soil and water exam 1 material

Why should we conserve soil?

Because there's very little of it, it's habitat for organisms, and essential for food security.

How long does it take to form 1 inch of soil?

500-1000 years (nonrenewable on human timescale).

6 Functions of soil in the ecosystem?

Support plant growth, regulate water, recycle nutrients, serve as habitat, engineering medium, impact atmosphere.

Definition of soil?

Unconsolidated material on Earth's surface, subject to weathering, able to support life, influenced by parent material, climate, topography, time, organisms.

Components of soil?

Mineral matter, organic matter, water, air.

What is loam?

Balanced mixture of sand, silt, clay (ideal for agriculture).

Order of soil particle size (largest → smallest)?

Sand> Silt > Clay.

Which soil drains fastest?

Sand.

Which soil holds the most water and nutrients?

Clay.

Which soil is most erodible?

Silt.

Which soil is least erodible?

Clay.

Types of soil water?

Gravitational,capillary,hygroscopic,

Gravitational

drains quickly, unavailable to plants.

Capillary

available to plants.

Hygroscopic

bound tightly, unavailable.

Field capacity?

Water held after gravitational water drains (plant-available).

Wilting point?

Water bound so tightly plants cannot use it.

Available water capacity?

Field capacity − Wilting point.

Bulk density (BD) definition + formula?

Dry soil weight ÷ total soil volume; typical 1.1-1.9 g/cm³.

Particle density (PD) definition?

Dry weight ÷ volume of solids; usually ~2.65 g/cm³.

Porosity (% pore space) formula?

[1 − (BD ÷ PD)] × 100.

Relationship between BD & pore space?

High BD = low pore space (compacted); low BD = high pore space (fluffy).

What is soil structure?

Arrangement of particles into aggregates.

Soil structure types?

Granular, platy, blocky, prismatic, columnar, massive, single grain.

Granular structure trait?

Crumbly topsoil, rich in organic matter.

Platy structure trait?

Thin, plate-like layers; slows water and root penetration.

Blocky structure trait?

Cube-like; angular or subangular.

Prismatic structure trait?

Vertical pillars with flat tops, clay-rich layers.

Columnar structure trait?

Vertical pillars with rounded tops; found in arid soils.

Massive structure trait?

Solid block, no structure; poor for plants.

Single grain structure trait?

Loose sand, no aggregation.

Gravity potential?

Force pulling water downward.

Matrix potential?

Attraction of water to soil particles (adhesion + cohesion).

Osmotic potential?

Effect of solutes on water movement.

% of global freshwater used in agriculture?

~70%.

Most common but least efficient irrigation method?

Flood irrigation.

Most efficient irrigation method?

Drip irrigation (limited by freezing/seasonal use).

Father of soil conservation?

Hugh Hammond Bennett.

When was the Soil Conservation Service founded?

1935 (became NRCS in 1994).

Invasive plant promoted for erosion control in the South?

Kudzu.

USLE equation?A = R × K × LS × C × P. (A = soil loss; R = rainfall erosivity; K = soil erodibility; LS = slope length/steepness; C = cover/management; P = conservation practice).

Types of erosion?

(splash,interill(sheet),rill,Gully,tunnel,streambanks)

Splash

raindrop impact, craters.

Interrill (sheet)

uniform soil loss.

Rill

small channels, fixed with tillage.

Gully

large channels, not fixed with tillage.

Tunnel

subsurface erosion.

Streambank

banks of rivers erode.

On-site impacts of erosion?

Soil/nutrient/organic matter loss, lower fertility, yield drop, infrastructure damage, reduced land value.

Off-site impacts of erosion?

Sedimentation, flooding, landslides, eutrophication, reduced water quality, higher treatment cost, loss of recreation.

Cost of erosion in the U.S.?

~$44 billion annually.

Main sources of water pollution in U.S. rivers/lakes?

Agriculture (nutrients, sediment).

Blue baby syndrome cause?

High nitrates in water displace oxygen in infant blood.

What crop yields are increasing annually?

Maize, rice, wheat, soybean (~0.9% per year).