Chapter 12: Necessary Nutrients

1. Chapter 12: Necessary Nutrients Soil

2. Sources for questions and info • 1. Holt Environmental Science • 2. Lab-Aids, Science and Sustainability • 3. Fertilizer University • 4. http ://interactive.usask.ca/ski/ agriculture/soils/soilphys/soilphys_sep.html

3. Image resources • 5.http://tiee.ecoed.net/vol/v3/experiments/ soil/abstract.html 6. http://www.agr.state.nc.us/cyber/kidswrld/ plant/label.htm 7. http://www2.kenyon.edu/Projects/ Farmschool/photos/stripbs.jpg 8. http://www2.kenyon.edu/Projects/Farmschool/ types/tillage.htm

4. 1. Define arable land • Fertile land that can be plowed to grow crops. (1)

5. 2. Lost arable land form 1989-2000 • Desertification (25 million hectares) • Salinization (60 million hectares) • Erosion (50 million hectares) • Road-building, urban development, industry (150 million hectares) • Total loss—285 million hectares (1)

6. 3. Why does plowing help crops grow? • It mixes up soil nutrients, loosens soil particles and uproots weeds (1)

7. 4. What is fertile soil composed of? • 1. Fertile soil is soil that can support rapid growth of healthy plants. • It contains • Rock particles • Air • Water • Organic matter • Living things help mix the soil and decompose the organic matter (1)

8. How do living organisms contribute to the fertility of soil? • They decompose or cause other organisms to decompose. • They may mix up the soil creating spaces for air and water (ex: earthworms, burrowing animals, insects, etc.) (1)

9. 5. Soil structure

10. 6. What is erosion? • The wearing away of topsoil by wind and water. (In the US about ½ of the topsoil has been lost to erosion in the last 200 years) • (1)

11. 7. What farming practices have encouraged topsoil erosion? How? • Plowing loosens the surface layer of soil which may more easily be blown or washed away. • Harvesting may take away roots and organic material that helps hold soil together. • (1)

12. 8. Describe desertification and how it can be prevented.

13. Answer #8 • Desertification occurs when soil fertility is so deteriorated that the land becomes desert-like • It can be caused by overgrazing, planting several crops a year, cutting down trees for fuel or animal feed can lead to soil loss • It can be prevented or slowed by rotating grazing areas and crops (1)

14. Sustainable Agriculture • This is a phrase used to describe methods that provides for continuing crop yields, but also maintains resources like soil. (4)

15. 9. What are some soil conservation practices? Contour plowing -pay attention to the slope of the land and plow across the slope. (1)

16. Ways to prevent soil erosion: • Leave strips of vegetation running across the hillside. Don’t plow the entire slope (1)

17. Ways to prevent erosion (cont.’d) Strip cropping: Alternating a field with strips of different crops (this can also reduce pests) (4) This picture shows corn, alfalfa, and wheat. http://www2.kenyon.edu/Projects/Farmschool/photos/stripbs.jpg

18. Ways to prevent erosion (cont.’d) • No - till farming—Plant new seeds in slits cut into the soil through the remains of the old crop. Old roots help hold soil and add organic matter to the soil (1)

19. . No-till farming whyfiles.org/199_soil/images/soil_map.gif

20. Soybeans growing in corn residue as an example of no-till farming http://www2.kenyon.edu/Projects/Farmschool/types/tillage.htm

21. Practices for Sustainable Agriculture • Windbreaks: Trees are planted along the edges of fields to reduce wind erosion. Most helpful in flat areas • Cover crops: “Planting winter cover crops like fall rye or winter wheat act as a ground cover and protect vulnerable soil from eroding. “

22. 10. What is aquaculture? How does it work? • Aquaculture is the raising of fish, shellfish, crustaceans, or seaweeds in artificial environments. (began about 4,000 years ago in China) • Fish farms—grow to maturity in ponds and then are harvested • Fish ranch-grow to a certain age and then released (capture and harvest when return to birthplace) (1)

23. Problems with aquaculture • Can cause problems • Can produce a lot of waste—pollution • Can deplete local water supplies • May damage sensitive wetlands • Most don’t harm their surroundings • (1)

24. 11. Compare low input and conventional farming • Low-input—farming without a lot of energy, pesticides, fertilizer, or water • Organic farmers use manure and compost, keep soil planted, and alternate crops • Conventional—after harvest the soil is plowed to turn over the soil and bury plant remains. It is raked before seeds are planted. Often irrigation and manufactured fertilizer is used. (1)

25. 12. Two ways irrigation can cause salination. • Water for irrigation from rivers or ground water has more salt than rain water • When land is irrigated, much of the water evaporates leaving salt behind. • It may also cause groundwater to rise close to the surface. When it is pulled to the surface and evaporates, it leaves salt behind. (1)

26. 13. Why might amaranth and glasswort provide food for the future? • Amaranth was a sacred food of the Aztecs. It can survive with little water and produces a grain-like fruit that is rich in protein. • Glasswort can be grown on saline soils and even be irrigated with salt water. • Scientists are looking for foods that are better adapted to different climates and produce high yields w/o large amounts of water, pesticides and fertilizers.

27. Activity 12.2: Dirty Differences • Purpose: • Discover how soils form and explore some of the important components of soil (2)

28. 1. What is soil? • A complex mixture of living and non-living matter • It contains air, water, minerals, particles of rock or sand, organic material in the process of decay, and soil dwelling organisms • Bacteria, fungi, worms, insects, gophers, moles • (2)

29. 2. What are the major factors determining a soil’s characteristics? • Type of rock from which soil is formed • Species of organisms living in and on the soil • Age of soil • Climate (2)

30. 3. Describe the structures of young and mature soils. • Young soil—thin and rocky; small plants • Mature soil—built over a long period of time and have a thick layer of soil; many plants including large trees (2)

31. 4. What is humus? • Soil that is very rich in organic matter. (2)

32. 5. What roles does the decaying organic matter have? • Source of essential nutrients • Helps absorb and retain water (2)

33. 6. What problems can be caused by soil that is too acidic or too basic? • It can convert nutrients to chemical forms that don’t dissolve in water or can’t be absorbed by plant roots. • It can inhibit the action of soil microorganisms. (2)

34. Fertilizer University - What's in the Bag? • The hyphenated numbers on the front label of any package of fertilizer stand for the major nutrients plants need ) nitrogen (N), phosphorus (P), and potassium (K). The numbers, always given in the same order, represent the percentages each of N, P, and K in the bag (by weight). Other nutrients are often found in fertilizer, but not in as large amounts as N, P, and K. The percentages of other nutrients are listed under the Guaranteed Analysis. (3)

35. Reading a fertilizer bag:

36. 7. What roles does nitrogen play in plant growth? • Directly involved in photosynthesis • Stimulates above-ground plant growth • Responsible for the green color of plants (2)

37. Nitrogen (N) • is the main nutrient for new, green growth. Plants that are almost all leaf (such as lawn grasses) need plenty of nitrogen, so the first number is especially high in fertilizers for lawns because grass must continuously renew itself after mowing. The higher the number, the more nitrogen the fertilizer provides.  (3)

38. 8. Why do plants need phosphorus? • Essential for the growth of new seedlings • Early growth of roots • Development of seeds and fruits • Major role in processes requiring a transfer of energy (like fat production) (2)

39. Phosphorus (P) • promotes root development which helps strengthen plants. It also increases blooms on flowers. Lots of phosphorous is great for bulbs, perennials, and newly planted trees and shrubs. They depend on strong roots, so fertilizers meant for these plants often have high middle numbers. (3)

40. 9. Why do plants need potassium? • Catalyst for plant metabolism • Strengthens a plant’s resistance to disease • Starch synthesis (2)

41. Potassium (K) • . improves the overall health of plants. It helps them withstand very hot or cold weather and defend against diseases. Most soils already have some potassium, so the third number in the fertilizer analysis is usually smaller than the other two. Fertilizers for some tropical plants, especially palms, contain extra potassium because these plants have a special need for it. Fertilizers meant for fall, such as Winterizer, also contain extra potassium to help prepare plants for cold weather. (3)

42. 10. How do agricultural practices affect ecosystems? • Nutrients are being removed and may not be replaced • Bare soil may be exposed to erosion by wind and rain • Rain water and irrigation may leach out nutrients and carry them away (2)

43. 11. List advantages and disadvantages of using fertilizer. • Adv.—enhances plant production • Disadv. • can contaminate groundwater with nitrates • Excessive nitrates in drinking water can cause a blood disorder in infants • May lead to eutrophication of water supplies • Promotes excessive growth of algae and plants which reduces sunlight and nutrients for other organisms (2)

44. Question 12 • Plant life has existed on Earth for hundreds of millions of years. Fertilizer has been manufactured for only about 100 years. How did plants survive for so long without manufactured fertilizer? Why do we need so much of it now? (2)

45. Soil Properties • Texture of soil refers to the size of mineral particles, ranging in size range from fine to coarse. There are three categories of sizes: clays, silt and sand. The proportion of sand, silt and clay particles in the soil determines whether a soil is classified as sandy, silty or clayey. A balanced soil (loam) contains about 40% sand, 40% silt and 20% clay and is preferred for growing crops. (4)

46. Soil Particle sizes (4)

47. Sandy soil • Sandy particles are the only particles which may be large enough to be seen with the naked eye. Predominantly sandy soil has a gritty feel (coarse-textured) when rubbed between the fingers. (4)

48. Silt Particles • Silt particles are smaller than sand particles. Predominantly silty soils feel powdery (like flour) and do not hold together well when wet, though they are more cohesive than sandy soils. (4)

49. Clay soil • Clayey soil has the smallest soil particles, and many small pore spaces. Soils with a high number of clay particles have a very high water holding capacity and are very fine-textured, making them feel smooth and sticky (like soap) when wet. (4)

50. Comparing soil particle size • If you imagine a clay particle is the size of a grain of salt, silt would be the size of a candy, and a sand particle would be the size of a stove of a candy. (The ratio is about 1:26:1025) (4)