Certified Crop Advisor Practice Exam

What form of phosphorus is primarily found in biosolids?

1. Phosphate

2. Ammonium

3. Nitrate

4. Sulfate

The correct answer is: Phosphate

Biosolids are treated sewage sludge that can be recycled and applied to land to improve soil quality and provide nutrients to crops. The primary form of phosphorus found in biosolids is phosphate. This is because, during the treatment process, organic phosphorus compounds in the sludge are converted into inorganic phosphate, which is the form of phosphorus that plants can readily absorb and use for growth. Phosphate plays a crucial role in plant metabolism, particularly in energy transfer and storage processes, as well as in the formation of nucleic acids and phospholipids. In comparison, ammonium, nitrate, and sulfate are other nutrient forms that may be present in biosolids but do not represent the primary source of phosphorus. Ammonium and nitrate mainly relate to nitrogen content, while sulfate pertains to sulfur, which, while important, does not fulfill the role of phosphorus in plant nutrition. Thus, when considering the forms of phosphorus in biosolids, phosphate stands out as the key nutrient form advantageous for crop production.