Soil

1. Soil APES

2. 6 Major components of soil • Eroded rock • Mineral nutrients • Decaying organic matter • Water • Air • Living organisms

3. Importance of Soil • Provides nutrients • Recycles/filters water • Stores water • Soil is the basis of life on Earth…why do you think? • Plants get nutrients from soil and plants provided glucose and oxygen (producers)

4. Terms associated with creation of soil • Infiltration • Downward movement of water through the soil • Leaching • Dissolving of minerals and organic matter in upper layers carrying them to lower layers ***soil type determines degree of leaching and infiltration

5. Formation of Soil (clay + mix of dead vegetation) • Physical weathering • Mechanical weathering • Any process that breaks down rock into smaller pieces without changing chemistry of rock • Wind and water • Chemical Weathering • Result of chemical interactions between water and atmospheric gases and the bedrock of the region • Oxidation: reaction with O2 • Hydrolysis: rxn with H2O • Acid action: Rxn with acids (H2CO3, H2CO4, H2SO3) • Dissoultion: chemical weathering from acid rain • Biological weathering • Takes place as a result of activities of living organisms • Can be combined with chemical processes • Chemosynthesis of bacteria • Roots of trees creating fissures in rocks exposing them to further mechanical and chemical weathering

6. Soil • 1 gram of soil has over 50,000 protozoa as well as bacteria, algae, fungi, earthworms and nematodes • Pores between grains of minerals in soil are filled with air or water • Plants need water and oxygen • Need to make glucose-use photosynthesis and cell respiration • Size of the particles that make up the soil determine the size of the pores between the soil particles • USDA has many ways to categorize • Color • Texture

8. Soil Horizons • O horizon (surface litter) • Uppermost\organic matter (leaves, twigs, crop waste, animal waste, organic matter) • Dark, crumbly material that results from decomposition of organic matter • Brown or black • A Horizon (Topsoil layer) • Porous mix of HUMUS and some inorganic particles (weathered rock) • LEACHING/ELUVIATION zone • Fertile soil=better crops • Holds water and nutrients for plants *** O and A are anchored by vegetation • B Horizon (subsoil) • Composed of inorganic minerals • Broke down rock (clay, silt, sand/gravel) • Receives all minerals leached out of A horizon as well as organic material that is washed down from the topsoil above • ILLUVIATION/ACCUMULATION zone • accumulation of soluble or suspended organic material, clay, iron, or aluminum • C Horizon (parent material) • Large pieces of rock that have not undergone much weathering • R Horizon • Bedrock

10. Soil Textures-3 major divisions • Clay • Smallest, very fine • Less than 0.002mm in diameter • Easily stick to each other • Little room between particles to store water • Extremely compact, feels sticky • Silt • 0.002-0.05 mm in diameter • Feels smooth • Holds water well • Resists filtration • Sand • 0.05-2.0 mm in diameter • Coarsest particle • Too large to stick together • Creates soil with large pores • Water filter through • (Gravel) • 2.0 mm and larger • Does not hold water well

11. Acidity and Alkalinity of Soil • What is pH? • Most soils pH= 4-8 (neutral to slightly acidic) • pH affects solubility of nutrients • Determines nutrient availability for absorption by roots of plants • If soil in a region is too acidic or basic, certain soil nutrients in that region will not be able to be taken up by plants • pH too acidic=BIG problems • Ions of heavy metals mercury (Hg) or aluminum (Al) can leach into the groundwater • These ions will then travel to streams and rivers=negative impact to plants and aquatic life • Ex. Aluminum ions can damage fish gills=suffocation of fish

12. Loamy • Soil composed of roughly the same amount of all three textures (clay, silt, sand) and organic matter • Loose and rich • When you squeeze it, forms a ball that crumbles when poked • Good at absorbing and storing water • Best for plant growth

13. Soil Types- Based on Water content • Pedocal • Dry, semi arid climate • Little organic matter • No mineral leaching • High limestone content • praries • Pedalfer • Enriched with aluminum and iron • Greater organic matter and leaching • Found in areas with high temp. and lots of forest cover • Laterite • Soggiest type • Tropical and subtropical climate zones • High organic matter • Low nutrients (lots of rain) • Aluminum hydroxide=red soil

17. Soil Porosity • Measure of the volume of pores or air spaces per volume of soil AND average distance between those spaces • Fine particles help retain water (precipitation goes into pores) • Large particles help create air spaces for filtration • Pores b/t organic solid particles and inorganic solid particles in upper and lower layers • Contain varying amounts of air (N and O) and water • Porous soil • Many pores • Can hold more water • Non porous soil • Not a lot of spaces • Cannot hold much water

19. Soil Permeability • Rate at which water and air move through the soil • Sand • High permeability • Water moves through quickly • Filters water • Clay • Low permeability • Water moves through slowly • Retain water

20. Topography • Mapping of the land by contours and physical features of areas • Since water runs downhill, it is easy for soil to be carried away during a heavy rainstorm • Slope percentage affects the speed of the water’s down hill path • Ex. 5% grade= more erosion than 1% grade

21. Soil Formation is influenced by 5 interrelated factors

22. How Soil is Formed

23. Soil Problems For and Caused By Humans • Properties humans look for in soil • Top soil • Nutrient rich soil layer, millimeters to meters deep • Contains a mix of organic matter and minerals • Renewable when replenished and cared for properly • Currently, thousands of acres bare due to erosion, nutrient deficiency, overtillage, and misuse • Arable: soil suitable/fertile for plant growth… • Fertility refers to soils ability to provide essential nutrients: N, K, and P • Humus also important b/c its rich in organic matter • Loamy soil • Composed of same amount of clay, silt, sand • Ability to aggregate (clump) • Best soils are aggregates of different soil types bound together by organic matter

24. Tillage • Repeated plowing • Breaks down soil aggregates leaving “plow pan” or “hard pan” (hard, unfertile soil) • Opening up Earth to plant new seeds • Increases soil erosion • It is done b/c it is thought to increase soil nutrients • Today, narrow chisel plows are used that leave 75% of crop residue on surface and open up only a thin ridge for seeds • No-till methods are beneficial • Pierce seeds through ground cover without opening up a seam in the earth • Keeps soil in place and prevents erosion

25. Monoculture • Planting of just one type of crop in large area • Decrease in genetic diversity of crop species • Lack of genetic variation=increased susceptibility to pests and diseases • Consistent planting of one plant in area LEACHES soil of specific nutrients needed for plant growth • Prevention Method: CROP ROTATION • Different crops are planted in growing area in each growing season • Machinery • Large machines • Agriculture industry is a huge consumer of energy • Energy is consumed by: • Production of pesticides • Production of Fertilizers • Use of fossil fuels to power farm machinery

26. Green Revolution=boom in agricultural productivity • Industrial revolution  mechanization of farming  increase world wide agricultural productivity in last 50 years of =detrimental to environment • Drawbacks • Increase in irrigation = Over irrigated soils= SALINIZATION • Soil becomes water logged and when it dries out, salt forms a layer on the surface, which leads to land-degradation • Dripirrigation is one way scientists have started combating problem • Allots area only necessary amounts of water • Water delivered straight to roots • Chemical pesticides=new insect species that are pesticide-resistant • Recently GM plants are helping solve pesticide problem

27. Soil Erosion • Bare soil=soil in which no plants are growing • More susceptible to erosion than soil covered by organic matter • Erosion: normal and natural process • Constant movement of wind and water on Earth’s surface • Drawbacks: • Removes valuable top soil • Over 25 billion tons of soil lost due to wind and water erosion • Erosion can lead to DESERTIFICATION • Deposits soil in undesirable places (i.e. bodies of water) • Farmers need healthy soil for planting • Humans rely on water uncontaminated water for drinking/living • Soil can contaminate water with pesticides and other harmful chemical • Causes • Deforestation • logging and slash-and-burn • Plants anchor in O and A horizons of soil • Removal of plants make soil susceptible to erosion • Over-cultivation of agricultural fields • Overgrazing • Urbanization ***All of these will continue to make ARABLE land for farmers hard to find ***New techniques must be utilized to preserve the integrity of the soil

29. Effects of Erosion • Top soil blown away by wind or washed away by rainfall • Weakened land Leads to… • Downstream flooding • Reduced water quality • Increased river and lake sedimentation • Build up of silt in reservoirs and navigation channels • Dust storms • Air pollution • Health issues • Allergies • Eye infections • Upper respiratory problems

30. Soil Conservation • Several management practices utilized to conserve soil resources • Return organic matter to soil • Slow down effects of wind • Reduce amount of damage done to soil by tillage (plowing) • Examples: • Use animal waste and the residue of plants to increase the amount of organic material in soil • Modify tillage practices to reduce the breakup of soil and reduce the amount of erosion (contour plowing and strip planting) • Use trees and other wind barriers to reduce forces of winds

31. Soil conservation • Contour planting • Plant across a hillside (instead of up and down), slows run off • Strip farming • Planting alternating crops in strips across land • In combination with contour planting, this slows erosion • Terracing • Similar to strip farming • Land is shaped…level ridges of land are created to hold water and soil in place • More expensive and time consuming but allows cultivation on steep grades and increases sustainability (this is how rice is grown in Asia) • Perennial plant growing • Coffee and tea • Plants that grow during several seasons • Do not have to harvested yearly AND hold soil longer • Ground cover plants (alfalfa) hold and protect soil from erosion if planted right after initial harvest

32. Soil Laws • 1977 Soil and Water Conservation Act • Soil and water conservation programs to aid landowners and users • Sets up conditions to continue evaluating the condition of the US soil, water and related resources • 1984 Food Security Act “Swampbuster” Act • Discouraged conversion of wetlands to non-wetlands • 1990 federal legislation denied federal farm supplements to those who converted wetlands to agriculture • Provided restoration of benefits to those who unknowingly converted lands to wetlands