Nutrient Management Flashcards

Which soil pH range is generally considered optimal for maximizing phosphorus availability to most agronomic crops?

Answer: 6.0–7.0

Phosphorus availability peaks between pH 6.0 and 7.0, where it is least likely to be fixed by aluminum, iron, or calcium.

A field soil test reveals a cation exchange capacity (CEC) of 25 meq/100g. Compared to a soil with CEC of 5 meq/100g, this soil will:

Answer: Retain more cations against leaching

Higher CEC soils have more negatively charged sites that hold cations such as Ca²⁺, Mg²⁺, and K⁺, reducing leaching losses.

The '4R' nutrient stewardship framework stands for applying the right nutrient at the right:

Answer: Rate, time, place, and source

The 4Rs are: right source, right rate, right time, and right place, forming the foundation of responsible nutrient management.

Luxury consumption of potassium is most likely to occur in which crop?

Answer: Alfalfa

Alfalfa is well known for luxury potassium uptake, absorbing K far beyond its physiological needs when soil K is high.

Which of the following is a primary advantage of split nitrogen applications compared to a single pre-plant application?

Answer: Lowers the risk of leaching and denitrification losses

Splitting N applications synchronizes supply with crop demand, reducing the window during which N is vulnerable to loss pathways.

Sulfur deficiency symptoms in corn most commonly appear as:

Answer: Uniform yellowing of new upper leaves

Sulfur is mobile in the soil but relatively immobile in the plant, so deficiency shows first on young upper leaves as uniform yellowing.

Which nitrification inhibitor is commonly paired with anhydrous ammonia to slow conversion of ammonium to nitrate?

Answer: Nitrapyrin

Nitrapyrin (N-Serve) is specifically formulated to be mixed with anhydrous ammonia and inhibits the Nitrosomonas bacteria responsible for nitrification.