Understanding soil texture and structure
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Understanding Soil Texture and Structure. Understanding Soil Texture and Structure. Objectives: Describe the concept of soil texture and its importance ; Determine the texture of a soil sample ; Describe soil structure, its formation, and importance ; and

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Understanding Soil Texture and Structure

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Understanding soil texture and structure

Understanding Soil Texture and Structure


Understanding soil texture and structure1

Understanding Soil Texture and Structure

Objectives:

Describe the concept of soil texture and its importance;

Determine the texture of a soil sample;

Describe soil structure, its formation, and importance; and

Identify various soil structures.


Soil texture

Soil Texture

  • Soil Texture:

    • Fineness or coarseness of a soil

  • What are the three soil particles?

    • Sand

    • Silt

    • Clay


  • Soil texture1

    Soil Texture

    • Why is soil texture important?

      • It affects

        • Water-holding Capacity

        • Permeability

        • Soil Workability

        • Ability of plants to grow


    Determine soil texture

    Determine Soil Texture

    • What would you do to determine the texture of a soil sample?

      • You can feel it


    Determine the texture

    Determine the Texture

    • Can be tested in a lab

      • The lab results will be in the form of percentages of the three soil particles.

    • So let’s say we had:

      • 40% sand

      • 10% clay

      • 50 % silt

        • How would this sample feel?


    Determine the texture1

    Determine the Texture

    • What do you do with those percentages?

      • 40% sand

      • 10% clay

      • 50 % silt

    • Use the Textural Triangle to determine the textural class


    Understanding soil texture and structure

    Sand: 20%

    Silt:30%

    Clay: 50%

    Sand: 40%

    Silt:45%

    Clay: 15%

    Sand: 17%

    Silt:44%

    Clay: 39%


    Determine the texture2

    Determine the Texture

    • What if you can’t send it to a lab?

    • What would you do?

    • The Ribbon Test

      • You can find 5 texture classes in the field with this method

        • Fine-textured

        • Moderately fine-textured

        • Medium textured

        • Moderately coarse-textured

        • Coarse textured


    Activity the ribbon test

    Activity – The Ribbon Test

    Watch the video


    Activity the ribbon test1

    Activity – The Ribbon Test

    • You need:

      • Soil

      • Water

    • Now roll your sleeves up

    • Put a small amount of your soil in your hand

    • Moisten it

    • Squeeze

    • Does it stay together?

    • Roll it into a ball

    • Will it stay in a ball?

    • Form a ribbon

    • Will it?

    • How long before it breaks?

    • What soil texture do you have?


    Soil structure function importance

    Soil Structure, Function, Importance

    • What is Soil Structure?

      • Arrangement of soil particles into aggregates. (clusters)

      • Many different sizes and shapes

    • Peds

      • Naturally occurring aggregates

    • Clods

      • Aggregates formed by tilling


    Soil structure function importance1

    Soil Structure, Function, Importance

    • Two waysto form soil structure

      • Clumps of soil particles stick together

        • Plant roots surround soil and break up clumps

        • Freezing and thawing of soil

        • Soil gets wet and then dries out

        • Soil is tilled

        • Fungal activity

      • Weak aggregates are cemented together making them distinct and strong.

        • Clay, iron oxides, and organic matter act as cement

        • Also gums produced by microorganisms


    Why is soil structure important

    Why is Soil Structure Important?

    • Soil structure:

      • Affects tilth

      • Affects permeability

      • Determines whether it resists beating action of raindrops or not

        • Minimizes formation of crusts


    Identify soil structures

    Identify Soil Structures

    • Eight of them

    • Granular

      • Aggregates are small, non-porous, and strongly held together

    • Crumb

      • Aggregates are small, porous and weakly held together


    Identify soil structures1

    Identify Soil Structures

    • Platy

      • Aggregates are flat, plates overlap causing slow permeability

    • Prismatic/Columnar

      • Aggregates are prism-like with the vertical axis greater than the horizontal;

      • Prismatic – flat caps

      • Columnar – rounded caps


    Identify soil structures2

    Identify Soil Structures

    • Blocky

      • Aggregates are block-like, with six or more sides; all three dimensions are about the same

    • Structureless

      • No apparent structure – 2 forms

      • Single grain

        • Soil particles are individual and do not form aggregates

      • Massive

        • Soil particles cling together in large uniform masses


    Soil structure affect on water

    Soil Structure affect on water


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