Data/hora: 19/06/2024 11:34:23

Biblioteca(s): | Embrapa Cerrados.
Data corrente: | 15/07/1999
Data da última atualização: | 15/07/1999
Autoria: | NEUFELDT, H.; RESCK, D. V. S.; AYARZA, M. A.; ZECH, W.
Título: | Soil organic matter in Oxisols of the Brazilian cerrados.
Ano de publicação: | 1999
Fonte/Imprenta: | In: THOMAS, R.; AYARZA, M.A., ed. Sustainable land management for the oxisols of the Latin American savannas: dynamics of soil organic matter and indicators of soil quality. Cali: CIAT, 1999.
Páginas: | p.89-109.
Idioma: | Inglês
Conteúdo: | Little is known about the sustainability of cultivation systems in the Brazilian savannas, also known as the Cerrados, despite its increasing significance for that country`s agriculture. To characterize management effects and follow alterations of organic compounds in different fractions, we studied wholesoil samples and particle-size separates from clayey and loamy Oxisols under crops, pastures, reforested sites, and savanna. We assessed soil organic carbon (SOC), polysaccharides, and CuO oxidation products (VSC-lignin). Few changes were found in SOC contents of topsoil (0-12 cm) under different land uses after 10-20 years. But organic carbon clearly diminished under continuous cropping on the loamy soil and under reforestation withpine on the clayey soil. Management effects on SOC were more apparent in sand fractions, suggesting that particulate organic matter (POM) was affected most. In the clay fraction, only minor effects were noted. Carbon-normalized polysaccharide contents were enriched under pastures and depleted under pine, but generally followed a similar distribution to that of SOC. Overall, both polysaccharides and VSC-lignin were closely related to soil porosity. Plant-derived polysaccharides and lignin contents were probably regulated by mater availability to soil microbes, so that decomposition was usually more advanced in the clayey soils. Tem years of continuous cropping lowered litter inputs, thus reducing POM, whereas humified organic matter (OM) was unaffected. Planting eucalyptus or well-managed pastures, which produce high amounts of POM, would thus rapidly reverse soil degradation. Continuous cropping does eventually reduce the humified fraction and results in a substantial loss of soil fertility, which is only slowly reversible. In the loamy soils, rotation with a SOC-productive system, such as pastures or eucalyptus, was needed earlier because of their higher proportion of POM. Depletion of SOC under pine occured because new litter was not incorporated into the mineral soil, forming a thick moder layer as decomposition continued. After felling trees, the organic layer could be rapidly incorporated into the mineral soil, thus replenishing lost OM. However, the acid litter may reduce soil organic matter quality.
Thesagro: | Cerrado; Matéria Orgânica; Oxisol; Solo.
Thesaurus Nal: | Ferralsols; organic matter; soil.
Categoria do assunto: | --
Registro original: | Embrapa Cerrados (CPAC)
Exemplares: | CPAC - (2457-1) - UPC - PL - -- - CRI4998 -  - CRI4998 - DIS