1. Soil

2. Characteristics Soil is a thin layer on top of earth’s land surface. Soil is a natural resource and deeply affects every other part of the ecosystem. Soil holds nutrient and water for plants and animals; water is filtered and cleansed as it flow through soils; and soils affect the chemistry of water and the amount of water that returns to the atmosphere to form rain

3. Soil is composed of 3 main ingredients Minerals of different size Organic materials from the remains of dead plants and animals Open spaces (pores) that can be filled with air or water

4. Good soil composition contains:

5. Factors in soil development: Parent Material: The rock or minerals from which the soil derives. The nature of the parent rock can either be native to the area or transported to the area by wind, water, or glacier. Has a direct effect on the ultimate soil profile. Climate: This is measured by precipitation and temperature. It results in partial weathering of parent material, which forms the substrate for soil. Living Organisms: These include nitrogen-fixing bacteria, Rhizobium, fungi, insects, worms, snails etc. that help decompose litter and recycle nutrients. Topography: This refers to the physical characteristics of the location when the soil is formed. Topographic factors that affect a soil’s profile include drainage, slope direction, elevation, and wind exposure.

6. Formation of mature soil With sufficient time, a mature soil profile reaches a state of equilibrium. Feedback mechanisms involving both abiotic and biotic factors work to preserve the mature soil profile. The relative abundance of sand, silt and clay are called the soil texture. The category with the smallest particles is clay (<0.002 mm). The next largest is silt (0.002-0.05mm in diameter). Sand is the coarsest soil with particles 0.05-2.0 mm in diameter. Sand particles are too large to sick together, and sandy soils have larger pores; which means they can hold more water. Clays easily adhere to each other and there is little room between particles for water; clay soils are extremely compact.

7. Soil Texture

8. Effect of pH on soil Another very important characteristic of soil types is soil acidity or alkalinity. pH ranges from 0-14 and is a measurement of the concentration of hydrogen ions. Most soils fall into the pH range of 4- 8, meaning that soils range from being neutral to slightly acidic. Soil pH is important because it affects the solubility of nutrients; and thus in turn determines the extent to which these nutrients are available for absorption by plant roots. If the soil is too basic or too acidic, certain soil nutrients will not be able to be used by regional plants.

9. WHERE DOES SOIL COME FROM? Soil is a combination of organic materials and rock that has been broken down by chemical and biological weathering. The types of minerals found in the soil in a particular region will depend on the type of base rock in that region. All weathering is placed into three broad categories: Physical weathering (mechanical weathering) – Any process that breaks rock down into smaller pieces without changing the chemistry of the rock. The forces responsible for it include wind and water. Chemical Weathering – Occurs as a result of chemical reactions between water and other atmospheric gases, and the bedrock in a region. Biological Weathering – Weathering that takes place as a result of the activities of living organisms.

10. SOIL LAYERS/HORIZION Horizon Name Description O Surface Litter Upper most layer. Leaves, waste, live organisms and partial decomposed organic debris including decomposing organisms. The dark, crumbly material resulting from decomposition of organic material is called humus. Maybe very thick in deciduous forests and very thin in tundra or desert. A Topsoil Made up of weathered rock and some organic matter that has traveled down from the O layer. Some living organisms and inorganic materials. Topsoil is typically very thick in grasslands. Important role in plant growth. E Zone of Leaching Dissolved and suspended materials move downward. B Subsoil Tends to be yellowish in color due to the accumulation of iron, aluminum, humic compounds, and clay leached down from the A and E horizons. It can be rich in nutrients in areas where rainwater leeched (washed) nutrients from the topsoil. C Weathered Parent Material Partially broken down organic minerals. Large pieces that have not undergone much weathering. R Bedrock Bedrock

12. SOIL COMPONENTS COMPONENT DESCRIPTION Clay Very fine particles. Compacts easily. Forms large, dense clumps when wet. Low permeability to water; therefore, upper layers become water logged. Gravel Coarse particles. Consists of rock fragments. Loam About equal mixtures of clay, sand, silt and humus. Rich in nutrients. Holds water but does not become waterlogged. Sand Sedimentary material coarser than silt. Water flows through too quickly for most crops. Good for crops and plants requiring low amounts of water. Silt Sedimentary material consisting of very fine particles between the size of sand and clay. Easily transported by water.

13. Water Retention and Availability Nutrient Storage Capability Air Space Primary Production CLAY SAND LOAM

14. Water Retention and Availability Nutrient Storage Capability Air Space Primary Production CLAY Sticky and easily waterloggedHighLowMedium/Low SAND Fast draining soil that dries out easily LowHighLow LOAM Medium to HighMedium

15. Primary productivity of soil depends on: mineral content drainage water-holding capacity airspaces biota potential to hold organic materials

16. Soil Degradation

17. Soil degradation concerns the decline of soil quality or quantity. Soil degradation results from changes to biological, geological or chemical components of a soil. Human activities such as overgrazing, deforestation, unsustainable agriculture and irrigation cause processes of degradation. These include soil erosion (loss of soil to wind and water), toxification and salinization (increase in salt concentration).

18. Soil erosion is the movement of weathered rock or soil components from one place to another. Erosion is caused by flowing water, wind and human activity (cultivating inappropriate land, burning of native vegetation, deforestation, and construction). Soil erosion destroys the soil profile, decreases water-holding capacity of the soil, and increases soil compaction. Because water cannot percolate through the soil, it runs off the land, taking more soil with it (positive feedback loop). Because the soil cannot hold water crops grown in areas of soil erosion frequently suffer from water shortages. In areas of low precipitation, erosion leads to significant droughts. Poor agriculture techniques that lead to soil erosion include monoculture, row cropping, overgrazing, improper plowing the soil and removing crop wastes instead of plowing the organic matter back into the soil. Erosion

19. Three types of soil erosion 1. Sheet erosion – soil moves off as a horizontal layer. 2. Rill erosion – fast-flowing water cuts small channels in the soil. 3. Gully erosion – extreme case of rill erosion, where over time, channels increase in size and depth.

20. Soil Conservation Measures Soil conditioners (for example, use of lime and organic materials) Wind reduction techniques (wind breaks, shelter belts, strip cultivation) Cultivation techniques (terracing, contour plowing) Efforts to stop plowing of marginal lands.

22. What does sustainability mean?

23. Sustainability Meeting the needs of the present without compromising the ability of future generations to meet their needs.

24. Assignment Read the article on “French Fries” Fill in the table on the back side As a group, pick ONE item that you are measuring around the school and fill in a chart as a group. This can only be one quantifiable item. Be prepared to present to the class. Read the other two articles and fill in a separate chart for both.