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Competency Area 1: Basic Soil Properties

PO 6. Understand soil structure and its importance to crop production and environmental protection.

Soil structure is defined as 'the arrangement of primary soil particles into groupings called aggregates or peds' (Brady and Weil, 1996). Soil structure determines properties such as total porosity, air-filled and water-filled porosity, pore-size distribution, soil tilth, and aggregate stability. A soil with a well-developed structure will have larger total porosity and greater air-filled porosity and therefore will be better drained and provide a better environment for root growth than the same soil with poor structure. The soil will also absorb water better. This water will be filtered by the soil before it is released to groundwater instead of running off. Runoff causes soil erosion and carries nutrients, organic matter, and pesticides to surface water, causing an environmental threat.