Transcript Salinity and Grape Irrigation

Cl-
Ca++
Na+
SO4=
Grape Irrigation and Salinity
K+
Mg++
HCO3-
Mike Kizer
OSU Extension Irrigation Specialist
CO3=
Salinity
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”
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.
Osmosis
Water with
higher salt
content
(Root wall)
Water with
lower salt
content
Dissolved salts will exert a negative pressure (suction) on water,
drawing it through a semi-permeable membrane (root tissue).
Osmosis
• 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)
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
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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)
• 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
• 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
• mg/l = milligrams/liter
 mg/l = micrograms/liter
ppm = parts per million
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
Salinity
• 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
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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
• ECe is the electrical conductivity of the
saturated soil extract
Example:
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% 
Conclusion:
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.
Grape Yield Potential vs. Soil Salinity
110
100
90
80
Relative Yield, (%)
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
EC, (dS/m)
7
8
9
10
11
12
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
Rootstock
Soil Extract Leaf Analysis
or Variety
(meq/L)
%, (g/g)
Salt Cr. 1613-3
40
0.5
Dog Ridge
30
0.5
Perlette,
Thompson
Cardinal,
Black Rose
25
0.5
10
0.5
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
• 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
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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
Salt and Water Balance in the Root Zone
Irrigation Water + Salt
Evaporation
Salt Residue Left by Evaporating Water (High ECe)
Crop Root Zone
Drainage Water + Salt
Rainfall
Salt and Water Balance in the Root Zone
Evaporation
Excess Irrigation Water
(and Salt) for Leaching
Irrigation Water + Salt
Reduced Salt Residue (ECe
Rainfall
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
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, 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.
Leaching Requirement as a function of ECi and T
Lr when ECi = 2.45 dS/m and T = 1.5 dS/m
Lr = 0.25
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
• 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) 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)
Potential for infiltration problems due to high Na+ water.
Potential for infiltration problems due to high Na+ water.
EC = 1.77 mmho/cm
SAR = 8.5
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
• 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)
Calcium Requirements to
Reclaim Sodic Soils
ESP
Gypsum
CaCl2
Sulfur
(%)
(ton/A)
(ton/A)
(ton/A)
1.70
3.40
4.91
6.70
8.48
10.26
1.07
2.19
3.26
4.37
5.36
6.69
0.31
0.62
0.94
1.25
1.56
1.87
10
20
30
40
50
60
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
• 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)
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)
1 mg/l = 1 ppm
1 mg/l = 1000 mg/l
1mg/l = 1 ppb
TSS = total soluble salts
TDS = total dissolved solids
TSS = TDS
TSS, (mg/l)  640 x EC, (mmho/cm)
Salinity Units and Terms
(Salt Concentrations)
meq/l = milliequivalents per liter
epm = equivalents per million
1 meq/l = 1 epm
Ion
ppm per meq/l
Ion
ppm per meq/l
Ca
20
CO3
30
Mg
12
HCO3
61
Na
23
SO4
48
K
39
Cl
35.5
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)