Certified Crop Advisor Practice Exam

Which of the following soil structures would likely have the lowest soil fertility?

1. Clay

2. Loam

3. Silt

4. Sand

The correct answer is: Sand

Soil fertility is influenced by a variety of factors, including soil texture and structure. Among the options presented, sand tends to have the lowest soil fertility due to its coarse texture and the large particles it contains. These larger particles create a structure with significant voids, which allows for rapid drainage of water and leaching of essential nutrients. This rapid drainage means that water and nutrients are not retained in the root zone for extended periods, making it difficult for plants to access them. While sandy soils can warm up quickly and provide good aeration, the lack of moisture and nutrient retention ultimately leads to lower fertility compared to soils with finer textures, such as loam, clay, or silt. Loam, for instance, is often referred to as an ideal soil because it balances sand, silt, and clay, allowing it to retain moisture and nutrients effectively while still providing good drainage. Clay soils, although they hold nutrients well due to their small particle size and high cation exchange capacity, can face problems with aeration and drainage. Silt soils have better fertility compared to sandy soils, as they provide a good balance for moisture and nutrient retention. Therefore, sand's inferior ability to retain nutrients and moisture ultimately results in the lowest soil fertility among