1. The Soil System Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

2. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

3. Soil formation is a slow process: Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

4. Mature soils are arranged in a series of zones called SOIL HORIZONS: “ O” HORIZON = freshly fallen and partially decomposed leaves, twigs, animal waste. You can find fungi and other organic materials. “A” HORIZON = porous mixture of partially decomposed organic matter (humus) as well as bacteria, fungi, earthworms, and other decomposer organisms interacting in complex ways. inorganic Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

5. “B” (subsoil) and “C” (parent material) HORIZON contain most of the soil’s inorganic matter, mostly broken-down rock consisting of varying mixtures of sand, silt, clay, and gravel.. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

6. Clay (very fine particles) <0.002mm Silt (fine particles) 0.002-0.05mm Sand (medium-size particles) 0.05-2.0mm Gravel (coarse to very coarse particles) >2.0mm Soil Texture is determined by the relative amounts of the different types and sizes of mineral particles. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Soil Content Loam is soil composed of sand, silt, and clay in relatively even concentration (about 40-40-20% concentration respectively). Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils. Loams are gritty, moist, and retain water easily.

7. 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 http://www.youtube. com/watch?v=knrmC bctGEA Soil Texture Triangle Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity.

8. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Soil texture helps determine SOIL POROSITY, a measure of the volume of pores or spaces per volume of soil and the average space between those spaces. INFILTRATION is the downward movement of water through soils. As the water seeps down, it dissolves various soil components in upper layers and carries them down to lower layers in a process called LEACHING.

9. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. SOIL PERMEABILITY is the rate at which water and air move from upper to lower soil layers. Water High permeabilityLow permeability

10. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Properties of Soils with Different Textures TextureNutrient Capacity InfiltrationWater- Holding Capacity AerationWorkability Clay GoodPoorGoodPoor Silt Medium Sand PoorGoodPoorGood Loam Good

11. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Soil erosion is the movement of soil components, especially surface litter and topsoil. The two main agents of erosion are: 1.wind 2.flowing water Loss of plant cover by farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation and other activities leave soil vulnerable to erosion.

12. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Two major harmful effects of soil erosion: 1.Loss of soil fertility and its ability to hold water 2.Runoff of sediment that pollutes water, kills fish and shellfish, and clog irrigation ditches, boat channels, reservoirs, and lakes. serious concern some concern Stable areas

13. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Desertification Desertification is the enlargement of deserts through human activities. Consequences Causes Worsening drought Famine Economic losses Lower living standards Environmental refugees Overgrazing Deforestation Surface mining Erosion Salinization Soil compaction

14. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. SALINATION 1.Irrigation water contains small amounts of dissolved salts. 2.Evaporation and transpiration leave salts behind. 3.Salt builds up in soil. WATERLOGGING Precipitation and irrigation water percolate downward. Water table rises. Causes roots to drown. Both result in stunted plant growth, lower crop yields, dead plants and ruined land.

15. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Soil Conservation involves reducing soil erosion and restoring soil fertility. http://www.youtube.com/watch?v=MQQcnId3Z7A

16. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Contour planting and strip cropping: each row acts as a small dam to help hold soil and slow water runoff.

17. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Alley cropping or agroforestry: several crops are planted together in strips or alleys between trees and shrubs that can provide fruit or fuel-wood, shade, help retain and slowly release soil moisture, and fodder for livestock.

18. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Windbreaks or shelterbelts of trees reduce wind erosion, help retain soil, supply wood for fuel, and provide habitats for birds, pest-eating and pollinating insects, and other animals.

19. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Terracing retains water for crops at each level and reduces soil erosion by controlling runoff.

20. Topic 3 The Soil System and Food Production Students will be able to: - to outline how soil systems integrate aspects of living systems. -compare the structure and properties of sand, clay and loam soils including their relevance to primary productivity. Soil Restoration Organic fertilizer Manure Compost crop rotation No till farming Contour farming Terracing Nitrogen fixation-legumes