Soil Physics WA - Soil Quality Knowledge Base

Understand soil structural features and their impacts

The Soil physical attributes section contains information on topics including soil processes, physical soil properties and the soil structural matrix. Pages within present an overview of the current state of knowledge of soil physical attributes, explain the principles and properties of different features, highlight insights from research, and Resources are suggested throughout.

Typical ironstone gravel at Williams in Western Australia. Photo: Anvil Media.

Gravel soil

Soil containing abundant ironstone gravel has poorer water holding capacity than soil of the same texture without gravel. Gravel varies in porosity which influences the extent of water and nutrient exchange within the soil profile.

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Deep ripping and soil testing. Photo: DPIRD.

Testing to determine aggregate stability; dispersion (top), slaking (bottom right), stable aggregate (bottom left) after 12 h submersion. Photo: Yoshi Sawada, UWA.

Soil stability

Soil consists of mineral particles (sand, silt and clay) and organic matter that will generally bind together to form aggregates; air and water that will be held in the soil pores, and soil organisms. Soil stability refers to the ability of a soil to maintain structural integrity on wetting.

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Soil compaction

Soil compaction occurs when soil particles are packed closer together. Compacted soil is stronger, denser and less porous. Less water and gas exchange occurs in a compacted soil, slowing root growth and inhibiting both water and nutrient uptake.

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Aerial photograph of wind-blown sand. Photo: DPIRD.

Water erosion in a dispersive sodic soil. Photo: DPIRD.

Soil erosion

Wind and water erosion result in the rapid loss of soil, nutrients and organic matter essential for plant growth. Deposition of this soil into sensitive environments such as waterways can impact ecosystem health.

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Dye in the soil indicates the spread of irrigation water in a horticulture system. Photo: DPIRD.

Even after rain, non-wetting soil can be dry at and below the surface. Photo: Justin Laycock, DPIRD.

Soil water

Soil is made up of solid particles, with gases, organic matter and water occupying the spaces in between – rather like a sponge. The chemical and physical nature of the soil influences water movement into and through the soil matrix.

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Water droplet sitting on the surface of a water repellent (non-wetting) sand. Photo: Frances Hoyle, Murdoch University.

Severe water repellence can impact crop establishment. Photo: Stephen Davies, DPIRD.

Soil water repellence

Soil that exhibits beading of water after rainfall or irrigation is referred to as water repellent. Repellent soil resists water entry and infiltration, so water flows unevenly via preferred pathways, leaving other parts of the soil dry.

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Waterlogging

Waterlogging is a highly variable phenomenon, associated with rapid seasonal changes in water-table levels. As a result of waterlogging, processes in the soil profile affect plant growth and crop production.

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