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Nutrient Sources and Management Flashcards

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

Read the first 7 Nutrient Sources and Management flashcards as text

  1. Diammonium phosphate (DAP, 18-46-0) applied in direct seed contact can injure seedlings mainly because:

    Answer: High ammonia concentration near seeds causes salt and ammonia toxicity

    DAP releases free ammonia as it dissolves, and the high salt index near seeds can cause germination injury if placed in direct contact.

  2. A farmer wants to sidedress corn with 28% UAN solution. The salt index of liquid UAN compared to granular urea is:

    Answer: Essentially the same per unit of nitrogen

    Salt index is expressed per unit of nutrient, so UAN and urea have similar salt index values per pound of nitrogen applied.

  3. Which cover crop or rotation practice can reduce the need for commercial nitrogen fertilizer by fixing atmospheric N₂?

    Answer: Hairy vetch before corn

    Hairy vetch is a legume that hosts Rhizobium bacteria capable of fixing significant amounts of atmospheric nitrogen that becomes available to the following corn crop.

  4. Phosphorus stratification in no-till systems refers to:

    Answer: Accumulation of P near the soil surface where fertilizer and residue are placed

    In no-till soils, surface-applied phosphorus is not incorporated, so P concentrates near the soil surface creating a stratified profile.

  5. Potassium fixation—where applied K becomes temporarily unavailable—is most common in soils high in:

    Answer: 2:1 expanding clays such as vermiculite and illite

    Expanding 2:1 layer clays like vermiculite and illite can trap potassium ions between clay layers, fixing them in non-exchangeable positions.

  6. Enhanced efficiency fertilizers (EEFs) that use urease inhibitors work by:

    Answer: Blocking the enzyme that converts urea to ammonium, reducing volatilization

    Urease inhibitors such as NBPT block the urease enzyme, slowing urea hydrolysis and reducing ammonia volatilization losses.

  7. Which practice best minimizes phosphorus loss to surface water via runoff from fields with high soil test P?

    Answer: Switching to subsurface banding and maintaining vegetated buffer strips

    Subsurface banding places P below the runoff zone, and vegetated buffer strips intercept dissolved and particulate P before it reaches water bodies.