Oak Hill Case
Soil Chemical Problems
SALT -SALT -RELATED RELATED
PROBLEMSPROBLEMS
SALT -SALT -RELATED RELATED
PROBLEMSPROBLEMS
Ion Toxicities
Ion Imbalances
Soil Permeability
Water Deficits
SALT -SALT -RELATED RELATED
PROBLEMSPROBLEMS
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 Ions
Ca2
+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
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
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)