Installation of Suction Lysimeters

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Abstract

Instructions for installing quartz suction lysimeters at the KBS LTER site. Lysimeters are installed semi-permanently in the C horizon, with enclosures installed at the surface to protect access tubing. Locations are chosen near treatment alleyways for convenient access and maintenance.

Protocol

Materials

  • a soil auger (to dig the hole); 2 in. dia., 6 ft. long
  • a tarp or plywood (to keep the horizons separate)
  • a quart container (to mix the silica flour slurry)
  • a stick (to stir the slurry)
  • Prenart┬« Super Quartz soilwater sampler, 21mm O.D. (Prenart Equipment ApS, Wildersgade 46B.4, 1408 Copenhagen K., Denmark, email: info@prenart.dk)
  • the tubing: polyethylene, 1/8 in O.D. × 1.5 mm I.D., 40 m; purchase from Prenart
  • clippers, very clean (to cut the tubing)
  • silica flour (to get the best contact between the lysimeter and the soil); purchase from Soilmoisture Equipment or from Prenart
  • 5+ L of deionized water (to prime the lysimeter)
  • syringe with an adapter for lysimeter tubing (to prime the lysimeter)
  • galvanized steel pipe, 1 in. O.D., 6 ft. long
  • Rubber mallet (to pound pipe)
  • Tamper: CPVC tubing, 3/4 in., with one end stoppered

Procedure

  1. Identifying the lysimeter location.
    1. Either choose an appropriate spot arbitrarily or use a suitable randomization technique, such as blind toss of a marker. It may be necessary to adjust location in consideration of traffic, field operations, etc.
  2. Digging
    1. Lay the tarp or plywood next to where you will be digging.
    2. Set the auger at an angle above 45┬░ , e.g. 60┬░ or so. Start turning.
    3. Take the soil you are removing and carefully place it on the tarp or plywood, keeping the horizons separate.
    4. Dig until you are 5-10 cm into the C horizon. You should be able to tell by the texture. The soil will become almost pure sand, right after the clayey B horizon.
    5. Remove auger and place pipe down into hole, centering it.
    6. Pound pipe until it has deepened the hole by 15 to 20 cm or so.
    7. Remove pipe carefully, retaining the soil in its core. Note that the hole should be smaller in diameter than that made by the auger.
    8. Bang pipe or use stick to clear out soil.
    9. Arrange pipe so that it is sticking in the hole again.
    10. Prepare the lysimeter either now or while you are digging.
  3. Preparing the lysimeter
    1. Attach a deterioration-resistant string securely to the lysimeter, for retrieval
    2. Unscrew the nut on the lysimeter, taking care not to lose the ferrules. Push tubing through back piece (tubing longer than that supplied will likely be necessary). This may take considerable effort: twisting with pliers may help.
    3. Cut the end of the tubing off at an angle. This is important because otherwise the tubing can suction itself against the wall of the lysimeter, which blocks passage of water. (It also removes any tubing damaged with pliers.)
    4. Screw the nut back onto the lysimeter, making sure that the ferrules are in place and that the tubing sticks out into the lumen of the lysimeter, but is not pressed all the way into the tip.
    5. Then take some deionized water into the syringe and attach syringe to tubing on opposite end of lysimeter.
    6. Squeeze the water into the lysimeter to force all the air out. Squeeze water into it until it flushes uniformly. The lysimeter is now ready to be installed. Make sure that you have enough tubing to reach from the lysimeter out to the alleyway.
  4. Preparing the hole and inserting the lysimeter
    1. Mix a trowel-full of silica flour with enough deionized water to make a slurry about the consistency of a malt.
    2. Stir the slurry well and then pour down the pipe.
    3. Send the lysimeter after, point first.
    4. Carefully remove the pipe, jiggling it slightly to settle the lysimeter into the silica flour.
  5. Closing up
    1. Carefully pack the soil back into the hole in the order that it came out, being careful to keep horizons separate and to pack the soil down as tightly as possible. Some sort of tamper can be helpful.
    2. Mark the spot with a flag.
  6. Setting up the enclosure.
    1. Select an appropriate access enclosure. It must be able to fit the Erlenmeyer flasks. Plastic picnic coolers tend to deteriorate after a few years. Conduit junction boxes work well.
    2. In the lab (if possible) drill holes in the enclosure of choice. Use a bit size that creates a hole through which the tubing fits relatively tightly.
    3. Note: if the enclosure must be located some distance from the installed lysimeter, use longer tubing and install it safely below plow depth using a power trenching tool, such as the Ditch Witch 100SX (www.ditchwitch.com).
    4. Fit tubing through the hole in the back of the cooler.
    5. Fit tubing through the rubber stopper, again using pliers if you need to and clipping off the mangled end.
    6. The rubber stopper must have a second tube going through it. This is what you use to create the suction on the system. You fit the stopper into the flask, attach your pump to the second tube, and pump it out. After you finish, you clamp off the second tube, using a large binder clip.

Date modified: Tuesday, Apr 26 2016

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Datatables

    This protocol was available as a draft since 10-23-2002. Minor additions to materials section were made on 3/20/2003 by Tim Bergsma at the request of Phil Robertson, by reference to an original protocol (hard copy) authored 2-9-1995 by Hamelink.

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