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Provedor de dados:  Scientia Agricola
País:  Brazil
Título:  A model to explain high values of pH in an alkali sodic soil
Autores:  Guerrero-Alves,José
Data:  2002-12-01
Ano:  2002
Palavras-chave:  Gapon selectivity coefficients
Calcium carbonate
Sodium bicarbonate
Alkaline hydrolysis
Resumo:  For alkali sodic soils (pH>8.5), the "hydrolysis of exchangeable sodium" has been used as a possible explanation for the alkalinity production and rise in pH of these soils. As an alternative to this hypothesis, a model was developed to simulate and to explain that the alkalinity production and rise in pH is possible in a soil that accumulates alkaline sodium salts and CaCO3. Several simulations were performed by using different combinations of CO2 partial pressures (P), presence or absence of MgCO3, along with experimental values of exchangeable sodium percentage (ESP) and ion concentrations in saturation extracts from an alkali sodic soil (named Pantanal). A hypothetical system with similar conditions to the Pantanal soil but with a Gapon selectivity coefficient (KG) of 0.01475 (mmol L-1)-1/2 was also considered. Good agreement was obtained between experimental and predicted values for pH and ion concentrations in the soil solution when the model (without MgCO3) was applied to the Pantanal soil. However, KG values calculated for the Pantanal soil were generally higher than 0.01475 (mmol L-1)-1/2. Moreover, high pH values and elevated ionic strength were obtained when a KG of 0.01475 (mmol L-1)-1/2 was used at high ESP (similar to those found in the Pantanal soil). KG values obtained for the Pantanal soil and the results obtained in the simulation of the hypothetical system are suggesting that a value higher than 0.01475 (mmol L-1)-1/2 should be used to adequately simulate the behavior of the Pantanal soil at low ionic strength and high ESP values.
Tipo:  Info:eu-repo/semantics/article
Idioma:  Inglês
Editor:  São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Relação:  10.1590/S0103-90162002000400021
Formato:  text/html
Fonte:  Scientia Agricola v.59 n.4 2002
Direitos:  info:eu-repo/semantics/openAccess

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