Use the tables on this page to assess the impact of irrigation water on plant quality
Table 1. Total salinity hazard classification guidelines for variable quality irrigation water based on Electrical Conductivity (ECw) and Total Dissolved Salts (ppm). Salinity Hazard Class ECw (dS/m) Total Dissolved Salts (ppm) Potential Injury & Management Requirements Low <0.75 <500 Low salinity hazard. No management. Medium 0.75 – 1.50 500 – 1,000 Damage only to very salt-sensitive plants. Occasional leaching to prevent salt accumulation may be necessary. High 1.5 – 3.00 1,000 – 2,000 Damage to plants with low tolerance to salinity will likely occur. Apply excess irrigation for leaching, and/ or periodic use of low- salinity water. Very High >3.00 >2,000 Damage to plants with high tolerance to salinity may occur. Use salt-tolerant plants. Site must have good drainage. Excess irrigation for drainage.
Table 2. Salt tolerance of selected turfgrass species. Tolerance Species ECw (dS/m) ppm Excellent Seashore paspalum >10 6,500 Good Bermudagrass Perennial ryegrass St. Augustinegrass Zoysiagrass 6-10 4,000 -6,500 Fair Annual ryegrass 3-6 2,000 - 4,000 Poor Bahiagrass Poa annua Poa trivialis <3 <2,000 *Salt tolerance can shift based on moisture stress, increasing temperatures, and soil infiltration/ percolation.
Table 4. Nutrient guidelines in irrigation water (ppm) Nutrient Low Normal High Very High P <0.01 0.1 – 0.4 0.4 – 0.8 >0.8 PO 4 <0.3 0.3 – 1.21 1.21 – 2.42 >2.42 P 2 O 5 <0.23 0.23 – 0.92 0.92 – 1.83 >1.83 K <5 5 – 20 20 – 30 >30 K 2 O <6 6 – 24 24 – 36 >36 Ca <20 20 – 60 60 – 80 >80 Mg <10 10 – 25 25 – 35 >35 N <1.1 1.1 – 11.3 11.3 – 22.6 >22.6 NO 3 <5 5 – 50 50 – 100 >100 S <10 10 – 30 30 – 60 >60 S O4 <30 30 – 90 90 – 180 >180
Table 3. Specific Ions in irrigation water
Degree of Problem
Ion in water Sodium (Na) Roots
Low
Medium
High
Table 5. Reclaimed water guidelines— recommended max. values TDS(ppm)........................................ 960
SAR
ppm <3
3-9 70-210
>9 >210
w
<70 <3 <69
Cl(ppm)............................................250 Na(ppm)..........................................200 Fe........................................................ 5.0 Mn...................................................... 0.2 Zn........................................................ 2.0 Cu........................................................ 0.2 Ni......................................................... 0.2
Leaves
meq/L ppm
>3 >69
EC w (dS/m).........................................1.5 w ....................................................5.7 SAR
Chlorine (Cl) Roots
adj SAR
w .......................................... 11.6
SAR
ppm <2
2-10 70-335
>10 >355 >3 >100
w
<70
RSC(meq/L)................................ <1.25 3 (ppm)..................................... 250 B(ppm)...............................................0.5 HCO
Leaves
meq/L ppm
<3 <100
Bicarbonate (HCO 3 )
meq/L
<1.5 0 - 120
1.5-8.5 120-180
>8.5 180-600
Table 6. Nutrient ratios in irrigation water and potential nutrient deficiencies* Ca:Mg
ppm
SAR
w = Sodium adsorption ratio of water
<3:1 >8:1
Ca deficiency Mg deficiency Ca deficiency K deficiency
Ca:K
<10:1 >30:1 >2:1 >10:1
Mg:K Mg deficiency K deficiency *Irrigation water with nutrient concentrations outside these ranges can be used; the fertility program must be adjusted to avoid deficiencies.
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