Describes the way in which the soil forms lumps or crumbs. A soil's structure controls the availability of water and air to plants and the ability of fine feeding roots to divide within the soil and hence to exploit the essential plant nutrient supply. It is influenced by agents such as:

• Organic matter
• Earthworms and other soil organisms
• Wetting and drying
• Freezing and thawing
• Presence of plant roots
• Cultivation
• Texture
• Drainage
• Compaction

Good soil structure is where the particles form firmly bonded, stable, crumb or granular rounded aggregates 1 - 5 mm in diameter. For this to occur there must be high to moderate organic matter content (3 - 10%). Poor soil structure leads to capping, puddling and sieving.