Soil Quality Illustration

Evolution of Soil in Montana

- Adapted from illustration by Doug Adamson.

Pre-Settlement Montana Soil.
Hardy, vigorous native plants, grasses, and trees grew on the Montana landscape before settlement. Natives adapt to summer heat and winter cold, drought, and windy conditions. These soils contain about 5 percent organic matter.

Agricultural Land.
Years of deep tillage and soil erosion from farming caused the loss of more than half the topsoil on most of Montana’s farmland slopes. Soils on agricultural land typically have only 1 to 2 percent organic matter content, a 60 to 80 percent reduction from native soils.

Compacted Urban Soil.
Many of today’s urbanized areas have disturbed and compacted soils. These areas have very little organic matter left to absorb rainfall and less pore space for water to infiltrate.

Restored Montana Soil.
Soil quality is best restored by doing deep tillage, applying compost, and planting native vegetation. This will increase pore space and raise organic matter content which will allow rainfall to infiltrate and be stored in the soil.

Pore Space.
Native soils have about 50 percent pore space, allowing for air movement and storage space for water infiltration.

Root Structure.
Native vegetation has a strong root structure that builds soil quality. Native plants reduce erosion, absorb rainfall, build soil structure, and increase organic matter content.

Earthworms.
Earthworm activities in the soil improve water movement, break down residues, distribute organic matter, improve nutrient availability, and enhance soil structure and soil stability. Earthworms usually indicate a healthy system with favorable moisture conditions. Soils that lose organic matter lose earthworm populations because organic matter is their main food source.

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Last Modified: 07/05/2007