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

Overview Soil Composition Parent Material Physical Properties

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

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

Parent Material How 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

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

Physical Properties of Soil Texture Structure Consistence Porosity Density Color Temperature

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

Texture Soil Separates Sand 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

Texture Soil Separates Silt 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

Texture Soil Separates Clay 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

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

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

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?”

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

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.

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

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

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