorescência induzida por laser mostrou que quanto maior a perda de C no solo devido à MUT para cana, maior o índice de humificação (HFIL) da matéria orgânica do solo (MOS). Em geral, a conversão dos agrossistemas (café, citros, cultura anual e pastagem) para cana-de-açúcar promoveu o aumento do HFIL da MOS. Em algumas profundidades, o HFIL mais do que dobrou em relação aos usos anteriores. Espera-se que os resultados gerados neste trabalho contribuam para o desenvolvimento de ações e políticas públicas visando fortalecer estratégias que possam potencializar ainda mais a mitigação de GEE, e garantir os benefícios ambientais do etanol de cana-de-açúcar no Brasil. The substitution of fossil fuel with sugarcane ethanol aiming to reduce emissions of greenhouse gases (GHGs) has recently been debated because of the possible emissions incurred from land use change (LUC). This work was based on GHG inventory from cultivation and LUC of recently established sugarcane plantation in south-central Brazil, with the purpose of estimating the impact of expansion on GHG balance, including emissions and removals due to LUC. Changes in quantity and quality of soil carbon (C) upon conversion of diverse agricultural systems (coffee, citrus, annual crops and pasture) to sugarcane in southern Brazil were also assessed through field experiments. The estimates show that sugarcane cultivation and its expansion during 2006-2011 in south-central Brazil presented an overall accumulated GHG balance of 217.1 Tg CO2eq by 2030, including emissions from cultivation activities and emissions/removals due to LUC. Expansion of sugarcane plantation contributed to attenuate part of GHG emissions from agricultural production phase. Similarly, the ethanol C offset by displacing fossil fuels could readily payback that C deficit. The data obtained by field experiments show that the LUC of coffee and citrus to sugarcane depleted soil C stock by 21.5% (26.8 Mg C ha-1) and 23.6% (34.9 Mg C ha-1) in the 0-100 cm layer after a period of 3 and 4 years, respectively. In contrast, there was no significant difference in soil C stocks in 0-100 cm depth upon conversion of pasture and annual crop into sugarcane. However, only the conversion of pasture into sugarcane decreased soil C stock in 0-20 cm depth, with depletion of 13.3 Mg C ha-1 (43.9%) over 8 years after the LUC. With regard to the quality of soil C, the data of Laser-Induced Fluorescence Spectroscopy (LIFS) showed that the higher the losses of soil C, the greater was the humification index (HLIFS) of soil organic matter (SOM). In general, conversion of the agrosystems (e.g., coffee, citrus, annual crop and pasture) into sugarcane increased HLIFS of SOM. For some depths, HLIFS more than doubled in comparison with the previous land uses. We expect that the results achieved in this work may contribute to the development of actions and public policies to strengthen strategies for GHG mitigation and ensure the environmental benefits of sugarcane ethanol in Brazil. CNPq: 142232/2012-2 CAPES: BEX 7765/13-4

Made available in DSpace on 2014-06-11T19:28:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-18Bitstream added on 2014-06-13T18:07:28Z : No. of bitstreams: 1 bordonal_ro_me_jabo.pdf: 463360 bytes, checksum: 6cb5546f1825775c527f6bb9e3db840e (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Há uma necessidade crescente dos setores produtivos no desenvolvimento de técnicas de mitigação de gases de efeito estufa (GEE) de forma a reduzir o efeito estufa adicional. Entretanto, o desafio para o setor agrícola é reduzir as emissões líquidas de GEE enquanto se aumenta a produção para atender a demanda crescente por alimentos, fibras e biocombustíveis. Neste estudo foi estimado (i) o balanço de GEE em cenários de produção da cana-de-açúcar (S0, S1, S2 e S3), cuja colheita manual com queima (CQ) é convertida para a mecanizada sem queima (CC, cana crua), levando em consideração a adoção de práticas agrícolas conservacionistas, tais como o preparo reduzido do solo e a introdução da rotação de culturas com Crotalaria juncea L. durante a reforma do canavial; e (ii) o potencial de mitigação de GEE no período de 2012 a 2041 devido à conversão das áreas de cana-de-açúcar colhidas com queima (safra 2010/2011) no Estado de São Paulo para três cenários de manejo (S1, S2 e S3). Baseando-se nas metodologias do IPCC (2006), o balanço anual das emissões de GEE inclui as fontes agrícolas e móveis (maquinários), de acordo com o consumo médio anual de diesel e insumos agrícolas por hectare. Nos cenários que envolvem a colheita crua, o potencial de acúmulo de carbono no solo também foi considerado. Os resultados apontaram que a adubação nitrogenada sintética e o consumo de diesel foram responsáveis pelas maiores emissões nos cenários de cana crua, enquanto a queima de resíduos na pré-colheita da cana-de-açúcar resultou na maior emissão observada no cenário de cana queimada. As emissões totais de GEE foram de 2.651,9 e 2.316,4 kg CO2eq ha-1 ano-1 para CQ (S0) e CC (S1), respectivamente. Considerando a taxa média de acúmulo de carbono no solo de 888,1 kg CO2 ha-1 ano-1 devido à conversão de CQ para CC, que... There is a growing need for all productive sectors to develop GHG (greenhouse gas) mitigation techniques to reduce the enhanced greenhouse effect. However, the challenge to the agricultural sector is reducing net emissions while increasing production to meet growing demands for food, fiber and biofuel. This study estimated (i) the GHG balance in sugarcane production scenarios (S0, S1, S2 e S3) in which the burned harvest system (BH) is converted to green harvest (GH, mechanized harvest), taking into account some conservationist practices such as reduced tillage and a 4-month crop rotation with Crotalaria juncea L. during sugarcane replanting; and (ii) the GHG mitigation potential in the period from 2012 until 2041 due to conversion sugarcane areas harvested with burning (2010/2011 crop season) in São Paulo State for 3 management scenarios (S1, S2 e S3). Based on the IPCC (2006) methodologies, the annual emission balance includes both agricultural and mobile sources of GHG, according to the mean annual consumption of diesel and supplies per hectare. The potential soil carbon accumulation was also considered in the GH plot. The results indicated that the synthetic N fertilizer and diesel consumption were responsible for higher emissions in GH plot, while the burning of straw in sugarcane pre-harvest resulted in higher emissions observed in BH plot. The total amount of GHG emission was 2,651.9 and 2,316.4 kg CO2eq ha-1 yr-1 for BH (S0) and GH (S1), respectively. Factoring in a mean annual soil carbon accumulation rate of 888.1 kg CO2 ha-1 yr-1 (due to the input from long-term crop residues associated with the conversion from BH to GH), the emission balance in S1 scenario decreased to 1,428.3 kg CO2eq ha-1 yr-1. A second reduction in GHG balance occurred when a reduced tillage strategy was adopted instead of... (Complete abstract click electronic access below)