Factors Affecting Soil Temperature and Its Control

After reading this article you will learn about the factors affecting soil temperature and its control.

Factors affecting Soil Temperature:

1. Soil texture:

Sandy soils, in general, warm up quicker than clayey or fine-grained soils. A fine-grained soil carries a large amount of water they are for this reason also slow to warm. Soil moisture is the most vital controlling factor in soil temperature.

Specific heat is the amount of hear required to raise the temperature of one gram of a substance by 1°C. The specific heat of dry soil is less than moist soil. Hence, moist soils are cooler than dry soils.

2. Soil structure:

Soil structure also affects soil temperature by controlling the pore space. Soils having good structure (granular or crumby) warm up more rapidly because there is no water-logging.

3. Soil composition:

The soil is composed partly of mineral matter and parly organic. The specific heat of mineral substances is less than that of organic materials (specific heat of iron is 0.11) whereas of humus is 0.44). Hence, mineral soils get heated more readily than organic soils.

4. Soil colour:

Dark-coloured soils usually warm up more readily than light-coloured soils. As they possess a greater capacity for absorbing the sun’s heat.

5. Soil moisture:

Specific heat of water is higher than soil. Moist soils have a higher specific heat than dry soils. Consequently, a moist soil has lower temperature than dry soil. The evaporation of water rather helps to lower the temperature of a moist soil. Moist soil gets heated more slowly.

6. Slope of the land:

The topography of the land, more particularly the ground slope, also affects the temperature of the soil.

7. Vegetative cover:

Soils that are covered with vegetation absorb less heat than those that bare. Vegetation acts as an interceptor and retards the warming of the soil surface.

On the other hand, plant cover prevents the soil from getting cool as it retards the loss of heat. Hence, soils carrying a dense plant cover are cooler in summer and warmer in winter than unprotected soils. Bare soils cool off more rapidly than those covered with vegetation.

8. Climate:

Climate has a great effect on soil temperature. Soils in temperate (cool) regions are cooler than those in tropical (warm) regions.

9. Season:

Soil temperature varies with different seasons of the year. It will be noticed that there is a close similarity between the variation in soil temperature, more especially of the surface soil and the variations in air temperature. During the cold months of December and January when the air temperatures are low, the soil temperatures are also low. The temperature of the surface soil is always higher than the air temperature.

Control of Soil Temperature:

Regulation of soil temperature is possible up to some extent, under field condition. The control of the amount of water in soil helps to regulate its temperature. Water-logged soil has a low temperature. The only way to increase the temperature of such soils is to remove excess water by providing suitable drainage. The removal of excess water lowers its specific heat and thus, increases the temperature.

The increase in the air content of the soil also helps to increase the soil temperature by lowering the specific heat. The temperature of surface soil can be modified by altering its colour. A black substance like charcoal powder when spread on the surface of the soil increase its temperature as it allows less reflection and hence, a greater absorption of heat.

Soil temperature can also be regulated by applying straw mulch. During the day time, mulch keeps the surface soil cooler by intercepting sun rays. At night however, it keeps the soil warmer by cutting off the outgoing radiation.

On the other hand, vegetative cover and mulch keep the soil temperature low. The shade helps in protecting young seedlings and shallow-rooted crops such as tea, coffee and tobacco etc., from the intense heat during summer.

Use of irrigation water also lowers the soil temperature and protect the crop from dry spells. The temperature of surface soil can also be lowered by altering its colour. Spreading a thin layer of a white substance like chalk lowers the temperature by reflecting much of the incoming radiant energy.