Certified Crop Advisor Practice Exam

Which nutrient is most likely to be depleted from soil with high leaching potential?

1. Calcium

2. Nitrogen

3. Phosphorus

4. Magnesium

The correct answer is: Nitrogen

The nutrient most likely to be depleted from soil with high leaching potential is nitrogen. This is primarily because nitrogen exists in forms that are soluble in water, such as nitrate and ammonium. When rainfall or irrigation causes water to move through the soil, these soluble nitrogen forms can easily be washed away, leading to a significant reduction in the available nitrogen for plants. Leaching is especially a concern in regions with high rainfall or where irrigation is heavily used, as these conditions promote the movement of water - and the nutrients within it - through the soil profile. While other nutrients can also be leached, nitrogen is particularly vulnerable due to its chemical nature and the forms it takes in the soil. Calcium, phosphorus, and magnesium, on the other hand, do not leach as readily. Calcium tends to form more stable compounds in the soil and is less mobile than nitrogen. Phosphorus is often bound to soil particles and does not wash away easily unless there is significant erosion or movement of sediment. Magnesium, while it can leach under certain conditions, does so less frequently compared to nitrogen. Therefore, nitrogen’s high solubility and mobility make it the nutrient most likely to be depleted through leaching in high leaching potential soils.