Soil

Objective: Explain soil horizon and soil texture, distinguish their meanings, and apply them to a described case.

Soil horizon: A soil horizon is a layer with characteristics produced by soil-forming processes. Soil texture: Soil texture describes proportions of sand, silt, and clay. Soil develops through interactions among parent material, organisms, climate, landform, and time. Texture influences water movement and storage but does not alone determine fertility. Organic matter contributes to structure and nutrient cycling. Erosion can remove productive surface material much faster than it forms. Salinity management depends on irrigation, drainage, and local conditions. A conservation practice should be evaluated for the particular slope, climate, crop, and soil rather than assumed universally effective. Application: A profile shows an organic-rich surface above altered subsoil. This most directly illustrates soil horizon. A soil sample contains a high proportion of clay particles. This most directly illustrates soil texture.

Objective: Explain soil organic matter and soil erosion, distinguish their meanings, and apply them to a described case.

Soil organic matter: Organic matter includes living or decomposing materials that influence nutrient cycling and soil properties. Soil erosion: Soil erosion removes surface material, potentially faster than new soil develops. Soil develops through interactions among parent material, organisms, climate, landform, and time. Texture influences water movement and storage but does not alone determine fertility. Organic matter contributes to structure and nutrient cycling. Erosion can remove productive surface material much faster than it forms. Salinity management depends on irrigation, drainage, and local conditions. A conservation practice should be evaluated for the particular slope, climate, crop, and soil rather than assumed universally effective. Application: Decomposing plant residues improve soil structure. This most directly illustrates soil organic matter. Heavy runoff carries topsoil from an exposed slope. This most directly illustrates soil erosion.

Objective: Explain soil salinization and soil conservation, distinguish their meanings, and apply them to a described case.

Soil salinization: Salinization is salt accumulation that can impair plant growth and soil function. Soil conservation: Conservation practices reduce degradation through context-appropriate cover, drainage, and land management. Soil develops through interactions among parent material, organisms, climate, landform, and time. Texture influences water movement and storage but does not alone determine fertility. Organic matter contributes to structure and nutrient cycling. Erosion can remove productive surface material much faster than it forms. Salinity management depends on irrigation, drainage, and local conditions. A conservation practice should be evaluated for the particular slope, climate, crop, and soil rather than assumed universally effective. Application: Evaporation concentrates salts in poorly managed irrigated soil. This most directly illustrates soil salinization. A farmer maintains cover vegetation to reduce runoff erosion. This most directly illustrates soil conservation.