Animal, Plant & Soil Science D2-3 Soil Erosion & Calculating Soil Loss

1. Animal, Plant & Soil ScienceD2-3Soil Erosion & Calculating Soil Loss

2. Interest Approach • Ask students who they would contact in case of a burglary. They will likely answer the police or detectives. It is the job of law enforcement officers to apprehend the thief. Soil erosion is a thief that steals the precious soil a producer needs to raise a profitable crop. In order for the producer to stop soil erosion, he or she must first understand how the soil has eroded.

3. Interest Approach • Ask students to identify visible signs of erosion. They may have been fishing and noticed muddy water or driving and had difficulty seeing because of a dust storm. They should be able to give many examples. Ask students where they think the soil came from. Ask if any problems are associated with this movement of soil. Ask what could be done to reduce this soil erosion. When discussion is complete, cover the learning objectives with the students as you begin the lesson.

4. Objectives • 1 Define soil erosion and describe the two classes of erosion. • 2 Identify the causes of soil erosion. • 3 Explain the ways in which different types of wind erosion occur and the associated problems. • 4 Distinguish between the different types of water erosion.

5. Objectives • 5 Estimate the amount of soil loss from water erosion using the Universal Soil Loss Equation. • 6 Identify urban management practices that reduce soil erosion. • 7 Identify agricultural management practices that minimize soil erosion. • 8 Identify the environmental and economic impacts of soil erosion.

6. Terms • _ accelerated erosion • _ contour • _ deposition • _ detachment • _ glacial erosion • _ gully erosion • _ land slippage • _ natural (geologic) erosion • _ rill erosion • _ runoff • _ saltation • _ sediment • _ sheet erosion • _ soil erosion • _ splash erosion • _ surface creep • _ suspension • _ transport • _ water erosion • _ wind erosion

7. Terms • conservation tillage • contour tillage • cover crops • diversion ditches • fallow • graded terraces • grassed strips • grassed waterway • level terraces • mulching • silt fences • strip-cropping • T value • terrace • Universal Soil Loss Equation (USLE) • wind breaks

8. What is soil erosion, and what are the two classes of erosion? • I. Soil erosion is the process by which soil is moved. When soil is eroded, it may become pollution in the water or air. Land that is eroded loses fertility. Vegetation and other coverings help prevent soil erosion. The two basic classes of erosion are natural (geologic) and accelerated.

9. What is soil erosion, and what are the two classes of erosion? • A. Natural (geologic) erosion occurs in nature without human influence. This type of erosion has changed the landscape of the earth. For example, it has rounded off mountains and filled in valleys. Deposits of eroded soil have formed new, highly fertile areas, such as the Mississippi Delta.

10. What is soil erosion, and what are the two classes of erosion? • B. Accelerated erosion removes topsoil at an excessive rate and usually results from human activity on the land. Such activity includes construction and plowing. Accelerated erosion causes large losses of soil from farm lands and loss of fertility.

11. What are the causes of soil erosion, and what are the steps in the erosion process? • II. Erosion is caused by many different weather factors, such as wind, water, and glacial movement. When land is cleared of protective covering, it is much more susceptible to erosion.

12. What are the causes of soil erosion, and what are the steps in the erosion process? • A. There are four basic types of erosion. • 1. Wind erosion is the loss of soil due to the movement of wind over the land. It usually occurs in dry climates where the soil is loose. Wind erosion occurs on newly plowed fields, construction sites cleared by large equipment, and land where vegetation has been grazed too short.

13. What are the causes of soil erosion, and what are the steps in the erosion process? • 2. Water erosion is the loss of soil due to water movement. It is the major cause of soil loss in North America. Water erosion occurs when excess rainfall creates runoff that carries soil away. Runoff occurs when rain falls faster than it can be absorbed into the soil. Runoff water carries soil particles as it makes its way into streams and rivers. This action causes water pollution and sediment. Sediment is the deposition of soil in the bottom of streams, riverbeds, ditches, etc.

14. What are the causes of soil erosion, and what are the steps in the erosion process? • 3. Glacial erosion occurs when the front edge of a glacier pushes soil, rocks, fallen trees, and other materials. Soil erosion from glaciers is of minor importance except in areas where glaciers exist. Glacial erosion was prevalent during the Ice Age, but glacial erosion has greatly diminished as the planet has warmed.

15. What are the causes of soil erosion, and what are the steps in the erosion process? • 4. Land slippage occurs on sloping land that is wet. Soil becomes saturated with water and slips down a hillside or mountain slope. Land slippage is also known as a mudslide or landslide. Banks along highways, streams, and ocean fronts are often subject to slides.

16. What are the causes of soil erosion, and what are the steps in the erosion process? • B. The process of soil erosion follows a simple, systematic progression each and every time. The erosion process involves three distinct steps. The first step is the loosening of soil particles. The second step is the moving of soil particles. The third step is the placement of soil particles. Terms that describe these three steps are detachment, transport, and deposition.

17. What are the causes of soil erosion, and what are the steps in the erosion process? • 1. Detachment is the step in which the impact of raindrops shatters surface aggregates and loosens soil particles. Some of the particles float into soil voids, sealing the soil surface so water cannot readily infiltrate the soil. The scouring action of running water also detaches some soil particles.

18. What are the causes of soil erosion, and what are the steps in the erosion process? • 2. Transport is the step during which the detached soil grains move in flowing water and are carried down slopes. • 3. Deposition is the step during which the soil is deposited as the water slows down.

19. What are the causes of soil erosion, and what are the steps in the erosion process? • C. Four factors determine how susceptible a soil is to soil erosion. • 1. Structure and texture—Soil structure influences infiltration of water. Good soil structure allows water to enter the soil, thus reducing water runoff. Soil texture has two effects on soil erosion. • a. Texture affects the rate at which water can enter the soil. Less water running on the surface of the soil means less soil can be transported. • b. Texture influences the ease of detachment of soil particles. Soil particles of different sizes vary in how easily they can be detached. Silt particles are the most easily detached.

20. What are the causes of soil erosion, and what are the steps in the erosion process? • 2. Slope—Two components determine slope. They are length and grade. • a. On a long slope, a greater surface area is collecting water, increasing flow volume. Running water can also pick up speed as it flows down a long slope. • b. Water runoff velocity will increase as slope grade increases. This causes an increase in the erosive energy of the runoff water.

21. What are the causes of soil erosion, and what are the steps in the erosion process? • 3. Surface roughness—A rough soil surface slows the downhill flow of water. Surface roughness depends a great deal on the tillage practice used on the land. In conventional tillage, the seedbed is left smooth with very few ridges. Chisel plowing leaves the seedbed rough. Tillage across slopes, or on the contour, also acts to slow water flow.

22. What are the causes of soil erosion, and what are the steps in the erosion process? • 4. Soil cover—Bare soil is fully exposed to the erosive forces of raindrop impact and the scouring of running water. Soil cover reduces the energy available to cause erosion to the soil. A mulch, a cover, or crop residue absorbs the energy of the falling raindrop. This reduces soil detachment.

23. What are the ways in which different types of wind erosion occur, and what are the associated problems? • III. Wind erosion causes air pollution, produces highway safety hazards, and fills drainage ditches. It occurs when persistent or frequent high-velocity winds and a dry, residue-free soil surface exist. Soil is moved by suspension, saltation, and surface creep.

24. What are the ways in which different types of wind erosion occur, and what are the associated problems? •  A. Suspension occurs when very small soil particles become airborne and enter the main airstream. They are carried in the same general direction as the wind. Because the soil particles are small, they remain in suspension.

25. What are the ways in which different types of wind erosion occur, and what are the associated problems? • B. Saltation occurs when the wind lifts medium-sized soil particles into the air. They are too heavy to remain in suspension, so they fall to the ground, loosening other soil particles. This process repeats itself.

26. What are the ways in which different types of wind erosion occur, and what are the associated problems? • C. Surface creep occurs as saltation takes place. The soil particles that are too heavy to be moved by saltation are moved along the surface by the impact of soil particles being displaced by saltation.

27. What are the different types of water erosion? • IV. Four kinds of water erosion can occur. They are splash erosion, sheet erosion, rill erosion, and gully erosion.

28. What are the different types of water erosion? • A. Splash erosion is the direct movement of soil by splashing. A soil grain can be thrown as far as 5 feet by a raindrop splash. Splashed particles fill the voids between other aggregates and seal the soil surface.

29. What are the different types of water erosion? • B. Sheet erosion results when thin layers, or sheets, of soil are worn away. Sheet erosion can occur on nearly level land or on sloping land. If muddy water is moving off a field, sheet erosion is occurring. This type of erosion may go unnoticed since no channels form. However, it may be just as problematic as erosion that is more apparent.

30. What are the different types of water erosion? • C. Rill erosion usually occurs on sloping land, where small channels are formed by running water. The signs of rill erosion can be masked by normal tillage practices.

31. What are the different types of water erosion? • D. Gully erosion occurs when rills continue to wash away and become more severe. It is more likely on steeper slopes and cannot be smoothed by normal tillage practices. Gullies are so large the equipment cannot cross them. Gullies usually begin to form near the bottoms of slopes or on steep slopes.

32. How is the amount of soil loss from water erosion estimated? • I. Erosion is a form of work, which requires energy.

33. How is the amount of soil loss from water erosion estimated? • A. Energy for water erosion comes from the energy of a falling raindrop or running water. • 1. The energy of a falling raindrop relates to its size and especially to its speed. A 2-inch-per-hour rainfall has the same energy as a 1-pound object falling 47 feet onto 1 square foot of soil. • 2. The erosive energy of running water depends on its volume and speed of flow.

34. How is the amount of soil loss from water erosion estimated? • B. Using various soil loss factors, the Universal Soil Loss Equation (USLE) has been developed to predict the average soil loss from sheet and rill erosion on a specific site. It was developed over several years by the Natural Resources Conservation Service. • 1. Producers can use the equation to estimate the rate of soil loss on their land and compare that rate with a soil’s T value. T value is soil loss tolerance value (i.e., the amount of soil loss that can be tolerated by that soil type). Each soil type has its own T value.

35. How is the amount of soil loss from water erosion estimated? • 2. The formula for USLE is A = R × K × LS × C × P. Each letter in the formula represents a specific soil loss factor. • a. Average annual soil loss (A)—“A” represents the average annual soil erosion loss in tons per acre. This factor should be less than the T value for the soil type.

36. How is the amount of soil loss from water erosion estimated? • b. Rainfall (R)—“R” represents the erosion potential inherent in the rainfall patterns of a particular area. The factors were developed from U.S. Weather Service data taken over a 22-year period.

37. How is the amount of soil loss from water erosion estimated? • c. Soil erodibility (K)—This factor reflects the fact that various soils erode at different rates because of different physical characteristics, such as texture, structure, organic matter content, and soil depth. Each different soil type has a specific K value.

38. How is the amount of soil loss from water erosion estimated? • d. Slope length and steepness (LS)—This factor represents the erosion potential for a particular combination of slope length and slope steepness. Slope length is not the distance from the highest point in the field to the lowest. It must be determined where the water will flow. Concentrate on natural water flow areas. Slope is determined by dividing the rise of the land by the run of the land.

39. How is the amount of soil loss from water erosion estimated? • e. Cropping factor (C)—This reflects the reduction in soil erosion when a specific cropping system is compared with continuous fallow (where the soil is tilled, but no crop is grown). The C factor of 1.0 is assigned to continuous fallow. C factors are determined by the climatic conditions of a region, crop rotation used, tillage methods used, and crop residue on the field.

40. How is the amount of soil loss from water erosion estimated? • f. Conservation practice (P)—This represents the reduction of soil erosion due to the implementation of various conservation practices, such as contour farming, strip cropping, and terracing.

41. What are some management practices that can be implemented in urban areas to reduce soil erosion? • II. In urban areas, the main concern is keeping the soil covered to control water runoff. This applies to construction sites, roads, parking lots, and recreational areas. Several practices are used to help conserve soil in urban areas.

42. What are some management practices that can be implemented in urban areas to reduce soil erosion? • A. Mulching is placing a layer of straw, burlap, or other material on the top of soil to protect it from wind and water. Mulch helps hold water and reduces the impact of water flow.

43. What are some management practices that can be implemented in urban areas to reduce soil erosion? • B. Silt fences are placed at the bottoms of slopes to hold the soil and still allow water to flow. This keeps sediment out of streams and lakes and prevents the loss of soil. Silt fences may be made out of bales of hay, plastic strips, or other materials.

44. What are some management practices that can be implemented in urban areas to reduce soil erosion? • C. Cover crops—Vegetation can be planted on excavated soil to hold it in place. Winter grass can be planted in the fall on new lawn areas to prevent erosion until the following spring, when a permanent sod can be established.

45. What are some management practices that can be implemented in urban areas to reduce soil erosion? • D. Building on the contour—Streets, buildings, and other structures can be located on the contour of the land to diminish water flow.

46. What are some management practices that can be implemented in urban areas to reduce soil erosion? • E. Stabilizing banks—Creeks and roadsides often have banks that will quickly erode. Riprap, fabrics, straw, vegetation, and concrete are some materials used to stabilize banks.

47. What are some management practices that can be implemented in urban areas to reduce soil erosion? • F. Planting trees and shrubs—Trees and shrubs can be planted in areas where erosion is possible. The roots hold the soil. The limbs and leaves on the tree slow the impact of rain, and fallen leaves cover the ground.

48. What are some management practices that can be implemented in urban areas to reduce soil erosion? • G. Storm water management—Curbs, ditches, and other structures may be installed to properly manage excess precipitation.

49. What management practices help to minimize soil erosion? • III. Preventing or stopping soil erosion is a major goal of every producer. Once a producer understands the causes of soil erosion and has estimated the amount of soil loss on his or her farm, a plan of action must be developed.

50. What management practices help to minimize soil erosion? • A. All methods of controlling water erosion are based on one of the following three actions: • 1. Reducing raindrop impact to lessen detachment • 2. Reducing or slowing water runoff to lessen detachment by scouring and reduce the amount of soil that can be transported • 3. Carrying excess water off a field safely