CFA Interpreting Fertilizer Labels Questions and Answers

Question 1

An applicator needs to apply 1.5 lbs of actual nitrogen (N) per 1,000 sq ft. They are using a fertilizer with a guaranteed analysis of 25-5-10. How many pounds of this fertilizer product must be applied per 1,000 sq ft?

Accepted Answer

6.0 lbs

Answer

The first number in the N-P-K analysis represents the percentage of nitrogen by weight. To find how much fertilizer product is needed to deliver a specific amount of actual nitrogen, divide the desired amount of nitrogen by the percentage of nitrogen in the bag (in decimal form). Calculation: 1.5 lbs N / 0.25 = 6.0 lbs of fertilizer product.

Question 2

A fertilizer label for a 50 lb bag of 10-20-20 also lists 'Potential Acidity: 400 lbs Calcium Carbonate Equivalent per ton'. What does this statement signify?

Accepted Answer

The fertilizer will lower the soil pH over time, and its acidifying effect is equivalent to that produced by 400 lbs of limestone per ton of fertilizer applied.

Answer

The 'Potential Acidity' on a fertilizer label indicates the product's tendency to lower soil pH over time. The value, expressed in Calcium Carbonate (limestone) Equivalent, represents the amount of limestone needed to neutralize the acidity caused by applying one ton of the fertilizer.

Question 3

A turf manager is applying fertilizer near newly germinated seeds and wants to minimize the risk of 'fertilizer burn'. Which of the following characteristics listed on a fertilizer label is the most direct indicator of this risk?

Accepted Answer

Salt Index

Answer

The Salt Index is a measure of the salt concentration a fertilizer induces in the soil solution. Fertilizers with a high salt index have a greater potential to cause 'fertilizer burn' or desiccation injury to seeds and young plants by creating an osmotic imbalance that draws water out of plant tissues.

Question 4

A fertilizer label displays a guaranteed analysis of 12-8-10. It also specifies that 3% of the total nitrogen is from ammoniacal nitrogen and 9% is from nitrate nitrogen. Which of the following statements is most accurate regarding this nitrogen composition?

Accepted Answer

The majority of the nitrogen is immediately available for plant uptake but is also more susceptible to leaching.

Answer

Nitrate nitrogen is a form that is immediately available for plants to absorb. However, because it is highly water-soluble and does not bind to soil particles, it is also the form most prone to leaching below the root zone. Since 9% of the 12% total N is nitrate, this is the dominant form.

Question 5

The guaranteed analysis on a fertilizer bag reads 15-0-30 and also guarantees 2% Magnesium (Mg) and 5% Sulfur (S). How many pounds of actual potash (K2O) and sulfur (S) are in a 50 lb bag of this product?

Accepted Answer

15 lbs of K2O and 2.5 lbs of S

Answer

The guaranteed analysis numbers are percentages by weight. To find the pounds of a nutrient in a bag, multiply the bag's weight by the nutrient's percentage (in decimal form). Potash (K2O) is the third number (30%), and Sulfur (S) is listed at 5%. Calculation: Potash = 50 lbs * 0.30 = 15 lbs. Sulfur = 50 lbs * 0.05 = 2.5 lbs.

CFA Practice Test

CFA Practice Test

CFA Interpreting Fertilizer Labels Questions and Answers