CHAPTER 11: SOILPresentation by: Alex Hezik

11.1 – SOIL AND PLANTS

Parent material (rock or sediments deposited by wind, water, or ice) is weathered to form soil

Soil separates are classified below the size of small stones; include gravel/cobble/boulder (particles larger than 2.0 mm) sand (made up of particles from 2.0 to 0.063 mm) silt (made up of particles from 0.063 to 0.004 mm) clay (made up of particles finer than 0.004 mm)

Soil texture refers to relative proportions of each type of particle in a given soil

Soil that consists of 40% sand, 40% silt, and 20% clay is called loam

11.1 – SOIL AND PLANTS

Soil Texture

Water Infiltration

Water-Holding Capacity

Nutrient-Holding Capacity

Aeration Workability

sand good poor poor good good

silt medium medium medium medium medium

clay poor good good poor poor

loam medium medium medium medium medium

11.1 – SOIL AND PLANTS

Soil Horizons•O horizon: humus (surface litter, decomposing plant matter)•A horizon: topsoil (mixed humus and leached mineral soil)•E horizon: zone of leaching (less humus, minerals resistant to leaching)•B horizon: subsoil (accumulation of leached minerals like iron oxides)•C horizon: weathered parent material (partly broken-down minerals)

11.2 – SOIL DEGRADATION

Erosion is the process of soil and humus particles being picked up and carried away by water or wind Water erosion is broken up into three distinct

phenomena:1. splash erosion (compaction of soil that results when

rainfall hits bare soil)2. sheet erosion (loss of a layer of soil from land

surface due to impact of rain and runoff from rainstorm)

3. gully erosion (produced by running water and resulting in formation of gullies)

11.2 – SOIL DEGRADATION

When wind removes fine particles from desert soil, a thin surface layer of stones and gravel is left behind, which is a called a desert pavement Desert pavement protects underlying soil against

further erosion Rainfall-clogged soil that is dried becomes

colonized by cryptogams (algae, lichens, and mosses), forming a cryptogamic crust that inhibits water infiltration and seed generation

11.2 – SOIL DEGRADATION

Practices that expose soil to erosion and lead to soil degradation include: overcultivation overgrazing deforestation

Sediments that result from soil erosion can clog up streams and rivers, causing sedimentation Can also build up in groundwater reservoirs,

depleting groundwater resources

11.3 – SOIL CONSERVATION

Laws involving soils include… Sustainable Agriculture Research and

Education (SARE) program: provides funding for investigating ways to accomplish goals of sustainable agriculture

Federal Agricultural Improvement and Reform Act (FAIR): reduced and eliminated subsidies and controls over many farm commodities; ended in failure, resulting in the maintenance of subsidies and controls FAIR initially targeted

11.3 – SOIL CONSERVATION

Farm Security and Rural Investment Act of 2002: successor to FAIR that continued to maintain subsidies to farmers

Food, Conservation, and Energy Act of 2008: maintains existing high levels of support and subsidies to farms

Wildlife Habitat Incentives Program (WHIP) and Environmental Quality Incentives Program (EQIP): encourages conservation-minded landowners to set aside portions of their land or address pollution problems