Soils that have been exposed to
heavy equipment or a lot of human or animal foot traffic are usually more
compacted. Compacted soils contain less air and/or water pore space than
soils not subjected to a lot of weight.
If a soil does not have sufficient pore space, it is limited in its ability
to function. Adequate pore space is essential for the movement of water, air
and soil organisms through compacted soil. In addition, plant growth can be
hindered because tender seedlings cannot grow through the soil very well.
Roots cannot grow very well either; they become stunted and aren’t able to
absorb as much water and nutrients as a plant in soil with lots of pore
spaces. Lack of sufficient pore space and the accompanying compaction also
restricts water infiltration, resulting in excessive runoff, erosion,
nutrient loss and potential water-quality problems.
Using cereal to illustrate particles/aggregates of soil and milk to imitate
rainwater, the following edible experiment shows how compaction affects the
infiltration, storage and rate of water movement through soils.
When soils are compacted, such as the cereal in the glass on the left, rain water cannot infiltrate, which increases the chance for excessive erosion, slowed root growth, nutrient loss and possible water quality problems.
How does compaction affect the infiltration of the milk? If this was water and soil instead of milk and cereal, how would this affect the growth of roots? Would there be much water available in the soil for the roots to absorb during the dry, hot summer?