CCA Nutrient Management 2 — Questions and Answers
Question 1: Which soil pH range is generally considered optimal for maximizing phosphorus availability to most agronomic crops?
- 5.0–5.5
- 6.0–7.0 (Correct answer)
- 7.5–8.0
- 4.5–5.0
Correct answer: 6.0–7.0
Phosphorus availability peaks between pH 6.0 and 7.0, where it is least likely to be fixed by aluminum, iron, or calcium.
Question 2: A field soil test reveals a cation exchange capacity (CEC) of 25 meq/100g. Compared to a soil with CEC of 5 meq/100g, this soil will:
- Leach nutrients more rapidly
- Retain more cations against leaching (Correct answer)
- Require less lime to change pH
- Have lower organic matter content
Correct answer: Retain more cations against leaching
Higher CEC soils have more negatively charged sites that hold cations such as Ca²⁺, Mg²⁺, and K⁺, reducing leaching losses.
Question 3: The '4R' nutrient stewardship framework stands for applying the right nutrient at the right:
- Rate, ratio, row, and residue
- Rate, time, place, and source (Correct answer)
- Rate, release, range, and record
- Rate, runoff, row, and season
Correct answer: Rate, time, place, and source
The 4Rs are: right source, right rate, right time, and right place, forming the foundation of responsible nutrient management.
Question 4: Luxury consumption of potassium is most likely to occur in which crop?
- Corn
- Alfalfa (Correct answer)
- Wheat
- Soybean
Correct answer: Alfalfa
Alfalfa is well known for luxury potassium uptake, absorbing K far beyond its physiological needs when soil K is high.
Question 5: Which of the following is a primary advantage of split nitrogen applications compared to a single pre-plant application?
- Reduces total nitrogen requirement
- Lowers the risk of leaching and denitrification losses (Correct answer)
- Eliminates need for soil testing
- Increases soil pH near the root zone
Correct answer: Lowers the risk of leaching and denitrification losses
Splitting N applications synchronizes supply with crop demand, reducing the window during which N is vulnerable to loss pathways.
Question 6: Sulfur deficiency symptoms in corn most commonly appear as:
- Interveinal chlorosis on older leaves
- Uniform yellowing of new upper leaves (Correct answer)
- Purple coloration on leaf undersides
- Brown necrotic leaf margins
Correct answer: Uniform yellowing of new upper leaves
Sulfur is mobile in the soil but relatively immobile in the plant, so deficiency shows first on young upper leaves as uniform yellowing.
Question 7: Which nitrification inhibitor is commonly paired with anhydrous ammonia to slow conversion of ammonium to nitrate?
- DMPP
- NBPT
- Nitrapyrin (Correct answer)
- DCD
Correct answer: Nitrapyrin
Nitrapyrin (N-Serve) is specifically formulated to be mixed with anhydrous ammonia and inhibits the Nitrosomonas bacteria responsible for nitrification.
CCA Nutrient Management 2
Which soil pH range is generally considered optimal for maximizing phosphorus availability to most agronomic crops?