Soil Physical Properties

Soil physical properties include both inherent and dynamic soil properties.  Inherent properties include soil texture, soil parent materials and soil depth. Dynamic properties are those that can be influenced by management include infiltration, aggregate stability, available soil water holding capacity, soil organic matter, soil porosity, compaction layers, crusting, bulk density, and structure.  Optimal soil physical properties reduce limitations to root growth and productivity, improve seedling emergence, nutrient and water retention, infiltration, and movement of air and water within the soil profile.  Physical properties are directly related to optimal chemical and biological properties which together improve nutrient and water cycling and other key soil functions.

supplies for rainfall infiltration demonstration

Permeability and Infiltration

Permeability is the ability of soils to transmit water and air through its layers. Infiltration is the rate at which water can move through a soil and its layers.

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Structure

The arrangement of soil particles and is affected by aggregates, aggregate stability, organic matter levels, calcium levels versus sodium and magnesium, air to water ratio and temperature.

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Texture

The particle size distribution and relative proportion of sand, silt and clay in the mineral component of soils.

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photo of slump test

Aggregation and Aggregate Stability

Soil aggregation is described as how well soil particles are bonded together. Aggregate Stability is the measured ability of a soil to hold together and maintain structure despite disruptive forces.

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Bulk Density

The mass of mineral and organic soil particles divided by its total volume. It is affected by organic matter levels, texture and structure.

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Compaction

The level at which soil particles are compressed together resulting in reduced pore space between them.

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photo of two thermometers, one in bare soil and one in soil with residue cover

Temperature

Soil temperature is defined as the temperature measured at a specific soil depth.

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photo of corn struggling to break through soil crust

Crusting

Soil crusting is the formation of a hard, compact layer at the soil surface that has reduced porosity and high penetration resistance.  This crusting is associated with reduced water infiltration, restricted seedling emergence, and increased erosion.

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Available Water Capacity

The part of water held between field capacity and permanent wilting point moisture levels.

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Moisture

The total amount of water held in soil pores at any given point and includes gravitational, capillary and hygroscopic types of water.

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Porosity

The space around mineral and organic soil particles or volume of pores in the total volume of soil occupied by air and water.

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