Unit 5: Soil and Land
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Objectives: Unit 8 - Soil and Agriculture 1. Differentiate between land and soil. 2. Describe soil which is good for crops and plants. 3. Describe "humus". 4. Diagram a soil profile. 5. Describe three soil horizons. 6. Describe how slope affects soil depth. 7. Recognize the term "erosion" and how it affects agricultural lands worldwide. 8. Recognize why deforestation is the leading cause of soil erosion and desertification. 9. Discuss how salinization of soil occurs and how it affects crop production. 10. Discuss soil conservation and describe five farming practices that can conserve soil. 11. List the advantages and disadvantages of monoculture farming. 12. Explain why chemical fertilizers are used. 13. Explain how chemical fertilizers effect the environment. 14. Explain why modern agriculture makes extensive use of pesticides. 15. Differentiate between persistent pesticides and nonpersistent pesticides. 16. Describe a case study of pesticide poisoning. 17. List four problems associated with pesticide use. 18. Define biological amplification. 19. Define organic farming. 20. Explain why integrated pest management depends upon a complete knowledge of the pest's life history. Unit 5: Soil and Land 1. Land is part of the world not covered by water. 2. Soil is a thin covering over the land that consist of a mixture of minerals, organic material, living organisms, air and water. 3. "Good" soils consist of 45% mineral, 25% air, 25% water, and 5% organic matter. 4. Humus is the organic material resulting from the decay of organic matter. It becomes mixed with top layers of broken rock particles and makes up an important ingredient in the soil. It provides nutrients for plants, increases the water holding capacity of the soil and its acidity so that organic nutrients become more available to the plant. 5. Soil Profile is a series of horizontal layers in the soil that differ in chemical composition, particle size and organic matter. Each of these layers is called a Horizon. 6. Horizon A, or topsoil, is the upper most layer and contains the most nutrients, living organisms and organic matter. It can vary from one meter to less then 1 centimeter thick. Nutrients from A "leach " into Horizon B. 7. Horizon B, or subsoil, is the layer below Horizon A. I t contains much less organics and living organisms but may contain an accumulation of nutrients leached from horizon A, making it important for plant growth. 8. Horizon C consists of weathered parent material and contains no organic material. It does contribute to the pH of the soil. It also helps determine the soils rate of absorption and retention of water 9. Slope often determines soil thick ness. Steep slopes often have thin soils whereas open plains have thick soils. 10. Erosion is the wearing away and transportation of soil by water and wind. 11. Soil erosion is a major problem world wide as agricultural land is being lost at alarming rates. Each year erosion carries away far more topsoil then is created. Annual loss of topsoil is over 25 billion tons! 12. Deforestation is the leading cause of soil erosion. 13. The loss of trees and too aggressive farming and ranching (overgrazing) is leading to desertification of many areas around the world including the US. 14. Salinization occurs when crops are irrigated with ground water containing salts and minerals. Over time evaporation leaves a crust of salt that kills plants and leads to greater erosion. 15. Soil conservation is critical in saving agricultural lands around the world. When topsoil is lost farmers then rely on more fertilizers to promote crops growth. This raises the cost of the foods we buy and leads to polluted waterways. 16. Soil conservation practices include: 1. No Till Farming - seeds are planted directly into the ground without turning over the topsoil and exposing it to the wind and rain. 2. Contour Farming - tilling at right angles to the slope of the land. It creates a series of small ridges, which act as dams to prevent water from running down slope and eroding the soil. 3. Strip Farming - is alternating strips of closely sewn crops with crops that are not so closelysewn. The closely sewn crops act as a buffer to prevent free flow of water through the crops that need more space to grow. 4. Terracing - are level areas constructed at right angles to steep slope to retain water. 5. Waterways - depressions in sloped land that collect water and carry it gentle away. 6. Windbreaks- planted rows of trees or other plants that prevent wind from blowing across the land. Windbreaks not only reduce wind speed and hence wind erosion, but they also help the soil to retain moisture. .