Physical Properties of Soil

1. Physical Properties of Soil Topic 2052 Developed by Amanda R. Moore

2. Overview • Soil Composition • Parent Material • Physical Properties

3. Soil Composition • Mineral and Organic Matter • Soil Organisms • increase soil productivity because of decomposition of organic matter by the organisms • Water and Air

4. Parent Material • Definition: The un-weathered material from which a soil is formed • “The stuff you start with!”

5. Parent MaterialHow does it affect the soil? • Soils resemble their parent material • Parent material can influence soil texture, mineral composition and layering • Has an indirect affect on natural vegetation • What grows depends on chemical and mineral composition of soil • The degree of layering of a soil can influence the properties and uses of a soil

6. Soils originating from different parent materials http://ltpwww.gsfc.nasa.gov/globe/index.htm Bolivia Florida Michigan

7. Physical Properties of Soil • Texture • Structure • Consistence • Porosity • Density • Color • Temperature

8. Texture • Definition: The relative proportion of sand, silt and clay(different size particles) found in soil • “The fineness or coarseness of soil” • 3 Separates • Sand • Silt • Clay

9. TextureSoil SeparatesSand • Ranges from very coarse(2.00mm) to very fine(0.05mm) • Has a gritty feeling, does not stick together • The presence of sand increases size of space between particles • Facilitates movement of air and water

10. TextureSoil SeparatesSilt • Very smooth and flour-like • Particle sizes between 0.05mm & 0.002 mm • Forms clods that crumble easily when wet • Water soaks in and moisture holds well • Soils with the larges water holding capacity for plant growth are high in silt

11. TextureSoil SeparatesClay • Particles are very fine – 0.002mm and smaller • Appear “platey”, fit very close together • Stick together, difficult to break when dry • Amount of clay in soil has a great influence on water-holding capacity • Are negatively charged and attract plant nutrients

12. Soil Structures http://ltpwww.gsfc.nasa.gov/globe/index.htm Blocky Granular Platy

13. Structure • Definition: Arrangement of primary soil particles into secondary particles • Influences soil by increasing the average size of pores in the soil • Structure is not permanent • Platy, prismatic, columnar, blocky, crumbly, granular and structureless

14. Soil Consistence • Definition: The resistance of soil to deformation or rupture. • Deals with the strength and nature of the forces between soil particles • Basically, “how well does it stick together?”

15. Pore Space/Porosity • Pore space is the volume or amount of space within a soil that is not occupied by particles of mineral and/or organic matter • Texture, structure and compaction affect amount of pore space

16. Density • The specific gravity of soil particles is 2.6g/cm3 This is the particle density of soil particles • A soil that has no spaces between the particles would weigh 2.6 g/cm3 (160lbs/ft3) • Particle density is the average density of the soil particles.

17. Density • Bulk density is the weight of soil/unit volume of soil, including pore space. • As bulk density increases, the amount of pore space decreases • The maximum bulk density would equal particle density • Low bulk density=loose soil • High bulk density=compaction

18. Color • An indirect measure of other important characteristics • Water drainage • Aeration • Organic matter content • Colors are determined by matching the color of sample with color chips in a soil-color book

19. Temperature • Affects nutrient and water movement • Chemical processes are temperature dependant • Cold soil temperature can inhibit elongation of roots • Alternate freezing and thawing affects structure formation