Soil porosity
 
 Soil porosity is the fraction of total soil mass occupied by pore spaces. The surface area of ​​the soil refers to the area of ​​the soil that contains air and water. 

pore space controls the amount of water and air in the soil and indirectly affects plant growth and agricultural production. In addition, the size of individual pores, rather than the total number of pores in the soil, is very important in relation to plant growth.

 Porosity or open space is closely related to bulk density. Porosity is calculated as a percentage of the soil surface:
 
Type of pore Space
 
Broadly speaking, there are two types of pores in soil. 

Macropores:

 Pores larger than 0.06 mm in diameter are called macropores. Macropores allow air and water to circulate easily. Sand and sandy soils have a large number of macropores.

 Micro or capillary pores: 

the diameter of these pores is less than 0.06 mm. The movement of air and water is restricted to some extent in micro or capillary pores. Clay and clay soils have a large number of micro or capillary pores. This is more important in plant growth relationships.
 
 
How to calculate soil porosity?

 Soil Porosity = (1 – (Parent Density ÷ Particle Density)) x 100. This formula gives the result that the soil has pores. 

Example: if a sandy soil, with an organic matter content of 20%, has an apparent density of 1.4 g cm-3 and an average density of 2.222 g cm-3 when the porosity of the soil is as follows:
 
(1 – (1.4 ÷ 2.222)) x 100 = (1 – (0.63) ) x 100 = 37%.
 
The remaining 63% is solid from the soil itself.

 Factors Affecting Soil porosity

1. Soil structure: 

The arrangement of particles determines the total surface area of ​​the soil. Soils with a granular and crumb structure have more open spaces than prismatic and platy soils. A well compacted soil structure has a larger open space compared to a random or uniform soil.

2.  Soil texture: 

Sandy soil has low pore space, while fine clay and loam clay have high pore space.

3.  Organic Matter:

 Adding organic matter increases the number of pore spaces by reducing bulk density. This causes the soil to drain.

4.  Compaction: 

If the soil is compacted by the movement of machines and planting tools, the interstitial space is reduced. Aggressive planting reduces land mass compared to fallow land.

Important of soil porosity

Soil porosity, and especially macroporosity (or expanded pores), affects air movement
water in the ground. Well-structured soils have high porosity between and within aggregates, but poorly structured soils have high water and air permeability.

 Poor air quality leads to the accumulation of carbon dioxide, methane and sulphides and reduces the ability of plants to obtain water and nutrients, especially nitrogen (N), phosphorus (P), potassium (K) and sulfur (S ). . Plants can use S and N in the form of oxygenated sulfate (SO42-), nitrate (NO3-) and ammonium (NH4+). Therefore, plants need aerated soil to work well into the body to withstand S and N. The number, activity and biodiversity of microorganisms and earthworms are also high in well-aerated soil and they are able to break down and recycle organic matter and other foods work well. 

 What makes the soil porous

Although the small micropores in clay soil can hold water and nutrients longer than sandy soil, the pores themselves are often too small for plant roots to access them properly. Oxygen, which is another important element that is important in soil pores for proper plant growth, can also be difficult to penetrate into clay soils. In addition, compacted soil has reduced open space to hold water, oxygen and nutrients that are essential for plant growth.