Soil Science Concepts and Techniques

Posted on Apr 6, 2025 in Geology

6) Eluviation/Illuviation Process

Luvisols vs. Podzols

Eluviation is the leaching or removal/transport of suspended or dissolved soil components to underlying horizons. This includes:

  • Degradation (removal of soluble salts)
  • Illimerization (removal of clay)
  • Podzolization (removal of Fe and Al oxides and organic substances, leading to E horizon formation)

Illuviation is the accumulation of substances removed from the overlaying horizon (eluviation), leading to the formation of argic/spodic/natric horizons.

Provide schematic drawings of Luvisol and Podzol soil profiles and define their basic characteristics.

7) Occurrence of Fluvisols

Fluvisols are young soils with weak horizon differentiation, mostly AC-profiles. They are predominantly brown (aerated soils) and/or grey (waterlogged soils).

12) Interpolation Methods

Various interpolation methods exist, including:

  • Linear interpolation
  • Polynomial interpolation
  • Spline interpolation
  • Interpolation via Gaussian processes
  • Triangulation
  • Natural neighbor/Nearest-neighbor
  • Inverse distance weighting/Moving average
  • Kriging/Geostatistical models

Weighted Average and Inverse Distance Weighting: Provide explanations.

13) Variogram and its Parameters

A variogram depicts the dependence of semivariance g(h) on the lag h.

N(h) represents the number of pairs of values separated by distance h, and z(xi) represents the values of variable z in xi.

Variogram Parameters:

  • Sill (c): Maximum semivariance (where the variogram levels off)
  • Range (a): Lag distance at which the variogram reaches the sill value (distance to which spatial dependence exists; autocorrelation is essentially zero beyond the range)
  • Nugget: Theoretically, the semivariance at the origin (0 lag) should be zero. Explain the significance of the nugget.

Include a schematic drawing of a variogram with labeled axes.

15) Remote Sensing Multi-Concepts

Remote sensing (RS) involves deriving information about Earth’s land and water areas from images (or point/line samples) obtained at a distance. It measures electromagnetic energy reflected or emitted from objects of interest. Resulting images reflect the physical characteristics of spatially distributed objects.

18) Soil Reflectance Influencers

Soil Texture: Reflectance decreases with increasing particle size.

Roughness: Buildings (man-made targets) with varying shapes, orientations, and construction elements exhibit high reflection and bright tones (corner effect). Explain how soil surface roughness influences reflectance.

21) Soil Survey: Direct Field Assessments

Soil surveys involve assessing soil cover for practical purposes (e.g., FAO land evaluation). They translate complex soil science characteristics into understandable forms for practical use and assess soil characteristics and qualities of soil units for various land uses. Fast reevaluation of soil map units is necessary due to:

  • Technical progress
  • New economic conditions
  • Changes in land use

22) Soil Survey: Laboratory Measurements

Laboratory measurements in soil surveys include:

  • Soil hydraulic properties
  • Soil thermal properties
  • Properties characterizing dissolved substance transport in soils

23) Geophysical Methods in Soil Survey

Geophysical methods used in soil surveys include:

  • Resistivity imaging and mapping
  • Magnetic mapping
  • Magnetic susceptibility mapping (measures how much a material becomes magnetized in an applied magnetic field)
  • Magnetic resonance imaging
  • Reflection seismology imaging
  • Ground penetrating radar

Explain the principles of one method in greater detail.