Nutrient Management Flashcards

A corn crop yielding 200 bu/acre removes approximately how many pounds of nitrogen in the grain?

Answer: 160 lbs N/acre

Corn grain contains roughly 0.8 lb N per bushel, so 200 bu × 0.8 = 160 lbs N removed in grain at harvest.

Denitrification is most likely to accelerate under which combination of conditions?

Answer: Warm, saturated soil with available carbon

Denitrifying bacteria thrive when soils are warm, anaerobic (saturated), and have readily available carbon as an energy source.

Which phosphorus soil test method is most widely recommended for soils with neutral to alkaline pH in western U.S. states?

Answer: Olsen (NaHCO₃)

The Olsen bicarbonate method is preferred for neutral to calcareous soils because Bray P-1 acid extraction underestimates available P at high pH.

The primary function of boron in plants is related to:

Answer: Cell wall formation and structural integrity

Boron is essential for cell wall cross-linking, pollen germination, and sugar transport, making it critical to structural development.

When computing a nitrogen budget using the maximum return to nitrogen (MRTN) approach, the primary economic inputs are:

Answer: Corn price and nitrogen fertilizer cost

MRTN calculations identify the N rate that maximizes profit by comparing the cost of N fertilizer against the value of the resulting yield response.

Which form of nitrogen fertilizer has the highest potential for ammonia volatilization when surface applied without incorporation?

Answer: Urea

Urea is rapidly hydrolyzed by urease to ammonium carbonate, which readily loses NH₃ gas at warm temperatures and high soil pH when not incorporated.

Iron chlorosis in soybeans on high-pH calcareous soils is best described as a deficiency of:

Answer: Plant-available iron due to limited solubility at high pH

Calcareous soils contain ample total iron but at pH above 7.5 Fe³⁺ solubility drops dramatically, making it unavailable for plant uptake.