Which set of factors is commonly used to evaluate soil erosion risk in rangelands?

• A. Slope length and gradient; soil erodibility; rainfall erosivity; cover/management
• B. Soil color, texture, structure, drainage
• C. pH, salinity, base saturation
• D. Bulk density, porosity, nutrient content

Answer: (B)

The main idea is that erosion risk in rangelands is driven by factors that control how much soil can be detached and moved by water. Specifically, you need to consider rainfall energy, how easily the soil can be detached, how runoff behaves on the landscape, and how much protective cover or management is in place.

Slope length and gradient determine how much runoff concentrates and how fast it flows downslope; longer, steeper slopes usually lead to more erosion because water has greater erosive power and can transport more soil. Rainfall erosivity measures the potential of rainfall events to cause detachment and runoff—the more intense and frequent the rainfall, the higher the erosion potential. Soil erodibility reflects how susceptible the soil is to detachment by runoff; soils with certain textures, structures, and organic matter contents detach more easily under the same flow. Cover and management capture the protective effect of vegetation, residue, and practices that reduce detachment and runoff, thereby lowering erosion risk.

The other set lists general soil properties like color, texture, structure, and drainage, which describe soil characteristics but do not on their own represent the dynamic factors used to evaluate erosion risk. Texture and structure relate to how soils behave, but without considering rainfall energy, slope-driven runoff, and cover/management, you don’t have a complete picture of erosion risk.