In the NC piedmont and mountains, the parent material is typically weathered bedrock known as saprolite. The predominate parent material varies by location in North Carolina. Collectively, the horizons make up the soil profile. Each layer can have two or more sublayers called horizons.

The layers are the topsoil, subsoil, and parent material. Most naturally occurring, undisturbed soils have three distinct layers of variable thicknesses. The Soil Profile Skip to The Soil Profile The distribution of soils and pore space in compacted and poorly drained soil is illustrated in Figure 1–1b and Figure 1–1c. But for plant growth, most soil scientists agree that 50% pore space, 45% mineral matter, and 5% organic matter make up an ideal ratio ( Figure 1–1a). The relative amounts of pore space and mineral and organic matter vary greatly among different soil types. The organic matter consists of decaying plant and microbial residues. The mineral materials are typically weathered rock of varying sizes called sand, silt, and clay. Soil solids are a blend of mineral materials and organic matter. For example, tilling increases pore space, while poor drainage and compaction reduce it. This distribution rarely occurs because pore space varies with soil texture and soil management. In this role, soil provides structural stability for plants and retains and relinquishes water and the nutrients necessary for plant growth.Īn ideal soil for plant growth contains 50% pore space and 50% solids, with the pore space filled with equal parts air and water. Soil is a living, breathing, natural entity composed of solids, liquids, and gases. Introduction: What Is Soil? Skip to Introduction: What Is Soil?

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