The Ground Beneath Our Feet

What Makes Up Healthy Soil? Mineral fragments, humus, air, water, and living things – Plant roots, Insects, Worms Humus – Organic Material – Can support the growth of vegetation Parent rock – source of mineral fragments in the soil

Soil Formation Soil starts out as rock The surface rocks break down into smaller pieces and is mixed with organic matter. Over time this creates a thin layer of soil. Decaying matter makes the soil thick and rich

Soil Texture The soil’s quality is based on the proportions of soil particles. Soil texture affects – Consistency: soil’s ability to be broken up. – Infiltration: ability of water to move through soil.

Sizes of Weathered Rock That Make Up Soil

Different Types of Soil Every soil type is a mixture of sand, silt, clay. The right mixture is called loam. Loam = 40% sand 40 % silt 20 % clay

Review Questions Which particle is the biggest one that goes in soil? – A. Clay – B. Silt – C. Quartz – D. Sand

Review Questions Which particle is the biggest one that goes in soil? – A. Clay – B. Silt – C. Quartz – D. Sand

Review Questions How does soil texture affect soil consistency? – A. It has nothing to do with it. – B. Allows water to pass through it easier. – C. The soil’s ability to allow farmers to manipulate it. – D. Allows for plants to grow easily.

Review Questions How does soil texture affect soil consistency? – A. It has nothing to do with it. – B. Allows water to pass through it easier. – C. The soil’s ability to allow farmers to manipulate it. – D. Allows for plants to grow easily.

Review Questions What is loam? – A. Loam is the perfect combination of sand, silt, and clay. – B. Loam is the combination of 30% sand, 40% mud, and 30% clay. – C. Loam is located on in horizon B. – D. Loam is the particle quality of any soil.

Review Questions What is loam? – A. Loam is the perfect combination of sand, silt, and clay. – B. Loam is the combination of 30% sand, 40% mud, and 30% clay. – C. Loam is located on in horizon B. – D. Loam is the particle quality of any soil.

What is a Soil horizon? O Litter from dead plants and animals A – Topsoil E – Zone of intense leaching. B – Collects dissolved substances from upper horizons C – Weathered bedrock R – Bedrock

Soil Profile The vertical display of soil horizons. Each soil profile is different from another. classification_genesis/soil_formation/soil_t ransform.swf classification_genesis/soil_formation/soil_t ransform.swf

Soil pH Have you ever seen this? Why does this happen? What creates CO 2?

Soil pH Carbonic acid and Humic acid changed the pH of the soil to be more acidic. Carbonic acid – come from Carbon Dioxide. Humic acid – various organic acids produced from humus.

Tropical Climate Very rich humus. Very little topsoil – Leeching of nutrients from topsoil to horizon B and C. – Plants demand a lot of nutrients.

Desert Climate Deserts get less than 25 cm rain a year. Slow rate of weathering = Slow rate of soil formation. Due to no water, salt gathers in the ground. Salt is toxic to plants!

Temperate Climate Lots of weathering = lots of fertile soil Most productive soil in the world. Most of Continental USA has a temperate climate.

Arctic Climate Very cold desert = Slow rate of soil formation. Low amount of humus due to cold temperatures. Cold temperatures slow down decomposition.

Review Questions What acids can change the pH of the soil? – A. Humic acid and Hydrochloric acid – B. Carbonic acid and Humic acid – C. Carbonic acid and water – D. Water and citric acid

Review Questions What acids can change the pH of the soil? – A. Humic acid and Hydrochloric acid – B. Carbonic acid and Humic acid – C. Carbonic acid and water – D. Water and citric acid

Review Questions Which climate is called the “breadbasket of the world”? – A. Tropical – B. Desert – C. Temperate – D. Arctic

Review Questions Which climate is called the “breadbasket of the world”? – A. Tropical – B. Desert – C. Temperate – D. Arctic

Review Questions Which climate has very little, but fertile topsoil? – A. Tropical – B. Desert – C. Temperate – D. Arctic

Review Questions Which climate has very little, but fertile topsoil? – A. Tropical – B. Desert – C. Temperate – D. Arctic