CFA Nutrient Management and 4Rs 2 — Questions and Answers
Question 1: Which of the 4R principles addresses applying fertilizer in a way that minimizes leaching losses below the root zone?
- Right Source
- Right Rate
- Right Time
- Right Place (Correct answer)
Correct answer: Right Place
Right Place focuses on positioning nutrients within the root zone to maximize uptake and minimize leaching or runoff losses.
Question 2: A soil test shows a pH of 5.2. Which nutrient is most likely to become toxic to plants under this acidic condition?
- Calcium
- Manganese (Correct answer)
- Phosphorus
- Molybdenum
Correct answer: Manganese
Manganese solubility increases dramatically at low pH, and concentrations can reach phytotoxic levels in acidic soils.
Question 3: A corn farmer applies nitrogen in the fall but experiences a wet spring. Which loss pathway is the greatest concern for the applied nitrogen?
- Volatilization
- Immobilization
- Denitrification (Correct answer)
- Fixation
Correct answer: Denitrification
Wet, warm, anaerobic soil conditions after fall nitrogen application promote denitrification, converting nitrate-N to gaseous N2 or N2O.
Question 4: The Cation Exchange Capacity (CEC) of a soil directly affects which fertilizer management decision?
- Choosing between foliar and soil application
- Determining split-application timing for nitrogen (Correct answer)
- Setting application rates for phosphorus
- Selecting between granular and liquid formulations
Correct answer: Determining split-application timing for nitrogen
Soils with low CEC hold fewer cations and are prone to nutrient leaching, making split applications more appropriate to avoid losses.
Question 5: Which fertilizer formulation would be most appropriate for correcting a mid-season sulfur deficiency in wheat?
- Ammonium sulfate broadcast pre-plant
- Foliar application of potassium sulfate (Correct answer)
- Banded MAP at planting
- Side-dress urea at tillering
Correct answer: Foliar application of potassium sulfate
Foliar potassium sulfate provides rapid sulfur correction mid-season when soil application would be too slow to correct the deficiency.
Question 6: Under the 4R framework, applying potassium in the fall for next year's corn crop is most consistent with which principle being compromised?
- Right Source
- Right Rate
- Right Time (Correct answer)
- Right Place
Correct answer: Right Time
Right Time means synchronizing nutrient availability with crop demand; fall K application for spring crops may be acceptable but applying N in fall misaligns timing.
Question 7: A field with a long history of poultry litter applications tests very high for phosphorus. The 4R recommendation would be to:
- Continue litter applications but reduce rates based on the P index
- Switch to a nitrogen-only fertilizer and eliminate phosphorus inputs (Correct answer)
- Apply the full nitrogen requirement from litter regardless of P buildup
- Double the litter rate to improve organic matter
Correct answer: Switch to a nitrogen-only fertilizer and eliminate phosphorus inputs
When soil P is very high, Right Rate means reducing or eliminating phosphorus inputs until soil P declines to agronomic optimum levels.
CFA Nutrient Management and 4Rs 2
Which of the 4R principles addresses applying fertilizer in a way that minimizes leaching losses below the root zone?