Salinity and Grape Irrigation

1
Cl- SO4
Ca Na
Grape Irrigation and Salinity
K Mg
HCO3- CO3
Mike Kizer OSU Extension Irrigation Specialist
2
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

3
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.
4
Osmosis
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).
5
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)

6
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
7
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)

8
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)

9
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

10
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

11
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)

12
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 _at_ ECe 11.9 dS/m
• ECe is the electrical conductivity of the
  saturated soil extract

13
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.
14
(No Transcript)
15
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

16
Grape Irrigation Water QualityChloride Tolerances
17
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

18
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

19
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

20
Salt and Water Balance in the Root Zone
Rainfall
Evaporation
Irrigation Water Salt
Salt Residue Left by Evaporating Water (High ECe)
Crop Root Zone
Drainage Water Salt
21
Salt and Water Balance in the Root Zone
Evaporation
Rainfall
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
22
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)
23
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.
24
Leaching Requirement as a function of ECi and T
25
Lr when ECi 2.45 dS/m and T 1.5 dS/m
Lr 0.25
26
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
27
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

28
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)

29
Potential for infiltration problems due to high
Na water.
30
Potential for infiltration problems due to high
Na water.
EC 1.77 mmho/cm SAR 8.5
31
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

32
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)

33
Calcium Requirements to Reclaim Sodic Soils
34
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

35
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

36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
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
40
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)
41
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
42
Derived Salinity Terms
SAR sodium adsorption ratio SAR Na
(CaMg)/2 Na sodium percentage Na (Na x
100) (CaMgKNa) RSC residual sodium
carbonates RSC (CO3 HCO3) - (Ca Mg) (the
3 calculations on this page are in meq/l)