Certified Crop Advisor Practice Exam

What is the textural class of soil that is 10 percent clay and 35 percent sand?

1. sandy loam

2. clay loam

3. silt loam

4. loamy sand

The correct answer is: silt loam

To determine the correct textural class of soil based on its particle size composition, it’s essential to use the soil textural triangle. In this case, with 10 percent clay and 35 percent sand, this combination does not align with the characteristics of silt loam. For silt loam, the typical composition includes a higher percentage of silt, which usually ranges from about 50 to 70 percent, along with lower percentages of clay (generally below 30 percent) and varying amounts of sand. Given that this soil sample has only 10 percent clay and 35 percent sand, it indicates that the proportion of silt is not adequate to classify it as silt loam. Instead, the correct classification for 10 percent clay and 35 percent sand would generally fall under the category of sandy loam. In sandy loam, one would anticipate a more balanced composition of sand and silt, where the clay content remains low but not to the extent seen in this case. Thus, sand predominates, allowing it to drain well while still holding some moisture, making it an ideal textural class for many agricultural applications. Understanding the relationships between sand, silt, and clay percentages is crucial in soil classification,