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Soil Formation, Erosion and Conservation. Soil Profile O Horizon – Organic O Horizon – Organic HUMUS: detritus, leaf litter and other organic material.

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Presentation on theme: "Soil Formation, Erosion and Conservation. Soil Profile O Horizon – Organic O Horizon – Organic HUMUS: detritus, leaf litter and other organic material."— Presentation transcript:

1 Soil Formation, Erosion and Conservation

2 Soil Profile O Horizon – Organic O Horizon – Organic HUMUS: detritus, leaf litter and other organic material lying on the surface. HUMUS: detritus, leaf litter and other organic material lying on the surface. dark because of the decomposition. dark because of the decomposition. decompose into nutrients that enrich the soils. decompose into nutrients that enrich the soils.

3 Soil Profile A Horizon – Topsoil A Horizon – Topsoil darker than the lower layers. darker than the lower layers. loose and crumbly with varying amounts or organic matter. loose and crumbly with varying amounts or organic matter. most productive layer of soil. most productive layer of soil.

4 Soil Profile B Horizon – Subsoil B Horizon – Subsoil Light colored, dense, and low in organic matter. Light colored, dense, and low in organic matter. materials leached and eluviated from the topsoil accumulate here. materials leached and eluviated from the topsoil accumulate here.

5 Soil Profile C Horizon – Weathered Parent Material C Horizon – Weathered Parent Material transition area between soil and parent material. transition area between soil and parent material. Partially disintegrated parent material. Partially disintegrated parent material. mineral particles. mineral particles. less organic/living matter. less organic/living matter.

6 Soil Advancement

7 Differentiate among the terms accumulation of humus, leaching, eluviation and capillary action. Humus is the accumulation of dead and decayed plant and animal matter that makes up the organic nature of soil. Occurs where there is substantial plant and animal growth. Humus is the accumulation of dead and decayed plant and animal matter that makes up the organic nature of soil. Occurs where there is substantial plant and animal growth. Leaching is the process where nutrients are washed down through the soil with the movement of liquids/water soluble minerals down the soil profile. Occurs where there is substantial rainfall. Leaching is the process where nutrients are washed down through the soil with the movement of liquids/water soluble minerals down the soil profile. Occurs where there is substantial rainfall.

8 Differentiate among the terms accumulation of humus, leaching, eluviation and capillary action. Eluviation is the lateral or downward movement of (solids / insoluble minerals) clay and other fine materials in suspension. Occurs where there is substantial rainfall. Eluviation is the lateral or downward movement of (solids / insoluble minerals) clay and other fine materials in suspension. Occurs where there is substantial rainfall. Capillary action results when water molecules are attracted to clay particles and drawn upward through the soil profile. Occurs where it is substantially dry. Capillary action results when water molecules are attracted to clay particles and drawn upward through the soil profile. Occurs where it is substantially dry.

9 Soil formation is slow and complex Parent material = the base geologic material of soil - Lava, volcanic ash, sedimentary rock, dunes - Bedrock = the continuous mass of solid rock comprising the Earths crust Weathering = the physical, chemical, or biological processes that break down rocks to form soil - Physical (mechanical) = wind and rain, no chemical changes in the parent material - Chemical = substances chemically interact with parent material - Biological = organisms break down parent material

10 Weathering produces soil FIGURE 7.2

11 Soil: The foundation for feeding a growing population Land devoted to agriculture covers 38% of Earths land surface Agriculture = practice of raising crops and livestock for human use and consumption Cropland = land used to raise plants for human use Rangeland or pasture = land used for grazing livestock Soil = a complex plant-supporting system consisting of disintegrated rock, organic matter, water, gases, nutrients, and microorganism

12 Population and consumption degrades soil Feeding the worlds rising human population requires changing our diet or increasing agricultural production We must find ways to improve the efficiency of food production; the key is how – biotech or intensive organic? There's a big debate on this... Mismanaged agriculture turns grasslands into deserts, removes forests, diminishes biodiversity, and pollutes soil, air, and water. Is it possible to create agricultural systems that support biodiversity and that enhance ecosystems? Have been examples in the past?

13 We lose 5-7 million hectares of productive cropland annually

14 Soil degradation has many causes Soil degradation results from deforestation, agriculture and overgrazing Over the past 50 years, soil degradation has reduced global grain production by 13% FIGURE

15 Tillage (Ploughing) According to Wikipedia, tillage has the following benefits: According to Wikipedia, tillage has the following benefits: It loosens and aerates the soil which in turn facilitates deeper penetration of roots. A drawback is the compaction of the lower layers of soil. It loosens and aerates the soil which in turn facilitates deeper penetration of roots. A drawback is the compaction of the lower layers of soil.aerates It helps in the growth of microorganisms present in the soil and thus, maintains the fertility of the soil, though fertility can decline as microorganisms' boom period after tilling is followed by a bust period. It is debatable whether worms benefit or suffer from tillage It helps in the growth of microorganisms present in the soil and thus, maintains the fertility of the soil, though fertility can decline as microorganisms' boom period after tilling is followed by a bust period. It is debatable whether worms benefit or suffer from tillage It helps in the mixing of organic matter (humus)and nutrients evenly throughout the soil. It helps in the mixing of organic matter (humus)and nutrients evenly throughout the soil. It is used for destroying weeds. It is used for destroying weeds. The downside is that it also compacts the soil and promotes erosion. The downside is that it also compacts the soil and promotes erosion.

16 Traditional vs. Industrial agriculture FIGURE

17 Traditional vs. Industrial agriculture Traditional agriculture = biologically powered agriculture, using human and animal muscle power - Subsistence agriculture = families produce only enough food for themselves - in between are cultures where farmers support a hierarchy of rulers and craftspeople Industrialized agriculture = using large-scale mechanization and fossil fuels to boost yields - Also uses pesticides, irrigation and fertilizers - Monocultures = uniform planting of a single crop 7-17

18 Soil degradation: problems and solutions Problems - Erosion - Desertification - Salinization - Chemical loading - Compaction - Overgrazing Solutions - Soil conservation - Restoring plant cover - Preventing salinization - Better fertilization practices - Better grazing practices 7-18

19 Soil erodes by two main methods Wind (aeolian) erosion Water erosion (splash, sheet, rill, gully) - Rill erosion moves the most topsoil, followed by sheet and splash erosion 7-19

20 Four kinds of water erosion Gully FIGURE 7.11 SplashSheetRill 7-20

21 Fertilizers boost yields but can be overapplied Fertilizer = substances that contain essential nutrients Inorganic fertilizers = mined or synthetically manufactured mineral supplements Organic fertilizers = the remains or wastes of organisms - manure, crop residues, fresh vegetation - Compost = produced when decomposers break down organic matter - Not perfect [can also contribute to eutrophication] 7-21

22 Environmental effects of over-fertilizing FIGURE

23 Grazing practices can contribute to soil degradation FIGURE

24 Effects of overgrazing can be striking Ungrazed plot Grazed plot 70% of the worlds rangeland is classified as degraded FIGURE

25 Irrigation: boosts productivity but can cause long-term soil problems Irrigation = Artificially providing water to support agriculture Waterlogging = over- irrigated soils which suffocates roots Salinization = the buildup of salts in surface soil layers. Can also be caused by excessive fertilization. Salinization inhibits production of 20% of all irrigated cropland, costing more than $11 billion/year FIGURE

26 Farmers can protect soil against degradation in various ways Crop rotation Contour farming Intercropping and agroforestry Terracing Shelterbelts Reduced tillage 7-26

27 Crop rotation Crop Rotation = alternating the crops grown field from one season or year to the next - Cover crops protect soil Contour Farming = plowing furrows sideways across a hillside, perpendicular to its slope, to prevent rills and gullies Contour farming FIGURE

28 Terracing = level platforms are cut into steep hillsides, forming a staircase to contain water Intercropping = planting different types of crops in alternating bands or other spatially mixed arrangements to increase ground cover Terracing Intercropping FIGURE

29 Shelterbelts or Windbreaks = rows of tall, perennial plants are planted along the edges of fields to slow the wind Shelterbelts Reduced tillage Reduced Tillage = furrows are cut in the soil, a seed is dropped in and the furrow is closed FIGURE Alley cropping = shelterbelts + intercropping

30 Plant cover reduces erosion Eroding banks along creeks and roadsides are stabilized by planting plants to anchor soil China has the worlds largest tree-planting program (monoculture) - Slows erosion - Forests are not ecologically functional FIGURE

31 Salinization is easier to prevent than to correct Choose crops appropriate for the area Irrigate with low-salt water Irrigate efficiently - Drip irrigation targets water directly to plants FIGURE

32 How would you farm? You are a farmer with land on both sides of a steep ridge. You want to plant one crop on the sunny and windy south slope and a crop that needs irrigation on the north slope. What types of farming techniques might maximize conservation of your soil? What other factors might you want to know about before you decide to commit to one or more methods? 7-32

33 Which process transports soluble inorganic matter downward through the soil? A) accumulation of humus B) capillary action C) eluviation D) leaching Which term refers to the process by which particles of insoluble inorganic matter are transported downward through the soil? (A) accumulation of humus (B) capillary action (C) eluviation (D) leaching

34 Which refers to the upward movement of soluble material through the soil by water? (A) capillary action (B) eluviation (C) erosion (D) leaching Which term refers to the process by which minerals and dissolved salts are transported upward through the soil? (A) accumulation of humus (B) capillary action (C) eluviation (D) leaching

35 Traditional subsistence agriculture uses all of the following, except: a)Animal power b)Irrigation c)Irrigation water d)Fossil fuels 7-35

36 Physical weathering is characterized by: a)The chemical interaction of water with parent material b)Organisms breaking down parent material c)Wind or rain breaking down parent material d)The dislodging or movement of soil by wind 7-36

37 a)Which horizon is the most valuable for agriculture? a)A horizon b)B horizon c)C horizon d)R horizon FIGURE

38 Erosion increases through all of the following, except: a)Excessive tilling b)Overgrazing c)Clearing forests d)All of the above increase erosion 7-38

39 Which sustainable farming method involves planting rows of trees along field edges to slow the wind? a)Terracing b)Crop rotation c)Shelterbelts d)Contour farming 7-39

40 7-40 Should developed nations fund reforestation projects in developing nations to combat erosion and deforestation? a)Absolutely, developing nations are facing a crisis b)No, not with money, but developed nations could give advice c)No, developed nations had to solve their problems, let the others solve their own problems d)I dont care, it doesnt really affect me

41 7-41 Should the Canadian government provide farmers with financial incentives to use technologies such as no-till farming and crop rotation? a)Absolutely, farmers may be more likely to switch to these techniques b)Yes, but farmers must put any money received into the farm c)No, its not the governments job to interfere with farming practices d)I dont care, it doesnt really affect me


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