Soil Management Flashcards

Which soil property best describes the ability of a soil to resist changes in pH when acids or bases are added?

Answer: Buffer capacity

Buffer capacity refers to a soil's ability to resist pH change when acids or bases are added, which is largely determined by organic matter and clay content.

A soil has a bulk density of 1.35 g/cm³ and a particle density of 2.65 g/cm³. What is its total porosity?

Answer: 49%

Total porosity = (1 - bulk density/particle density) × 100 = (1 - 1.35/2.65) × 100 ≈ 49%.

Which tillage practice involves cutting and mixing residue into the top few inches of soil without full inversion?

Answer: Vertical tillage

Vertical tillage uses straight or slightly angled blades to cut and minimally mix residue in the surface layer without inverting the soil profile.

Which soil order is characterized by an argillic or natric horizon and is commonly found in semi-arid grasslands?

Answer: Alfisols

Alfisols have an argillic horizon with moderate-to-high base saturation and are typically found under temperate forests or semi-arid grasslands.

What is the primary mechanism by which nitrogen is lost from waterlogged soils?

Answer: Denitrification

Denitrification occurs when anaerobic bacteria convert nitrate (NO₃⁻) to nitrogen gases (N₂, N₂O) under waterlogged, oxygen-depleted conditions.

Which aggregate stability test is most commonly used to evaluate a soil's susceptibility to surface sealing and crusting?

Answer: Slake test

The slake test measures how quickly aggregates break apart when submerged in water, indicating susceptibility to surface sealing and crusting.

When managing saline-sodic soils, which amendment is typically applied first to displace sodium before leaching?

Answer: Gypsum (CaSO₄)

Gypsum supplies calcium that displaces sodium from cation exchange sites, making sodium available for leaching from the root zone.