Measuring Soil Variability

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Measuring Soil Variability
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How does soil variability effect yield?

• Primary effects
• Fertility
• Water
• Typically these two factors limit the genetic
  yield potential
• Many SS practices have concentrated on fertility
  management

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Soil Variability

• Fertility
• NPK
• Secondary Nutrients
• Calcium
• Magnesium
• Sulfur
• Micronutrients
• Boron, Copper, Iron, Manganese, Zinc, Molybdenum

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Soil Variability (cont.)

• Soil Chemistry
• Salinity
• Infiltration rates
• Cation Exchange Capacity (CEC)
• Water Holding Capacity http//www.bsyse.wsu.edu/sa
  xton/soilwater/soilwater.htm
• Organic Matter
• Slope and Topography

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Soil Properties

• Physical Properties
• Compaction
• Texture (sand and clay content)
• Anchorage

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Sampling Methods

• Grid sampling
• Selected or Directed
• Continuous Sensing

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Grid Sampling

• Field is divided in to a uniform grids
• Grid shapes may vary Ex Square, Offset square,
  etc.
• Grids 2-4 acres
• Strengths
• Weakness

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Selected or Directed

• Sample location based on other data
• Yield
• Remote Sensing (imagery)
• Direct Sensing
• Strengths
• Weakness

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Continuous Sampling

• Soil variability is measured using a sensor.
• Ex. Veris, EM, OM, etc.
• Commonly used in combination with directed
  sampling
• Strengths
• Weakness

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Soil Sampling Frequency

• Consider
• Cost
• Monitoring of remediation programs
• Higher frequency in problem areas.
• 2-4 year cycle for fertility

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When to Sample

• For fertility
• Samples taken at the same time of the year will
  allow better comparison between years
• Annual vs. Perennial crops
• For physical properties
• After leveling
• ??????

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Using Soil Sample Data

• Convert from points to grids
• Interpolate points
• Each variable creates a layer (N,P,K, texture,
  etc.)
• Analysis using multiple regression techniques to
  determine which factors are important.

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Data Collection -gt Action