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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.

Read the first 7 Nutrient Management and 4Rs flashcards as text

  1. A soil test report shows 'Bray P1 = 45 ppm' for a corn field. This level is typically interpreted as:

    Answer: Excessive — reduce or eliminate phosphorus application

    Bray P1 values above 35-40 ppm are generally considered excessive, meaning yield response to additional P is unlikely and applications should be reduced.

  2. Which factor is the primary driver of nitrogen use efficiency (NUE) differences between corn hybrids?

    Answer: Root architecture and N uptake kinetics

    Root architecture and N uptake kinetics determine how efficiently a hybrid can capture available soil nitrogen at different growth stages.

  3. Secondary macronutrients include calcium, magnesium, and sulfur. Which crop is most commonly deficient in sulfur in the US?

    Answer: Corn on sandy soils in high-rainfall areas

    Corn on sandy soils in high-rainfall regions is most vulnerable to sulfur deficiency because sulfate leaches readily from coarse-textured soils.

  4. The term 'luxury consumption' in plant nutrition refers to:

    Answer: Plant uptake of a nutrient beyond what is needed for maximum growth

    Luxury consumption occurs when plants absorb more of a nutrient than required for maximum yield, storing the excess without additional growth benefit.

  5. A grower applying liquid UAN (32% N) through a pivot irrigation system should be most concerned about which application issue?

    Answer: Foliar burn from solution contacting wet leaves

    UAN applied through overhead irrigation can wet foliage directly, and the urea and ammonium nitrate components can cause foliar burn, especially at high rates.

  6. Which soil characteristic most strongly controls the risk of potassium leaching from agricultural fields?

    Answer: Soil texture and CEC

    Coarse-textured soils (sands) have low CEC and hold little exchangeable K+, making them most prone to potassium leaching under rainfall or irrigation.

  7. Under 4R stewardship, a Nutrient Management Plan (NMP) should be updated most frequently when:

    Answer: Crop rotation, yield goals, or manure application rates change significantly

    NMPs must be updated when key variables change—crop rotation, realistic yield goals, or manure nutrient contributions all directly affect nutrient rate recommendations.