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Soil Quality Measurement

Unit: Soil Science Lesson 7

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Objectives

  • Define: soil quality, soil series, erosion
  • Describe two methods to assess soil quality
  • Create a model that represents signs of erosion
  • List and describe causes of erosion
  • Explain the role of soil management in determining soil quality
  • Determine percent slope of a specific land area
  • Explain how climate impacts soil
  • Explain how longitude and latitude impact soil
  • Identify environmentally sensitive areas
  • Determine when to properly sample soil
  • Determine where to sample soil
  • Explain the guidelines for selecting sampling sites
  • Explain the need for collecting multiple samples
  • Use the Nebraska Soil Quality Card

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Soil Quality

  • Soil Quality integrates the physical, chemical, and biological components of soil and their interactions.
  • There are two fundamental ways to assess soil quality:
    • Take measurements periodically over time to monitor changes or trends in soil quality
    • Compare measured values to a standard or reference soil condition.

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Field or Site Characterization

  • Soil series:
    • name of soil
    • found in the county soil survey.
  • Signs of erosion include
    • Gullies and rills
    • development of pedestals
    • exposed areas of subsoil
    • wind damage or plants
  • Management history includes
    • description of past and present land and crop management
    • kind, amount and method of fertilization
    • prior tillage
    • land leveling.

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Field or Site Characterization

  • Slope and topography includes
    • percent slope at sampling sites
    • note any hills, knolls, ridges, potholes, depressions, etc.
  • Location of field includes a record of
    • longitude and latitude
  • Climatic information includes
    • precipitation and high and low average temperatures for each month
  • Location of environmentally sensitive areas includes location
    • Ponds and creeks
    • Wetlands
    • other environmentally fragile sites.

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Erosion

  • Soil erosion involves the breakdown, detachment, transport, and redistribution of soil particles by forces of water, wind, or gravity.

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Type of Erosion

Causes

Picture or Example

Water Erosion

  • Lack of protection against raindrop impact,
  • Decreased aggregate stability,
  • Long and steep slopes,
  • Intense rainfall or irrigation events when plant or residue cover is at a minimum,
  • Decreased infiltration by compaction or other means

 

Mechanical Erosion

  • Removal by harvest of root crops,
  • Tillage and cultivation practices that move soil downslope.

 

Wind Erosion

  • Exposed surface soil during critical periods of the year,
  • Occurrence of wind velocities that are sufficient to lift individual soil particles,
  • Long, unsheltered, smooth soil surfaces

 

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Slope

  • Slope is the steepness of the land usually measure in a percentage.

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Soil Sampling

  • When to sample?
    • Annual sampling of a field is recommended
    • Sample when the climate is most stable and there have been no recent disturbances such as after harvest or the end of the growing season
  • Where to sample?
    • Consider rows, soil type, management, plant growth, salt affected areas, erosion, slope, and drainage
    • Select sample sites that are representative of the field
    • For trouble spot assessment, select areas that are representative to trouble spots
    • When comparing management systems make sure sites selected for comparison have the same soil type
    • When making changes to soil make sure samples are taken after each change
  • How many samples?
    • Sample number will depend on the variability of the field
    • Take a minimum of three samples on any one soil type

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