Distribution of magnesium forms in surface soils of Central Southern Nigeria

Abstract

The distribution of various Mg forms in selected surface soils of the Edo State of Central Southern Nigeria was studied to contribute for a basic understanding of where and in what fractions Mg was located. Twenty surface (0 – 15cm) soil samples collected from pre-classified sites were investigated. The various Mg forms were determined by fractionation. Exchangeable [Mg(e)], organic complexed [Mg(o)], acid-soluble [Mg(a)], mineral [Mg(m)], and total [Mg(t)] ranged from 0.64 – 2.10, 0.12 – 0.63, 2.52 – 5.25, 2.94 – 5.04 and 7.35 – 12.60 cmol kg−1 with means of 1.36, 0.33, 3.69, 3.86 and 9.65 cmol kg-1, respectively. The Mg(o) averaged less than 3.42% of the Mg(t) in the soils. Mg(t) content of the soils appeared to be influenced by parent materials. The amounts of the various chemical forms of Mg could be ranked in terms of abundance in soils in the following order: Mg(m) > Mg(a) > Mg(e) > Mg(o). Mg(a) was positively and significantly correlated with Mg(m) and Mg(t) (P ≤ 0.05) while Mg(m) was positively and significantly correlated with Mg(t) (P ≤ 0.001). The soils were adequate in Mg(e) based on established critical levels for Nigerian soils.