Bulk density and porosity

Macropores

Drainage occurs Good for gas exchange Penetrable by roots and organisms

Plow pan

Man made hard pan

Micropores

No air movement Usually filled with water Not all water available to plants

Graded

ParMany different size grains (poorly sorted)

Sorted

Particle of smaller size (poorly graded)

Micropore size

less than 0.08mm

Tillage

loosens soil initially but depletes organic matter and then increases bulk density

Sandy soils have

low porosity and high drainage

Forest soils naturally have ____ lower

lower

Intraped pores

spaces within peds (micropores)

Factors that affect bulk density

1. soil texture and aggregation 2. Depth in profile 3. Management practices

Packing

Loose or tighter

Soil strength is dependent on

Moisture and texture

How does porosity affect bulk density?

More pores= lower bulk density

Arrangement

Sorted and graded

Interped pores

Space between peds (macropores)

Tighter packing has _____ porosity

higher

Depth in profile

Weight of soil above Less biopores Less aggregation Hardpan (lower A or B)

Soil strength

ability of a soil to resist deformation

Macropore size

greater than 0.08mm