Chapter 10 3 From Bedrock to soil WHAT

Chapter 10. 3 From Bedrock to soil WHAT IS THE SOURCE OF SOIL? HOW DO THE PROPERTIES OF SOIL AFFECT PLANT GROWTH? HOW DO VARIOUS CLIMATES AFFECT SOIL?

SOURCE OF SOIL-a loose mixture of: 1) weathered rock & mineral fragments 2) air 3) water 4) decayed organic material called humus (dark colored, forms as plants & animals decay & creates space for air & water & is rich in N, S, Ph, K *w/out humus most plants can’t grow BEDROCK: -solid layer of rock beneath soil

PROPERTIES OF SOIL 1. ) Soil texture: rock particles classified by size -gravel (2 mm +) -sand (<2 mm) -silt (< 1/16 mm) -clay (< 1/256 mm) *TOO much of any particle will result in poor soil *texture affects ability of water to move thru soil Loam: a type of soil that is crumbly texture w/almost equal parts of clay, sand, & silt. B/c it holds water & air it is best for plants. *Draw a pie graph of composition of loam (25% each air &

2. ) Soil structure: arrangement of soil particles *particle clumps can affect soil moisture 3. ) Soil fertility: ability to hold/supply nutrients to plants 4. ) Soil p. H: (< 7 is acidic ) (> 7 is basic) influences how nutrients dissolve in soil

SOIL HORIZONS 5. ) Soil horizons: series of layers of soil -(A) topsoil--humus-rich -(B) subsoil-sediment below humus -(C) partially weathered rock -bedrock on bottom (Draw & label the soil horizons)

SOIL HORIZONS FORM IN 3 STEPS 1. 2. 3. Horizon (C) forms as bedrock weathers & rock breaks up soil into particles (A) develops from (C) when plant roots weather bedrock (B) develops as rain washes clay & minerals from (A) to (B)

RATE OF SOIL FORMATION � Rate depends on 1) climate *faster weathering in warm, humid climates 2) type of rock *some rocks weather faster (ex. softer rock limestone weathers fast)

HOW CLIMATES AFFECT SOIL Tropical- humidity /temp /rain /humus topsoil & nutrient-poor soil Desert- <25 cm rain/yr chem. weathering soil water leaves chemicals behind toxic levels of salt Temperate Forest/Grasslands- weathering rich, most-productive soils Arctic- rain/chem. weathering thin soil temps decomposition nutrients

CH. 10. 4 SOIL CONSERVATION � What are 3 important benefits that soil provides? � What are 4 methods of preventing soil damage and loss?

3 BENEFITS OF SOIL 1. ) provide minerals/nutrients for plants & animals get energy from plants 2. ) provides places for animals to live 3. ) stores water for plants & prevents runoff

4 METHODS OF PREVENTING SOIL EROSION 1. ) Contour plowing-planting rows across a slope like dams to channel rainwater 2. ) Terracing-changing a step hill into smaller, flat hills 3. ) No-till farming-leaving old stalks as cover to reduce water runoff 4. ) Cover crop-crops planted btwn harvestsreduce erosion/replace nutrients Crop rotation-plant different crops in same spot