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Fertilizer Sources and Application Flashcards

7 cards from real CCA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the most common cause of 'salt burn' injury when starter fertilizer is placed too close to the seed?

    Answer: Osmotic stress as high fertilizer salt concentration draws water away from the seed

    High salt concentration from nearby fertilizer lowers the soil water potential, pulling water out of the germinating seed and root tissue through osmosis, causing injury.

  2. Which potassium fertilizer source also supplies a significant amount of sulfur?

    Answer: Potassium sulfate (K2SO4)

    Potassium sulfate (K2SO4, 0-0-50) contains approximately 17% sulfur in addition to 50% K2O, making it a dual-nutrient source.

  3. When calculating fertilizer blends, which law states that the analysis of a bulk blend equals the weighted average of its components?

    Answer: Law of averages for nutrient blending

    In bulk blending, the final nutrient analysis is calculated as the weighted average of each component's contribution, based on proportions mixed—a fundamental principle of fertilizer blending.

  4. Which foliar micronutrient application is most widely used to correct boron deficiency in broadleaf crops?

    Answer: Solubor (sodium octaborate) foliar spray

    Solubor is a highly water-soluble boron source ideal for foliar sprays, providing rapid correction of boron deficiency in crops like canola and alfalfa.

  5. The nitrogen stabilizer NBPT (N-(n-butyl) thiophosphoric triamide) works by:

    Answer: Inhibiting the urease enzyme to delay urea hydrolysis

    NBPT temporarily inhibits the urease enzyme that converts urea to ammonia, slowing hydrolysis and reducing volatilization losses from surface-applied urea.

  6. Which fertilizer application method is most appropriate for correcting zinc deficiency observed mid-season in corn?

    Answer: Foliar application of zinc sulfate or zinc chelate solution

    Mid-season foliar application of soluble zinc sources provides rapid correction of zinc deficiency since root uptake is slow when soil conditions limit zinc availability.

  7. What is the recommended maximum N rate from fertilizer in a '2x2' starter placement to avoid seed germination injury?

    Answer: 30 lbs N/acre

    Industry guidelines generally recommend no more than 30 lbs N+K2O/acre in a 2x2 starter placement to avoid salt/ammonia injury to germinating seeds.