Unit 5: Soil Systems & Society

• All of the food we consume depends on soil • Soil is a habitat for many organisms • Soil stores both water and nutrients for ecosystems • Soil filters the water that passes through it and alters its chemistry

15-100 years (depending on climate)

soil sphere; a thin bridge between the biosphere and lithosphere

soil is produced by the weathering of rock, deposition of sediments, and decomposition of organic matter

200-1000 years

• mineral particles from underlying rock • organic remains that have come from plants and animals • water within the spaces between the grain • air within the spaces between the grain

Soil is typically a 50:50 mixture of solids and pore space

provides oxygen for organisms and plant roots

• allows dissolved mineral salts to be available to plants • rapid downward movement of water causes leaching • rapid upward movement causes salinization • large volumes of water in the soil can cause water logging leading to anoxic conditions and acidification

minerals dissolved in water move through soil

provides the skeleton of the soil

• gives the soil a dark color • as it breaks down, it returns mineral nutrients back to the soil • absorbs and holds on to a large amount of water

• decompose dead organic matter • larger soil animals help to mix and aerate soil

soil invertebrates, microorganisms, and large animals

insoluble and soluble

gravel, sand, silt, clay, and chalk

mineral salts, compounds of nitrogen, phosphorus, potassium, sulphur, magnesium, etc.

partially decomposed bodies of dead plants and animals

mainly nitrogen and oxygen

water either seeps down from precipitation or moving up from underground sources by capillary action

separate zones (horizontal layers) within soil

cross-section view of soil

surface litter

top soil