Certified Crop Advisor Practice Exam

At which of the following soil test levels would you expect the greatest crop response?

1. Very high

2. Medium

3. Low

4. Optimal

The correct answer is: Low

The expectation of the greatest crop response occurs at low soil test levels. When nutrient levels in the soil are low, plants often exhibit a significant deficiency in essential nutrients. This creates a scenario where the addition of those nutrients can lead to marked improvements in crop growth, yield, and overall health. In contrast, when soil nutrient levels are classified as very high or even optimal, the potential for further crop response diminishes because the plants already have sufficient access to the necessary nutrients. In medium test levels, while there may still be room for improvement, the magnitude of response typically observed at low levels is not as pronounced, since the soil might already provide a reasonable supply of nutrients for plant growth. Enhancing nutrient levels in low-testing soils can trigger substantial improvements, making it the condition where you can expect the most significant crop response from nutrient applications.