CFA Nutrient Management & Application Planning 3 — Questions and Answers
Question 1: A soil test report shows high magnesium levels relative to calcium. The MOST appropriate corrective action would be to apply:
- Dolomitic limestone to add more magnesium
- Calcitic limestone to supply calcium without additional magnesium (Correct answer)
- Potassium sulfate to displace excess magnesium
- No corrective action is ever needed for high magnesium
Correct answer: Calcitic limestone to supply calcium without additional magnesium
Calcitic limestone supplies calcium to correct the Ca:Mg ratio imbalance without adding more magnesium as dolomitic limestone would.
Question 2: The cation exchange capacity (CEC) of a soil is important for nutrient management because it indicates:
- The soil's ability to retain anions like nitrate
- The soil's ability to hold cationic nutrients against leaching (Correct answer)
- The rate at which organic matter decomposes
- The soil's water-holding capacity in inches per foot
Correct answer: The soil's ability to hold cationic nutrients against leaching
CEC measures the soil's ability to hold positively charged nutrient ions (K+, Ca2+, Mg2+, NH4+) and resist their leaching, informing application rate decisions.
Question 3: When preparing a field nutrient budget, manure nutrient credits must be included. For nitrogen in manure, applicators must account for:
- Only the total N listed on the manure analysis
- Both the immediately available inorganic N fraction and the slow-release organic N fraction (Correct answer)
- The manure N content minus rainfall losses
- Only the organic N fraction since inorganic N volatilizes immediately
Correct answer: Both the immediately available inorganic N fraction and the slow-release organic N fraction
Manure nitrogen exists as both quickly available inorganic N (NH4+) and slowly mineralizing organic N, and both fractions must be credited in the nutrient budget.
Question 4: Variable rate technology (VRT) in fertilizer application is most beneficial when:
- Fields are uniform in soil type and productivity
- Significant within-field variability in soil test values exists (Correct answer)
- The applicator wants to reduce equipment maintenance costs
- Fertilizer prices are at historic lows
Correct answer: Significant within-field variability in soil test values exists
VRT provides the greatest economic and environmental benefit when significant within-field soil variability exists, allowing site-specific nutrient applications.
Question 5: Sulfur deficiency symptoms in crops typically appear first as:
- Yellowing of older lower leaves (interveinal chlorosis)
- Yellowing of young upper leaves since S is immobile in plants (Correct answer)
- Dark green coloration of all leaves
- Brown necrotic spots on leaf margins
Correct answer: Yellowing of young upper leaves since S is immobile in plants
Sulfur is immobile within plants, so deficiency symptoms appear first in the youngest leaves (growing points) rather than in older tissue.
Question 6: A certified fertilizer applicator is reviewing a nutrient management plan for a field adjacent to a waterway. The plan should include what type of buffer consideration?
- Increase fertilizer rates near the waterway to compensate for nutrient losses
- Establish a no-application or reduced-rate buffer zone near the waterway (Correct answer)
- Apply only liquid fertilizers within 100 feet of the waterway
- No special considerations are needed if fertilizer is incorporated
Correct answer: Establish a no-application or reduced-rate buffer zone near the waterway
Buffer zones with no or reduced fertilizer application near waterways are a best management practice to minimize nutrient runoff and water quality impacts.
Question 7: The term 'nitrogen use efficiency' (NUE) refers to:
- The percentage of applied N that reaches groundwater
- The ratio of crop N uptake to total N applied (Correct answer)
- The speed at which nitrogen fertilizer dissolves in soil water
- The cost per pound of nitrogen in different fertilizer products
Correct answer: The ratio of crop N uptake to total N applied
Nitrogen use efficiency is calculated as crop nitrogen uptake divided by total nitrogen applied, expressing how effectively the crop uses applied N.
CFA Nutrient Management & Application Planning 3
A soil test report shows high magnesium levels relative to calcium.
The MOST appropriate corrective action would be to apply: