Soil is a material covering layer on the surface and is formed by weathering of rocks. Soils change in their characteristics due to various reasons such as biological, climatic, geological, and topographic influences. These changes in the natural properties of soil are known as soil formation.
The soil temperature significantly influences soil formation; it speeds up the chemical reactions, which helps control how fast the weathering process or rocks happen and dead organisms decompose. A warmer soil temperature aids in faster soil development compared to cold or extremely hot soil temperature.
Soil temperature is the function of heat exchanges between the soil and the atmosphere. The main source of soil temperature is solar radiation. The use of a thermometer can measure the heat on the soil. Soil temperature can vary seasonally and daily; this can be as a result of the changes
Factors Influencing Soil Temperature
There are many factors that can influence the temperature of the soil. These factors will affect the overall formation of the soil in a region.
- The slope of the land surface
The amount of solar radiation reaching a land surface at an angle is scattered at a larger area compared to the amount of radiation that reaches a flat land surface. Therefore there is a decrease in radiation per unit as there is an increase in slope.
The evaporation of moisture from the soil requires a large amount of energy. The moisture in soil utilizes the heat energy from the sun for evaporation, making it unavailable for heating the soil. The greater the evaporation rate in the soil, the more the soil is cooled.
- Soil color
Darker colored soils absorb more heat from the sun and retain it compared to light-colored soils. Darker colored soils will have higher temperatures than light-colored soils.
- Vegetative cover
Vegetation cover is the thermal insulator of soil; bare soil will absorb heat quicker on hot days while releasing heat faster on cold days. Having a vegetative cover will influence the temperature of the soil.
- Solar radiation
Solar radiation is the amount of heat from the sun that reaches the earth’s surface. The amount of heat that the earth’s surface receives and absorbs will affect the temperature of the soil. As the solar radiation levels increase, there is an increase in soil temperature.
- Soil moisture content
The moisture content of the soil affects heat dispersion down the soils profile. The flow of heat will be higher in wet soil than in dry soil, where the soil’s pores are filled with air.
Effects of Soil Temperature on Soil Formation
There are several effects of soil formation. The effects can be grouped into categories which are biological, chemical, and physical properties.
- Soil structure
The increase in the temperature of the soil causes the dehydration of clay minerals, leading to interactions among clay particles, which in turn yields less clay to silt-sized particles in the soil. High soil temperature can lead to cracks in the sand particles in the soil. This temperature rise will change the physical structure of the soil.
- Soil aeration
The temperature of the soil can influence the amount of carbon dioxide content that is in soil air. The high temperature of the soil encourages the production of microorganisms which results in higher production of carbon dioxide.
- Aggregate stability
When a soil temperature is above 30 degrees, the aggregate stability of the soil increases, the strength of the aggregate is due to the thermal transformation of aluminum and iron oxide, making them act as cementing agents in the soil.
- Soil micro and macro-organisms
Soil microorganisms require temperatures between 10 degrees and 35 degrees for their activities. Soil microbial activities usually decrease with lower soil temperature, and at freezing temperatures, most activities stop. The best temperature range for their metabolisms is between 10 degrees and 24 degrees for macro-organisms activities.
- Organic matter decomposition
Soil matter accumulation increases at a temperature below 0 degrees due to a slow decomposition rate. There is a slower decomposition rate due to a decrease in microbial activities and biochemical processes.
An increase in soil temperature will increase soil nitrogen mineralization rate by increasing microbial activity and decomposition of organic matter in the soil. Soil temperature that is below the freezing point will stop mineralization b inhibition of microbial activities.
- Available phosphorus
Soil with lower temperatures has low phosphorus availability because as weathering occurs, soluble phosphorus is released and may be used by organisms and transformed into secondary minerals.
- Soil pH
At temperatures between 25 degrees Celsius and 39 degrees, the pH of soil increases due to organic acid. With a lower soil pH, the number of nutrients and chemicals that are soluble in water will be produced less. This lower production of nutrients in the soil can affect the soil structure and poor plant growth.
Management of Soil Temperature
As the temperature of the soil is a massive factor in soil formation, it also has vast effects on plants growth. It is necessary to manage the rise and fall of temperature in the soil surface. It is possible to alter the temperature of the soil by adopting suitable practices as follows.
Irrigation and Drainage
In tropical areas, the use of irrigation causes a rapid and substantial reduction in high soil temperatures in summer while an increase in minimum soil temperature in the winter. The water absorbs the heat from solar radiation in the soil.
This has been a significant factor used in the reduction of soil temperature. The vegetative cover of a place protects young seedlings from intense heat during the summer and lowers the soil’s temperature.
Tillage increases porosity and decreases the thermal conductivity of soil by making the soil loose and friable. The upper tilted surface of the ground usually has a higher temperature compared to the lower surface; tillage lowers the temperature of soil through its influence of aeration in the soil.
Soil formation is crucial in maintaining plant life, supplying nutrients and water. Soil temperature is the stimulant for biological processes, and this is because soil temperature affects soil moisture and the availability of suitable nutrients for plant growth.