Response of Andisols to intensive agricultural land use: Implication on changes in P accumulation and colloidal surface charge

Abstract

The response of Andisols to intensive agricultural practices were not fully explored although intensive cultivation has been practiced for a long period of time. The objective of the review is to bring together all findings, which have been documented with the focus on changes in soil organic matter, P content and retention, and colloidal surface charge. The Andisols contain an abundance of nano-clay consisting mainly of hollow allophane spherules forming globular aggregates of about 100 nm in diameter, indicating the large reactive surface area. A huge quantity of P has been accumulated in the uppermost two soil horizons, deriving from residue of continuous application of P fertilizer. Andisols have a strong ability to retain organic C through ligand exchange of metal hydroxyl functional groups with organic functional groups. The soil colloids bear a positive charge at soil pH less than 5. The colloidal negative charge is continuously increased with increasing soil pH over 5.0. Hence, the Andisols should be managed by maintaining soil pH above pH 5.0 by adding lime or compost to allow soil capability to retain cation and reduce P fixation. Nano-clay has positive impact on carbon stabilization and therefore C sequestration.