The cation exchange capacity of a sandy soil in southern Brazil: an estimation of permanent and pH-dependent charges

Autor: Edson Campanhola Bortoluzzi, J. L. Julien, Danilo dos Santos Rheinheimer, Daniel Tessier
Rok vydání: 2005
Předmět:
Zdroj: European Journal of Soil Science. 57:356-364
ISSN: 1351-0754
Popis: Summary In soils in general, the cation exchange capacity is an important factor in soil fertility because it determines both cation retention and selectivity, and in turn controls most of the other soil properties. The main goal of this paper was to estimate the cation exchange capacity (CEC) and the contribution of permanent charges and pH-dependent charges and their respective importance in soil CEC as a function of pH, clay and organic matter content in soils. A multiple regression method was developed from 75 samples under different soil management practices. The permanent charge (∼ 140 mmolc kg−1 of clay) estimated by this approach was independent of the analytical method used, i.e. a French method (MF) and a Brazilian method (MB), and is consistent with the presence of 2:1 clay minerals. However, the pH-dependent charges were closely related to the buffering capacity inherent in each protocol (MF protocol using NH4+, and MB using a SMP solution proposed earlier by other workers, both at pH 7). For the MF protocol, the proposed method appeared to be well adapted for reproducing soil component properties under different management conditions. In the soil samples studied, the contribution of organic carbon to negative charges ranged from 12.3 to 55.8% of effective CEC and from 14.1 to 59.2% of CEC at pH 7. However, the clay contribution, notably its permanent charges, can contribute to 31% and more of the CEC in the lower horizons of soil profiles. The proposed approach can accurately evaluate the effective and pH 7 CECs when the MF protocol is used but evaluation is less accurate with the MB protocol. Resume Dans les sols la capacite d'echange en cations est un facteur important de la fertiilite du fait qu'elle determine la retention et la selectivite des cations, et ainsi controle une grande partie des proprietes des sols. Le principal objectif de cet article est d'estimer la capacite d'echange en cations (CEC) et la contribution des charges permanentes et variables et leur importance respective a la CEC du sol en fonction du pH, de la teneur en argile et en matieres organiques dans un sol subtropical du Sud du Bresil. Une methode de regression lineaire multiple a ete developpee a partir de soixante quinze echantillons sous differentes pratiques. La charge permanente estimee est independante de la methode utilisee, i.e. methode francaise (MF) et bresilienne (MB). Ce resultat est en accord avec la presence de mineraux 2:1 (∼ 140 mmolc kg−1 d'argile). Cependant les charges variables sont etroitement reliees au pouvoir tampon inherent a chaque protocole (protocole MF avec NH4+ et solution SMP pour le protocole MB, l'un et l'autre a pH 7.0). L'approche apparait ainsi adaptee pour decrire les proprietes des sols sous differentes gestions. Dans les echantillons de sols etudies la contribution du carbone organique aux charges negatives est comprise entre 12.3 et 55.8% de la CEC effective et de 14.1 a 59.2% pour la CEC a pH 7.0. Cependant, la contribution des charges permanentes de l'argile peut contribuer a hauteur de 31% et plus a la CEC des horizons inferieurs. Les deux types de CEC peuvent etre evalues par cette approche, mais avec une plus grande precision avec le protocole MF.
Databáze: OpenAIRE
Externí odkaz: