Page 99 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 87

6.1 Relationship between Soil Water, Soil Temperature,
and Air Temperature

Water in soils is deposited in soil pores, particularly those with micro or
meso in size. Therefore, the soil water content is dependent on the size of the soil
pores. The soil capacity to stock water is better in soil with high portions of
micropores and mesopores. Various factors affecting the size of soil pores such as
soil texture, structure, and porosity will influence the soil water content. Hence, it
is probable that clay soils will have higher water contents than do silt soils and silt
soils will have higher water contents than do sand soils. This prediction is based on
the asumption than the portions of micro and mesopores in soils follows the
following order: sand soils < silt soils < clay soils.
The above order may change with soil particle aggregation that affects the
soil structure and pore distribution. Clay and silt soils with good structure may
possess more macropores and retain less water because most of the water are
easily drained. As a result, the order of water contents may change to be: sand
soils > silt soils > clay soils. The changes are shown in Fig. 6.2.

70

60
Water Content (%) 40 Clay
50

30
Silt
20

10 Sand
0
Poor Good
Structure Structure

Fig. 6.2. The changes in water contents of soils with different textures
and structures (Salam, 2012).

Abdul Kadir Salam - 2014