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Irrigation Water Sample Analysis (AE1360 )

The NDSU Soil and Water Testing Laboratory has been making soil-water compatibility recommendations since the early 1960s. These recommendations are based on the electrical conductivity (EC) and sodium adsorption ratio (SAR) determined on the irrigation water and the soil series present on the land to be irrigated.

Tom Scherer, Extension Agricultural Engineer

Larry J. Cihacek, Associate Professor, School of Natural Resource Sciences


Soil-Water Compatibility Recommendations

Soil surveys of every county in North Dakota have been completed and documented. Many counties have printed copies, but official, up-to-date soil survey information can be found only on the internet at http://websoilsurvey.nrcs.usda.gov. Your local Natural Resources Conservation Service office or county office of the NDSU Extension Service can help you obtain soil series information for your fields.

Each soil series in North Dakota has been classified as unsuitable for irrigation, conditional or irrigable. The irrigation classification for specific soils can be found in the publication ”Compatibility of North Dakota Soils for Irrigation”.

Soil-water compatibility recommendations are made based on how high the irrigation water salinity and sodicity are relative to the tolerance limits of the soils to be irrigated. For example, we may have an irrigation water with an EC of 1,585 micromhos per centimeter (µmhos/cm) and an SAR of 5.9. We could use this water on a soil such as a Hecla, which has tolerance limits of 3,000 µmhos/cm for EC and 12 for SAR. On the other hand, this water would not be compatible with a Bearden soil, which has tolerance limits of 1500 µmhos/cm for EC and a SAR of 6.

Soil-water compatibility determinations should be done before irrigation systems are established. Failure to obtain compatibility recommendations can result in soil hardening. The soil becomes impenetrable and loses productivity.

Even where soil-water compatibility recommendations have been obtained, and soils and water have been found to be compatible, soils should be sampled to a minimum depth of 6 feet in 1-foot increments and analyzed for pH, EC and SAR. This should be done before irrigation commences in a field and again every three to five years. This allows the irrigator to monitor any detrimental changes that may occur due to irrigation and become problems before they cause major soil degradation.

Soil-water compatibility recommendations can be obtained for $60 from the Soil and Water Testing Laboratory at NDSU with the submittal of a water sample and legal description of the field to be irrigated. Use the form on the reverse side of this sheet.

A soil-water compatibility recommendation for irrigation can be only as good as the information supplied.

Please fill out the fillable form completely.

Note:

Water to be used for drinking is tested by the North Dakota Health Department Laboratory in Bismarck, N.D. Water to be used for livestock is tested by the Veterinary Diagnostic Laboratory at NDSU in Fargo, N.D.

Sampling Instructions

Use a clean ½- to 1-pint bottle. DO NOT use a bottle that contained any chemicals such as bleach or agricultural chemicals. Rinse the container several times with the sample water before filling. If the sample is from a well, pump the well for 10 to 15 minutes to obtain a uniform sample.

 

 

 

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