Certified Crop Advisor Practice Exam

If phosphorus-based recommendations are used for manure applications, what additional nutrient might be necessary?

1. Potassium

2. Calcium

3. Supplemental nitrogen

4. Magnesium

The correct answer is: Supplemental nitrogen

In the context of manure applications, phosphorus is often the focal point because it is a crucial nutrient for plant growth but can also be a pollutant if over-applied. When phosphorus levels in the soil are sufficiently high, there's a potential that other essential nutrients may be overlooked in terms of their adequacy for crop growth. Supplemental nitrogen is often necessary because manure tends to be rich in phosphorus but may not provide sufficient nitrogen to meet the needs of crops. Many crops, particularly those with high yield potential, require a balance of nitrogen relative to phosphorus to support healthy growth and development. In the absence of adequate nitrogen, crops can exhibit stunted growth, poor yields, or other nutrient deficiency symptoms. Thus, when planning manure applications based on phosphorus needs, it becomes critical to assess the nitrogen levels as well and consider supplementation if necessary to achieve optimal nutrient balance for crop health and productivity.