Soil An important resource

No Soil…No Life…

WHAT is it??? Mixture of weathered/eroded rock, nutrients, decaying organic matter, water, air and…

billions of organisms!

Different sizes and types of minerals determine soil texture: Clay: very fine and ultrafine particles Silt: fine particles

Sand: medium size particles Gravel: course to very course particles

If soil feels: Gritty: lots of sand Sticky: lots of clay Smooth: lots of silt (like flour) Loam: a mixture best suited for plant growth

Texture Lab… Using a soil triangle to determine texture Determining the texture of a soil sample

Texture determines Porosity: Porosity: the volume of pore spaces (air spaces) Porous soil: has many pores so can hold more air and water. Permeability: the rate at which water and air move from upper to lower layers.

Porosity and Permeability Labs… Determine the porosity of two soil samples. Determine the permeability of two soil samples.

Clay: low permeability Sand: high permeability

Soil Nutrients Basic Chemistry…

The Soil Profile Layers of soil (horizons) each have their own distinct textures and composition. Cross section of horizons = Soil Profile

Notes: Soil Horizons: Layers Soil Profile: Cross-Section

Different Ecosystems have different Profiles: Grasslands have a deep/rich layer of topsoil due to yearly decomposition of grasses. PERFECT for farming – nutrient rich. (“breadbasket” of United States)

Years of over-plowing + drought = Dust Bowl of the 1930’s However, poor agricultural practices have depleted this resource; plowed soil left to the elements of wind and rain is easily eroded. Years of over-plowing + drought = Dust Bowl of the 1930’s In some areas of the Great Plains, topsoil has decreased in thickness from 12 inches to less than 4 inches due to human activities!!

Tropical Rain Forest have thin, very acidic soil due to rapid cycling of nutrients and leaching of nutrients due to excessive rainfall HORRIBLE for farming Topsoil is only 1 to 2 inches thick

However, the world’s rainforests are being deforested or burned to provide room for more farmland (a response to the pressures of overpopulation…) These farms are usually abandoned within one to two years after what little nutrients from the soil are used up… and the cycle of burning continues…

Borneo: Deforestation