Educators PPT file chapter 6
- 1. Chapter 6 Environmental Science, Soil Conservation, and Land Use Management
- 2. Sustainability is existence maintained over time. A sustainable system is one where current and developing practices can continue without exhausting the natural resource on which that existence depends. Resources are renewed or replenished rather than depleted. Sustainability Image Credit: USDA soils4teachers.org/KSKL
- 3. Best management practices are activities that landowners and managers can use to help conserve soil and water resources. BMPs are proven to reduce soil erosion and pollution and improve water and environmental quality. Management practices can address the source of the problem, the outcome, or both. Best Management Practices Image Credit: USDA-NRCS soils4teachers.org/KSKL Fig. 6-18. Contour strip cropping.
- 4. NATURAL PROCESSES AFFECTING SOIL DEGRADATION Natural processes that affect soil in both natural and agricultural ecosystems include erosion, acidification, desertification, and salinization. soils4teachers.org/KSKL
- 5. Erosion occurs when soil particles are detached, transported, and deposited. Erosion Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 soils4teachers.org/KSKL Fig. 6-1.
- 6. Because of the way they are managed, agricultural ecosystems may experience accelerated wind and water erosion, so soil erodes faster than it forms. If more soil erodes than forms, the amount of available soil decreases over time, threatening long-term sustainability. soils4teachers.org/KSKL Erosion Image Credit: USDA
- 7. Water erosion is caused by two detaching forces: raindrop impact and flowing water. Three types of water erosion can occur: sheet, rill, and gully. soils4teachers.org/KSKL Erosion by Water Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-9. Rill erosion Fig. 6-10. Gully erosion
- 8. Water control methods attempt to decrease the kinetic energy of the water by limiting soil detachment, decreasing transportation, and encouraging deposition. The most effective way to control erosion is to keep the soil surface covered, either with growing plants or residues from past crops. soils4teachers.org/KSKL Water Erosion Control Methods Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-11. Irrigated cotton planted after wheat.
- 9. Wind erosion damages millions of hectares of land in the United States annually, especially in the Great Plains. Less precipitation in the West means there is less vegetation. The landscapes are generally flatter, with few hills and trees to slow the wind at the soil surface. The soils also tend to have less organic matter to hold aggregates together, making the soils more susceptible to wind erosion. soils4teachers.org/KSKL Erosion by Wind Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-17(b). Conventional plowing.
- 10. Sand particles are heavier and are moved a few centimeters to a few kilometers, but silt particles can be carried for a few hundred kilometers and clays for thousands. soils4teachers.org/KSKL Erosion by Wind Image Credit: USDA
- 11. The main principles for controlling wind erosion are similar to those for controlling water erosion: protect the surface and reduce energy. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-20. Conventional tillage left no residues on the soil surface to protect it from wind erosion. Wind Erosion Control Methods
- 12. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-24. Areas of the world most vulnerable to human-induced desertification. Desertification Desertification is the extreme degradation of productive land in arid and semiarid regions. It is a natural process associated with global climate changes. Desertification can also be brought on by improper management practices.
- 13. Grasslands adjacent to deserts can have low precipitation amounts, and such grasslands are often used as rangeland for grazing livestock. This can lead to overgrazing, resulting in the death of the perennial grasses. The lack of soil cover increases erosion of soil. Without sufficient precipitation, the perennial grasses do not recover, and characteristic desert vegetation encroaches. soils4teachers.org/KSKL Desertification Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-25. Degraded rangeland with crusted soils and sparse annual vegetation.
- 14. Adequate vegetative cover should be maintained to prevent accelerated erosion. Range management BMPs include controlling the livestock stocking rate and grazing intensity, keeping livestock out of sensitive areas, and providing livestock with alternative locations for water and shade. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-26. Degraded rangeland improvement project. Desertification Control Methods
- 15. Acidification occurs when base cations leach from the soil during times of excess precipitation, leaving acidic cations behind. The pH decreases as the soil becomes more acid. Producers managing acid farmlands regularly apply lime (calcium carbonate or similar minerals) to mitigate the acid in the soil. soils4teachers.org/KSKL Acidification Image Credit: USDA
- 16. Salinization, or the buildup of salts, occurs when water evaporates from soil and leaves behind previously dissolved salts. These salts begin to accumulate in the soil because there is little rainfall to wash out, or leach, the salts. Improperly managed irrigation, especially in arid and semiarid areas, can result in salinization and rising groundwater tables. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-28. Salt accumulated on soil surface and base of plants. Salinization
- 17. HUMAN ACTIVITIES AFFECTING SOIL DEGRADATION Human activities can accelerate erosion, acidification, desertification, and salinization beyond natural rates on a global scale. soils4teachers.org/KSKL
- 18. The effects of tree loss on soil are significant. Trees and shrubs can shield the ground from the force of raindrops, so the removal of this vegetation can expose soil to rain splash. This loosens soil and dislodges soil particles, eroding soil and create a more impermeable bare surface, which increases runoff. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-29(a). Deforested landscape. Deforestation
- 19. Every year, urbanization removes more land from food production, putting more pressure on the remaining farmland, often in areas with more marginal soil productivity, to produce more crops and livestock. soils4teachers.org/KSKL Urban and Rural Issues Image Credit: USDA
- 20. Urbanization also contributes to runoff and erosion potential because of the preponderance of houses, roads, parking lots, and other impermeable surfaces. When native landscapes are converted to urban uses, runoff increases several fold. soils4teachers.org/KSKL Urban and Rural Issues Image Credit: USDA
- 21. Soil loss due to construction activity is a small fraction of the whole, but is still a common occurrence. Construction sites are often stripped of all vegetation, leaving bare, compacted soils with little infiltration, increasing runoff and erosion potential.Regulations and construction codes now require mitigation and erosion control practices to be used. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-33.A silt fence as the only erosion method may fail. Urban and Rural Issues
- 22. One of the greatest challenges associated with human, livestock, and food production wastes and byproducts is the quantity of nutrients they contain. These wastes contain nutrients that may enter surface waters through runoff and erosion or through leaching. When nutrients get into surface waters, nutrient overload (eutrophication) results. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Fig. 6-36. Eutrophication in a small livestock pond. Land Application of Manures and Treated Wastes
- 23. Most meat animals today are fed in confined animal feeding operations (CAFOs). Feed (along with the nutrients in the feed) are imported from elsewhere. Concentrating so many animals in one place greatly increases the efficiency of production. soils4teachers.org/KSKL Land Application of Manures and Treated Wastes Image Credit: USDA
- 24. In CAFOs, the amount of manure and effluent (liquid waste from runoff or washing production floors) produced per area increases several fold. These operations are considered point sources of pollution and are regulated under federal law. soils4teachers.org/KSKL Land Application of Manures and Treated Wastes Image Credit: USDA
- 25. The wastes contain plant nutrients and are typically disposed of through land application. Increased nutrient loads in leachates to groundwater and runoff to surface waters can result when the wastes are applied improperly. When wastes are applied to the same land over many years, nutrients may increase to levels that limit plant growth. soils4teachers.org/KSKL Land Application of Manures and Treated Wastes Image Credit: USDA
- 26. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Mineland Reclamation Fig. 6-37. Reclamation of the Standard Mine Superfund site in Colorado. The reclamation activities involved efforts to avoid surface and groundwater contamination, revegetation, land use controls to minimize human exposure to contaminants and monitoring.
- 27. Historical methods of agricultural production include inverting the soil to bury crop residues and break up soil aggregates, leaving a bare, uniform surface in which to plant seeds. Bare soil aggregates are exposed to energy in raindrops and wind, accelerating erosion. This results in loss of fertile ground, necessitating increased use of fertilizer to sustain crop yield, which in turn increases cost of food production. soils4teachers.org/KSKL Image Credit: Know Soil Know Life, D. Lindbo, D. Kozlowski, and C. Robinson - Editors, © 2012 Agriculture and Soil Degradation Fig. 6-4. Conventional inversion tillage.
- 28. To control erosion, farmers employ a variety of BMPs: reduced tillage, conservation tillage, residue management, contour plowing, strip cropping, cover crops, crop rotations, diversions, terraces, grassed waterways water control structures, and buffer strips. soils4teachers.org/KSKL Agricultural BMPs to Control Erosion Image Credit: USDA
- 29. • Challenges to soil that reduce productivity include: Erosion, Desertification, Acidification, Salinization. • Human activities that are degrading the soil are: Deforestation, Urbanization, Disposal of wastes, Mining reclamation. • Best management practices prevent loss of arable soil. soils4teachers.org/KSKL Key Points