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 St. Augustinegrass Zoysiagrass Bermudagrass Kikuyugrass 6-10 4,000 -6,500 Fair Perennial ryegrass Tall fescue Annual ryegrass 3-6 2,000 - 4,000 Poor <3 <2,000
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 SO 4 <30 30 – 90 90 – 180 >180 Table 5. Reclaimed water guidelines—
Centipede Bahiagrass Poa annua Poa trivialis Creeping Bentgrass
*Salt tolerance can shift based on moisture stress, increasing temperatures, and soil infiltration/ percolation.
Table 3. Specific Ions in irrigation water
recommended max. values TDS(ppm)........................................ 960 w (dS/m).........................................1.5 EC w ....................................................5.7 w .......................................... 11.6 RSC(meq/L)................................ <1.25 3 (ppm)..................................... 250 B(ppm)...............................................0.5 adj SAR HCO SAR
Degree of Problem
Cl(ppm)............................................250 Na(ppm)..........................................200 Fe........................................................ 5.0 Mn...................................................... 0.2 Zn........................................................ 2.0 Cu........................................................ 0.2 Ni......................................................... 0.2
Ion in water Sodium (Na) Roots
Low
Medium High
SAR w ppm
<3 <70 <3 <69
3-9 70-210
>9 >210
Leaves
meq/L ppm
>3 >69
Chloride Roots
SAR w ppm
<2 <70
2-10 70-335
>10 >355 >3 >100
Table 6. Nutrient ratios in irrigation water and potential nutrient deficiencies* Ca:Mg
Leaves
meq/L ppm
<3 <100
<3:1 >8:1
Ca deficiency Mg deficiency Ca deficiency K deficiency
Bicarbonate (HCO 3 )
Ca:K
<10:1 >30:1 <2:1 >10:1
meq/L
<1.5 <90
1.5-8.5 90-500
>8.5 >500
ppm
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.
SAR
w = Sodium adsorption ratio of water
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