What do earthworms do for soil?

• A. Improve soil color visibility
• B. Break down organic matter and improve structure
• C. Fix soil pH
• D. Attract earthworms to the surface

Answer: (B)

Earthworms are key players in soil health because they break down organic matter and dramatically improve soil structure. They eat plant residues and other organic material, accelerating decomposition and turning it into nutrient-rich casts that plants can use. As they move through the soil, their burrows and the mixing action (bioturbation) loosen compacted layers and create a network of tiny pores. This boosts soil porosity, aeration, and water infiltration, while the stable soil aggregates formed by their activity improve soil stability and reduce erosion. All of these changes enhance root growth, microbial activity, and nutrient cycling, which support healthier, more productive soils in rangelands.

The other options don’t fit as the primary role. Soil color isn’t a direct function of earthworms, pH isn’t fixed by worm activity (it’s controlled by chemical processes and amendments), and while worms may surface after rain, that isn’t why they’re beneficial to soil health.