Hydrophobic soil

Hydrophobic soil is most familiarly formed when a fire or hot air disperses waxy compounds found in the uppermost litter layer consisting of organic matter.

It is much more difficult to entirely coat a silt or clay particle with more surface area, but when it does happen, the resulting water repellency of the soil is severe.

[7] This, however, depends on the type of microbial activity present in the soil as it can also hinder the development of hydrophobic compounds.

[8] This test is executed by recording the time it takes for one droplet of water to infiltrate a specific soil, indicating the stability of repellency.

It has also been observed that if the test droplet is placed on hydrophobic soil, it will rapidly develop a particulate skin before disappearing.

[2] Results of the WDPT:[9] Table 1: Characterizing the degree of hydrophobicity in soils based on the water droplet penetration test.

[10] The MED test uses solutions of ethanol of varying surface tensions to observe soil wetting within a time frame of 10 seconds.

The results of the MED test depend on the molarity of the ethanol solution whose droplets were absorbed in the allotted 10 seconds.

If irrigation or precipitation events are large, the water could potentially flow below the root zone, making it unavailable to any plant life and oftentimes taking fertilizers and nutrients with it.

[6] Generally, the degree of hydrophobicity is more severe in the soils of legume-grass pastures compared to cultivated agricultural fields.

[3] The liming process consists of adding calcium carbonate, which increases the pH of the soil towards neutral.

Figure 1: The structure of a hydrophobic sand particle versus an unaffected soil particle. The hydrophobic soil particle is coated in a wax-like lipid compound [ 4 ] with a hydrophilic head is attached to the individual particle and the hydrophobic tail is surrounding the outside of the particle. This hydrophobic tail shields any water from being absorbed by soil particles when many are affected. [ 2 ] The unaffected sand particle does not have this coating meaning that water can infiltrate through the sandy soil.