BIG IDEA: Abiotic & biotic factors influence the environment

SOIL•organic and inorganic•formed by weathering, breakdown as a result of the physical actions

WEATHERING•freezing and thawing•dissolving•attached organisms (lichens)

MINERAL CONTENTdependent on:•type of rock forming soil•type of organisms in soil•amount of precipitation

4 LAYERS OF SOIL•topsoil:organic and organisms; contains humus•subsoil:rock particles and organics•rock parts: weathered •rock parts: unweathered

Soil Horizons

• O horizons or layers: Layers dominated by organic material; consist of undecomposed or partially decomposed litter (such as leaves, needles,twigs, moss, and lichens)

• A horizons(topsoil): Mineral horizons which have formed at the surface or below an O horizon; mixture of partially decomposed organic matter called humus and some inorganic mineral particles

• B horizons (subsoil): zone of accumulation; mineral-rich; contain more inorganic than organic material– mostly broken down rock consisting of sand, silt, gravel, clay

• C horizons (parent material): transition to rock

• R horizons: hard bedrock

As the roots of the grasses die they form a layer of organic matter called

The humus helps hold water and provides nutrients and food for the grasses and other organisms to grow.

SOIL CLASSIFICATION•organics•minerals•pH•size of particles

is the symbol for the degree of acidity or alkalinity (base) of a substance

•plants require a certain pH to grow properly•acid rain can ‘burn’ plants and the animals drink it

1908 1969

SOIL CONSERVATION•strip cropping•terracing•contour farming•windbreaks•dams•crop rotation•fertilizers

SOIL CONSERVATION•strip cropping: cover crops are planted between strip crops so no exposed soil is left open to erosion

SOIL CONSERVATION•terracing: flat areas dug in hillside to prevent surface water (carrying soils) from running down hill

SOIL CONSERVATION•contour farming: rows across slopes on uneven landscapes; mounds formed by plow prevent runoff

SOIL CONSERVATION•windbreaks: used to prevent wind erosion, usually made of trees

SOIL CONSERVATION•crop rotation: growing different crops in succeeding years; prevents soil depletion (reduction of nutrients)

SOIL CONSERVATION•fertilizers: replace essential nutrients removed by crops; include natural (e.g. manure) and chemical