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