Bellwork Sand, Silt and Clay are the three components of soil. Describe each in your own words.

Today’s Objectives Identify components of soil and how their proportions affect soil texture. Describe the concept of soil texture and its importance. Identify various soil structures.

Definition of Soil Texture Soil texture is the fineness or coarseness of a soil. It describes the proportion of three sizes of soil particles. These are: Sand—large particle Silt—medium-sized particle Clay—small particle

Importance of Soil Texture Texture is important because it affects: Water-holding capacity—the ability of a soil to retain water for use by plants Permeability—the ease with which air and water may pass through the soil Soil workability—the ease with which soil may be tilled and the timing of working the soil after a rain Ability of plants to grow—some root crops like carrots and onions will have difficulty growing in a fine-textured soil How will various proportions of each component affect these? -High Clay? -High Sand?

Bell Work Draw the three soil particles proportional to their size

Determining Soil Texture Soil texture may be determined in one of two ways: 1. The percentages of sand, silt, and clay may be tested in the lab. Once tested, you may determine the textural class of the soil by referring to the textural triangle. There are 12 basic textural classes. 2. The relative amounts of sand, silt, and clay may also be determined in the field using the ribbon method. Five textural classes may be determined using the ribbon method. We will be doing a lab using the ribbon method

Soil Triangle COME BACK TO AT THE END OF THE PERIOD IF TIME Walk through various examples on Smart Board: -40% Sand, 22% Clay, 38% Silt (Medium Loam) -60% Silt, 15% Sand, 25% Clay (Silty Loam) -45% Clay, 45% Sand, 10% Silt (Sandy Clay)

Soil Structure Granular—aggregates are small, non-porous, and strongly held together. Crumb—aggregates are small, porous, and weakly held together. Platy—aggregates are flat or plate-like. Plates overlap, usually causing slow permeability. Structure is how Sand, Silt and Clay stick together in the soil – dependent on many factors

Soil Structure Prismatic or Columnar—aggregates are prism-like with the vertical axis greater than the horizontal. Prismatic has flat caps while columnar has rounded caps. Blocky—aggregates are block-like, with six or more sides. All three dimensions are about the same.

Soil Structure Structureless—there is no apparent structure. It may be found in one of two forms: Single grain—soil particles exist as individuals and do not form aggregates. Massive—soil particles cling together in large uniform masses.

Examples of Soil Structure

Soil Texture Lab