Top Five Questions: Evaluating a Water Supply for Suitability to Irrigate Nut Crops

  • Does the salt concentration (ECw) pose a potential problem (osmotic effects)?

Degree of Growth or Yield Reduction
CropUnitNoneIncreasingSevere
Almond, Walnut & PrunedS/m< 1.11.1 - 3.2> 3.2
PistachiodS/m< 4.04.0 - 8.0> 8.0

 

  • Are there specific elements (B, Cl, and Na) that could accumulate in the tree or soil to potentially toxic levels?

Degree of Growth or Yield Reduction
ElementUnitCropNoneIncreasingSevere
B (boron)mg/l (ppm)Almond, Walnut, & Prune<0.50.5 - 3.0>3.0
Pistachio<4.04.0 - 10>10.0
Cl (chloride)meq/lAlmond, Walnut, & Prune<4.04.0 - 10>10.0
Pistachio<20.020 - 40>40.0
Na (sodium)SAR (none)Almond, Walnut, & Prune<3.03.0 - 9.0>9.0
Pistachio<5.05.0 - 10>10.0
Na (sodium)meq/lAlmond, Walnut, & Prune<4.04.0 - 7.0>7.0
Pistachio<20.020 - 40>40.0

 

  • Could the water chemistry reduce soil tilth, porosity, and cause slower water infiltration rates?

Potential of Water Infiltration Problems Developing
Lab InformationUnitUnlikelyIncreasing LikelihoodLikely
Ratio of SAR/ECwratio<5.05.0- 10.0>10
Ratio Ca/Mgratio< 4.02.0- 1.0<1.0

 

  • Could the water chemistry be prone to plugging drip emitters, microsprinklers, or filters and reduce irrigation distribution uniformity?

Potential for Plugging Problems Developing
Lab InformationUnitUnlikelyIncreasing LikelihoodLikely
ECwdS/m<0.80.8 to 3.0>3.0
HCO3+CO3meq/l<2.02.0 - 4.0>4.0
Mn (manganese)mg/l<0.10.1 - 1.5>1.5
Fe (iron)mg/l<0.20.1 - 1.5>1.5

 

  • How much nitrate-nitrogen is in an irrigation water supply?

If lab reports NO3-N, then:
NO3-N (mg/l, ppm) x 2.7 = lbs N per acre-foot of water

If lab reports NO3, then:
NO3 (mb/l, ppm) x 0.6 = lbs N per acre-foot of water

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