Soil Fertility and Analysis Flashcards

Luxury consumption of potassium is most commonly observed in which crop species?

Answer: Alfalfa and small grains

Alfalfa and certain small grains absorb K far beyond their growth requirements when soil K is high, a phenomenon called luxury consumption that does not increase yield.

Which micronutrient deficiency is most likely in a high-pH, calcareous Midwestern soil and typically corrected with foliar or chelated applications?

Answer: Iron

Iron chlorosis is common in high-pH soils because Fe3+ precipitation reduces availability; chelated iron or foliar sprays bypass soil fixation.

The nitrogen use efficiency (NUE) of most cereal crops typically falls within which range?

Answer: 20–50%

NUE for cereals is commonly 20–50%, meaning the majority of applied N is lost through leaching, volatilization, denitrification, or immobilization.

A soil with 3% organic matter contains roughly how many pounds of total N per acre in the top 6 inches (assume 2 million lb soil/ac-6in)?

Answer: 3,000 lb

OM is approximately 5% N, so 3% OM × 2,000,000 lb soil × 0.05 = 3,000 lb total N/ac, though only 1–3% mineralizes annually.

Magnesium deficiency symptoms in corn appear as:

Answer: Interveinal chlorosis (striping) on older leaves

Mg is mobile in the plant, so deficiency appears first on older, lower leaves as interveinal chlorosis, leaving the veins green.

Split nitrogen applications for corn are primarily recommended to:

Answer: Improve synchrony between N supply and crop N demand, reducing losses

Splitting N applications aligns nutrient availability with peak crop uptake periods (V5–VT), reducing leaching and denitrification losses compared to a single pre-plant application.

Which statement best describes the difference between soil test correlation and soil test calibration?

Answer: Correlation links soil test values to crop yield response; calibration defines the critical level that separates responsive from non-responsive soils

Correlation establishes the relationship between soil test values and crop yield response in field trials, while calibration determines the critical soil test level below which yield response to fertilization is likely.