Certified Crop Advisor Practice Exam

Under which condition would potassium deficiency most likely occur?

1. 10% clay, pH 6.0

2. 20% clay, pH 8.3, double cropped

3. 40% clay, pH 5.5

4. 30% clay, single cropped

The correct answer is: 20% clay, pH 8.3, double cropped

Potassium deficiency is most likely to occur in conditions where clay content is moderate, soil pH is high, and the crop is double cropped. In this scenario, the 20% clay and pH of 8.3 indicate a more alkaline soil environment, which can affect potassium availability. High pH soils can lead to reduced solubility of potassium ions, making it less accessible to plants. Additionally, double cropping means that nutrients are removed from the soil more frequently due to continuous harvesting, putting additional stress on potassium availability. Clay soils can retain potassium better than sandy soils, but the alkaline conditions at higher pH levels can hinder its effective uptake. The requirement for potassium is also heightened in a double cropping system since the crops will be competing for the same nutrients within a shorter timeframe without allowing adequate recovery or replenishment of soil nutrients. All these factors combined increase the likelihood of potassium deficiency under these specific conditions.