Decomposição de resíduos de eucalipto e efluxo de C-CO2 em solos em diferentes locais do Brasil

• Autor(a) principal: Brandani, Carolina Braga
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5430
• topic: Resíduos da colheita de eucalipto; Nitrogênio; Evolução de C-CO2; Eucalyptus residue; Nitrogen; Evolution of de C-CO2; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The eucalypt plantations generate a large amount of residues after the tree harvest. The residues, when left on the soil may become a potential contributor to the C fraction of soil organic matter, or CO2 to the atmosphere. The Residue decomposition is complex and it leads to causes changes in the chemical composition and in the microorganism succession that is able to use the residue with distinct compositions. In addition, the soil and climate characteristics and the tillage adopted may have strong influence on the decomposition rate of the harvest residue. In this context, a field experiment was carried out at six different locations in Brazil: Eunápolis-BA, Aracruz-ES, Belo Oriente, Virnigópolis, Três Marias e João Pinheiro - MG. The purpose was to evaluate the decomposition rate of the eucalyptus residues and the soil C-CO2 efflux under different managements tillage. Instead of using litter bags, tubes of polyvinyl chloride (PVC) with 15 cm of diameter and 15 cm length, were inserted 10 cm deep into the soil, and then, the treatments applied. The treatments consisted of a 2x2x3 factorial combinations (with and without the addition of 200 kg/ha of N as ammonium nitrate with residue kept on the surface or incorporated in the soil at a depth of 5 cm, in the absence of residue, residue with or without. The experimental design was randomized blocks with plots split in time, with four repetitions. The tubes were kept in the field during 0, 90, 180 e 365 days, occasions at which they were excavated, immediately transported to the laboratory and incubated in a respirometry room, so that the evolution of de C-CO2 could be assessed. The eucalypt residues contribution to respired CO2 was estimated based on the natural variation of 13C/12C-CO2. Subsequently, the residue was separated from the soil, dried at 65 ºC and weighted to obtain the residual dry matter (MSREM) in the four assessed time intervals. Exponential equations were fitted to the MSREM data, which, enabled the assessment half-life (t1/2) of the residue. It was observed that in regions where the soil is sandy, the rate of the harvest residue decomposition was greater, the stabilization of C derived from the eucalypt residue was smaller and the labile C and N contents were smaller. The N fertilization resulted in a smaller contribution of eucalypt residue to the C- CO2 efflux (resulting in a greater stabilization of residue - derived C) and greater content of labile N. The incorporation of eucalypt residue into the soil accelerated its decomposition and, in the absence of bark, increased the residue contribution to the respired CO2, indicating a smaller stabilization in the soil. The presence of bark resulted in a greater C-CO2 evolution; however, it reduced the contribution of the respired CO2, indicating greater C residue stabilization in SOM, especially in sandier soils.