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Why is soil important?
• Media for plant growth• Regulator of Water Supplies• Recycler of Raw Materials• Modifier of the Atmosphere• Habitat for Soil Organisms• Engineering Medium
“Ecstatic skin of the earth”- William Bryant Logan
“Whether we intend to modify, exploit, preserve, or simply understand the landscape, our success will depend on our knowing how soil properties relate to the environment on each site and to the landscape as a whole” – N. Brady and R. Weil
What is soil?3-phase Ecosystem Comprised of Solids, Liquids, and Gases
Solids: Mineral and Organic
Organic – Biomass (10%), Residues and by-products (15%), and humus (75%)- 2-5% by weight- Influences soil productivity, water
retention, nutrient holding
Mineral - Delineated by particle size.• The three sizes that determine soil texture
are Sand, Silt, and Clay.
Soil Texture: Sand, Silt, ClayHow do we figure this out? Aka Particle Size Analysis
Laboratory Methods:• Sieving • Particle counting• Sedimentation: with hydrometer, and
pipette methods
In the Field:• Texture by feel
OR
Soil Textural Triangle
Pore space: Macropores and MicroporesBasic cross-section of approximately 20 mm wide of soil as a porous, biologically active mineral-organic matrix. Red arrows show non-living components while purple arrows show biological components. Large macroporesresulting from good soil structure allow adequate drainage and air entry to a soil for biological activity, while smaller mesoporesand micropores hold water at varying degree of availability for plant roots. Macrofauna such as earthworms (;2mm approximate dimension) are also very important but would occupy too much of the diagram to show.Credit: Steven Vanek, adapted from Steven Fonte.
Soil Solution vs. Water
Air in Pores
Where does soil come from?
5 Soil Forming Factors• Parent Material (in MD… Fall Line)• Climate (Precip., temperatures)
• Landscape position (slope and aspect)• Organisms (Channels, Organic Matter)
• Time
“PLOCT”
Drainage Catena
Slide by Chris Seubert, PhD
Where does soil come from?
4 Soil Forming Processes• Additions• Losses• Transformations• Translocations
Soil Horizons
• Soils are 3-D• Can be broken into
horizons by depth• Color, structure,
chemical differences
Copyright NC state Flicker https://www.warrenswcd.com/education-connection-a-blog/archives/12-2016
• Tilth: The state of aggregation of a soil especially in relation to its suitability for crop growth.
• Friable: Easily broken into smaller pieces.
Slide by Chris Seubert, PhD
Soil Structure: The formation and grouping of the soil particles into aggregates.
Aggregate stability or structure, is easily destroyed, but not easily improved.
Function of texture, organic matter and cultural practices
Improved by organic matter, plant root growth, microorganisms and earth worms.
Destroyed by frequent tillage, tilling when wet, compaction.
Slide by Chris Seubert, PhD
Drainage• Function of structure, texture
and natural water table• Improve with raised beds,
artificial drainage, or create a mini-wetland.
Color• Black soils are high in organic
matter.• Gray soils indicate poor
drainage• Red and yellow soils contain
iron
Slide by Chris Seubert, PhD
A wall of dust approaches a Kansas town in 1935 U.S. Public Health Service Reprint # 1707 , Public Health Reports vol. 50, no. 40, 10/4/1935
Slide by Chris Seubert, PhD
Effects of Dust Bowl: Dallas, South Dakota, May 13, 1936.Soil Conservation Service RG 114
Slide by Chris Seubert, PhD
Urban Soils – “Urbents” anthropic soil• What is special about Urban
Soil?• Fill – where does it come
from what is it?• High human activity –
compaction, contamination• Paved over
Hydrologic/water cycle in Soil
Nitrogen Cycle
Phosphorous Cycle
Bound to Iron Oxides -unavailable
Soil pH and nutrient availability
Liming – Raises soil pH
Kansas State Extension
CEC – Cation Exchange Capacity
http://bio1152.nicerweb.com/Locked/media/ch37/37_06SoilToRootHair.jpg
http://blog.botanicare.com/selectivity-of-plant-nutrient-ion-uptake/
CEC- measured in cmol/kg
Resources
extension.umd.edu/hgic extension.umd.edu/learn/ask-gardening marylandgrows.umd.edu
extension.umd.edu/mg
This program was brought to you by University of Maryland Extension
Master Gardener ProgramBaltimore City
