Nutrient Sources and Management Flashcards

Which fertilizer material is considered an organic nitrogen source because it releases nitrogen through microbial decomposition?

Answer: Feather meal

Feather meal is an organic nitrogen source that releases nitrogen slowly as soil microbes break down the protein.

A fertilizer label reads 10-20-10. What is the percentage of phosphate (P₂O₅) in this product?

Answer: 20%

The second number in the N-P-K grade always represents the percentage of available phosphate (P₂O₅), which is 20%.

Which form of phosphorus do plant roots actually absorb from the soil solution?

Answer: Orthophosphate (H₂PO₄⁻ or HPO₄²⁻)

Plant roots absorb phosphorus as orthophosphate ions (H₂PO₄⁻ or HPO₄²⁻) from the soil solution.

Sulfur-coated urea releases nitrogen more slowly than regular urea primarily because:

Answer: The coating must degrade before water can dissolve the urea

The sulfur coating acts as a physical barrier; moisture must penetrate or degrade it before the urea core dissolves and becomes available.

When manure is surface-applied without incorporation, the greatest nutrient loss risk is:

Answer: Ammonia volatilization from nitrogen

Ammonium-nitrogen in unincorporated manure readily volatilizes as ammonia gas, especially in warm, windy conditions.

Which potassium fertilizer also supplies sulfur, making it useful on sulfur-deficient soils?

Answer: Sulfate of potash (K₂SO₄)

Sulfate of potash (K₂SO₄) provides both potassium and sulfur, benefiting crops on sulfur-deficient soils.

A soil test recommends 60 lb P₂O₅/acre. If triple superphosphate (0-46-0) is used, approximately how many pounds per acre are needed?

Answer: 130 lb/acre

Dividing the recommendation by the decimal fraction of P₂O₅: 60 ÷ 0.46 ≈ 130 lb/acre of triple superphosphate.