Grape Irrigation and Salinity

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 @ECe = 11.9 dS/m • ECeis 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.

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 Evaporation Rainfall 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

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/lIon 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 (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)