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Cl - SO 4 =. Ca ++ Na +. Grape Irrigation and Salinity. K + Mg ++. HCO 3 - CO 3 =. Mike Kizer OSU Extension Irrigation Specialist. Salinity. All irrigation water will contain dissolved mineral salts. These salts can affect plant growth by: increasing the osmotic potential of the soil

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Grape irrigation and salinity





Grape Irrigation and Salinity





Mike Kizer

OSU Extension Irrigation Specialist


All irrigation water will contain dissolved mineral salts. These salts can affect plant growth by:

  • increasing the osmotic potential of the soil

  • toxic effects on the plant

  • affecting soil physical properties

The water tug of war
The Water “Tug-of-War”

To take up water from the soil the water potential (suction) on the plant side of the root membrane must be stronger than the potential due to the pull of gravity, plus the suction of the soil pores, plus the osmotic potential due to salt in the soil.


Water with higher salt content

Water with lower salt content

(Root wall)

Dissolved salts will exert a negative pressure (suction) on water, drawing it through a semi-permeable membrane (root tissue).


  • Adding salt to the soil raises its osmotic potential

  • Plant tissues must dry out more to generate a greater potential in order to take up water

  • Plants in saline soil respond as though they are in soil with a lower water content (drier soil)

Grape irrigation and salinity

Salinity and Soil Water Potential

Salt Concentrations

0.1% = 1000 mg/l

0.2% = 2000 mg/l

0.3% = 3000 mg/l

0.4% = 4000 mg/l

Measures of salinity
Measures of Salinity

  • Electrical Conductivity (EC)

  • Total Dissolved Solids (TDS)

  • Total Soluble Salts (TSS)

  • Individual mineral concentrations

  • Calculated salinity values products (SAR, ESP, Na%, etc)

Electrical conductivity ec
Electrical Conductivity(EC)

  • Pure water will not conduct electric current

  • The more minerals dissolved in water, the more current it conducts

  • EC is a good estimator of total mineral content (TDS or TSS)

Units ec
Units - EC

  • mmho/cm = (millimho per centimeter)

  • mmho/cm = (micromho per centimeter)

  • dS/m = (deciSiemen/meter)

  • mS/cm = (milliSiemen per centimeter)

  • 1 mmho/cm = 1 dS/m = 1mS/cm

  • 1 mmho/cm = 1000 mmho/cm

Units tds
Units - TDS

  • mg/l = milligrams/liter ppm = parts per million

  • mg/l = micrograms/liter ppb = parts per billion

  • 1 mg/l = 1 ppm in water chemistry (1 liter of water weighs 1,000,000 mg)

  • 1 mg/l = 1000 mg /l

  • 1 mg /l = 1 ppb in water chemistry


  • TDS and TSS are interchangeable (for all practical purposes)

  • EC (mmho/cm) x 640  TSS mg/l (This equivalence is approximate and depends on the ions causing the salinity)

Irrigation water quality salinity
Irrigation Water QualitySalinity

  • Grapes are moderately sensitive to salinity

  • Threshold ECe for yield reduction:1.5 dS/m

  • Yield reduction rate:9.6% / added dS/m

  • Estimated Zero-yield @ECe = 11.9 dS/m

  • ECeis the electrical conductivity of the saturated soil extract

Grape irrigation and salinity


Your salinity management test from the OSU SWFAL shows your vineyard's soil ECe = 2450 mmho/cm (2.45 mmho/cm)

For grapes T = 1.5 mmho/cm (1500 mmho/cm), and S = 9.6%/mmho/cm (9.6%/1000 mmho/cm)

Yr = 100% - S(ECe - T) [Yr = relative yield]

Yr = 100% - 9.6% (2.45 - 1.5) = 90.9% 


All other things being equal, your grapes will yield only about 91% of what they would were the soil salinity less than the threshold value of 1500 mmho/cm.

Chloride toxicity
Chloride Toxicity

  • Grapes are moderately sensitive to chloride

  • Chloride toxicity symptoms usually appear as burning or drying at tips of older leaves, progressing stemward along leaf edges

  • Excessive leaf burn will lead to defoliation

Grape irrigation water quality chloride tolerances
Grape Irrigation Water QualityChloride Tolerances

Chloride toxicity1
Chloride Toxicity

  • Overhead sprinklers can lead to chloride toxicity at lower ion concentrations due to foliar absorption

  • Primarily a problem during high temperature, low humidity weather conditions

  • Frequent wetting/drying cycles lead to greater leaf damage

Irrigation water quality boron
Irrigation Water QualityBoron

  • Grapes are very sensitive to boron

  • Threshold soil concentration for yield reduction: 0.5 - 0.7 mg/L

  • Typical Boron toxicity symptoms for grapes are spotting, yellowing and/or drying at tips and edges of older leaves

Reclamation of saline soils
Reclamation of Saline Soils

  • Natural leaching with rainfall

  • Artificial leaching with excess irrigation

  • Subsurface drainage below root zone

  • Addition of soil amendments (Calcium)

  • Reclamation should be done whenever salt levels reach an economic threshold

Grape irrigation and salinity

Salt and Water Balance in the Root Zone



Irrigation Water + Salt

Salt Residue Left by Evaporating Water (High ECe)

Crop Root Zone

Drainage Water + Salt

Grape irrigation and salinity

Salt and Water Balance in the Root Zone



Excess Irrigation Water (and Salt) for Leaching

Irrigation Water + Salt

Reduced Salt Residue (ECe Weighted EC of Irrigation Water + Rainfall)

Crop Root Zone

Built-up salt is leached below the crop root zone

Subsurface Drains to Carry Away Drainage Water + Salt

Leaching fraction l
Leaching Fraction, L

L = Dd/Di = Ci/Cd = ECi/ECd

L = Leaching fraction

D = Water depth

C = Water mineral concentration (TDS)

EC = Water electrical conductivity

i = Irrigation water (consistent units: in/in,

d = Drainage water ppm/ppm, dS/m/dS/m)

Leaching requirement l r
Leaching Requirement, Lr

Lr = Leaching requirement (i.e., the leaching fraction required)

There are simple models which estimate the amount of leaching required to maintain an acceptable level of soil salinity, based on a linear distribution of accumulated salts in the root zone.

Grape irrigation and salinity

Lr when ECi = 2.45 dS/m and T = 1.5 dS/m

Lr = 0.25

Grape irrigation and salinity

Boron Leaching

Boron leaching efficiency is 1/3 the leaching efficiency for soluble salts such as NaCl.

20% of Boron remaining

7% of soluble salt remaining

Sodium na hazard
Sodium (Na) Hazard

  • Na generally creates soil physical problems (infiltration problems) before toxic concentrations are reached

  • Extremely hot, dry weather conditions and overhead sprinkling can lead to leaf burning due to Na toxicity

Sodium na hazard1
Sodium (Na) Hazard

  • Na reduces soil permeability by dispersing clay particles which seal larger pore spaces

  • Na hazard is greater in soils with higher clay content

  • Na hazard is greater in expanding clays (montmorillonite) than on non-expanding clays (illite or kaolinite)

Grape irrigation and salinity

Potential for infiltration problems due to high Na+ water.

EC = 1.77 mmho/cm

SAR = 8.5

Residual carbonates
Residual Carbonates

  • Excessive residual bicarbonate and carbonate in irrigation water will combine with Ca and Mg ions in soil

  • This effectively increases the SAR and leads to greater risk of infiltration problems

Reclamation of sodic soils
Reclamation of Sodic Soils

  • Addition of ions to displace Na from clays

  • Ca is the usual ion used to displace Na - Gypsum - Calcium chloride - Sulfur (if sufficient lime is in the soil)

  • Adequate drainage is required

  • Incorporation of dry amendments may be needed to prevent loss (1” - 2” deep)

Irrigation water testing
Irrigation Water Testing

  • Test irrigation water source before planning irrigation system development

  • Irrigation water test at OSU SWFAL Lab. costs $12

  • Take 1 pint of water to OSU Cooperative Extension Service County Office

Salinity management test
Salinity Management Test

  • Test for developing salinity problems if you irrigate

  • The poorer quality your water and the more sensitive your crop the more frequently you should test

  • Salinity management test is $10 at OSU SWFAL Lab. Get sample bags at OSU Cooperative Extension county Office

Salinity units and terms electrical conductivity
Salinity Units and Terms(Electrical Conductivity)

1 mmho/cm = 1 dS/m

1 mmho/m = 1000 mmho/cm

1 dS/m = 1 mS/cm

EC = electrical conductivity of water

ECe = electrical conductivity of saturated extract

Salinity units and terms salt concentrations
Salinity Units and Terms(Salt Concentrations)

1 mg/l = 1 ppm

1 mg/l = 1000 mg/l

1mg/l = 1 ppb

TSS = total soluble salts

TDS = total dissolved solids


TSS, (mg/l)  640 x EC, (mmho/cm)

Salinity units and terms salt concentrations1
Salinity Units and Terms(Salt Concentrations)

meq/l = milliequivalents per liter

epm = equivalents per million

1 meq/l = 1 epm

Ion ppm per meq/lIon ppm per meq/l

Ca 20 CO3 30

Mg 12 HCO3 61

Na 23 SO4 48

K 39 Cl 35.5

Derived salinity terms
Derived Salinity Terms

SAR = sodium adsorption ratio

SAR = Na (Ca+Mg)/2

Na% = sodium percentage

Na% = (Na x 100) (Ca+Mg+K+Na)

RSC = residual sodium carbonates

RSC = (CO3 + HCO3) - (Ca + Mg)

(the 3 calculations on this page are in meq/l)