Soil Bulk Density, Particle Density and Porosity |

Particle density

Soil Bulk density, particle density and Porosity

What is soil made up of?

Soil is made up of 4 components

1. Soil Solids containing minerals and other solid particles that constitute 45 percent

2. Soil Water constitutes 25 percent

3. Soil Air constitutes porespaces i.e. part not occupied by water or solids

4. Organic matter constitutes 5 percent

What is Particle Density?

Particle density

It is the ratio of a given mass (or weight) of soil solids to that of its volume

It is usually expressed in terms of g/cm3

if 1 cm3 of soil solids weigh 2.6 g, the particle density measures 2.6 g/cm3

What is the average Particle density values of soil?

The values for most mineral soils usually vary between the narrow limits of 2.6 to 2.75 g/cm3

Does Particle Density depend on size of soil particles?

No, Particle density is not dependent on

1. size of the soil particles and

2. arrangement of the soil solids

Why is particle density required?

Knowledge of particle density is necessary for determination of total, capillary and non-capillary porosity

What is Bulk density?

Bulk density

It refers to the ratio of a given mass of an oven dried soil to that of its field volume (i.e., solids + pore spaces)

How is bulk density calculated?

The given sample of soil is oven dried

Bulk density is calculated by the following formula

Bd = wt of oven dried soil (g) / total field volume of soil (cubic cms)

The unit of bulk density is g / cubic cm

What is the importance of bulk density?

Knowledge of bulk density is required in

1. Determination of depth of water for a given depth of soil

2. The permeability of soil for water, air and penetration of plant roots is also influenced by bulk density

3. Compression or compaction of soil particles increases bulk density

4. Increase in bulk density lowers Soil porosity and as a result soil water storage capacity is reduced

What are values of bulk density for different soil textural classes?

The bulk density values for various soil textural classes in (g / cc) is as follows

1. Sandy 1.60 – 1.70

2. Loamy sand 1.60 – 1.70

3. Sandy loam 1.55 – 1.65

4. Fine sandy loam 1.50 – 1.60

5. Loamy soil 1.45 – 1.55

6. Silty loam 1.40 – 1.50

7. Silty clay loam 1.35 – 1.45

8. Sandy clay loam 1.40 – 1.50

9. Clay loam 1.30 – 1.50

10. Clay soil 1.25 – 1.35

What is porosity of soil?


It is the space in a given volume of soil that is occupied by air and water or not occupied by the soil solids

It is an index of pore volume in the soil

What is formula for calculation of total porosity?

The total porosity is calculated as follows

TP = (1 – bulk density / particle density) x 100

What is the value of total porosity for different soils?

Total porosity value generally lies in the range of

1. 30 to 60% for arable soils

2. 35 – 50% for coarse textured soils

3. 40 – 60% fine textured soils

What is the significance of soil porosity?

Knowledge of porosity in a given volume of soil is very important with respect to irrigation water management, because it is an index of

1. moisture storage capacity and

2. aeration conditions

these two are most important factors that influence the plant growth and development

Further readings and references on bulk density, particle density porosity

Handbook of Agriculture


Author: agristudent

Team Agristudent is a young and dynamic team of Agriculture specialists who have acquired specialised knowledge in their respective subjects. Their mission is to create a unique online encyclopedia of agriculture, which can be useful to millions around the world as an online reference library

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