Title: Unit C1
1Unit C1
- Basic Principles of Agricultural/Horticultural
Science
2Understanding Soil Texture and Structure
3Bell Work
- How would you describe soil texture?
- Why is soil texture so important to Agriculture?
- What texture soil do you have around your house?
4Next Generation Science/Common Core Standards
Addressed!
- CCSS.ELA-Literacy.RST.9-10.4 - Determine the
meaning of symbols, key terms, and other
domain-specific words and phrases as they are
used in a specific scientific or technical
context relevant to grades 910 texts and topics. - CCSS.ELA-Literacy.RST.9-10.5 - Analyze the
structure of the relationships among concepts in
a text, including relationships among key terms
(e.g., force, friction, reaction force, energy). - CCSS.ELA-Literacy.RST.9-10.6 - Analyze the
authors purpose in providing an explanation,
describing a procedure, or discussing an
experiment in a text, defining the question the
author seeks to address.
5Interest Approach
- Provide students with various samples of soil.
- One sample should be nearly all sand
- One nearly all clay
- One nearly all silt.
- Ask students to determine how the samples differ.
- Would each sample be equally productive?
- Indicate that the samples vary according to the
size of soil particles. - Ask students how particle size might affect
various soil properties.
6Learning Objectives
- Describe the concept of soil texture and its
importance. - Determine the texture of a soil sample.
- Describe soil structure, its formation, and
importance. - Identify various soil structures.
7Important Terms
- Clods
- Loam
- Peds
- Permeability
- Soil structure
- Soil texture
- Soil workability
- Textural triangle
- Water-holding capacity
8What is soil texture and why is it important?
- 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
9Texture 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.
10Texture is important because it affects
- 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
11- The Relative Sizes of Sand, Silt and Clay
Particles
12How is the texture of soil determined?
- Soil texture may be determined in one of two
ways - 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. - The ribbon method.
13Ribboning Soil
14Textural Triangle 12 basic textural classes
- Silt
- Silt loam
- Silty clay loam
- Loam
- Sandy clay loam
- Loamy sand
- Sand
- Sandy loam
- Sandy clay
- Clay loam
- Silty clay
- Clay
15(No Transcript)
16The Ribbon Method.
- Fine-textured a ribbon forms easily and remains
long and flexible. - Moderately fine-textured a ribbon forms but
breaks into pieces ¾ to 1 inch long. - Medium-textured no ribbon forms.
- The sample breaks into pieces less than ¾ inch
long. The soil feels smooth and talc-like.
17The Ribbon Method.
- Moderately coarse-textured no ribbon forms.
- The sample feels gritty and lacks smoothness.
- Coarse-textured no ribbon forms.
- The sample is composed almost entirely of gritty
material and leaves little or no stain.
18What is soil structure, how does it form, and why
is it important?
- Soil structure is the arrangement of the soil
particles into clusters or aggregates of various
sizes and shapes. - Aggregates that occur naturally in the soil are
referred to as peds, while clumps of soil caused
by tillage are called clods.
19What is soil structure, how does it form, and why
is it important
- Structure is formed in two steps.
- 1. A clump of soil particles sticks loosely
together. These are created through - Plant roots surrounding the soil and separating
clumps - Freezing and thawing of soil
- Soil becomes wet and then dries
- The soil is tilled
- Fungal activity
20What is soil structure, how does it form, and why
is it important
- 2. Weak aggregates are cemented to make them
distinct and strong. - Clay, iron oxides, and organic matter may act as
cements. - When soil microorganisms break down plant
residues, they produce gums that also glue peds
together.
21What is soil structure, how does it form, and why
is it important
- Soil structure is important for several reasons
- It improves soil tilth.
- It improves permeability.
- It resists the beating action of raindrops,
minimizing the formation of crusts that reduce
crop stands.
22What are the various soil structures and what do
they look like?
- There are eight primary types of structure. They
are - Granular
- Crumb
- Platy
- Prismatic or Columnar
- Blocky
- Structureless
- 1. Single grain
- 2. Massive
23(No Transcript)
24Review / Summary
- Describe the concept of soil texture and its
importance. - Determine the texture of a soil sample.
- Describe soil structure, its formation, and
importance. - Identify various soil structures.