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An Introduction to Soil Bryan McElvany Research Coordinator Warnell School of Forest Resources Patrick Davies.

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Presentation on theme: "An Introduction to Soil Bryan McElvany Research Coordinator Warnell School of Forest Resources Patrick Davies."— Presentation transcript:

1 An Introduction to Soil Bryan McElvany Research Coordinator Warnell School of Forest Resources Patrick Davies

2 DIRT This is the stuff under your fingernails

3 Why is soil science intimidating? Whole new vocabulary Whole new vocabulary Hard to visualize Hard to visualize Somewhat complex topics like chemistry and physics Somewhat complex topics like chemistry and physics

4 What is soil? Several different ways to define soil Several different ways to define soil 1) Geologic definition: Loose surface of the earth as distinguished from solid bedrock (support of plant life not required). 2) Traditional definition: Material which nourishes and supports growing plants (includes rocks, water, organic material, air).

5 What is soil made of? Mineral Matter Mineral Matter Organic Matter Organic Matter Air Air Water Water

6 What is the function of soil? Plant medium Plant medium Recycling system for nutrients Recycling system for nutrients Animal home Animal home Engineering medium Engineering medium System for water supply and purification System for water supply and purification

7 The ability of soil to perform those functions is dependant upon: Soil Texture Soil Texture Soil Structure Soil Structure Soil Chemistry Soil Chemistry Soil Age Soil Age Site Factors (topography, water, etc) Site Factors (topography, water, etc) Etc. Etc.

8 Soil Formation Factors There are five main factors that influence soil formation processes. There are five main factors that influence soil formation processes. 1) Type of Parent Material 2) Climate 3) Topography 4) Biotic Components 5) Time

9

10 Parent Material Two major divisions in type of parent material Two major divisions in type of parent material 1) Residual-Formed in place (Residuum) 2) Transported-Parent material was moved by: - wind (Eolian) - ice (Glacial) - gravity (Colluvial) - water:  rivers (Alluvial)  oceans (Marine)  lakes (Lacustrine)

11 Soil Formation Processes Transformations – modification of soil constituents. Mineral weathering, organic matter breakdown. Transformations – modification of soil constituents. Mineral weathering, organic matter breakdown. Translocations – movement up, down, or laterally of soil constituents. Translocations – movement up, down, or laterally of soil constituents. Additions – movement of soil material in from outside sources. Organic material from leaves, dust from atmosphere. Additions – movement of soil material in from outside sources. Organic material from leaves, dust from atmosphere. Losses – movement of soil material out of the soil. Transportation to groundwater, erosion of surface materials. Losses – movement of soil material out of the soil. Transportation to groundwater, erosion of surface materials.

12 Soil Formation Processes

13 Soil Formation in Action The soil formation processes, operating under the influence of the soil formation factors, is the driving force in soil genesis. The soil formation processes, operating under the influence of the soil formation factors, is the driving force in soil genesis. Important questions to remember are: Important questions to remember are: What transformations and translocations took place in the parent material to form this soil? What transformations and translocations took place in the parent material to form this soil? What materials were removed? What materials were removed? What was added? What was added? How did the climate and topography affect those processes over time? How did the climate and topography affect those processes over time?

14 Soil Horizons As soils develop they form layers called Horizons. As soils develop they form layers called Horizons. These horizons have distinct characteristics produced by soil forming processes. These horizons have distinct characteristics produced by soil forming processes. Master horizons include the O, A, E, B, and C horizons. Master horizons include the O, A, E, B, and C horizons. Not every soil contains every horizon based on the level of development of the soil. Not every soil contains every horizon based on the level of development of the soil. Depth of each horizon varies between different soils. Depth of each horizon varies between different soils.

15 O Horizon Layer of accumulated organic matter such as leaves, grass, twigs Layer of accumulated organic matter such as leaves, grass, twigs Material can be in various states of decomposition Material can be in various states of decomposition Generally dark in color Generally dark in color A E B C R O

16 A Horizon Zone of incorporation of organic matter into the mineral soil Zone of incorporation of organic matter into the mineral soil Generally it’s the most productive horizon Generally it’s the most productive horizon High biological activity High biological activity Generally dark in color Generally dark in color Topsoil Topsoil A E B C R O

17 E Horizon Zone of Eluviation or leaching Zone of Eluviation or leaching Eluviation is the movement of soil material out of a layer of soil Eluviation is the movement of soil material out of a layer of soil Soluble minerals and organic material move out of this horizon Soluble minerals and organic material move out of this horizon Generally a lighter “washed” appearance in color Generally a lighter “washed” appearance in color A E B C R O

18 B Horizon Zone of illuviation or deposition Zone of illuviation or deposition Accumulation of materials “washed” from horizons above Accumulation of materials “washed” from horizons above This material is commonly clay, humus, sesquioxides, or a mixture of the three This material is commonly clay, humus, sesquioxides, or a mixture of the three Variable in color from reds and yellows to browns and grays Variable in color from reds and yellows to browns and grays A E B C R O

19 C Horizon Parent material Parent material The unconsolidated material that has been affected little by the soil forming processes The unconsolidated material that has been affected little by the soil forming processes A E B C R O

20 Soil Texture Soil Texture is the relative proportion of the primary particles in the soil. Soil Texture is the relative proportion of the primary particles in the soil. Sand = 2mm – 0.05mm Sand = 2mm – 0.05mm Silt = 0.05mm – 0.002mm Silt = 0.05mm – 0.002mm Clay = < 0.002mm Clay = < 0.002mm

21 Soil Texture This proportion of sand, silt, and clay can be grouped into textural classes. This proportion of sand, silt, and clay can be grouped into textural classes. Soil texture has a great deal to do with many other soil characteristics. Soil texture has a great deal to do with many other soil characteristics.

22 Soil Texture Coarse textured soil – soil that has a higher proportion of larger particles. Sand, Loamy sand, Sandy loam. Coarse textured soil – soil that has a higher proportion of larger particles. Sand, Loamy sand, Sandy loam. Fine textured soil – soil that has a higher proportion of smaller particles. Clay, Silty clay, sandy clay. Fine textured soil – soil that has a higher proportion of smaller particles. Clay, Silty clay, sandy clay.

23 Soil Structure Soil structure is the arrangement of soil particles into aggregates. Soil structure is the arrangement of soil particles into aggregates. Structureless soils do occur as either single grained or massive. Structureless soils do occur as either single grained or massive.

24 Pore Space The voids between soil particles are called pores. These can either be filled with water or air. The voids between soil particles are called pores. These can either be filled with water or air. Soil texture plays a major role in total pore space as well as size of pores. Soil texture plays a major role in total pore space as well as size of pores. Coarse textured soils (sandy) have larger pores, but less total pore space. Coarse textured soils (sandy) have larger pores, but less total pore space. Fine textured soils (clayey) have smaller pores, but more total pore space. Fine textured soils (clayey) have smaller pores, but more total pore space.

25 Soil Permeability Permeability is a measure of how fast air and water can move through a soil. Permeability is a measure of how fast air and water can move through a soil. Soil texture and soil structure both pay a role in soil permeability. Soil texture and soil structure both pay a role in soil permeability.

26 Soil Texture and Permeability

27 Soil Structure -Permeability Granular Blocky Platy

28 Soil Water Saturated soil is when that soils pores are full of water. Saturated soil is when that soils pores are full of water. Gravitational water is that water that moves out of the soil due to gravity. This water is generally in the larger Macro-pores. Gravitational water is that water that moves out of the soil due to gravity. This water is generally in the larger Macro-pores. Capillary water is that water that is held in the soil due to adhesion and cohesion against the pull of gravity. This water is generally held in the smaller Micro-pores and as a film around soil particles. Capillary water is that water that is held in the soil due to adhesion and cohesion against the pull of gravity. This water is generally held in the smaller Micro-pores and as a film around soil particles.

29 Soil Water After a major rain event, once the gravitational water has left the soil, the soil is at Field Moisture Capacity. After a major rain event, once the gravitational water has left the soil, the soil is at Field Moisture Capacity. The wilting point is reached when soil water levels decline to the point that all remaining water is held too tightly by soil particles to be removed by the plant. The wilting point is reached when soil water levels decline to the point that all remaining water is held too tightly by soil particles to be removed by the plant.

30 Soil Water

31 Available Water Capacity Available water capacity is a measure of the water available to plants. Available water capacity is a measure of the water available to plants. Commonly defined as the difference between the amount of water at field moisture capacity and the amount at the wilting point. Commonly defined as the difference between the amount of water at field moisture capacity and the amount at the wilting point. This is the water a plant has a chance of utilizing. This is the water a plant has a chance of utilizing.

32 Available Water Capacity

33 The End Thanks


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