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Soil Air

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.

Soil Air

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.






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