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Oak Hill Case. Soil Chemical Problems. Water Deficits. Ion Toxicities. SALT -RELATED PROBLEMS. Ion Imbalances. Soil Permeability. Water Deficits. Ion Toxicities. SALT -RELATED PROBLEMS. Ion Imbalances. Soil Permeability.

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Oak hill case

Oak Hill Case

Soil Chemical Problems


Water deficits
Water Deficits

Ion Toxicities

SALT -RELATED PROBLEMS

Ion Imbalances

Soil Permeability


Water deficits1
Water Deficits

Ion Toxicities

SALT -RELATED PROBLEMS

Ion Imbalances

Soil Permeability


Water deficits reflect salinity problems from salt concentrations
Water deficits reflect salinity problems from salt concentrations

Soil permeability reflects sodicity problemsfrom sodium concentrations


Salinity

Salinity

A measure of the salt concentration of water


Common Salt Ions

Ca2+

K+

NO3-

HCO3-

Mg2+

Cl-

Na+

CO32-

SO42-


Salinity measurement
Salinity Measurement

  • Measured as the electrical conductivity of water (ECw)

  • Expressed as decisiemens per meter (dS/m); formerly as mmhos/cm.


sw vs ECe


Transpiration

High salt concentration


Salt induced water deficits

¯ stomatal opening

¯ cell-turgor pressure

¯ cytokinin synthesis

­ leaf wilting

¯ cell-turgor extensibility

¯ transpirational cooling

¯ photosynthesis

­ respiration

­ DESICCATION

¯ GROWTH

Salt-Induced Water Deficits

¯ WATER UPTAKE


C1-S4

C2-S4

C3-S4

C1-S3

Sodium

C4-S4

C2-S3

Hazard

C1-S2

C3-S3

C2-S2

C4-S3

C3-S2

C1-S1

C4-S2

C2-S1

C3-S1

C4-S1

0.25 0.75 2.25

EC(dS/m)

1 2 3 4

at 25

C

Class Salinity Hazard

o


Sodicity

Sodicity

A measure of the sodium [Na+] concentration in relation to the calcium [Ca+2] and magnesium [Mg+2] concentrations of water


Sodicity measurement
Sodicity Measurement

  • Measured as the sodium absorption ratio of water (SARw)

  • Expressed as the ratio:

    Na+/ ([Ca+2 + Mg+2]/2) 1/2

  • Where the concentration of each ion is expressed in milliequivalents per liter (meq/L)


Problem

Problem

With a water-quality report providing sodium, calcium, and magnesium concentrations as 76, 146, and 39 mg/L, how do we express these in meq/L?




Sodium: 76 mg/L / 23 mg/meq = 3.3 meq/L

Calcium: 146 mg/L / 20 mg/meq = 7.3 meq/L

Magnesium: 39 mg/L / 12 mg/meq = 3.2 meq/L

SARW = 3.3/ ([7.3+3.2]/2) 1/2 =

3.3/(5.25) 1/2 = 3.3/2.29 = 1.44


C1-S4

C2-S4

C3-S4

C1-S3

Sodium

C4-S4

C2-S3

Hazard

C1-S2

C3-S3

C2-S2

C4-S3

C3-S2

C1-S1

C4-S2

C2-S1

C3-S1

C4-S1

0.25 0.75 2.25

EC(dS/m)

1 2 3 4

at 25

C

Class Salinity Hazard

o


Problem1

Problem

With a water-quality report providing a bicarbonate concentration of 366 mg/L, how do we express this in meq/L and what is its significance?


Residual Sodium Carbonate

RSC = [CO3-2] + [HCO3-] - [Ca+2] + [Mg+2]

Where [ ] = ion concentrations in

milliequivalents per liter (meq/L)



Residual Sodium Carbonate

RSC = [0] + [6.0] - [7.3] - [3.2] = -4.5



Amendments Required to Neutralize Residual Carbonates

RSC * 234 lbs gypsum/acre-foot

RSC * 133 lbs sulfuric acid/acre-foot



H

H

H

O

O

H

+

H

H

Na

O

O

H

H

H

O

O

H

H

H


Na effects on soil permeability
Na Effects on Soil Permeability

¯ O2 status ­hardness

water

¯ infiltration ¯ drainage

¯ percolation ­ retention

aeration strength

Soil Porosity

¯ macroporosity

¯ pore continuity







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