1. Soil Formation, Erosion and Conservation

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

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

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

5. Soil Profile C Horizon – “Weathered Parent Material”
transition area between soil and parent material.
Partially disintegrated parent material.
mineral particles.
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.
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.
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 Earth’s 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 9

10. Weathering produces soil
FIGURE 7.2 10

11. Soil: The foundation for feeding a growing population
Land devoted to agriculture covers 38% of Earth’s 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 11

12. Population and consumption degrades soil
Feeding the world’s 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? 12

13. We lose 5-7 million hectares of productive cropland annually13

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 7.7
7-14 14

15. Tillage (Ploughing)‏
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 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 is used for destroying weeds.
The downside is that it also compacts the soil and promotes erosion. 15

16. Traditional vs. Industrial agriculture
FIGURE 7.9
7-16 16

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 17

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

19. Wind (aeolian) erosion Water erosion (splash, sheet, rill, gully)‏
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 19

20. Four kinds of water erosion
Splash
Sheet
Rill
Gully
FIGURE 7.11
7-20 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 21

22. Environmental effects of over-fertilizing
FIGURE 7.17
7-22 22

23. Grazing practices can contribute to soil degradation
FIGURE 7.18
7-23 23

24. Effects of overgrazing can be striking
Ungrazed plot
Grazed plot
FIGURE 7.19
70% of the world’s rangeland is classified as degraded
7-24 24

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.
FIGURE 7.16
Salinization inhibits production of 20% of all irrigated cropland, costing more than $11 billion/year
7-25 25

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

27. Contour farming Crop rotation
FIGURE 7.14
Contour Farming = plowing furrows sideways across a hillside, perpendicular to its slope, to prevent rills and gullies
Crop Rotation = alternating the crops grown field from one season or year to the next
Cover crops protect soil
7-27 27

28. Intercropping Terracing
FIGURE 7.14
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
7-28 28

29. Reduced tillage Shelterbelts
FIGURE 7.14
Reduced Tillage = furrows are cut in the soil, a seed is dropped in and the furrow is closed
Shelterbelts or Windbreaks = rows of tall, perennial plants are planted along the edges of fields to slow the wind
Alley cropping = shelterbelts + intercropping
7-29 29

30. Plant cover reduces erosion
Eroding banks along creeks and roadsides are stabilized by planting plants to anchor soil
China has the world’s largest tree-planting program (monoculture)
Slows erosion
Forests are not ecologically functional
FIGURE 7.15
7-30 30

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 7.16
7-31 31

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 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

35. Traditional subsistence agriculture uses all of the following, except:
Animal power
Irrigation
Irrigation water
Fossil fuels
Answer: d
7-35 35 35

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

37. Which horizon is the most valuable for agriculture? A horizon
B horizon
C horizon
R horizon
Answer: a
FIGURE 7.3
7-37 37 37

38. Erosion increases through all of the following, except:
Excessive tilling
Overgrazing
Clearing forests
All of the above increase erosion
Answer: d
7-38 38 38

39. Which sustainable farming method involves planting rows of trees along field edges to slow the wind?
Terracing
Crop rotation
Shelterbelts
Contour farming
Answer: c
7-39 39 39

40. Should developed nations fund reforestation projects in developing nations to combat erosion and deforestation?
Absolutely, developing nations are facing a crisis
No, not with money, but developed nations could give advice
No, developed nations had to solve their problems, let the others solve their own problems
I don’t care, it doesn’t really affect me ?
Answer: any
7-40 40 40

41. Should the Canadian government provide farmers with financial incentives to use technologies such as no-till farming and crop rotation?
Absolutely, farmers may be more likely to switch to these techniques
Yes, but farmers must put any money received into the farm
No, it’s not the government’s job to interfere with farming practices
I don’t care, it doesn’t really affect me ?
Answer: any
7-41 41 41