Chemical migration during soil water retention curve evaluation

Luiz F Pires,Felipe C.A Villanueva,Nivea M.P Dias,Osny O Santos Bacchi,Klaus Reichardt

doi:10.1590/s0001-37652011005000032

Luiz F Pires, Felipe C.A Villanueva + Show 3 more

Open Access

https://doi.org/10.1590/s0001-37652011005000032

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Abstract

Wetting and drying (W-D) cycles can induce important elemental migrations in soils. The main purpose of this work was to study the possible existence of soil chemical elemental migrations in samples submitted to repeated W-D cycles during evaluations of soil water retention curve (SWRC). The experimental measurements were carried out by Atomic Absorption Spectrometry (AAS) for Ca(2+), Mg(2+) and K(+) on samples of three different Brazilian tropical soils (Geric Ferralsol, Eutric Nitosol and Rhodic Ferralsol). Results demonstrate an increase in the electrical conductivity of the water extracted from the samples and significant losses of Ca(2+), Mg(2+) and K(+) during the applications of up to nine W-D cycles. It was also observed differences in SWRC for all soils when samples submitted to the application of several W-D cycles were compared with samples not submitted to it. These differences occurred at the region of both structural and textural pores. A possible explanation for these results could be the soil chemical migration during the sequences of W-D cycles, which can affect the soil structure development.

Highlights

The relationship between soil water matric potential ( m) and the respective water content (θ ), identified as the soil water retention curve (SWRC), represents a fundamental part of the soil hydraulic and physical characterization (Richards 1941)
It is possible to infer from these results that the Geric Ferralsol (GF) and Rhodic Ferralsol (RF) soils presented the greatest migration of chemical elements due to wetting and drying (W-D) cycles
The investigation of the migration of chemical elements of the soil by Atomic Absorption Spectrometry (AAS) led to the quantification of some ion losses when a soil is submitted to several W-D cycles

Summary

Introduction

The relationship between soil water matric potential ( m) and the respective water content (θ ), identified as the soil water retention curve (SWRC), represents a fundamental part of the soil hydraulic and physical characterization (Richards 1941). The SWRC is used to predict the retention of water available to plants and water movement through the soil This hydraulic property is several times taken as a static characteristic of a given soil (Klute 1986). When the procedure to measure the SWRC involves repeated W-D cycles on the same soil sample, possible chemical elements migration can occur as a consequence of these cycles. This migration can lead to important changes in the content of some chemical elements of the soil, e.g. Ca2+, K+ and Mg2+, and influence the water retention mainly at the region of low m

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