Title:	Apparent ecec in some brazilian soils with variable charges determined using three different extractors
Authors:	DURIEZ, M. A. de M. MELO, M. E. C. C. M. JOHAS, R. A. L. ARAUJO, W. S. de
Affiliation:	MARIA AMELIA DE MORAES DURIEZ, CNPS; M. E. C. C. M. MELO, SNLCS; RUTH ANDRADE LEAL JOHAS, CNPS; WILSON SANT ANNA DE ARAUJO, CNPS.
Date Issued:	1988
Citation:	In: INTERNATIONAL SOIL CLASSIFICATION WORKSHOP, 8., 1986, Rio de Janeiro. Classification, characterization and utilization of oxisols: proceedings. Rio de Janeiro: EMBRAPA-SNLCS: USDA-SMSS: University of Puerto Rico, 1988. pt. 1, p. 49-55.
Description:	This is a study of the relationships among three different extractors for the determination of apparent ECEC values in 40 soil samples with dominant variable charges selected from 25 soil pedons. In the first method (Servico Nacional de Levantamento e Conservacao de Solos), N KC1 was used to extract calcium, magnesium, and extractable acidity, and North Carolina extractor was used for sodium and potassium. The second method used NH4OAc for calcium, magnesium, sodium, and potassium and the same values of NKC1 for extractable acidity. The third one used unbuffered dilute silver thiourea (AgTU) solution (0.01MAg+) for measuring exchangeable bases and extractable acidity. The apparent ECEC was obtained by the sum of all cations expressed in meq/100g soil or meq/100g clay. Potassium and sodium were measured by flame photometry, calcium and magnesium by atomic absorption spectro photometry, and extractable acidity by volumetric titration with dilute NaOH using phenolfralein as indicator. All soil samples used satisfied the criteria for low activity caly: apparent ECEC < 12 meq/100g 100g caly. The apparent ECEC values are highly correlated when referred to 100g of soil or 100g of clay. According to statistical analysis and tests of paired observations, AgTU extractor is significantly different from the others.
Thesagro:	Classificação do Solo
NAL Thesaurus:	Oxisols
Type of Material:	Artigo em anais e proceedings
Access:	openAccess
Appears in Collections:	Artigo em anais de congresso (CNPS)