28. Climate controls weathering and soil formation directly through what two thi

Question

28. Climate controls weathering and soil formation directly through what two things?

29. Climate controls weathering and soil formation indirectly through what?

30. Which type of bedrock tends to form thicker soils?

31. How long does it take for a soil to form?

32. When does soil contamination occur?

33. What is salinization?

34. What is the effect of soil erosion on soil fertility?

35. What are the major causes and contributors to the desertification process in arid, semi-arid, and subhumid areas?

36. What is the definition of fertile soils?

37. What are productive soils?

38. What do productive soils depend on?

39. Productive soils cover what percentage of the Earth’s land surface?

40. Productive soils produce what percentage of the world’s food?

41. Moderate desertification results in reductions of crop yields by what percentage?

42. Severe desertification results in reductions of crop yields by what percentage?

43. Very severe desertification results in reductions of crop yields by what percentage?

44. In the past few decades, about what percentage of the world’s farmland has been at least moderately desertified?

45. How many people are estimated to live in arid lands that are vulnerable to desertification?

46. What is a potentially dangerous side effect of desertification?

47. What may dust generated by winds blowing over desertified areas contain?

48. What is contour plowing?

49. What is crop rotation?

50. How do wind breaks aid in the conservation of soils?

Explanation / Answer

28.through the amount of precipitation and the temperature...... 29.through the kinds of vegetation that can cover the land...... 30.granitic... 31.The time needed to form a soil depends on the latitude: in environments characterized by a mild climate, it takes 200-400 years to form 1 cm of soil in wet tropical areas soil formation is faster, as it takes 200 years in order to accumulate enough substances to make a soil fertile it takes 3000 years................ 32.Soil contamination or soil pollution is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activity, agricultural chemicals, or improper disposal of waste............... 33.Soil salinity is the salt content in the soil...... 34.Soil erosion results in the loss of soil fertility and makes the land barren. There are more than 25 million hectares of barren lands in the world now. Soil erosion also leads to desertification. Desertification refers to increase of desert areas........ 35.Some of the human activities that can cause desertification are: cultivation of soils that are fragile, or exposed to erosion by wind or water; reduction in the fallow period of soils, and lack of organic or mineral fertilizers; overgrazing - often selectively - of shrubs, herbs and grasses; overexploitation of woody resources, in particular for fuelwood; uncontrolled use of fire for regenerating pasture, for hunting, for agricultural clearing, or for settling certain social conflicts; agricultural practices that destroy the soil structure, especially the use of unsuitable agricultural machinery; agricultural practices that result in the net export of soil nutrients, leading to loss of the soil fertility, such as cash-cropping; diversion of rivers to create irrigation schemes; or irrigation of soils prone to salinization, alkalinization or even waterlogging................ 36.(Fertile soil) Soil is the characteristics that supports life............. Fertile soil has the following properties: It is rich in nutrients necessary for basic plant nutrition, including nitrogen, phosphorus and potassium. It contains sufficient minerals (trace elements) for plant nutrition, including boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulfur, and zinc. It contains soil organic matter that improves soil structure and soil moisture retention. Soil pH is in the range 6.0 to 6.8. Good soil structure, creating well drained soil. A range of microorganisms that support plant growth. It often contains large amounts of topsoil. In lands used for agriculture and other human activities, fertile soil typically arises from the use of soil conservation practices.................

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