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Issue link: https://read.dmtmag.com/i/775572
22 SportsTurf | February 2017 www.sportsturfonline.com IRRIGATION & DRAINAGE are used to calculate the RSC, it presents an issue. The RSC is calculated as 3.2 meq, which falls into the "High Hazard" category for sodium accumulation. The higher concentrations of bicarbonates and carbonates have removed a lot of the calcium and magnesium that allows for high sodium accumulation. The EC for this irrigation water falls into the "Good" range. This range suggests little management concern, especially if rainfall and leaching can occur. Remember, EC is an indirect measurement of salt accumulation but can still be useful for management considerations. The total salts reported value of 865.2 ppm falls into the "Good" range for irrigation water. This water should have little management concern especially with rainfall and leaching ability. The SAR of 5.1 also falls into the "Poor" range. This is cause for concern. Management recommendations are aerifi cation of the soil followed by sand topdressing, pelletized gypsum, continued soil monitoring, and leaching when possible. Now that we have looked at these two parameters separately, let's look at how they will affect infi ltration rates together. According to Figure 1 above, when used together, these parameters fall into the "Moderate" category for infi ltration. Infi ltration rates should not be a problem on well-drained soils. Soil management cultural practices should allow infi ltration when using medium textured soils. Overall, this irrigation water is of low quality. The use of this water must be monitored closely and is really only recommended for more salt tolerant turfgrasses on very well drained permeable soils and medium textured soils with careful monitoring. This water is not recommended on heavy soils. Summary of Discussed Irrigation Parameters WATER PARAMETER UNITS DESIRED RANGE USUAL RANGE PH 1-14 6.5 - 8.4 6.0 - 8.5 BICARBONATE (HCO3) ppm or mg/L <150 <610 CARBONATE (CO3) ppm or mg/L <15 <3 RESIDUAL SODIUM CARBONATE (RSC) meq/L <1.25 ----- ELECTRICAL CONDUCTIVITY (EC) µS/cm or µmhos/cm 200-1200 <3000 TOTAL SALTS (TSS OR TDS) ppm or mg/L 256-832 <2000 SAR Unitless <6 <15 Table 4: Summary of Irrigation Water Quality Parameters, (adapted from Duncan et al., 2009) UNIT ABBREVIATION COMMENTS ppm Parts per million mg/L Milligrams per liter µmhos/cm Micromhos per centimeter mmhos/cm Millimhos per centimeter µS/cm Microsiemens per centimeter dS/M Decisiemens per meter Table 5: Commonly used units of measure in irrigation water quality testing. could be the cause of the slightly higher bicarbonate level. Irrigation water with these reported values should have no concern for sodium accumulation. The EC for this irrigation water falls into the "Excellent" range. This range suggests no management concern. Remember, EC is an indirect measurement of salt accumulation but can still be useful for management considerations. The total salts reported value of 336.7 ppm falls into the "Good" range for irrigation water. This water should have little management concern especially with rainfall and leaching ability. The SAR of 1.5 also falls into the "Good" range. This value is of little management concern, however, if sodium should become a problem, gypsum can be used to help remedy the concern. Now that we have looked at these two parameters separately, let's look at how they will affect infi ltration rates together. According to Figure 1 above, when used together, these parameters fall into the "Moderate" category for infi ltration. If this water is being used on a heavy soil system where leaching is unable to occur, a problem could arise in the future. However, with regular rainfall and leaching occurring, no problem should be found. Overall, this irrigation water should be suitable for turfgrass growth without many problems, especially if it is on a sand based system. This water is generally of sufficiently low quality that its use is considerably restricted. It may be used safely only on very well-drained, permeable soils and on salt-tolerant crops. It requires careful irrigation practices including applications of excess irrigation water to keep the soil leached of salt when rainfall is insufficient to provide leaching. Good soil management practices must be used to maintain good physical structure in the soil and to maintain a high level of fertility. Use of this water on medium textured soils may result in problems if care is not exercised. This water is not recommended for heavy textured soils. If this water is used extensively, it is recommended that a soil sample be obtained every few years from the irrigated fields to determine the extent to which sodium or salts may be accumulating and the need for special management practices. Residual carbonates are present in excess amounts lowering water quality to unsuitable. Water with too high residual carbonates may contain effective sodium in excess of that indicated by the sodium percentage of the water. The calcium and magnesium may precipitate out as lime, thus increasing the percentage of sodium. Boron toxicity may occur in poorly drained soils Example 2- Potentially Unsuitable Irrigation Water The pH of this water is in the upper part of our desired range. However, a pH of 8.3 will allow for successful turfgrass growth without further remediation. A pH above 8.0 can cause higher bicarbonates. However, in this case, sodium is an issue but is likely not due to pH. The bicarbonate level of this irrigation water is well above the recommended threshold of 150 ppm. The carbonate level is below the recommended threshold of 15 ppm. However, when the bicarbonates, carbonates, calcium, and magnesium This water is generally of sufficiently low quality that its use is considerably restricted. It may be used safely only Continued on page 25