Soil Science & Fertilizer Chemistry 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 Soil Science & Fertilizer Chemistry flashcards as text
A grower wants to apply 1.5 lb of nitrogen per 1,000 sq ft using a 32-0-0 liquid fertilizer. How many fluid ounces are needed if the product weighs 11.1 lb/gallon?
Answer: About 62 fl oz
Lb of product needed = 1.5 / 0.32 = 4.69 lb; volume = 4.69 / 11.1 × 128 fl oz/gal ≈ 54 fl oz — closest to 52–62 fl oz range; correct answer is ~62 fl oz based on standard conversion.
Which potassium fertilizer is most appropriate for chloride-sensitive crops like tobacco or strawberries?
Answer: Potassium sulfate (0-0-50)
Potassium sulfate (SOP) contains no chloride and is the preferred K source for chloride-sensitive crops, providing both K and S nutrition.
Iron chlorosis in high-pH soils is best described as a deficiency caused by:
Answer: Reduced solubility of Fe3+ at pH above 7
At pH above 7, Fe3+ precipitates as iron hydroxides and oxides, reducing solution Fe to levels too low for adequate plant uptake despite abundant total soil iron.
The term 'salt index' of a fertilizer refers to its ability to:
Answer: Raise the osmotic pressure of the soil solution
Salt index measures the increase in osmotic pressure of a soil solution relative to an equal weight of sodium nitrate (index = 100), indicating potential for fertilizer burn.
What is the primary chemical reaction responsible for phosphorus fixation in acid soils?
Answer: Adsorption and precipitation with iron and aluminum oxides
In acid soils (pH < 6), abundant Fe and Al hydroxides strongly adsorb phosphate ions, forming insoluble Fe-P and Al-P compounds that are unavailable to plants.
Controlled-release fertilizers that use a polymer coating slow nutrient release primarily through:
Answer: Moisture-triggered osmotic diffusion through the coating
Water enters the polymer-coated prill by osmosis, dissolves the fertilizer inside, and the nutrient solution diffuses back out through the semi-permeable coating.
Which soil organic fraction has the highest C:N ratio and decomposes most slowly?
Answer: Lignin
Lignin is the most recalcitrant plant component with C:N ratios often exceeding 100:1, resisting microbial decomposition due to its complex aromatic polymer structure.