1. Soils and their processes IB Syllabus: 3.8.1-3.8.5 AP Syllabus Chapter 10

2. Syllabus Statements 3.4.1: Outline how soil systems integrate aspects of living systems 3.4.2: Compare and contrast the structure and properties of sand, clay, and loam soils including their effect on primary productivity 3.4.3: Outline the processes and consequences of soil degradation 3.4.4: Outline soil conservation measures 3.4.5: Evaluate soil management strategies in a named commercial farming system and in a named subsistence farming system

3. vocabulary Soil Soil profile Biodegradable

4. Soils and living systems Sun Producer Precipitation Falling leaves and twigs Producers Primary consumer (rabbit) Secondary consumer (fox) Carbon dioxide (CO 2 ) Oxygen (O 2 ) Water Soil decomposers Soluble mineral nutrients

5. Links to lithosphere, atmopshere, and living organisms What are they? Inputs  organic materials, parent materials, precipitation, infiltration, Energy Outputs  leaching, uptake by plants, mass movement Transfers  deposition Transformations  decomposition, weathering & nutrient cycling

6. Soil as a resource? Produced very slowly – almost nonrenewable Production by… –Weathering of rock (parent material) – chemical & mechanical  this adds inorganic components –Deposit of sediments by erosion –Introduction of living organisms – succession  the biotic component –Decomposition of organic materials and dead organisms Development is slow 200-1000 years to produce 1 inch of topsoil Soil is different in different areas

7. The horizon Mature soils arranged in zones or layers called horizons –Different texture and composition Cross sectional view of soil horizons is called a soil profile Most mature soils have at least three horizons

8. Typical Horizons Surface litter = O horizon –Fresh and partly decomposed organics Topsoil layer = A horizon –Humus mixed with inorganics –Most life in O & A Subsoil = B horizon –Broken down Inorganics Parent material (bedrock) = C horizon

9. Flatworm Rove beetle Ant Centipede Mite Pseudoscorpion Ground beetle Adult fly Millipede Fly larvae Sowbug Mite Earthworm Slug Snail Roundworms Protozoa Bacteria Organic debris Beetle Mite Fungi Springtail Actinomycetes O & A horizon inhabitants

10. Living layers Organisms in the A & O layers are those that break down the organics to form the soil A & O are where plant roots are, abosorbing water and nutrients Humus = partly decomposed organics  fertile and good for plant production Topsoil color indicates condition –Dark brown good lots of nitrogen and organics –Grey, yellow and red soils low in nutrients

11. Profiles from different biomes, will show different horizon size and composition

12. Weak humus- mineral mixture Mosaic of closely packed pebbles, boulders Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Desert Soil (hot, dry climate) Grassland Soil (semiarid climate) Alkaline, dark, and rich in humus Clay, calcium compounds

13. Acidic light- colored humus Iron and aluminum compounds mixed with clay Forest litter leaf mold Humus-mineral mixture Light, grayish- brown, silt loam Dark brown Firm clay Acid litter and humus Humus and iron and aluminum compounds Light-colored and acidic Tropical Rain Forest Soil (humid, tropical climate) Deciduous Forest Soil (humid, mild climate) Coniferous Forest Soil (humid, cold climate)

14. What else is in there? Spaces between particles hold gases mostly N 2 and O 2 Precipitation, Percolates down through soil in the process of Infiltration Water dissolves compounds and carries them through soil = Leaching Nutrients in soil from breakdown of mineral components and biological cycling

15. Nitrogen fixing by lightning Commercial inorganic fertilizer 10-6-4 N-P-K Organic fertilizers, animal manure, green manure, compost Crop plant Dead organic matter Application to land Nitrogen fixing by bacteria Nitrogen fixing Weathering of rock Nutrient removal with harvest Decomposition Supply of available plant nutrients in soil Nutrient loss by bacterial processes such as conversion of nitrates to nitrogen gas Nutrient loss from soil erosion Absorption of nutrients by roots Further Interactions Detailed

16. Composition of Soils Soils vary in their content of … –Clay: very fine particles –Silt: fine particles –Sand: medium sized particles –Gravel: coarse to very coarse particles Soil texture determined by amounts of these components If mixture is relatively equal it is a loam

17. Texture by Feel Moisten some soil and rub it between your thumb and forefinger Gritty = lots of sand Sticky, can form clumps = lots of clay Smooth like flour = silt Crumbly, spongy with loose clumping = loam

18. 100%clay Increasing percentage silt Increasing percentage clay 0 20 40 60 80 60 40 20 0 100%sand80604020100%silt Increasing percentage sand sandy clay silty clay silty clay loam clay loam silty loam silt sandy clay loam sandy loam loamy sand

19. Soil Texture Soil Porosity: measure of the volume of space in a volume of soil Fine particles = water retention Coarse particles = air retention More porous  more water and air Size of spaces in soil determines soil permeability rate at which water and air move from upper to lower soil levels

20. Texture continued Soil structure: the organization and clumping of soil Loams are best for growing crops, hold water but not too tightly that plants can’t absorb it. Clay less porous, less permeable  lead to water logged crops above

21. Water High permeabilityLow permeability Particle Size and Permeability

22. Sand Soils 1.Mineral content: moderate 2.Drainage: highest 3.Water-holding capacity – low, = 10% 4.Air spaces: highest, = 40% 5.Biota: space to live 6.Potential to hold organic matter: high 7.Links to primary production: pure sand = low productivity

23. Clay Soils 1.Mineral content: limited 2.Drainage: poor 3.Water-holding capacity- highest = 40% 4.Air spaces: lowest = 10% 5.Biota: little space for colonization 6.Potential to hold organic matter: low 7.Links to primary production – water logged crops above

24. Loam Soils 1.Mineral content: high 2.Drainage: intermediate 3.Water-holding capacity: intermediate = 25% 4.Air spaces: intermediate = 15% 5.Biota: highest 6.Potential to hold organic matter - good mix of organic matter 7.Links to primary production – highest productivity in balanced soil

25. Soil gets degraded by human activities Overgrazing – plants exposed to intensive grazing over long periods of time or without sufficient recovery period Deforestation - Removal of large sections of forest habitat Unsustainable agriculture – Monoculture using high chemical & fertilizer input and fossil fuels Irrigation – especially done in arid areas b/c evaporation leaves everything but H2O behind Lead to degradation by erosion, toxification, salinization, desertification

26. Overgrazing Impacts Reduces Biodiversity Causes Desertification and Erosion Increases Erosion by loss of cover species and loss of roots that held the soil in place Erosion leads to loss of organics and drop in productivity In marginal lands this may lead to desertification as grassland becomes desert when productivity plummets

28. DO NOT POST TO INTERNET

29. DO NOT POST PHOTOS TO INTERNET

30. First yearSecond yearThird yearFourth yearFifth yearSixth year First yearSecond yearThird yearFourth yearFifth yearSixth year First yearSecond yearThird yearFourth yearFifth yearSixth year Pasture A Pasture B Pasture C Deferred Grazed last Grazed second Grazed first Grazed first Grazed second Grazed first Grazed second Deferred Grazed last Grazed second Grazed first Grazed second Grazed first Grazed first Grazed second Deferred Grazed last

31. Deforestation Impacts Increases rates of erosion by increasing runoff and reducing litter protection on the surface Roads created and machinery used also increases erosion Roots may hold soil in place and canopies may disperse the force of percipitation On steep slopes deforestation can cause landslides

32. Soil Erosion Erosion = the movement of soil components especially surface litter and topsoil, from one area to another Caused by WIND and WATER Plant roots usually anchor soils in place Effects 1.Loss of soil fertility and water holding capacity 2.Runoff sediment pollutes water, kills organisms, clogs ditches, channels, lakes 3.Increased use of fertilizers 4.Increased runoff and flooding

34. Areas of serious concern Areas of some concern Stable or nonvegetative areas World Erosion concerns

35. Colorado Kansas Dust Bowl Oklahoma New Mexico Texas MEXICO

36. Historical Wind Erosion 1930’s “ The dirty thirties” Combination of –drought, –removal of native plants which held in soil, –cultivation leaving land bare for months –Overgrazing “Dust Bowl” formed (The Grapes of Wrath)

37. Desertification Desertification  enlargement of deserts through human activities The productive potential of arid or semiarid land falls by 10% due to 1.Natural climate change  prolonged drought 2.Human activities reducing & degrading soil Moderate = 10-25% productivity drop Severe = 25-50% drop Very severe >50% drop = sand dunes & gullies

38. Consequences Causes Worsening drought Famine Economic losses Lower living standards Environmental refugees Overgrazing Deforestation Surface mining Erosion Salinization Soil compaction Causes and Consequences Every year 11 million hectares of arable land is lost from production through the soil degradation process

39. Desertification Statistics World wide 8.1 million km 2 desertified in past 50 years Yearly 150,000 km 2 additional Economic losses of $42 billion / year WE CAN 1.Reduce overgrazing, deforestation, bad agriculture practices 2.Plant trees & grasses to anchor soil, hold water, reduce global warming threat

40. ModerateSevereVery Severe World Desertification concerns

41. Unsustainable Agriculture Characteristics of Modern Agriculture –High water input –High pesticide use –High inorganic fertilizer use Traditional agriculture where soil is tilled at the end of a growing season Idea good in practice – add nutrients to the soil – but bare soil exposed to erosion Tillage also deteriorates soil structure Can cause increased erosion, toxification and salinization

42. Unsustainable Agriculture Impacts Toxification of soil –When nonbiodegradable pesticides and inorganic fertilizers build up in the soil they make it toxic –Kills useful bacteria (N fixing) fungi, and decreases productivity –Can also result from release of toxic metals like Al +3 when acidity increases (N based fertilizers mixing with water forming Nitric Acid) Soil erosion rates increase

43. Biodiversity Loss Loss and degradation of habitat from clearing grasslands and forests and draining wetland Fish kills from pesticide runoff Killing of wild predators to protect livestock Loss of genetic diversity from replacing thousands of wild crop strains with a few monoculture strains Soil Erosion Loss of fertility Salinization Waterlogging Desertification

44. Air Pollution Greenhouse gas emissions from fossil Fuel issue Other air pollutants from fossil fuel use Pollution from pesticide sprays Water Aquifer depletion Increased runoff and flooding from land cleared to grow crops Sediment pollution from erosion Fish kills from pesticide runoff Surface and groundwater pollution from pesticides and fertilizers Overfertilization of lakes and slow-moving rivers from runoff of nitrates and phosphates from fertilizers, livestock wastes, and food processing wastes

45. Human Health Nitrates in drinking water Pesticide residues in drinking water, food, and air Contamination of drinking and swimming water with disease organisms from livestock wastes Bacterial contamination of meat

46. Improper irrigation Often results from unsustainable agriculture in areas that are too arid Remember that water includes more than just H2O –Improper drainage or high evaporation leads to salt deposition  crop damage, reduction of productivity –Unirrigated or underirrigated land can lead to build up of toxic agricultural waste products

47. Unsustainable irrigation

48. Salinization can result Irrigation increases productivity BUT Irrigation water contains salts Evaporation leaves crust of salts on surface Accumulation of salts = salinization –Stunts crop growth –Lowers crop yields –Kills plants and ruins land Reduced crop yield by 21% on irrigated land

49. Severe Salinization

50. Water logging Attempt to solve salinization Apply large amounts of water to leach salt deeper into soil Water accumulates underground then raises water table Saline water envelopes roots lowering productivity  death 10% irrigated land is waterlogged

51. Evaporation Transpiration Evaporation Waterlogging Less permeable clay layer

52. PreventionCleanup Reduce irrigation Switch to salt- tolerant crops (such as barley, cotton, sugar beet) Flushing soil (expensive and wastes water) Not growing crops for 2-5 years Installing under- ground drainage systems (expensive) Solving the Salty Problem

53. Solutions: Soil Conservation Goal: Reduce soil erosion, restore fertility Conventional Tillage Farming is bad  plow land in the fall, bare & erodable all winter Conservation Tillage Farming disturb the soil as little as possible while planting crops Minimum tillage or No till farming Using conservation tillage on 80% of farmland would reduce soil erosion by 50%

54. AdvantagesDisadvantages Reduces erosion Saves fuel Cuts costs Holds more soil water Reduces soil compaction Allows several crops per season Does not reduce crop yields Can increase herbicide use for some crops Leaves stalks that can harbor crop pests and fungal diseases and increase pesticide use Requires investment in expensive equipment Conservation Tillage Facts

55. Cultivation Techniques 1. Terracing –Convert steep slopes into a series of broad, nearly level terraces running across the land contour –Retains water for crops controls runoff –Marginal areas, Poor farmers, little time / manpower 2. Contour Plowing –Plowing and planting crops in rows across the contour of gently sloping land –Each row holds soil and slows runoff

56. TerracingContour planting and strip cropping

57. Reducing Wind Erosion 1. Strip cropping - planting alternative strips of (1) row crop like corn and (2) another crop like grass or legumes that completely covers the soil - Cover strips (1) trap soil that erodes from row crop (2) catch & reduce runoff, (3)help prevent spread of pests, (4) restore soil fertility

58. Strip Cropping

59. Alley cropping Windbreaks

60. Reducing Wind Erosion 2. Alley Cropping -Crops planted in strips or alleys between rows of trees and shrubs which themselves are harvestable for wood or fruit -Trees & shrubs provide 1. Shade, reducing evaporation water loss 2. Retain and slowly release soil moisture 3. Provide fruit, fuelwood, clippings for mulch (green manure) 4. Livestock fodder 3. Shelter Belts / Wind breaks Reduce wind effects 1. Less erosion 2. Retain soil moisture 3. Supply products 4. Habitat for animals including birds and insects that eat pests

61. Can we Maintain & Restore soil Fertility? Soil Conditioners Fertilizers: compounds that partially restore important soil nutrients lost by erosion, leaching and harvesting crops Condition soils with –Organic Fertilizers: made of plant and animal materials that are biodegradable –Lime: Increase alkalinity of the soil  improves fertility

62. Organic Fertilizer Benefits Organic Fertilizers 1.Animal Manure: improves soil structure, nutrients, stimulates bacteria & fungus growth 2.Green Manure: Vegetation plowed into the soil increases organic content 3.Compost: Brown humus material, aerates soil, improves water holding, prevents erosion, recycles nutrients 4.Fungus spores: moisture control, disease resistance Inorganic Fertilizers 1.Nitrogen, Phosphorous, Potassium 2.Easily available, transported, stored and supplied 3.Help Produce crops in 3 rd world BUT 1.Not adding humus or other essential nutrients 2.Lower oxygen, organic matter in soil 3.Raise N 2 O in atmosphere (greenhouse gas)

63. Soil Management Strategies Differ depending on the agricultural system you are observing Comparison of Florida sugar cane farming (commercial farming) and slash and burn (subsistence farming)

64. Slash and Burn Agriculture Mainly associated with Tropical Rainforest areas Madascar, Malasia, Central America Usually small scale subsistence Practiced in areas with poor soils Harvest wood, burn unusable portions Temporary pulse of nutrients from burning Ash also increases pH of soil Burning can drive off pests too

65. Slash and Burn II Land only fertile for a few years Abandoned when fertility declines Forces burning of more land

66. References http://www.mo15.nrcs.usda.gov/

67. Review Points Know your horizons: O, A, B, C Soil composition: sand, silt, gravel, clay Wind and water erosion Desertification and Salinization Soil conservation Methods Fertilizer uses

68. Florida sugar Cane Soils of everglades Agricultural area are rich in organics formed from 4,400 years of sawgrass decomposition Soils are “muck soils” and must be drained for crop growth Even with high organic matter need inputs to keep soil fertile – N, P, K all added on the order of 0-30 lbs per acre each year depending on specific area differences Soil subsidence happening because of uptake of organics Water is seasonally available so may need suplementation

69. Big Sugar and Florida An Uncertain Future

70. 2006 Cornell University Study The United States is losing soil 10 times faster -- and China and India are losing soil 30 to 40 times faster -- than the natural replenishment rate. The economic impact of soil erosion in the United States costs the nation about $37.6 billion each year in productivity losses. Damage from soil erosion worldwide is estimated to be $400 billion per year. As a result of erosion over the past 40 years, 30 percent of the world's arable land has become unproductive. About 60 percent of soil that is washed away ends up in rivers, streams and lakes, making waterways more prone to flooding and to contamination from soil's fertilizers and pesticides. Soil erosion also reduces the ability of soil to store water and support plant growth, thereby reducing its ability to support biodiversity. Erosion promotes critical losses of water, nutrients, soil organic matter and soil biota, harming forests, rangeland and natural ecosystems. Erosion increases the amount of dust carried by wind, which not only acts as an abrasive and air pollutant but also carries about 20 human infectious disease organisms, including anthrax and tuberculosis.