CFA Fertilizer Application Techniques & Equipment 3 — Questions and Answers
Question 1: Variable rate technology (VRT) applicators rely primarily on which data source to adjust fertilizer rates across a field?
- Operator manual adjustments
- Prescription maps derived from soil sampling or remote sensing (Correct answer)
- Weather station data only
- Crop insurance maps
Correct answer: Prescription maps derived from soil sampling or remote sensing
VRT systems use GPS-referenced prescription maps created from soil test data, yield maps, or remote sensing to automatically adjust application rates zone by zone.
Question 2: When applying anhydrous ammonia, the minimum recommended soil moisture condition for effective sealing is:
- Bone dry, dusty soil
- Soil that is moist enough to close knife slots behind the applicator (Correct answer)
- Saturated, waterlogged soil
- Frozen soil surface
Correct answer: Soil that is moist enough to close knife slots behind the applicator
Adequate soil moisture allows the disturbed soil to collapse and seal behind the knife, trapping anhydrous ammonia and preventing escape to the atmosphere.
Question 3: A rate controller on a variable rate applicator receives a new prescription zone but the gate position does not change. The most likely fault is:
- GPS signal too strong
- Communication failure between the controller and the gate actuator (Correct answer)
- Prescription map loaded correctly
- Ground speed sensor working normally
Correct answer: Communication failure between the controller and the gate actuator
A communication failure between the rate controller and the gate/servo actuator prevents the mechanical adjustment needed to change output despite receiving the new prescription.
Question 4: Which fertilizer application scenario presents the highest risk of surface water contamination?
- Subsurface injection on level ground
- Broadcast application on frozen or saturated soil before rain (Correct answer)
- Slow-release granule application in midsummer
- Side-dress application in dry soil
Correct answer: Broadcast application on frozen or saturated soil before rain
Fertilizer applied to frozen or saturated soil has no infiltration pathway and is highly susceptible to runoff into surface water when precipitation or snowmelt occurs.
Question 5: The purpose of using a urease inhibitor with surface-applied urea is to:
- Increase nitrogen content of the urea
- Slow the conversion of urea to ammonia, reducing volatilization (Correct answer)
- Prevent nitrogen from leaching to groundwater
- Acidify the soil around the granule
Correct answer: Slow the conversion of urea to ammonia, reducing volatilization
Urease inhibitors temporarily block the urease enzyme that converts urea to ammonium, giving time for rain or irrigation to move urea into the soil before volatile losses occur.
Question 6: When operating a pneumatic dry fertilizer applicator, an increase in fan speed while maintaining the same gate opening will generally:
- Decrease application rate
- Increase uniformity of distribution and potentially delivery rate (Correct answer)
- Have no effect on distribution pattern
- Cause product to clog the delivery tubes
Correct answer: Increase uniformity of distribution and potentially delivery rate
Higher fan speed improves product flow through delivery tubes and can improve distribution uniformity, though gate opening remains the primary rate control.
Question 7: A certified applicator notices the spinner discs on a centrifugal spreader are worn unevenly. The most immediate operational concern is:
- Increased hopper capacity
- Asymmetrical distribution pattern causing uneven crop nutrition (Correct answer)
- Reduced ground speed requirement
- Improved fertilizer flow from hopper
Correct answer: Asymmetrical distribution pattern causing uneven crop nutrition
Uneven disc wear changes the trajectory of particles on each side differently, creating an asymmetrical spread pattern that results in striping or uneven nutrient distribution.
CFA Fertilizer Application Techniques & Equipment 3
Variable rate technology (VRT) applicators rely primarily on which data source to adjust fertilizer rates across a field?