SOILS FORMATION, EROSION, AND CONSERVATION

1. SOILSFORMATION, EROSION, AND CONSERVATION CHAPTER 10

2. I. Soil: Formation Erosion, and Conservation A. Soil – Defined as a complex mixture of eroded rock, minerals, decaying organic matter, water,air , and living organisms. 1. Produced by… -Weathering of rock -Depositing of sediment -Decomposition of matter

3. Soil Zones (MATURE) -Mature Soil is arranged into zones called SOILHORIZONS, each with distinct textures and compositions -A cross-section of soil horizons is called a SOIL PROFILE -Most mature soils have at least three of the possible horizons

4. LAYERS/HORIZONS O Horizon – Top layer/Surface Liter Layer -Characterized by debris and animal waste -Dark Brown/Black in color

5. A Horizon – Top Soil Layer -Consistsof porous mixture of partially decomposedorganic matter calledHUMUSand *inorganic minerals -Generally darker and more loosely compact than lower levels. -Most *plant roots and organic matter found here.

7. B Horizon – Subsoil Layer and C Horizon – Parent Material -Contain most of soil’s inorganic matter and varying mixtures of sand, silt,clay, and gravel -C Horizon lies on BEDROCK

8. Soils: Zones Immature soil O horizon Leaf litter A horizon Topsoil Regolith B horizon Subsoil Young soil C horizon Parent material Mature soil Bedrock

10. -Spaces, pores, between particles contain varying amounts of water and air. -Some of the precipitation that reaches the soils moves down through layers by a process known as… Infiltration- Water moving through the soil layers -Leaching- Soil components from upper layers being carried to lower layers when water moves through soluble soil layers. Ex: dumping oil in yard

11. C. Soil Properties 1. Soils vary in content of … Clay - very fine particle Silt – fine particles Sand – medium particles Gravel – coarse/very course particles -Relative amounts of different size and types determines SOIL TEXTURE -LOAMS – soils of equal mixture….not a particle size used to determine soil texture.

12. 2. Soil texture(s) can be determined by… A. Feel – Mixing a small sample of top soil and water, rub it between the fingers and thumb. -Gritty = a lot of sand -Sticky = high amounts of clay, rolls -Silt = smooth like flour -Loams = between the extremes B. Use of “texture chart”

13. CLAY SAND SILT

14. 3. Soil texture helps to determine… - SOIL POROSITY, the measure of the volume of pores and distance of pores per volume of soil. (important for water/air amounts)

15. Water Water High permeability Low permeability -Porosity helps to determine SOIL PERMEABILITY, the rate at which water and air can move through soil.

16. -Porosity also is influenced by SOILSTRUCTURE, the way that particles are organized.

17. TextureNutrient Infiltration Water-Holding Aeration Tilth CapacityCapacity Clay Good Poor Good Poor Poor Silt Medium MediumMediumMediumMedium Sand Poor Good Poor Good Good Loam Medium MediumMediumMediumMedium Loams – best for crops Sands – easy to work but decrease water Clay – soils can easily become water-logged

18. -pH can be changed by adding LIME to acidic soils and SULFUR to those soils that are basic/alkaline 4.pH- Measure of alkalinity or acidity

20. II. Soil Erosion 1. Defined as the movement of soil components, especially surface litter and topsoil, from one place to another *Two main agents are… -Flowing water -Wind

21. 2. Types Of Water Erosion A. Sheet – Moving of water in wide flow B. Rill – Fast moving water that cuts small channels

22. C. Gully – Ditches and gulleys caused by fast moving water over steep, exposed soil

24. Global Soil Erosion Areas of serious concern Areas of some concern Stable or nonvegetative areas

25. 3. U.S. Soil Erosion -1/3 of the original top soil has been washed or blown away. -USDA states that soil is eroding 16X faster than it can form. -USDA estimated loss of $30 billion dollars in 1997

26. The Dust Bowl

27. 4. Other Problems Associated With Soil A. Desertification- Process whereby the productive potential of arid or semiarid land falls by 10% or more due to human activities and climate changes. **Can be caused by prolonged drought, overgrazing, and soil compaction B. Salinization-The accumulation of salts in soil -often a result of irrigation -stunts growth, decrease productivity, kills plants making the land unproductive

28. C. Waterlogging- An over abundance of water within the soil -Often caused from trying to “wash out” salts. -Occurs due to decrease drainage -Irrigation often results in waterlogging

29. Evaporation Evaporation Transpiration Waterlogging Less permeable clay layer

30. III. Soil Conservation Soil Conservation involves reducing soil erosion and restoring soil fertility.

31. Farming Techniques 1.Conventional-tillage farming-plowing, breaking up, and smoothing soil in fall to plant in the spring. 2. Conservation-tillage farming-decreases erosion Tillage refers to the workability of soil

33. C. Terracing – Creation of broad, nearly level terraces that run across the contour of the lands -Mostly used on very steep gradients to prevent erosion.

34. D. Contour Farming- Plowing/planting crops in rows across the sloped contour of the land at 90 degree angles.

35. E. Strip Cropping- Alternating rows of crops with low, ground hugging vegetation.

36. F. Alley Cropping/Agroforestry- several crops planted together in strips or alleys between trees or shrubs that are used for fuel wood or fruits.

37. G. Windbreaks/Shelterbelts- Rows of trees to reduce wind erosion.

38. H. Organic fertilizer -Animal manure -Green manure -Compost

39. Commercial inorganic fertilizer

40. Drawbacks to Commercial Inorganic Fertilizers They don’t add humus to soil Show decreased ability to hold water Lower oxygen content in soil Supply 2 or 3 of 20 needed nutrients.