CCA Fertilizer Sources and Application 2 — Questions and Answers
Question 1: Which fertilizer source has the highest nitrogen content by weight at approximately 82%?
- Urea
- Anhydrous ammonia (Correct answer)
- Ammonium nitrate
- Urea-ammonium nitrate (UAN)
Correct answer: Anhydrous ammonia
Anhydrous ammonia (NH3) contains approximately 82% nitrogen by weight, making it the most concentrated dry or liquid nitrogen fertilizer source.
Question 2: What is the primary advantage of polymer-coated urea over conventional urea?
- Higher nitrogen content
- Reduced volatilization and controlled release over time (Correct answer)
- Lower cost per unit of nitrogen
- Better solubility in water
Correct answer: Reduced volatilization and controlled release over time
Polymer-coated urea releases nitrogen slowly over weeks to months, reducing volatilization losses and synchronizing N supply with crop demand.
Question 3: Diammonium phosphate (DAP) has an approximate analysis of:
- 10-52-0
- 18-46-0 (Correct answer)
- 21-0-0
- 46-0-0
Correct answer: 18-46-0
DAP (diammonium phosphate) has a standard analysis of 18-46-0, meaning 18% N and 46% P2O5.
Question 4: When applying potassium chloride (muriate of potash) to a chloride-sensitive crop, what is the best alternative potassium source?
- Potassium nitrate
- Potassium sulfate (Correct answer)
- Potassium bicarbonate
- Potassium permanganate
Correct answer: Potassium sulfate
Potassium sulfate (K2SO4) provides potassium without chloride and is preferred for chloride-sensitive crops like tobacco and some fruits.
Question 5: Which application method best reduces ammonia volatilization loss when surface-applying urea?
- Applying during midday heat
- Incorporating urea into the soil or injecting it (Correct answer)
- Broadcasting urea on wet foliage
- Applying urea to alkaline soils only
Correct answer: Incorporating urea into the soil or injecting it
Incorporating urea into the soil through tillage or injection dramatically reduces ammonia volatilization by keeping urea in contact with soil moisture and cation exchange sites.
Question 6: What is the primary reason sulfur-coated urea releases nitrogen more slowly than uncoated urea?
- Sulfur reacts with nitrogen to form stable compounds
- The sulfur coating must degrade or crack before water can dissolve the urea (Correct answer)
- Sulfur increases soil pH, slowing nitrification
- Sulfur blocks urease enzyme activity indefinitely
Correct answer: The sulfur coating must degrade or crack before water can dissolve the urea
The sulfur coating acts as a physical barrier; as it weathers and cracks, water enters and dissolves the urea, releasing nitrogen gradually.
Question 7: A producer wants to apply 120 lbs N/acre using urea (46-0-0). How many lbs of urea per acre are required?
- 55 lbs/acre
- 120 lbs/acre
- 261 lbs/acre (Correct answer)
- 552 lbs/acre
Correct answer: 261 lbs/acre
Divide the desired N rate by the N fraction: 120 ÷ 0.46 = 261 lbs urea/acre.
CCA Fertilizer Sources and Application 2
Which fertilizer source has the highest nitrogen content by weight at approximately 82%?