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Learn Soil Physics, Genesis and Classification with Rahul

Soil Water Potential (SWP)

  • Soil Water Potential (SWP) measures the energy state of soil water compared to pure, free water in a reference state (a hypothetical pool of pure water at atmospheric pressure, zero elevation, and isothermal conditions).
  • Since soil water has lower free energy than pure water, energy is required to move it from soil to the reference state, this energy is the soil water potential.

 

Components of SWP:
SWP is influenced by multiple forces, each contributing to the total potential:

  1. Gravitational Potential (Ψ₉): Due to elevation differences.
  2. Matric Potential (Ψₘ): Results from soil’s adsorption and capillary forces.
  3. Osmotic Potential (Ψₒ): Caused by dissolved solutes.
  4. Submergence Potential (Ψₛ): Pressure from overlying water in saturated soils.

 

Significance:

  • Determines water movement (flows from high to low potential).
  • Helps estimate plant water uptake effort—lower SWP means plants must expend more energy to extract water.
  • All components collectively influence soil water behaviour.
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