slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Tonight PowerPoint Presentation
Download Presentation
Tonight

Loading in 2 Seconds...

play fullscreen
1 / 43

Tonight - PowerPoint PPT Presentation


  • 294 Views
  • Uploaded on

Tonight. Review mineralogy and soil colloids Soil Reaction Soil Water Assignment 3 due Assignment 4 and Water calculations handed out. Soil Reaction. Soil reaction is the degree of acidity or alkalinity of a soil, usually expressed as a pH value. Soil pH = -log [H + ]

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Tonight' - sokanon


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
tonight
Tonight
  • Review mineralogy and soil colloids
  • Soil Reaction
  • Soil Water
  • Assignment 3 due
  • Assignment 4 and Water calculations handed out
soil reaction
Soil Reaction
  • Soil reaction is the degree of acidity or alkalinity of a soil, usually expressed as a pH value.
  • Soil pH = -log [H+]
  • Soil pH is an indicator of physical, chemical and biological properties in soil.
  • Soil pH is also related to the cations present on the exchange complex.
ph of common materials
pH of Common Materials
  • Milk of magnesia: ~10.5
  • Bicarbonate of soda: ~8.3
  • Pure water: 7.0
  • Milk: ~6.8
  • Natural rain: 5 to 6
  • Beer/coffee: ~4
  • Lemon Juice: ~2
slide6

Dark Gray

Luvisol

Orthic Humo-Ferric

Podzol

Orthic Black

Chernozem

Fig. 7.1. Soil have distinct properties

Credit: Pedosphere.com

soil ph vs soil type depth
Soil pH vs Soil Type & Depth
  • Let us study data in Table 7.2 (Section 7.3)
soil ph vs cation composition
Soil pH vs Cation Composition
  • Total cation exchange capacity (TCEC) is a function of quantity of clays, organic matter and iron and aluminum oxides (Section 6)
  • Types of clay are very important! (Section 6)
soil ph vs cation composition9
Soil pH vs Cation Composition
  • Base cations (Ca++, Mg++, K+, Na+) concentration decreases as soil becomes more acidic (pH decreases)
  • Let us study data in Table 7.3 (Section 7.3)
slide10

Percent Base Saturation

  • Basic cations: Ca++, Mg++, Na+, K+
  • Acidic cations: Al+++, H+
  • Percent base saturation: A measure of the proportion of basic cations occupying the exchange sites of a soil
formula
Formula
  • Cation exchange capacity is the sum of all cations on the exchange complex
  • % Base saturation =  (Ca++, Mg++, K+, Na+) x 100

Cation Exchange Capacity

ph of diagnostic horizons
pH of Diagnostic Horizons
  • Let us studyTable 7.4
slide13

Fig. 6.9. Impact of soil pH on net charge ofnoncrystalline aluminum oxide. At low pH, H ions become bound to Al and Fe oxides

Credit: Pedosphere.com

dissolution of amorphous al oh 3
Dissolution of amorphous Al(OH)3
  • Al(OH)3 + H+ Al(OH)2++ H2O
  • Al(OH)2++ H+ Al(OH)+++ H2O
  • Al(OH)+++ H+ Al++++ H2O
  • The equilibrium reactions result in buffering of soil
buffering mechanisms table 7 6
Buffering Mechanisms (Table 7.6)
  • Oxidation of pyrite and reduced S minerals; dissolution of minerals: pH 2 to 4
  • Aluminum compounds: pH 4.0 to 5.5
  • Cation exchange: pH 5.5 to 6.8
  • Organic matter and minerals: pH 6.8 to 7.2
  • Ca and Mg carbonates: pH 7.2 to 8.5
  • Exchangeable Na+; Dissolution of solid sodium carbonate: pH 8.5 to 10.5
soil acidity types
Soil Acidity Types
  • Active acidity: The activity of hydrogen ions in solution
  • Reserve acidity: The acidity that is associated with the exchange complex. It is neutralized by lime or other alkaline material
slide18

Classification of Soil Acidity

-

+

-

+

+

-

-

+

+

+

-

-

+

-

+

+

-

Clay

surface

+

-

+

Bulk solution

+

+

-

-

+

+

-

+

+

-

+

-

-

+

-

Fig. 7.4. Hydrogen is part of the crystal lattice,and can be present as an exchangeable cation and in the soil bulk solution

nutrient availability
Nutrient Availability
  • The availability of nutrients is strongly related to its solubility at different pH values
  • At extreme pH values, solubility of some nutrients increases tremendously, leading to toxicity of plants
  • Let us study Fig. 7.5 in Section 7.7
acidification
Acidification

Use of ammonium-based fertilizers

(NH4)SO4 + 4O22HNO3 + H2SO4 + 2H2O

Acid Deposition

Nitric (HNO3) + Sulfuric (H2SO4) acids

acidification21
Acidification
  • Drainage of some coastal wetlands leads to the oxidation of pyrite (FeS2), iron sulfide (FeS) and elemental S and formation of sulfuric acid
liming soils

Micelle

Micelle

Liming soils

Use liming materials: CaCO3; Ca(OH)2,CaO; MgCO3

-H+ + CaCO3 = -Ca2+ +H2O and CO2

Are CaCl2 or CaSO4 liming materials?If yes, why? If not, why not?

lecture material
Lecture Material
  • Motivation
  • Classification of soil water
  • Soil water potential curves
  • Water movement
  • Water properties and texture triangle
particle size pore space

16 r

Particle size & pore space

Large

Particle

2 x 2 x 2 = 8

Pore

radius = 4r

particle size pore space25

16 r

Particle size & pore space

Medium

Particle

4 x 4 x 4 = 64

Pore

radius = 2r

particle size pore space26

16 r

Particle size & pore space

Small

Particle

Pore

8 x 8 x 8 = 512

radius = r

slide28

Fig. 3.3. Soil textural classes in the

Canadian System of Soil Classification

Credit: CSSC & Pedosphere.com

slide30

Fig. 8.4. Capillary rise and capillary retention

Credit: Brady & Weil, 1996; Kohnke, 1968

slide31

Fig. 8.6. Interaction of water molecules with clay surfaces, and cations and anions in soil

Credit: Pedosphere.com

slide32

Fig. 8.5. Classification of soil water (after Heaney, Crown and Palylyk, 1995).

Credit: Pedosphere.com

matric potential
Matric Potential
  • Matric Potential: Adhesion of water to surfaces through adsorption and capillarity; markedly reduces the energy state of adsorbed water molecules
  • Matric potential is universally important and is used in calculations of water movement
osmotic potential
Osmotic Potential
  • Osmotic Potential: Attraction of ions and other solutes for water reduces the energy level of water molecules
  • Osmotic potential is attributable to the presence of solutes in the soil solution.
gravitational potential
Gravitational Potential
  • Yg = ghwhere g is the acceleration due to gravity and h is the height of soil water above a reference elevation.
  • Gravity plays an important role of removing excess water from the upper rooting zones following heavy precipitation or irrigation.
soil water potential
Soil Water Potential
  • The difference in energy levels between pure water and soil water is termed soil water potential
  • Difference in energy level determines the direction and rate of water movement in soils and plants
soil water potential37
Soil Water Potential
  • Soil water potential is made up of matric, osmotic and gravitational potentials
  • Water flows from a point which has a higher water potential to another point which has a lower soil water potential
slide38

Fig. 8.5. Classification of soil water (after Heaney, Crown and Palylyk, 1995).

Credit: Pedosphere.com

water movement
Water Movement
  • Saturated flow: Vertical movement of water due to force of gravity in a soil in which all the pores are completely filled with water.
  • Movement can be defined by Darcy’s equation
slide42

Table 8.2. Hydraulic conductivity in soils

with different textures

Credit: After Hanks and Ashcroft, 1980