Certified Crop Advisor Practice Exam

Which factor has the greatest impact on soil filtration?

1. Soil pH

2. Surface soil texture

3. Organic matter content

4. Soil temperature

The correct answer is: Surface soil texture

The correct choice related to which factor has the greatest impact on soil filtration is indeed surface soil texture. Soil texture refers to the relative proportions of different sizes of soil particles, namely sand, silt, and clay. These particle sizes significantly influence the movement of water and air through the soil, which directly impacts how well the soil can filter these elements. Soil with a higher sand content facilitates more rapid filtration due to larger pore spaces that allow water to move more freely. Conversely, clay soils, with their smaller particle sizes, tend to retain water and can slow filtration rates due to the presence of smaller pores that can become compacted. The balance of these textures in the top layer of soil ultimately dictates how effectively it can filter water, nutrients, and other substances. While factors such as soil pH, organic matter content, and soil temperature certainly play important roles in overall soil health and function, they do not have as direct a correlation with soil filtration rates as surface soil texture does. For instance, organic matter can improve the structure of the soil and affect drainage, but the primary determinant of filtration capacity remains the arrangement and size of soil particles.