BULK DENSITY

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Unit

• BULK DENSITY
• OF SOIL

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Objectives
1. Describe the concept and importance of soil
density.
2. Determine soil density.
3. Explain how to alter soil density.
4. Describe the effect of soil density on
erosion, water holding capacity and flooding.
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Terms
Bulk density
Consistence
Particle density
Structure
Texture
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Describe the concept and importance of soil
density.
What is bulk density?
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- Bulk density is a measurement of how tightly
soil particles are pressed together.
- Density is the mass of an object divided by the
volume.
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Bulk density
- Texture, the relative proportion of soil
separates in a soil, affects the density, as
different separates have different masses and
have corresponding pore space.
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Structure
- the arrangement of soil particles into
aggregates or peds, also determines density
because various soil arrangements will compact
more easily than others.
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Particle Density
- of the soil is the mass per unit volume of soil
particles excluding the pore space.
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-The soil consistence,
the soils response to pressure at various
moisture levels, can be described as hardness,
friability, stickiness, and plasticity.
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Determine soil density.
How can you determine soil density?
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- Soil density is the mass of the soil particles
divided by volume.
- When removed from the earths crust the soil
contains air and water that will affect the mass
readings and do not constitute soil density.
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- The soil needs to be dried in order to find the
true density.
- Density is usually expressed in grams per cubic
centimeter.
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Explain how to alter soil density.
How can you change soil density?
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- Soil density is affected by tillage and
non-tillage systems.
- The working of the subsoil by a subsoil tillage
system can decrease the density of the soil by
encouraging more pore space per volume.
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B. Some seedbeds and fields have too little soil
density so rolling the field or working the soil
with a finisher may provide better seedbed
density.
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- At construction sites it is important to have a
compacted subsoil so settling will not occur once
the building is completed.
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Describe the effect of soil density on erosion,
water holding capacity, and flooding.
What effect does soil density have on various
soil characteristics?
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IV. Soil density affects soil characteristics.
A. With higher the soil density the amount of
pore space decreases, thus decreasing the water
holding capacity of the soil. This decrease in
water holding capacity is especially significant
in the larger pore spaces that are readily
available to hold water which plants can utilize.
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Erosion

• can also be affected by density, as water will
  not infiltrate the soil as readily
• will stay in contact with the topsoil for a
  longer period of time.

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Flooding

• Flooding will result from excessive runoff and
  decreased infiltration in wet years.
• Puddling can result from localized compaction, as
  is the case in tractor tire ruts.

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Bulk Density Equation.
oven - dry weight in grams
Bulk density
volume of cylinder in cubic centimeters