WQ - 1 -- Irrigation Water Quality Sampling

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### [Why Sample: Effects of Poor Water Quality on Soils]{.underline}

Irrigation water quality refers to the kind and amount of salts present
in the water and their effects on crop growth and development. Soil
samples as well as water quality samples must be taken to determine the
quality. If levels of calcium, magnesium, and sodium, as well as
chlorides, sulfates, and bicarbonates, as a group or alone, are too
high, crop growth can be hurt. High levels can even cause crop failure.
Often it is associated with poor soil structure.

Crop growth reductions because of dissolved substances in the soil are
similar to drought-stressed effects. An osmotic gradient on salty soils
is formed. Water uptake by plant roots is increasingly restricted as the
concentration of soil salts increases. Because of this, as soil salts
build up in the soil, more frequent irrigation is necessary to help
flush out salts and reduce water stress.

A breakdown of soil structure is a major effect of elevated sodium. Soil
aggregates are bonded by calcium and magnesium. High levels of dissolved
sodium tend to displace these bonding elements and disperse the
aggregates. As sodium increases, dispersion increases and soil tilth
declines. Soil dispersion caused by sodium can make soils run together,
crust easier, and can limit water infiltration.

**[How to Take Irrigation Water Quality Samples]{.underline}**

Levels and specific makeup of dissolved substances in irrigation water
affect crop productivity and soil structure. They also determine if
water is suitable for irrigation.

Water analyses can only be as accurate as the sample taken. Contact your
laboratory first to obtain the form and any specific procedures to
follow. Follow these simple guidelines when collecting a water sample:

**Containers and Handling**

Sample early in the week to avoid having the sample sit in a lab over
the weekend. Samples should be collected in a new clean, plastic bottle
(at least a pint) with a screw cap. Rinse the plastic bottle and cap 3
times with the water you wish to sample to eliminate any contamination.
Fill the bottle to the top and cap tightly. Wipe the bottle dry. Clearly
identify each container with a simple sample identification which
matches the request form for the laboratory. Tape the bottle shut so
that it doesn't leak. When mailing, place bottles in a box and pack with
a loose, soft packing material to prevent crushing. Avoid glass
containers, as boron concentrations may change and glass has higher
potential for breakage. Some samples may require overnight delivery. If
the sample can't be sent immediately, refrigerate it before sending to
the laboratory. Keep good records of the date and location of each
sample. This can best be done by keeping a copy of the laboratory
information sheet that must be submitted with each sample.

**Well Water**

Let the pump operate twenty minutes to an hour before taking the sample
to be sure the water is representative of what is being tested. Take the
sample from water at the pump so that residues from the lines do not
contaminate the sample. If two or more wells supply an irrigation
system, one sample may be taken from the system after pumping (flushing)
for at least one hour. However, if a water test indicates a problem, all
wells supplying the system will need to be tested individually to
determine the source of the problem. Sometimes one poor quality well can
dramatically reduce the quality of a mixture.

**Other Water Sources**

Testing should also be done on irrigation water from ponds, reservoirs,
streams, canals, or other surface water sources. Samples can be obtained
by collecting water from a faucet near the pumping station after
operating for twenty minutes or longer. For irrigation water sources
where no pump is present, obtain samples by attaching a clean bottle to
a pole or extension and collecting and mixing several samples into a
"composite" which is sent to the laboratory. Samples from lakes,
streams, or ponds should be taken below the surface for a representative
sample. Where sprinkler or pivot irrigated, fill the bottle directly
from the sprinkler or point of emission.

**[What Analyses to Request]{.underline}**

In most cases, a routine irrigation water analysis is the most
appropriate test to request for irrigation water. Regardless of
laboratory selected, be certain that the analysis includes the three
major factors -- total soluble salts, sodium hazard (SAR) and individual
potentially toxic ions. The most recommended analyses to request are:

Ammonia (for nitrogen loading)

Carbonates

pH

R~adj~

Bicarbonates

Chlorides

Phosphorus

Sodium

Boron

Magnesium

Potassium

Sulfate

Calcium

Nitrate nitrogen

Salinity

Total nitrogen

Electrical Conductivity

(for nitrogen loading)

SAR

(for nitrogen loading)

Fluoride

Total dissolved solids

**Special Analyses Processing -**

For microbiological analysis see instructions for specific lab.

**Water Quality and Subsurface Drip Irrigation systems:**

The irrigation water to be used in a drip system should be evaluated
carefully to assess any potential clogging problems. Materials suspended
in the water, such as sand, silt, and algae, can block emitter flow
passages or settle out in the drip lines. Other contaminants, such as
calcium, bicarbonate, iron, manganese, and sulfide, can also precipitate
to clog emitter flow passages. All water needs to be tested to determine
levels of dissolved salts, pH, and turbidity (sediment levels). Growers
need to be aware of high levels of pH (7.5) and high dissolved
bicarbonate levels (=\> 5.6 meq/liter). If water quality analysis
indicates these levels, sulfuric acid and/or gypsum should be injected
to acidify the water to lower the pH to prevent the emitters from
clogging with precipitates. A pH of 6.5 is favorable for injecting
fertilizers or other agricultural chemicals into the system.

**NM Certified Laboratories for Drinking Water Analyses -- Can be Used
for Irrigation**

  ------------------------- -------- ------------------------------------------------------ ---------------
  Albuquerque Water Quality \*       Albuquerque, NM                                        \(505\) 873
                                                                                            6249

  Assaigai Aanlytical       **\* +** Albuquerque, NM                                        \(505\) 345
  Laboratories                                                                              8964

  City of Carlsbad          **\***   Carlsbad, NM                                           \(505\) 887
                                                                                            1191

  Diagnostic & Technology   **\***   Alamogordo, NM                                         \(505\) 434
  Center, Inc.                                                                              4944

  Indepth Water Testing     **\***   Santa Fe, NM                                           \(505\) 471
                                                                                            2023

  City of Farmington Env.   **\***   Farmington, NM                                         \(505\) 599
  Lab                                                                                       1373

  Gallup Micro Biology Lab  **\***   Gallup, NM                                             \(505\) 863
                                                                                            2001

  Hall Environmental        \+       Albuquerque                                            (505)345 3975
  Analysis                                                                                  

  City of Hobbs             **\***   Hobbs, NM                                              \(505\) 397
                                                                                            9315

  International Lubrication **\***   Rio Rancho, NM                                         \(505\) 892
  & Fuel Consultants, Inc.                                                                  1666

  Kramer & Associates, Inc  **\***   Albquerque, NM                                         \(505\) 881
                                                                                            0243

  City of Las Vegas         **\***   Las Vegas, NM                                          \(505\) 454
                                                                                            1533

  Micro Biology Lab         **\***   Milan, NM                                              \(505\) 287
                                                                                            2208

  NM American Water Co.     **\***   Clovis, NM                                             \(505\) 763
                                                                                            5538

  NM Water Testing Lab, Inc **\***   Espanola, NM                                           \(505\) 753
                                                                                            6028

  OMI Inc                   **\***   Farmington, NM                                         \(505\) 325
                                                                                            6953

  Pinnacle                  \+       Albuquerque                                            \(505\) 344
                                                                                            3777

  Raton Water Works         **\***   Raton, NM                                              \(505\) 445
                                                                                            3861

  Town of Red River         **\***   Red River, NM                                          \(505\) 754
                                                                                            6671

  Scientific Labaratory     **\* +** Albquerque, NM                                         \(505\) 841
  Division/DOH                                                                              2510

  City of Silver City       **\***   Silver City, NM                                        \(505\) 538
                                                                                            3731

  SWAT Lab                  **\* +** Las Cruces, NM                                         \(505\) 646
                                                                                            4422

  Triangle Laboratories     dioxin   Research Triangle Park, NC                             \(919\) 544
                                                                                            5729

  City of Tucumcari         **\***   Tucumcari, NM                                          (505)461-4372

  \* for microbiology + for          Source:                                                Updated 9/27/06
  chemicals                          http://www.nmenv.state.nm.us/dwb/certified_labs.html   
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