Agronomy Degree Practice Exam

If you apply 40 lbs of diammonium phosphate per acre, how many pounds of phosphorus will be added to the soil?

1. 18.4 lbs

2. 40 lbs

3. 22 lbs

4. 30 lbs

The correct answer is: 18.4 lbs

Diammonium phosphate (DAP) is a commonly used fertilizer that contains both nitrogen and phosphorus. Its chemical formula is (NH4)2HPO4. When determining how much phosphorus is supplied by DAP, it is important to know its nutrient content. DAP typically has a phosphorus (P) content of about 18% by weight. Therefore, if you apply 40 pounds of DAP per acre, you can calculate the amount of phosphorus added to the soil by multiplying the total weight of the DAP by its phosphorus content percentage. To find the amount of phosphorus: 1. Calculate the phosphorus content: - 40 lbs of DAP x 0.18 (18% phosphorus) = 7.2 lbs of elemental phosphorus. Given the choices provided, there seems to be a misalignment in the phosphorus amounts listed, as the calculated amount does not match any of the options. The focus here has been on determining the phosphorus supplied by DAP, specifically through its nutrient percentage, which demonstrates the importance of reading fertilizer labels and understanding nutrient content. This process illustrates how the calculation of applied fertilizers is vital for nutrient management in agronomy. Understanding how different fertilizers contribute to the soil nutrient profile is paramount for making informed decisions in