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
A grower applies 120 lb N/acre as anhydrous ammonia. What is the approximate volume of product needed if the fertilizer contains 82% N and weighs 5.15 lb/gallon?
Answer: 28 gal/acre
First find pounds of product: 120 ÷ 0.82 ≈ 146 lb; then divide by density: 146 ÷ 5.15 ≈ 28 gal/acre.
Calcium and magnesium deficiency symptoms typically appear first on which plant tissue?
Answer: Youngest upper leaves and growing points, because these elements are not phloem-mobile
Calcium and magnesium have limited phloem mobility (especially Ca), so deficiency symptoms appear first in young tissues and growing points.
Which nitrogen transformation converts organic nitrogen in crop residue and soil organic matter into ammonium (NH₄⁺)?
Answer: Mineralization (ammonification)
Mineralization (ammonification) is the microbial process that converts organic nitrogen in residues and humus into plant-available ammonium.
The critical nutrient concentration concept states that maximum crop yield is achieved when tissue nutrient level is:
Answer: At or above the level where additional nutrient provides no yield increase
The critical concentration is the tissue level at or above which yield is maximized; below it, deficiency limits production.
Boron is especially important for which crop process, making it critical to apply before or during bloom?
Answer: Pollen viability, fertilization, and fruit set
Boron is essential for pollen tube germination and fertilization; deficiency during flowering causes poor fruit and seed set.
When a nutrient management plan calls for crediting manure nitrogen, which fraction is typically credited as 'plant-available nitrogen' in the year of application?
Answer: Only the inorganic ammonium-N fraction at a utilization rate
Plant-available nitrogen (PAN) credits the inorganic ammonium-N fraction (adjusted for application method/volatilization loss) plus a portion of mineralizable organic N.
Acidifying fertilizers such as ammonium sulfate lower soil pH over time mainly because:
Answer: Nitrification of ammonium produces hydrogen ions as a byproduct
As soil bacteria oxidize ammonium to nitrate (nitrification), two hydrogen ions are released per ammonium ion, acidifying the soil over time.