Sludge disposal provides which resource to soils?

• A. Carbon
• B. Nutrients
• C. Salts
• D. Heavy metals

Answer: (B)

Sludge disposal provides nutrients to soils. Biosolids contain essential plant nutrients, especially nitrogen and phosphorus (and also potassium), which become available to plants as the material decomposes. This nutrient supply is the primary benefit to soils when applied properly, supporting crop growth and soil fertility. The organic matter in biosolids also helps improve soil structure, water-holding capacity, and microbial activity. While carbon is part of the organic matter, the nutrient content is the resource most directly useful to plants. Salts and heavy metals can be present as contaminants and are managed under regulatory limits; they are not considered resources.