Unit 2 Topic 2 soil

What is soil and why do we care about it?  complex mixture:  weathered mineral materials from rocks  partially decomposed organic molecules  Ecosystem services  complex mixture:  weathered mineral materials from rocks  partially decomposed organic molecules  Ecosystem services

Soil formation  Many factors contribute to this LONG process  Parent material, Time, Topography, Climate, Organisms  Help determine soil type

Soil Texture  Ratio of soil particle size determines some soil properties

Determining soil type % Increasing Clay

Soil Properties: Porosity  Affects water infiltration, water holding capacity, aeration, workability

Soil Properties: Chemical  Cation exchange capacity (aka nutrient holding capacity)  Base saturation

SOIL Profile

Weak humus- mineral mixture Mosaic of closely packed pebbles, boulders Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Desert Soil (hot, dry climate) Grassland Soil (semiarid climate) Alkaline, dark, and rich in humus Clay, calcium compounds Soil Profiles in Different Biomes aridisols mollisols

Acidic light- colored humus Iron and aluminum compounds mixed with clay Forest litter leaf mold Humus-mineral mixture Light, grayish- brown, silt loam Dark brown firm clay Tropical Rain Forest Soil (humid, tropical climate) Deciduous Forest Soil (humid, mild climate) Soil Profiles in Different Biomes oxisols alfisols

Soil Properties: Biotic  surface = algae  top few cm of soil =  bacteria & fungi  roundworms, segmented worms, mites, insects  farther down: burrowing animals--gophers, moles, insect larvae, worms  even farther: some plant roots  surface = algae  top few cm of soil =  bacteria & fungi  roundworms, segmented worms, mites, insects  farther down: burrowing animals--gophers, moles, insect larvae, worms  even farther: some plant roots

Soil Community

Soil Community -- Mycorrhizae Redwood seedlings with (right) and without (left) mycorrhizae. Pine seedling showing how mycorrhizal roots from one tree spread to inoculate other tree roots.  mycorrhizal symbiosis - mutualism between plant roots & fungi

Soil degradation and loss

Soil conservation and improvement  Organic vs. inorganic fertilizers  Sustainable agriculture practices  Erosion control  Organic vs. inorganic fertilizers  Sustainable agriculture practices  Erosion control