Course Content
Concept, scope and importance of soil physics in agriculture
0/4
Introduction
Importance of soil physics
Structure of Water
Physical Properties of Water
Soil Water Energy Concept and soil moisture characteristics curve
0/15
Introduction
Factors affecting the potential energy of water
Soil Water Potential (SWP)
Water Movement Based on Soil Moisture Levels
Gravitational Potential (yg)
Matric Potential (ym)
Osmotic Potential (yo)
Submergence Potential (ys)
Soil Moisture Content
Soil Moisture Measurement
Soil moisture characteristics curve (SMCC), moisture extraction/retention curves or Soil water potential curve
Factors Affecting Soil Moisture Characteristic Curve
Hysteresis
Quantitative Description of Soil Wetness or Classification of Soil Water
Plant Water Availability
Soil water movement under saturated and unsaturated conditions
0/7
Introduction
Poiseuille’s Law
Darcy’s Law
Saturated Water Flow in Vertical Column of Soil
Saturated Hydraulic Conductivity and  Unsaturated Water Flow in Soil
Key differences between saturated and unsaturated water flow in soil
Relationship between k and ym
Air and heat movement in soil and infiltration characteristics in soil
0/7
Water Vapor Movement in Soils
Heat movement in soil
Factors affecting soil thermal regime
Modes of thermal energy transfer
Conduction of heat in soil
Latent heat transfer (LHT)
Soil temperature management
Surface sealing, its effect on soil and crop growth and its management
0/4
Surface sealing
Soil crusting
Renewal of soil air
Impact of poor aeration
Structural management of arable soil
0/4
Introduction
Soil management
Factors involved in genesis and stability of soil aggregate
Aggregate stability
Soil profile development
0/2
Soil Profile
Horizon boundaries and horizon continuity in pedon
Surface and subsurface soil horizons
0/3
Introduction
Diagnostic surface horizons (Epipedons)
Diagnostic Subsurface Horizons
Soil moisture and temperature regimes
0/2
Soil Moisture Regime
Soil Temperature Regime
Soil classification on the basis of USDA soil taxonomy
0/8
Introduction
Soil taxonomy (USDA Soil Taxonomy)
Bases for Soil Classification in Soil Taxonomy
Major Soil orders of Nepal according to USDA taxonomy
Baldwin and Associate’s Genetic Approach
Orders of Genetic Approach
Limitations in Genetic Systems of Soil Classification
New Comprehensive System of Soil Classification (USDA Soil Taxonomy)
The FAO-UNESCO soil classification system
0/1
Introduction
Concept and development of land capability classification
0/2
Introduction
The USDA Land Capability Classification System
Learn Soil Physics, Genesis and Classification with Rahul

Quantitative Description of Soil Wetness or Classification of Soil Water

a. Saturation Capacity

  • All soil pores filled with water
  • Matric potential ≈ 0 kPa
  • Occurs during heavy rain/irrigation
  • Volumetric water content = total porosity

 

 

b. Field Capacity (FC)

  • Moisture content after gravity drainage (1-3 days)
  • Upper limit of water held against gravity
  • Matric potential: -10 to -33 kPa
  • Large pores contain air; small pores hold water

 

Factors increasing FC:

  • High clay content (especially 2:1 clay minerals)
  • Good soil structure
  • High organic matter

 

Agricultural significance:

  • Maximum plant-available water
  • Optimal for tillage
  • Balanced air-water ratio for microbes

 

c. Permanent Wilting Point (PWP)

  • Soil moisture at -1500 kPa
  • Plants cannot extract enough water
  • Results in irreversible wilting

 

d. Hygroscopic Water

  • Tightly-bound water films (4-5 molecules thick)
  • Matric potential: -3100 kPa
  • Only moves as vapor
  • Unavailable to plants

 

e. Gravitational Water

  • Drains freely by gravity
  • Matric potential: 0 to -10/-33 kPa
  • Unavailable to plants (moves too quickly)
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