Certified Crop Advisor Practice Exam

Overapplication of phosphorus is often a result of using what type of fertilizer?

1. Chemical fertilizers

2. Organic fertilizers

3. Animal manures

4. Synthetic fertilizers

The correct answer is: Animal manures

Overapplication of phosphorus is often associated with the use of animal manures due to their variable nutrient content and application rates. Animal manures, such as poultry litter or cow dung, can be rich in phosphorus, and if not applied at appropriate rates based on soil testing and crop requirements, they can lead to excessive phosphorus levels in the soil. This can result in environmental issues, such as nutrient runoff into water bodies, contributing to problems like algal blooms. When using animal manures, farmers need to consider the phosphorus content, which can fluctuate depending on the type of manure and the diet of the animals, as well as the method of application and timing. If application rates are not strictly managed, it is easy to inadvertently apply more phosphorus than necessary, especially if there is not sufficient knowledge about the nutrient content of the manure being used. In contrast, chemical and synthetic fertilizers typically have more uniform nutrient content and are often evaluated based on standard application rates determined through soil testing, which makes it easier to avoid overapplication. While they can also contribute to phosphorus overload if mismanaged, the variability and complexity of manure management practices often lead to a higher risk of overapplication. Organic fertilizers may similarly have balanced nutrients, but they are not generally associated with the same