3 What is Soil?Renewable resource that can be replaced over LONG periods of time. 100’s or 1,000’s of years for just 1 inch of topsoil to form.Mix of biotic and abiotic componentsTopsoil is made up of living organisms, rock particles, water, air, and dead or decomposing organisms.Quality depends upon composition
4 Soil as an ecosystemSoil consists of mineral and organic matter, air, and waterDead and living microorganismsDecaying materialBacteria, algaeHabitat for earthworms, insects, mammals, reptiles, and amphibiansSince soil is composed of interacting living and nonliving matter, it is considered an ecosystem
5 Soil Formation Factors EffectsClimateSoil forms faster in warm, wet climates.OrganismsEarthworms and other burrowing animals mix and aerate soil, add organic matter, and affect the composition of the soil.Land-formsHills and valleys affect exposure to sun, wind, and water.Parent MaterialChemical and physical characteristics of parent material influence what type of soil will be formed.TimeSoil formation takes decades, centuries, or millennia
7 Soil FormationWeathering: can be physical or chemical method of breaking down rocks and minerals.Deposition: dropping off of eroded material in a new locationDecomposition: breaking down of organic material
8 Soil ComponentsSoil is made up of 45% mineral matter, 5% organic matter, and 50% water and air.Parent material can be lava or volcanic ash, rock or sediment deposited by glaciers, sand dunes, sediment deposited by rivers, or bedrock.
9 Soil Horizons make Soil Profiles Soil is sorted into 6 distinctlayers called soil horizons.O = Top of the ground.A = Topsoil: where most plant nutrients are found.E = minerals leach from here down into the B layer.B = subsoilC= weathered parent material.R= Parent material
10 Soil CharacteristicsThe soil horizons that we just looked at are what makes up a “typical” sample of soil.U.S. soil scientists classify soils into 12 major groups based on how the soil is formed.
11 Soil CharacteristicsColor: dark soil = nutrient richness, light soil does not.Texture: texture is based upon particle size.-Clay particles are tiny-Silt particles are medium-Sand particles are largeStructure: Arrangement of soil particles. Too clumpy, soft, or hard can be bad!pH: Needs to be in the neutral range –too acidic or too alkaline (basic) can create poor growing conditions.