Chapter 8: Soil

1. Chapter 8: Soil

2. The Formation of Soil You may simply list these – without having to write descriptions. Factors that determine the formation of soil: • Parent material - what the soil is made from influences soil formation • Climate - what type of climate influences soil formation • Topography - the surface and slope can influence soil formation and erosion • Organisms - plants and animals (especially fungi and macroinvertebrates)can have an effect on soil formation • Time - the amount of time a soil has spent developing can determine soil properties.

3. The Formation of Soil • Parent Material - the rock material from which soil is derived. When rock is exposed at Earth's surface, it begins to break down through the processes of weathering and erosion. (see next slides)…

4. Weathering Physical weathering. (a) Water can work its way into cracks in rock, where it can wash away loose material. When the water freezes and expands, it can widen the cracks. (b) Growing plant roots can force rock sections apart.

5. Erosion • Erosion: the physical removal of rock fragments from a landscape or ecosystem. • Wind, water, and ice can transport soil. • living organisms can burrow through soil. • Deposition: the accumulation or depositing of eroded material such as sediment, rock fragments or soil.

6. Soil Horizons Transfer these layer descriptions to the diagram Mr. Sierra provided in class. O horizon- (organic layer) composed of the leaves, needles, twigs and animal bodies on the surface. A horizon- (topsoil) the zone of organic material and minerals mixed together. B horizon- (subsoil) composed primarily of mineral material with very little organic matter C horizon- (parent material) the least weathered horizon and is similar to the parent material. As soils form, they develop characteristics layers.

7. Soil Horizons Same information as last slide, but a more detailed look…

8. Soil Horizons OHorizon • Humus- dark, soft, spongy residue of organic matter as a result of decomposition of organic matter such as leaves and dead wood • #1 source of nutrients in soil systems

9. Soil Horizons AHorizon • Top soil-mixture of humus and leachable mineral soil • Thin roots extend into this layer

10. Soil Horizons EHorizon May occur below the O or A horizons • Eluviation: process of leaching • Minerals are “leached” into this layer from H2O movement downward

11. Soil Horizons BHorizon • Subsoil • Often high in iron, aluminum, and calcium • Often high in clay content

12. Soil Horizons • Weathered parent material • Glacial deposits, volcanic ash • Reveals history of the land CHorizon

13. Classes of Soil Don’t need to write in notebooks Mollisols- very fertile, dark, found in temperate grasslands, best agricultural soil, Deep A horizon Oxisols- soil of tropical and subtropical rainforest layer of iron and Al oxides in B horizon, little O horizon Alfisols- weathered forest soil, not deep, but developed OAE+B typical of most temperate forest biome. Need fertilizer for agriculture Aridsols- dry lands + desert, lack of vegetation, lack of rain  unstructured vertically, irrigation leads to salinization b/c of high evaporation.

14. Physical Properties of Soil • Porosity: how quickly the soil drains (which depends on its texture)

15. Physical Properties of Soil Texture: the percentage of sand, silt and clay the soil contains.

16. Loamis theoretically the ideal soil40% sand 40% silt 20% clay Color in the blank pyramid Mr. Sierra provided in class as closely to this diagram as possible. Page 280

17. Chemical Properties of Soil Soil bases-calcium, magnesium, potassium and sodium Soil acids-sulfur, aluminum and hydrogen Essential Nutrients (tested by farmers): itrogen: Nitrogen is a key element in plant growth. It is found in all plant cells, in plant proteins and hormones, and in chlorophyll. hosphorous: Phosphorus helps transfer energy from sunlight to plants, stimulates early root and plant growth, and hastens maturity. = Potassium:Potassium increases vigour and disease resistance of plants, helps form and move starches, sugars and oils in plants, and can improve fruit quality. N P K

18. Biological Properties of Soil Many organisms are found in the soil including fungi, bacteria, protozoans, rodents and earthworms. Examples on following pages… 18

19. Microbes in Topsoil Bacteria • A single teaspoon of topsoil can contain 100,000 to 1 million bacteria! • Rhizobia is quite common; it aids in a plant's uptake of nitrogen, and is particularly helpful for vegetable and legume plants. • Bacteria are helpful in many other areas, such as decomposing soil materials, improving soil structure and degrading any topsoil pollutants. Microbes in Topsoil | eHowhttp://www.ehow.com/list_5979001_microbes-topsoil.html#ixzz2W1KxByvs

20. Microbes in Topsoil Fungi • Fungi can be either beneficial or harmful in soil. • The number of fungi in 1g of soil can range from 100,000 to 1 million.

21. Fantastic Fungithis is a YouTube video but may take a while to load/play This is the first in a collaboration of Louie Schwartzberg of Blacklight films ( http://bit.ly/FantasticFungi ) and Paul Stamets of Fungi Perfecti ( http://fungi.net )

22. Microbes in Topsoil Protozoa • Protozoa are larger than bacteria, and feed on fungi, bacteria and other protozoa. • The three types of protozoa are ciliates, amoebae and flagellates. • Protozoa thrive in moisture, and tend to live near plant roots. They are responsible for increasing soil nutrients and regulating the number of bacteria in soil.

23. Acts & Laws Public Policy for Soil If we have time, we’ll break these into groups to research and present to the class… Low Input sustainable Agriculture (LISA) -started by US Defense of Agriculture in 1988 Conservation Reserve Program- 1985 Food Security Act of 1985 Federal Agriculture Improvement and Reform (FAIR) 1996 Environmental Quality Incentive Program (EQUIP) *Agriculture & Farming Research Initiative (AFRI)