CCA Fertilizer Sources and Application 3 — Questions and Answers
Question 1: Which fertilizer application timing strategy delivers nitrogen closest to peak crop demand, minimizing leaching risk?
- Pre-plant incorporation in fall
- Split application with starter plus side-dress at V6 (Correct answer)
- Single broadcast application at planting
- Aerial application at grain fill
Correct answer: Split application with starter plus side-dress at V6
Split application—starter at planting plus side-dress near peak uptake—synchronizes nitrogen supply with the period of highest crop demand, reducing leaching losses.
Question 2: The '4R' nutrient stewardship framework stands for right source, right rate, right time, and:
- Right region
- Right place (Correct answer)
- Right rainfall
- Right residue
Correct answer: Right place
The 4R framework stands for Right Source, Right Rate, Right Time, and Right Place—collectively improving nutrient use efficiency and environmental stewardship.
Question 3: Which micronutrient fertilizer is most commonly applied to correct iron deficiency chlorosis in soybeans grown on calcareous soils?
- Iron sulfate broadcast
- Chelated iron (Fe-EDTA or Fe-EDDHA) applied as foliar or soil application (Correct answer)
- Iron oxide slag
- Ferric chloride solution
Correct answer: Chelated iron (Fe-EDTA or Fe-EDDHA) applied as foliar or soil application
Chelated iron forms (EDTA or EDDHA) remain plant-available in high-pH calcareous soils where inorganic iron is rapidly fixed, making them the most effective treatment.
Question 4: What is the primary environmental concern associated with excessive phosphorus fertilization on sandy soils near water bodies?
- Acidification of groundwater
- Phosphorus leaching leading to eutrophication of surface waters (Correct answer)
- Denitrification of soil nitrogen
- Increased soil salinity
Correct answer: Phosphorus leaching leading to eutrophication of surface waters
On coarse sandy soils, phosphorus can leach into groundwater and reach surface water bodies, causing algal blooms and eutrophication.
Question 5: Fertigation through drip irrigation is most advantageous because it:
- Eliminates the need for soil testing
- Delivers soluble nutrients directly to the root zone with high precision and efficiency (Correct answer)
- Allows use of insoluble granular fertilizers
- Increases soil pH uniformly across the field
Correct answer: Delivers soluble nutrients directly to the root zone with high precision and efficiency
Fertigation via drip irrigation places nutrients precisely in the active root zone, improving uptake efficiency and reducing runoff and volatilization losses.
Question 6: Which of the following is a liming material rather than a fertilizer, but is often applied to improve nutrient availability?
- Gypsum (calcium sulfate)
- Calcitic limestone (CaCO3) (Correct answer)
- Triple superphosphate
- Potassium chloride
Correct answer: Calcitic limestone (CaCO3)
Calcitic limestone is a liming material that raises soil pH, improving the availability of most macro and micronutrients rather than supplying large amounts of plant-available nutrients directly.
Question 7: Nitrogen in urea-ammonium nitrate (UAN) solution is present in which three forms?
- Nitrate, nitrite, and ammonium
- Urea, ammonium, and nitrate (Correct answer)
- Urea, nitrate, and nitrite
- Ammonium, nitrite, and organic N
Correct answer: Urea, ammonium, and nitrate
UAN solution contains urea-N (~50%), ammonium-N (~25%), and nitrate-N (~25%), giving it a blend of fast- and slower-release nitrogen fractions.
CCA Fertilizer Sources and Application 3
Which fertilizer application timing strategy delivers nitrogen closest to peak crop demand, minimizing leaching risk?