5: Bulk Density

Question 1

Importance of micro and macropores + balance

Answer 1

Micropores hold water tightly, macropores allow water to drain. The balance between the two allows good water drainage and aeration while holding on to enough water

Micropores are <0.08 mm, macropores are anything larger (simplified)

Question 2

Soil bulk density

Answer 2

The mass per unit volume of dry soil, including pore space

(dry meaning no water)

Soil bulk density = weight oven dry soil (g)/total volume soil (cm3)

Question 3

Soil particle density

Answer 3

The mass per unit volume of soil solids, excluding pore space

(dry meaning no water)

Used to calculate soil porosity
Commonly assumed to equal 2.65 g/cm^3
Particle density = weight oven dry soil (g)/volume of solid soil particles (cm3)

Question 4

Soil porosity

Answer 4

The percentage of the soil volume that is pore space

Soil porosity (%) = [volume of soil pores (cm^3)/soil volume (cm^3)] x 100

or

[1-(Bulk density/particle density)] x 100

Question 5

Biopores

Answer 5

A type of macropore formed by organisms such as earthworms, insects, and plant roots

Question 6

Soil consistence

Answer 6

The ease with which soil can be reshaped or ruptured

Question 7

Soil bearing strength

Answer 7

The capacity of a soil mass to withstand stresses without rupturing or becoming deformed