Certified Crop Advisor Practice Exam

Which situation is expected to yield the highest nitrogen mineralization?

1. Untreated soil

2. Amended with biosolid

3. Dry soil

4. Infertile soil

The correct answer is: Amended with biosolid

Biosolid amendment to soil is an effective way to enhance nitrogen mineralization. Biosolids are organic materials made from treated sewage sludge and are rich in nutrients, including nitrogen. When biosolids are incorporated into soil, they provide a slow-release source of nitrogen, which can be microbially decomposed to produce ammonium and nitrate, the forms of nitrogen that plants can readily absorb. The microbial activity stimulated by the presence of organic matter in biosolids promotes the breakdown of this material and releases nitrogen into the soil. Consequently, this leads to an increase in nitrogen availability for plant uptake, which is crucial for their growth and development. In contrast, untreated soil lacks the nutrient enhancements provided by biosolids, leading to lower levels of nitrogen mineralization. Dry soil may inhibit microbial activity due to lack of moisture, and therefore nitrogen mineralization would also be reduced significantly. Infertile soil generally has limited nutrient availability, including nitrogen, which would further suppress the process of mineralization. Thus, the addition of biosolids represents the most effective approach to enhance nitrogen mineralization in the soil compared to the other situations presented.