Soil Fertility Quiz #2

Which statement best defines soil fertility as presented in the lecture?

The ability of soil to provide essential nutrients to plants in adequate amounts and proportions for optimal growth

A nutrient that is highly mobile in the soil but relatively immobile in the plant is most likely to show deficiency symptoms first in which tissues?

young leaves, because the nutrient cannot be readily moved from older tissues

Montmorillonite is a

2:1 expanding clay

When plant roots absorb more cations than anions from the soil solution, what is the most likely effect in the rhizosphere?

Release of hydrogen ions, increasing acidity around the roots

Which of the following is the most direct consequence of leaching in humid regions with respect to soil acidity?

Loss of base cations from the soil profile and replacement by H and Al on exchange sites

A function of calcium within the plant is

to stabilize cell walls

Which soil pH range is generally considered optimal for most agronomic crops due to balance nutrient availability and microbial activity?

6.0 to 7.0

The source of charge in illite clay comes

mostly from isomorphic substitution

A soil with pH 5.0 has how many times higher hydrogen ion activity than a soil with pH 7.0?

100 times higher

an example of mobile nutrient is the plant is

potassium

Root interception is especially important for the uptake of which type of nutrient behavior in soil?

Relatively immobile nutrients like calcium and phosphorus

Which process best explains why ammonium-based fertilizers can contribute to increased soil acidity over time?

Nitrification of ammonium to nitrate releases hydrogen ions

Which soil factor is most likely to decrease the diffusion rate of phosphate ions to plant roots in the field?

very dry conditions

Which statement best distinguishes apoplastic from symplastic transport in roots?

Apoplastic transport moves through cell walls and intercellular spaces until blocked by the Casparian strip.

What soil property best explains why some soils can retain more nutrient cations than others?

Cation exchange capacity (CEC)

Mycorrhizal fungi most directly enhance plant nutrient uptake by which mechanism?

extending the effective root surface area through hyphae that explore more soil volume

Which buffering mechanism is primarily responsible for resisting changes in soil pH in the range of approximately 5.5 to 7.0?

Cation exchange reactions involving clay and organic matter

Why are primary macronutrients most likely to limit crop growth?

They are required in large quantities and frequently removed or lost from soils

Which fertilizer material would be expected to have the strongest acidifying effect per unit of nitrogen applied?

Ammonium sulfate

Illite has a CEC of

40 cmol/kg