Environmental Assessment
Volume B-3.3
Mine
Soils
Ambatovy Project
30
January 2006
3.3
SOILS
3.3.1
Introduction and Study Area
This section presents the Environmental Assessment for the effects of the mine
on soils, as per the Ambatovy Project (the project) Terms of Reference.
The mine site study area for soils is the mine project footprint study area
presented in Volume A, Figure 7.2-1. It includes the mine and water intake
pipeline direct disturbance areas.
3.3.2
Baseline Summary
3.3.2.1 Regional Overview
Soils of the mine region have developed on old, geomorphically stable terrain
with almost no vestige of the original rock structure. Intense weathering in the
humid tropics from high temperatures, abundant moisture and time has resulted
in deep soil development.
Tropical soils are generally low in nutrients due to the high rainfall which
promotes weathering and leaching of minerals through the soil profile and out of
the root zone. High soil temperatures and moisture conditions favour high levels
of biological activity including organic matter production and its rapid
degradation, which result in low organic matter. Nutrient holding capacity of
soils in the humid tropics is mainly a function of humus content and is very low
where humus content is low (Whitmore 1975). Roots are concentrated at the soil
surface even though many tropical subsoils do not have any physical
characteristic that would restrict rooting. Reclamation of vegetation in tropical
soils is challenging because the soils are low in nutrients, notably nitrogen and
phosphorus (Zonn 1986).
The soils in the mine region are generically known as laterites, which are defined
as highly weathered iron-rich tropical soils (Young 1976). The word laterite has
been widely used in the literature to describe soils of the tropical and subtropical
regions of the world. These general terms are often used to describe various
morphologic, physical and chemical properties.
