Page 182 - Area 9 - Relevant Document

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A.5. LIGHTNING
- plays a very important role in the electrical fixation of
atmospheric nitrogen

B. SOIL FACTORS: fertility, ph range, depth, texture nature of parent
material, permeability, drainage, aeration, moisture regimes, soil
faunal composition.

B.1. SOIL DEPTH

- determines the stability and availability of water and
nutrients
- Liable to vary extensively. Trees with deep penetrating
root system require deep soils. Those with fibrous root
system need medium to deep top soil.

B.2. MOISTURE REGIME

- Available moisture at the driest period of the year is very
critical.
- Different species vary in their soil moisture optimum
requirements and the limits of such.
- Surface rooted species are more sensitive to water stress
than deeply rooted ones.
- Water holding capacity of the soil largely determines the
type of species to be grown.

B.3. NATURE OF PARENT MATERIAL

- Impervious subsoil may limit availability of water and
nutrients to trees.

B.4. SOIL PH

- Extremes soil reactions are not favorable to tree growth.
- Plant species differ with high rainfall and humidity
generally tend to be acidic while those found in arid zones
to be alkaline.

B.5. SOIL TEXTURE

- Fertility of the soil is commonly related with the
percentage of fines in the soil. These includes the mineral
silt and clay particles and similarly sized organic matter.
- Affects site quality, influencing the chemical properties of
the soil, soil moisture and air relations and root
development.