Soil – A Renewable Resource

1. Soil – A Renewable Resource Chapter 13: Food, Soil, Conservation, and Pest Management January 2012

2. What is Soil? • “Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, air, and billions of living organisms” • Produced by physical, chemical, and biological weathering

3. Soil Horizons

4. Layers in Mature Soils • Infiltration: the downward movement of water through soil. • Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers. • The soil type determines the degree of infiltration and leaching.

5. Mosaic of closely packed pebbles, boulders Weak humus-mineral mixture Alkaline, dark, and rich in humus Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil semiarid climate) Fig. 3-24a, p. 69

6. Forest litter leaf mold Humus-mineral mixture Light, grayish-brown, silt loam Dark brown firm clay Deciduous Forest Soil (humid, mild climate) Fig. 3-24b, p. 69

7. Acidic light-colored humus Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Fig. 3-24b, p. 69

8. Acid litter and humus Light-colored and acidic Humus and iron and aluminum compounds Coniferous Forest Soil (humid, cold climate) Fig. 3-24b, p. 69

9. Soil Properties • Particle size: clay, silt, and sand • Soil texture: relative amounts of each different particle size • Porosity: how well water infiltrates the soil • Soil Moisture: how much water is retained in the soil • % Organic Matter • Percolation Rate – how fast water infiltrates the soil

10. Silt Clay Sand less than 0.002 mm Diameter 0.002–0.05 mm diameter Water Water 0.05–2 mm diameter High permeability Low permeability Fig. 3-25, p. 70

11. SOIL QUIZ WHIP AROUND DIRECTIONS: • Select a partner. • Find an open area where you can move around. • Stand back to back. • Take one step away from each other. • Make sure that you both can see the screen. • Wait for further directions.

12. SOIL EROSION AND DEGRADATION • Soil erosion is the movement of soil components, especially surface litter and topsoil, by wind or water. • lowers soil fertility • overload nearby bodies of water with eroded sediment. • increases through activities such as farming, logging, construction, overgrazing, and off-road vehicles.

13. TYPES OF SOIL EROSION • Sheet erosion: surface water or wind peel off thin layers of soil. • Rill erosion: fast-flowing little rivulets of surface water make small channels. • Gully erosion: fast-flowing water join together to cut wider and deeper ditches or gullies.

14. Sheet erosion

15. Rill erosion

16. Gully erosion

17. Global Outlook: Soil Erosion Figure 13-10

18. Soil Erosion in the U.S. • Soil erodes faster than it forms on most U.S. cropland, but since 1985, has been cut by about 40%. • 1985 Food Security Act (Farm Act): farmers receive a subsidy for taking highly erodible land out of production and replanting it with soil saving plants like grasses and trees for 10-15 years.

19. Desertification • “Occurs when the productive potential of drylands falls by 10% or more because of a combination of natural climate change that causes drought and human activities that reduce or degrade topsoil.” • Natural oscillating process that has been accelerated by human activities • Affects 1/3 of world’s land and 70% of all dry lands.

20. Moderate (10-25% drop) Severe (25-50% drop) Very severe (>50% drop) Fig. 13-11, p. 280

21. Causes and Consequences of Desertification Causes Consequences Overgrazing Worsening drought Deforestation Famine Erosion Economic losses Salinization Lower living standards Soil compaction Natural climate change Environmental refugees Fig. 13-12, p. 280

22. Salinization results from repeated irrigation in dry climates where salts gradually accumulate in the upper soil layers. Waterlogging occurs when farmers apply too much irrigation water to leach salts deeper into the soil. Salinization and Waterlogging Figure 13-13

23. The Effects of Soil Salinization Figure 13-14

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

25. Agricultural Best Management Practices and the Consequences of Traditional Agriculture Chapter 13: Food, Soil, Conservation, and Pest Management February 2011

26. DIRECTIONS: • Select a partner. • Find an open area where you can move around. • Stand back to back. • Take one step away from each other. • Make sure that you both can see the screen. • Wait for further directions.

27. Question #1 How many plants are known to have parts that can be eaten? • 1,000 • 10,000 • 30,000 • 100,000

28. Question #2 A cash crop is a plant grown primarily to be sold as cash rather than consumed by the farmer. What is the largest cash crop in the U.S.? • corn • rice • marijuana • soybeans http://www.epa.gov/oecaagct/ag101/cropmajor.html

29. Question #3 U.S. Consumers spend about 2% of their annual income on food. About what percentage of income do the poorest billion people in the world spend on food? • 10% • 30% • 70% • 100%

30. Question #4 When the energy required to plant, grow, store, process, package, transport, refrigerate, and cook plant and animal food in developed countries is considered, how much more nonrenewable energy is consumed to produce 1 unit of food energy? • 2 units • 5 units • 10 units • 15 units

31. Question #5 An alternative to traditional agriculture is interplanting in which several crops are grown on a plot of land together. Which of the following interplanting types involves growing trees along with crops? • Polyvarietal cultivation • Alley cropping • Intercropping • Polyculture

32. Question #6 In 1999, Ingo Potrykus and Peter Beyer developed a genetically modified crop designed to supplement vitamin A, a nutrient deficient in the diet of millions of children in developing countries. What is this GMO crop? • sugarbeet 131 • α-sweet potatoes • Hybrid corn • Golden rice

33. Question #7 First generation pesticides are derived from the natural defensive chemicals in plants. Which of the following first generation pesticides was derived from the heads of chrysanthemum flowers? • rotenone • pyrethrum • DDT • atrazine

34. Three Types of Agriculture Traditional Agriculture • Low input • Usually multiple crops/animals are grown • Two varieties • Traditional subsistence agriculture • Traditional intensive agriculture Industrialized Agriculture/Agribusiness • high input • monoculture

35. From King Corn…What we’ve learned about industrialized agriculture

36. Case Study of Industrial Food Production • 30,000 plants are known with edible parts • 90% of world food is provided by just 14 of these - plus 9 terrestrial animal • Industrialized agriculture (high-input agriculture) is a northern hemisphere phenomenon devoted primarily to just 3 of these crops (wheat, rice, and corn). • Major cash crops in U.S. are corn, soybeans, hay, and wheat. Major black market cash crop is marijuana. • Southern hemisphere sometimes practices plantation agriculture mostly for commodity crops consumed in the north (i.e. cocoa, coffee, bananas, sugarcane, soybeans, and peanuts.) • Livestock (mostly cattle, pigs, and chickens) are grown in feedlots or animal factories. • Agribusiness is the largest industry in the United States - makes up over 18% of U.S. GDP

37. 10 units of nonrenewable energy are used to produce 1 unit of food energy in the U.S. In traditional subsistence agriculture the ratio is 1 to 10.

39. Alternatives to Monocultures • Interplanting – growing several crops on the same plot simultaneously • Polyvarietal cultivation • Intercropping • Agroforestry (alley cropping) • Polyculture

40. Polyvarietal cultivation Definition: Planting a plot of land with several genetic varieties (natural or transgenic) of the same plant. Example: hybrid rice and sticky rice grown together to provide greater genetic resistance to rice blast (Magnaporthe grisea), a fungus that produces necrotic holes in rice leaves.

41. Intercropping Definition: Two or more different crops are grown at the same time on a plot. Example: Seed corn in is rotated with wheat and soybeans (right) in Nebraska) to replenish soil nutrients and produce multiple yields from the same plot.

42. Alley Cropping Definition: Crops and trees are grown together Example: Left: Corn is grown between two strips of black walnut trees. Below: Crop between banana trees

43. Polyculture Definition: Many different plants are planted together.

45. Advantages to Interplanting • Crops maturing at different times extend the harvest. • Reduces erosion • Reduces need for fertilizers • Reduces need for water • Reduced need for herbicides and pesticides • Higher yields per hectare than high-input monoculture

46. SOIL CONSERVATION • Soil conservation involves reducing soil erosion and restoring soil fertility mostly by employing vegetation. • Conservation tillage • Strip cropping/contour planting • Terracing • Alley cropping • Shelter breaks/windbreaks • Cover crops • Livestock rotation

47. Conservation Tillage

48. Strip Cropping/ Contour Planting

49. Terracing

50. Shelter Belts / Windbreaks