e-ISSN 2231-8542
ISSN 1511-3701
C.I. Fauziah, I. Jamilah and S.R. Syed Omar
Pertanika Journal of Tropical Agricultural Science, Volume 20, Issue 2&3, August 1997
Keywords: C E C , acid tropical soils, variable-charge soils, correlation study
Published on:
The cation exchange capacity (CEC) of soil is an important criteria for assessing soil fertility beside its use in soil classification. Seven methods, namely, (1) BaCl2 - triethanolamine of BaCl2 - TEA (pH 8.2), (2) NH4OAc (pH 7.0) - leaching, (3) NH4OAc (pH 7.0) - shaking, (4) compulsive exchange method of Gillman (1979) (CECCŁ), (5) modified compulsive exchange method of Gillman (1986) (GECJ, (6) Summation of Ca from method 5 with 1 MNHJSI03 exchangeable Al (CEC p and (7) summation ofNH4OAc (pH 7.0) exchangeable bases with 1 M KCl exchangeable Al (CEC J, were used to determine and compare the CEC values of five acid tropical soils. All methods gave different CEC values which followed the order BaCl2 - TEA > NH4OAc shaking = NH4OAc leaching > CEC = CEC > CEC— = CECR. Methods with pH conditions close to field situations gave much lower CEC values than the buffered methods. The buffered methods generate charge on the variable-charge colloids, thus resulting in inflated CEC values, while the unbuffered methods do not. There is a high correlation between BaCl2 - TEA and NH4OAc (pH 7.0) leaching method; CEC(lt and CECsum; and, CECR and CEC(otal. Amongst the methods evaluated, the NH4OAc (pH 7.0) leaching is recommended in routine soil analyses for classification purposes while CEC is recommended for agronomic evaluation.
ISSN 1511-3701
e-ISSN 2231-8542