Chemical composition of cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate soils

Abstract

The purpose of this study was to investigate the influence of soil geochemistry on the concentrations of Ca, K, Mg, P, Co, Ni, Zn, Mn, Cu, and Fe in cabbage (Brassica oleracea L. var. capitata) grown on acid sulfate (AS) soils in Western Finland. A total of 11 topsoil (0-20 cm) and corresponding cabbage samples and three whole-soil profiles (≈ 0-260 cm) were collected on three agricultural fields. The concentrations of Co and Zn in cabbage were correlated with the NH 4 Acextractable (easily available) concentrations in the topsoil, indicating that the uptake of these elements in cabbage is largely governed by soil geochemistry. Yet, the concentrations of Co and Zn in cabbage were not in general elevated relative to that of Finnish average values, although some AS soils showed enriched concentrations of these metals in the soil and cabbage. Significant geochemical differences (e.g., oxidation depth, organic-matter and S content, pH) were observed among the studied AS soils, while, on the other hand, the concentrations of Ca, K, Mg, P, Ni, Mn, Cu, and Fe in cabbage were relatively similar. The hydroxylamine-extractable concentrations of these elements in the topsoil were not correlated to those in cabbage, suggesting that uptake is not governed by the oxide-bound fraction of these elements in the soil. Similarly, the easily available concentrations of Ca, P, Ni, Mn, Cu, and Fe in the topsoil were not correlated to those in cabbage, indicating that uptake is independent of the easily available concentrations in the soil. Hence, it is suggested that cabbage can regulate and thus optimize its concentrations of Ca, P, Ni, Mn, Cu, and Fe. Oxidation depth affected neither the easily available concentrations of Co, Ni, Zn, and Mn in the topsoil nor the concentrations in cabbage. However, the subsoil with a lower oxidation depth, which is to a smaller extent affected by leaching, may partly be enriched in these metals. Nevertheless, these showed no increased concentrations in cabbage. Based on these findings, it is suggested that the large amounts of metals mobilized in AS soils are easily lost to drains, subsequently contaminating nearby waterways and estuaries whereas they are only partly enriched in cabbage and other previously studied crops (oat).

The Importance of Sustainable Management of Acid Soils in the Humid Tropics Under Climate Change and the Future Research Directions

“…The main impacts associated with ASS are acidification and accumulation of potentially toxic contaminants (Fältmarsch et al, 2010). Under severe conditions, the acid produced lowers the soil pH to <4 if ANC is absent (Nordmyr et al, 2008).…”

Acid sulfate soils: A challenge for environmental sustainability

“…In Finland, metal leakage from AS soils is greater than that of the country's entire industry (Sundström et al, 2002). However, crops grown in AS soils are not enriched with these metals (Fältmarsch et al, 2010) because their roots do not enter the horizons where the metals are dissolved.…”