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Soil & Ag Unit Review. AP Objectives Soil and Soil Dynamics (Rock cycle; formation; composition; physical and chemical properties; main soil types; erosion.

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Presentation on theme: "Soil & Ag Unit Review. AP Objectives Soil and Soil Dynamics (Rock cycle; formation; composition; physical and chemical properties; main soil types; erosion."— Presentation transcript:

1 Soil & Ag Unit Review

2 AP Objectives Soil and Soil Dynamics (Rock cycle; formation; composition; physical and chemical properties; main soil types; erosion and other soil problems; soil conservation) Agriculture 1.Feeding a growing population (Human nutritional requirements; types of agriculture; Green Revolution; genetic engineering and crop production; deforestation; irrigation; sustainable agriculture) 2.Controlling pests (Types of pesticides; costs and benefits of pesticide use; integrated pest management; relevant laws) Rangelands (Overgrazing; deforestation; desertification; rangeland management; federal rangelands)


4 Soil Importance Microorganisms depend on it for shelter, food & water Plant anchor, nutrient and water supply

5 What’s in the “soil”? Mineral particles (45% of “typical” soil) Organic matter (about 5%) Water (about 25%) Air (about 25%)

6 Factors in Soil Formation 1)parent material (bedrock) 2)Climate (precipitation & temperature) 3)vegetation (organic matter or peat) 4)topography 5)time

7 How parent material becomes soil Weathering: bedrock is broken down Physical = erosion Chemical = CO 2 produced from cellular respiration diffuses into soil, reacts with H 2 O & forms carbonic acid (H 2 CO 3 ) which breaks down rocks

8 Vocabulary Infiltration: the downward movement of water through soil. Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers.

9 Fig. 3-23, p. 68 Fern Mature soil Honey fungus Root system Oak tree Bacteria Fungus Actinomycetes Nematode Pseudoscorpion Mite Regolith Young soil Immature soil Bedrock Rock fragments Moss and lichen Organic debris builds up Grasses and small shrubs Mole Dog violet Wood sorrel Earthworm Millipede Springtail Red Earth Mite

10 Organic Layer (O-horizon) uppermost layer rich in organic material (peat) Plant litter accumulates & gradually decays Note: In desert soils the O-horizon is completely absent

11 Topsoil (A-horizon) rich in organic matter (peat) and humus (won’t break down any further) granular texture nutrient-poor due to the loss of many nutrient minerals to deeper layers by leaching

12 Subsoil (B-horizon) Accumulation of minerals rich in iron and aluminum compounds Contains clay (small particles that moved down with water)

13 Parent Material (C-horizon) weathered pieces of rock borders the unweathered solid parent material Most roots do not go down this deep and it is often saturated with groundwater.

14 Physical and Chemical Properties Texture/Structure Permeability Shrink/swell pH Nutrient content (N, P, K)

15 Texture Percentage of different sized particles of sand, silt and clay

16 Texture > 2mm in diameter = gravel/stones (not actually considered soil because it doesn’t have direct value to plants) 0.05 to 2mm = sand (the largest soil particles) can be seen easily with the eye. 0.002 to 0.05mm = silt – about the size of flour and barely visible with the eye. < 0.002mm = clay – only seen under an electronic microscope

17 Permeability The rate at which water and air moves from upper to lower soil layers.

18 Shrink-Swell Potential Some soils, like clays, swell when H 2 O gets in them, then they dry and crack. This is bad for house foundations, etc.

19 pH The pH of most soils ranges from 4.0 to 8.0 plant and animal life prefer a range Can affect availability of nutrients

20 Erosion is the movement of soil components, especially surface litter and topsoil, from one place to another.

21 earth-caves-limestone-erosion.html earth-caves-limestone-erosion.html Erosion

22 SOIL EROSION AND DEGRADATION Soil erosion increases through activities such as farming, logging, construction, overgrazing, and off-road vehicles. Figure 13-9

23 Global Outlook Soil is eroding faster than it is forming on more than one-third of the world’s cropland. Figure 13-10

24 Soil erodes faster than it forms on most U.S. cropland, but since 1985, has been cut by about 40%. –Food Security Act of 1985: farmers receive a subsidy for taking highly erodible land used for wheat and feed grain and instead using it for haying and grazing. –Food, Conservation & Energy Act of 2008: funding for local farmers market programs & credit for growing biofuels

25 Trouble in the Soil Desertification Salinization Waterlogging

26 Desertification: dry lands getting drier About one-third of the world’s land has lost some of its productivity because of drought and human activities that reduce or degrade topsoil. Figure 13-12

27 Salinization and Waterlogging Repeated irrigation can reduce crop yields by causing salt buildup in the soil and waterlogging of crop plants. Figure 13-13

28 Fig. 13-15, p. 281 Cleanup Prevention Soil Salinization Solutions Reduce irrigation Switch to salt- tolerant crops (such as barley, cotton, sugarbeet) Flush soil (expensive and wastes water) Stop growing crops for 2–5 years Install underground drainage systems (expensive)

29 Help is on the Way! t_s_wrong_with_our_food_system.html t_s_wrong_with_our_food_system.html Shelterbelts Minimum or No Tillage Contour farming Strip cropping Cover crops

30 Erosion Control Shelterbelts – Long rows of trees partially block the wind, retain soil moisture

31 Minimum Tillage – disturb the soil as little as possible while planting crops. Special tillers break up and loosen the subsurface soil without turning over the topsoil

32 Contour Farming – sloping growing crops; terraces stop soil from running down a steep slope; plowing and planting crops in rows across, rather than up and down, the sloped contour of the land.

33 Strip Cropping – a row crop such as corn alternates in strips with another crop that completely covers the soil, reducing erosion. It catches and reduces water runoff and helps prevent the spread of pests and plant diseases.

34 Cover crops: planted between crop rotations; left in fields (no tillage); increase organic material in O horizon; decrease erosion and weeds; alleviate soil compaction; nutrient scavenging Examples ~ Lentils (beans) Family Brassicaceae: radishes spinach Oats

35 World Population as of Jan. 31, 2011: 6,896,894,506

36 THE GREEN REVOLUTION Since 1950, high-input agriculture has produced more crops per unit of land to feed a growing population. Figure 13-17

37 Fig. 13-18, p. 285 Biodiversity LossSoil Water Air PollutionHuman Health Loss and degradation of grasslands, forests, and wetlands Erosion Water waste Greenhouse gas emissions from fossil fuel use Nitrates in drinking water Loss of fertility Aquifer depletion Pesticide residues in drinking water, food, and air Salinization Increased runoff and flooding from cleared land Other air pollutants from fossil fuel use Fish kills from pesticide runoff Waterlogging Sediment pollution from erosion Greenhouse gas emissions of nitrous oxide from use of inorganic fertilizers Contamination of drinking and swimming water with disease organisms from livestock wastes Desertification Killing wild predators to protect livestock Fish kills from pesticide runoff Surface and groundwater pollution from pesticides and fertilizers Belching of the greenhouse gas methane by cattle Loss of genetic diversity of wild crop strains replaced by monoculture strains Bacterial contamination of meat Overfertilization of lakes and rivers from runoff of fertilizers, livestock wastes, and food processing wastes Pollution from pesticide sprays

38 Gene Revolution Genetic engineering involves splicing a gene from one species and transplanting the DNA into another species. Figure 13-19

39 Where’s the Beef?

40 PRODUCING MORE MEAT half of the world’s meat is produced by livestock grazing on grass half is produced in feedlots where densely packed livestock are fed grain or fish meal

41 Fig. 13-21, p. 289 Trade-Offs Animal Feedlots AdvantagesDisadvantages Increased meat production Need large inputs of grain, fish meal, water, and fossil fuels Higher profits Concentrate animal wastes that can pollute water Less land use Reduced overgrazing Reduced soil erosion Antibiotics can increase genetic resistance to microbes in humans Help protect biodiversity

42 Managing and Sustaining Grasslands Overgrazing: exceed carrying capacity; increased erosion; compacted soil and decreased permeability; invasion of inedible plants Solution: control # and distribution of livestock through rotational grazing; restore riparian zones

43 What’s more sustainable? Figure 13-22


45 Aquaculture: Aquatic Feedlots World’s fastest growing type of food production Cultivating & harvesting fish in a controlled environment Genetic monoculture Often infected with parasites

46 Fig. 13-24, p. 292 Trade-Offs Aquaculture AdvantagesDisadvantages High efficiencyNeeds large inputs of land, feed, and water High yield in small volume of water Large waste output Destroys mangrove forests and estuaries Can reduce overharvesting of conventional fisheries Uses grain to feed some species Low fuel use Dense populations vulnerable to disease Tanks too contaminated to use after about 5 years High profits Profits not tied to price of oil

47 Pesticides 2.Controlling pests (Types of pesticides; costs and benefits of pesticide use; integrated pest management; relevant laws)

48 Composed of compounds that retain their toxicity for long periods of time. Bioaccumulation/ Biomagnification Ex: DDT Hard/Persistent Pesticides

49 Reduced-risk pesticides. They are short-term and don’t harm the environment or man. Ex: soaps, oils, plant extracts, baking soda, dish liquid Soft Pesticides

50 Benefits of Pesticide Usage: Disease control Increase Food production

51 Disease Control Prevent insect-transmitted diseases: malaria (mosquito) bubonic plague (rat fleas) typhus (body lice & fleas) sleeping sickness (tsetse fly)

52 Increase Food Production Currently, 55% of the world’s food supply is lost to pests Losses would be worse and food prices would rise w/o pesticides

53 Problems Associated with Pesticide Usage Non-target Impact/Persistence Superbugs New Pests “Pesticide Treadmill” Synergism

54 Impact on Non-target Organisms & Persistence Not all chemicals reach their intended target The rest end up in the environment… stay in the environment… effecting everything in the environment Long term effect?

55 Superbugs/weeds Starts with one or two with a genetic resistance to pesticide/herbicide Insects/weeds breed rapidly; within 5-10 years new population of superbugs/weeds Option 1: Create new chemicals Option 2: ???

56 Formation of New Pests The natural predators, parasites or competitors of a pest may be killed by a pesticide Minor pest becomes MAJOR pest

57 Pesticide Treadmill Must increase use of and types of pesticides to keep up!

58 Synergy 2 + processes interact so that the combined effect is greater than the sum of their separate effects EPA & toxicologists test for potential synergistic interactions

59 US Regulation Federal Food, Drug, and Cosmetic Act; sets pesticide tolerance levels Federal Insecticide, Fungicide & Rodenticide Act; states what must be on a pesticide label & requires registration of all pesticides. Remember, rules don’t always apply to imported foods.

60 LD-50 (Median Lethal Dose) The LD-50 is the amount of pesticide it will take, in one dose, to kill ½ of all the target organisms.

61 A limited use of pesticides along with other practices. Integrated Pest Management (IPM)

62 There’s Gotta Be Another Way! 80F66C63C38C&blnFromSearch=1&productcode=US 80F66C63C38C&blnFromSearch=1&productcode=US “Waste and Insect Management in the Everglades” Physical Predators/Parasites Strip Cropping Genetic Engineering

63 Physical Rotating between different crops, selecting pest-resistant varieties, planting pest-free rootstock, and vacuuming up harmful bugs.

64 Biological Control Using natural predators & parasites to control population of pests Problem: Could attack non-pests, too Ex: Cane toads!

65 Strip Cropping – a row crop such as corn alternates in strips with another crop that completely covers the soil, reducing erosion. It catches and reduces water runoff and helps prevent the spread of pests and plant diseases.

66 Pheromones Chemical communication b/t organisms Used to disrupt insect mating cycles; ex: pinworm moth Used in traps Considered ORGANIC

67 Increase pest resistance: Genetic engineering Artificial selection/breeding programs Increasing genetic diversity

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