Data/hora: 23/09/2024 19:47:40

Biblioteca(s): 	Embrapa Cerrados.	
Data corrente: 	16/02/2000	
Data da última atualização: 	16/02/2000	
Autoria: 	NEUFELDT, H.; AYARZA, M. A.; RESCK, D. V. S.; ZECH, W.	
Título: 	Distribution of water-stable aggregates and aggregating agents in Cerrado Oxisols.	
Ano de publicação: 	1999	
Fonte/Imprenta: 	Geoderma, Amsterdam, v.93, p.85-99, 1999.	
Idioma: 	Inglês	
Conteúdo: 	The effects of structural changes on Cerrado Oxisols in Brazil after land-use change are still insufficiently studied. Therefore, topsoil samples of loamy and clayey Cerrado Oxisols under crop pasture and reforestation were fractionated using a wet-sieving procedure to obtain the distribution of water-stable aggregates and compared to samples from natural savanna. The results were correlated to organic and inorganic soil compounds to identify the main aggregating agents and discussed in relation to changes in the pore-size distribution of the soils. Clayey soils showed a significantly higher macro-aggregation than loamy soils. Compared to natural savanna, macro-aggregation was clearly reduced at the crop sites, whereas aggregation of soils under pasture and reforestation was only slightly affected. In both the clayey and the loamy soils, bonding of polysaccharides was the main aggregating agent. In the clayey soils, liming was also very important for disaggregation by weakening the electrostatic forces between positively and negativeley charged soil compounds, whereas in the loamy soils, binding of macro-aggregates by roots was significant. The introduction of crop-pasture rotations was therefore proposed to take advantage of the strong rooting and polysaccharide production of pastures. Management-induced disaggregation strongly affected the pore-size distribution by compacting the soils. Thereby, macro-porosity was reduced and the ampunt of meso-pores was increased, while micro-porosity was unaffected from management and only differed between the two substrates. Considering the low pore space at plant-available matrix potentials typical of Cerrado Oxisols, the increase might be important for annual crops during the frequent dry spells in the rainy season.	
Thesagro: 	Cerrado; Estrutura do Solo; Uso da Terra.	
Thesaurus Nal: 	Ferralsols; land use; soil structure.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Cerrados (CPAC)	
Exemplares: 	CPAC - (11944-1) - UPC - SP - -- - CRI5090 -  - CRI5090 - DIS