Soil air is an important component of soils.
It occupies those pore spaces not occupied by soil water. Soil air competes
with soil water for the pore spaces in the soil, hence it moves in as water
moves out.
For optimum plant growth, soil air has to be adequate in both amount and composition.
Similar to soil water, the volume of soil air
present in the soil is highly dynamic. However, the volume of air in the soil
depends on only one factor, which is, the volume of water present in the soil. Therefore,
the more of water a soil has, the less of air it will have and vice versa. This
makes the soil’s air-water relationship to be inverse as well as dynamic.
The major source of soil air mostly is the
atmosphere above the soil. However, the content and composition of soil air
differs from that of atmospheric air as it determined largely by the soil-water
relationship. In addition, reactions involving gases can greatly modify the
composition of soil air.
Ordinarily, soil air occupies the large sized
pores (macro-pores) and as the soil dries out, the intermediate sized pores
(meso-pores): the micro-pores do not readily dry out. This explains why soils
with a high proportion of micro pores tend to be poorly aerated.
Soil air has the
following characteristics:
– It exists in assort of discontinuous phase,
separated by soil solids. This accounts for variations in its composition from
place to place.
– It generally has higher moisture content than
atmospheric air, with its relative humidity approaching 100% when the soil
moisture is optimum.
– It has a higher carbon dioxide concentration than
the 0.03% of the atmospheric air and an oxygen concentration lower than that of
the atmospheric air.
Therefore, it is important that soils be
aerated for pants roots to have adequate supplies of oxygen through soil air.
Further Studies in
this theme:
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