Certified Crop Advisor Practice Exam

Which of the following factors is not used in determining a lime recommendation?

1. Exchangeable sodium %

2. Soil pH

3. Soil texture

4. Organic matter content

The correct answer is: Exchangeable sodium %

The choice pertaining to exchangeable sodium percentage as a factor in determining a lime recommendation is accurate because lime recommendations primarily focus on soil acidity and the conditions that affect crop growth. When assessing soil for lime application, key factors include soil pH, soil texture, and organic matter content. Soil pH is crucial because it indicates how acidic or alkaline the soil is, and lime is applied specifically to raise the pH of acidic soils to optimal levels for crop growth. Soil texture influences how lime interacts with the soil. For instance, finer-textured soils may require different lime rates compared to coarse-textured soils due to differences in surface area and reaction rates. Organic matter content is also important as it affects the soil's buffering capacity and how it responds to lime applications. Higher organic matter can lead to increased soil acidity over time, and accounting for it in lime recommendations helps improve the efficiency of liming practices. In contrast, while exchangeable sodium percentage provides information about soil salinity and can impact soil structure and water movement, it is not directly related to the primary goal of liming, which is to correct soil acidity. Thus, it does not play a role in determining lime needs.