1. #1—Put soil grain in order from smallest to largest #2—Draw the soil layers #3—Get ready for Chapter 12 mingle

2. Soil texture Determined by size of particles Three main categories:
Clay = particles < mm diameter
Silt = particles 0.002–0.05 mm diameter
Sand = particles 0.05–2.0 mm diameter
Best for plant growth is loam, an even mix of these three types.

3. Soil texture

4. Soil profile Consists of layers called horizons Simplest: A = topsoil
B = subsoil
C = parent material
But most have O, A, E, B, C, and R
Soil profile

5. Soil profile O Horizon: Organic or litter layer
A Horizon: Topsoil; mostly inorganic minerals with some organic material and humus mixed in; crucial for plant growth
E Horizon: Eluviation horizon; loss of minerals by leaching, a process whereby solid materials are dissolved and transported away
B Horizon: Subsoil; zone of accumulation or deposition of leached minerals and organic acids from above
C Horizon: Slightly altered parent material
R Horizon: Bedrock

6. Regional soil differences and agriculture
Soil and soil profiles vary from place to place, with implications for agriculture.
Amazonian rainforest soil = lots of rain; leaches nutrients from topsoil out of reach of plant roots. Other nutrients taken up by lush vegetation, leaving little in soil.
Thus when farmed, soil gives out after a few years.
Kansas prairie soil = low rainfall keeps nutrients in topsoil, where plants take them up and recycle them back into soil when they die. Topsoil rich and productive.

7. Copy--Many environmental problems result from agriculture
“…agriculture has greater impact on the environment than any other single human endeavor.” -soil erosion -sediment transport and deposition downstream -degradation of water aquifers -on-site pollution -accumulation of toxic metals -deforestation -desertification -loss of biodiversity

8. Sustainable Agriculture

9. From Hunter and gatherer….

10. To an agrarian lifestyle…

11. Origins of agriculture
Agriculture originated independently in several regions.
Origins of agriculture

12. To today….

13. How can we make it sustainable?

14. What is Sustainable Agriculture?
The goal is to sustainably produce enough food and fiber and repair the damage caused by the process.

15. Soils can be degraded or destroyed.
Image: NRCS
Soils-6-2

16. Soils need to be protected from erosion by wind and water.
Image: NRCS
Soils-6-3

17. Soils need to be protected from depletion of organic matter and nutrients.
Image: NRCS
Soils-6-4

18. Loss of topsoil—Dust Bowl
Occurred during a drought that resulted in the huge volumes of soil

19. The Dust Bowl
Drought and degraded farmland produced the 1930s Dust Bowl.
Storms brought dust from the U.S. Great Plains all the way to New York and Washington, and wrecked many lives.

20. Soil conservation As a result of the Dust Bowl,
the U.S. Soil Conservation Act of 1935 and
the Soil Conservation Service (SCS) were created.
SCS: local agents in conservation districts worked with farmers to disseminate scientific knowledge and help them conserve their soil.

21. Soil conservation Many nations followed the U.S. lead:
Today local soil conservation agents help farmers in many places in the world.
Brazil’s no-till effort is based on local associations.

22. Soils are becoming degraded in many regions.
World soil conditions

23. Causes of soil degradation
Most soil degradation is caused by:
Livestock overgrazing
Deforestation
Cropland agriculture

24. Soil can be lost and deposited downstream

25. Conserve the SOIL! Carefully manage these factors: Land management
Ground cover
Tillage system
Climate
Soil type

26. Mulch

27. What do these do?
Contour farming works across the hill rather than down, slowing down the erosive process.
Strip-farming allows the farmer to harvest one crop while leaving the other crop behind to hold the soil in place.

28. Contour Farming

29. Contour Farming

30. Strip farming

31. Strip farming and contour farming

32. Terracing

33. Terracing This method Involves shaping The land to create
Shelves to hold
Soil and water
And nutrients.

34. Reduce the Tillage Impacts

35. Moldboard Plow Controls weeds Controls pests Brings nutrients up
Reduces competition
Provides good seedbed
Improved drainage
Improved aeration

36. LESS IS MORE Less Plowing and cultivation: Better water management
Preserves soil
Saves energy
Increases crop yields

37. Central Case: No-Till Agriculture in Brazil
Southern Brazil’s farmers were suffering falling yields, erosion, and pollution from agrichemicals.
They turned to no-till farming, which bypasses plowing.
Erosion was reduced, soils were enhanced, and yields rose greatly. No-till methods are spreading worldwide.

38. Summarize with your group
Agriculture and soil

39. Water Use

40. Irrigation The artificial provision of water to support agriculture.
70% of all freshwater used by humans is used for irrigation.
Irrigated land globally covers more area than all of Mexico and Central America combined.
Irrigation has boosted productivity in many places … but too much can cause problems.

42. CA Drought Discussion

43. Aquifers

44. Waterlogging and salinization
Overirrigation can raise the water table high enough to suffocate plant roots with waterlogging.
Salinization (buildup of salts in surface soil layers) is a more widespread problem.
Evaporation in arid areas draws water up through the soil, bringing salts with it. Irrigation causes repeated evaporation, bringing more salts up.

45. Improved irrigation
In conventional irrigation, only 43% of the water reaches plants. Efficient drip irrigation targeted to plants conserves water, saves money, and reduces problems like salinization.

46. Water Use for Cattle

47. Fertilizers Supply nutrients to crops
Inorganic fertilizers = mined or synthetically manufactured mineral supplements
Organic fertilizers = animal manure, crop residues, compost, etc.

48. Global fertilizer usages
Fertilizer use has risen dramatically in the past 50 years.

49. Fertilizer runoff Overapplied fertilizer can
run off into local water bodies, infiltrate into aquifers, and evaporate into air.
Nitrates and phosphates can cause health problems.

50. On-site pollution--pesticides

51. Agricultural losses from weeds are estimated to be >$16 billion annually in the US
$3.6 billion annually is spent on weed control in the US
DDT was introduced around WWII

52. Crop rotation
Alternating the crop planted (e.g., between corn and soybeans) can restore nutrients to soil and fight pests and disease.

53. Accumulation of toxic metals
DDT accumulation in the food chain

54. GMO developed as a way to reduce pesticide ise

55. Deforestation

56. Desertification

57. Review Questions

58. Which statement is NOT correct?
a. Soil consists of disintegrated rock, organic matter, nutrients, and microorganisms.
b. Healthy soil is vital for agriculture.
c. Soil is somewhat renewable.
d. Soil is lifeless dirt.
e. Much of the world’s soil has been degraded.
Answer: d

59. The A horizon in a soil profile… ?
a. Is often called the “zone of accumulation”
b. Is often called “topsoil”
c. Contains mostly organic matter
d. Is the lowest horizon, deepest underground
Answer: b

60. Erosion occurs through… ?
a. Deforestation
b. Excessive plowing
c. Overgrazing rangelands
d. All of the above
Answer: d

61. Drip irrigation differs from conventional irrigation in that … ?
a. It is much less efficient
b. It can cause salinization
c. Water is precisely targeted to plants
d. About 40% is wasted
Answer: c

62. You are farming an extremely steep slope that is sunny and very windy
You are farming an extremely steep slope that is sunny and very windy. What strategies would you consider using?
a. Crop rotation
b. Contour farming
c. Intercropping
d. Terracing
e. Shelterbelts
f. No-till farming
Answer: any

63. Soil that is 20% clay, 60% silt, and 20% sand is… ?
a. Silty clay
b. Silty loam
c. Sandy loam
d. Sandy clay
Answer: b

64. a. Risen sharply over 50 yrs
Fertilizer use has… ?
a. Risen sharply over 50 yrs
b. Fallen sharply
c. Decreased since 1980
d. Increased since 1995
Answer: a

65. How can we best protect the condition of soil while we farm?
a. Pass soil conservation laws.
b. Increase the number of agricultural extension agents working with farmers.
c. Give incentives for farmers to use strategies like no-till, contour farming, and shelterbelts.
d. Make sure all farmland is privately owned, giving owners incentive to treat soil with care.
Answer: any

66. #2--Graph and interpret
Time
Per Capita Meat Consumption in US (kg)
Per Capita Meat Consumption Globally (kg)
1961 72 21
1965 76 22
1970 84
22.5
1975 80 23
1980 87 26
1985 88 29
1990 31
1995 90 37
2000 93
39.5
2003
100 40