Oak Hill Case

Soil Chemical Problems

SALT -SALT -RELATED RELATED

PROBLEMSPROBLEMS

Ion Toxicities

Ion Imbalances

Soil Permeability

Water Deficits

SALT -SALT -RELATED RELATED

PROBLEMSPROBLEMS

Ion Toxicities

Ion Imbalances

Soil Permeability

Water Deficits

Water deficits reflect salinity problems

from salt concentrations

Soil permeability reflects sodicity problems

from sodium concentrations

Salinity

A measure of the salt concentration of water

Common Salt IonsCa2+

K+ NO3-

Mg2+ HCO3-

Na+

SO42- CO3

2-

Cl-

Salinity Measurement

• Measured as the electrical conductivity of water (ECw)

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

sw vs ECe

- 0.36 bar 1.0 dS/m

- 0.72 bar 2.0 dS/m

- 1.44 bar 4.0 dS/m

- 2.16 bar 6.0 dS/m

Transpiration

High salt concentration

Salt-Induced Water Deficits WATER UPTAKE

cytokinin synthesis leaf wilting

cell-turgor pressure

cell-turgor extensibility

DESICCATION GROWTH

stomatal opening

photosynthesis respiration

transpirational cooling

Sodium Hazard

0.25 0.75 2.25 1 2 3 4

Class Salinity HazardEC(dS/m) at 25oC

C1-S4 C1-S3 C1-S2 C1-S1

C2-S4 C2-S3 C2-S2 C2-S1

C3-S4 C3-S3 C3-S2 C3-S1

C4-S4 C4-S3 C4-S2 C4-S1

Sodicity

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

magnesium [Mg+2] concentrations of water

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

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

meq/L?meq/L?

Atomic WeightsElement Atomic Weight (g/mole)

Calcium, Ca 40 Carbon, C 12 Chlorine, Cl 35.5 Copper, Cu 63.5 Hydrogen, H 1 Iron, Fe 55.9 Magnesium, Mg 24.3 Manganese, Mn 55 Nitrogen, N 14 Oxygen, O 16 Phosphorus, P 31 Potassium, K 39 Sodium, Na 23 Sulfur, S 32 Zinc, Zn 65.4

Atomic WeightsElement Atomic Weight (g/mole)

Calcium, Ca 40 Carbon, C 12 Chlorine, Cl 35.5 Copper, Cu 63.5 Hydrogen, H 1 Iron, Fe 55.9 Magnesium, Mg 24.3 Manganese, Mn 55 Nitrogen, N 14 Oxygen, O 16 Phosphorus, P 31 Potassium, K 39 Sodium, Na 23 Sulfur, S 32 Zinc, Zn 65.4

Ion Molecular Wt. (mg/mmole)

Valence (#)

Equivalent Wt. (mg/meq)

Sodium (Na+)

23 1 23

Calcium (Ca2+)

40 2 20

Magnesium (Mg2+)

24 2 12

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

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

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

SARSARWW = 3.3/ ([7.3 = 3.3/ ([7.3 +3.2]/2) +3.2]/2) 1/2 1/2 ==3.3/(5.25) 3.3/(5.25) 1/2 1/2 = 3.3/2.29 = 1.44= 3.3/2.29 = 1.44

Sodium Hazard

0.25 0.75 2.25 1 2 3 4

Class Salinity HazardEC(dS/m) at 25oC

C1-S4 C1-S3 C1-S2 C1-S1

C2-S4 C2-S3 C2-S2 C2-S1

C3-S4 C3-S3 C3-S2 C3-S1

C4-S4 C4-S3 C4-S2 C4-S1

Problem

With a water-quality report providing a With a water-quality report providing a bicarbonate concentration of 366 mg/L, how do bicarbonate concentration of 366 mg/L, how do

we express this in meq/L and what is its we express this in meq/L and what is its significance?significance?

Residual Sodium CarbonateResidual Sodium Carbonate

RSC = [CORSC = [CO33-2-2] + [HCO] + [HCO33

--] - [Ca] - [Ca+2+2] + [Mg] + [Mg+2+2]]

Where [ ] = ion concentrations in Where [ ] = ion concentrations in milliequivalents per liter (meq/L)milliequivalents per liter (meq/L)

Atomic WeightsElement Atomic Weight (g/mole)

Calcium, Ca 40 Carbon, C 12 Chlorine, Cl 35.5 Copper, Cu 63.5 Hydrogen, H 1 Iron, Fe 55.9 Magnesium, Mg 24.3 Manganese, Mn 55 Nitrogen, N 14 Oxygen, O 16 Phosphorus, P 31 Potassium, K 39 Sodium, Na 23 Sulfur, S 32 Zinc, Zn 65.4

Residual Sodium CarbonateResidual Sodium Carbonate

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

RSC Hazard

RSC HAZARD

< 0 none

0-1.25 low

1.25-2.50 medium

>2.50 high

Amendments Required to Neutralize Residual Amendments Required to Neutralize Residual CarbonatesCarbonates

RSC * 234 lbs gypsum/acre-footRSC * 234 lbs gypsum/acre-foot

RSC * 133 lbs sulfuric acid/acre-footRSC * 133 lbs sulfuric acid/acre-foot

soil aggregate

O

O

O

O

O

O

NaNa

H

H

H

H

H

H

H

H

H

H

H

H +

Na Effects on Soil PermeabilityO2 status hardness

water

infiltration drainage percolation retention

Soil Porosity macroporosity

pore continuity

aeration strength

Salt-Affected Soils

Soil Types

SOIL TYPE ECe pH ESP SAR

Saline >4 dS/m < 8.5 <15% < 12

Sodic < 4 dS/m >8.5 >15% >12

Saline-Sodic >4 dS/m >8.5 >15% >12

Soil Salinity Hazard

ECe* HAZARD

< 1.5 low

1.6-3.9 moderate

4.0-5.0 high

>5.0 very high

Soil Sodium Hazard

ESP SAR HAZARD

< 3 < 2.1 low

3-9% 2.1-7.0 moderate

9-15% 7.1-12.0 high

>15% >12 very high

Turfgrass Salinity Tolerance

TOLERANT (ECe 6.1-10)

MODERATELY TOLERANT (ECe 3.1-6.0)

MODERATELY SENSITIVE (ECe 1.6-3.0)

HIGHLY SENSITIVE (ECe <1.5)

seashore paspalum (8.6)

buffalograss (5.3) Kentucky bluegrass (3.0)

centipedegrass (1.5)

alkalaigrass (8.5) blue grama (5.2) zoysiagrass (2.4)

annual bluegrass (1.5)

fairway wheatgrass (8.0)

hard fescue (4.5) colonial bentgrass (1.5)

western wheatgrass (8.0)

strong creeping red fescue (4.5)

rough bentgrass (1.5)

St. Augustinegrass (6.5)

common bermudagrass (4.3)

tall fescue (6.5) hybrid bermudagrass (3.7)

perennial ryegrass (6.3)

creeping bentgrass (3.7)

slender creeping red fescue (6.3)