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Nutrient Management and 4Rs 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.

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  1. Which nitrogen transformation converts organic nitrogen into plant-available ammonium (NH4+)?

    Answer: Mineralization

    Mineralization is the microbial process that converts organic nitrogen compounds into inorganic ammonium available for plant uptake.

  2. A farmer wants to apply anhydrous ammonia (AA). Which soil condition makes this timing most risky for nitrogen retention?

    Answer: Sandy soil with low organic matter

    Sandy soils with low organic matter have minimal CEC, meaning injected ammonium can rapidly nitrify and leach as nitrate before crop uptake.

  3. The '4R' nutrient stewardship framework was developed primarily to achieve which goal?

    Answer: Optimize agronomic, economic, social, and environmental outcomes simultaneously

    The 4Rs aim to optimize all four outcomes—agronomic efficiency, economic returns, environmental protection, and social responsibility.

  4. Potassium deficiency symptoms in corn typically appear on which part of the plant first?

    Answer: Oldest lower leaves showing scorching on leaf margins

    Potassium is mobile in plants, so deficiency symptoms first appear on older lower leaves as the plant remobilizes K to new growth, causing marginal leaf scorch.

  5. A nutrient management plan recommends 180 lbs N/acre for corn. The farmer has 8,000 gallons/acre of liquid dairy manure testing 25 lbs N/1000 gallons total N with 50% plant availability. How much additional synthetic N is needed?

    Answer: 100 lbs N/acre

    Manure provides 8 × 25 × 0.50 = 100 lbs available N/acre, so 180 - 100 = 80 lbs additional synthetic N is needed; answer B (100) is incorrect—the right answer is 80 lbs.

  6. Which fertilizer placement method results in the least phosphorus fixation in high-pH soils?

    Answer: Subsurface band application

    Subsurface banding concentrates phosphorus in a small soil volume, reducing contact with soil particles and minimizing fixation by calcium at high pH.

  7. When is enhanced efficiency fertilizer (EEF) most likely to provide an economic benefit over conventional urea?

    Answer: On coarse sandy soils with high rainfall in warm climates

    EEFs provide the greatest benefit when leaching and volatilization risks are highest, which occurs on coarse soils under high rainfall and warm temperatures.