NBS01 Belowground Plot Experiment: Soil water chemistry from Lysimeters


To address the potential interactive effects of fire, aboveground biomass removal, and nutrient amendments on above- and belowground responses, a long-term field experiment was initiated in 1986 as part of the Konza Prairie Long-Term Ecological Research (LTER) program. The general goals of this experiment are: 1) to document both short- and long-term responses of plants and soils to fire, aboveground biomass removal (a surrogate for grazing in these small plots), and nutrient amendments (additions of N and/or P); and 2) to provide a better understanding of the mechanisms underlying tallgrass prairie responses to fire, aboveground biomass removal and nutrient enrichment. Soil water nitrogen composition is measured using porous cup lysimeters from samples from nitrogen fertilized and control plots. Measurements include nitrate, ammonium, phosphate, and organic nitrogen and phosphorus

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To measure NO3-N, NH4-N, PO4-P and organic N and P in soil water from control and N fertilizer plots in Belowground Studies Plots.


Location of Sampling Stations: HQC on control plots (C) and nitrogen fertilizer plots (N) in Belowground Studies Plots.

Frequency of Sampling: All collectors were pumped to a vacuum of about ~50 kpa and checked weekly. Annual sampling began at thaw (about 15 March) and continued until the collectors failed to obtain a sufficient volume of soil water (ca. 50 mL/collector). Sampling was re-instituted, however, if sufficient rainfall occurred again to saturate the soil prior to winter freeze-up around 1 December.

Variable Measured: Volume of soil solution was recorded for each lysimeter and the samples were returned to the laboratory for analysis of NO3-N, NH4-N, PO4-P, and sub sample was frozen for analysis of organic N and P.

Installation of lysimeter:

  1. A 5 cm diameter auger was used to drill a hole to 20 cm.
  2. The soil taken out with the auger was carefully removed in the sequence that it was brought up (later, the soil was replaced in reverse sequence to its removal).
  3. 100 cc of silica powder (silicon powder 140 mesh and finer - Fisher Scientific) was poured into the hole.
  4. 50 mL of distilled H2O was poured into the hole.
  5. The lysimeter was used to mix the silica and water, making a silica-mud paste in the base of the hole.
  6. The lysimeter was put into place.
  7. An additional 100 cc of silica powder was poured into the hole, around the lysimeter.
  8. Soil was carefully dropped into place around the lysimeter. A meter stick was used to tamp and compress the soil.
  9. Step 8 was repeated until the space around the lysimeter is filled. Construction of collector.

Collection of sample: The pinch-clamps were removed to release any remaining vacuum. A collection bottle capped with a stopper fitted as shown for the lysimeters was connected to the tube extending to the bottom of the lysimeter. A hand vacuum pump was connected to the other tube leading from the collection bottle, and the lysimeter was pumped dry. The vacuum was reapplied to the lysimeter, and the tubing was clamped for another week. Foil was used to cover the lysimeters to reduce temperatures and infrared damage to the lysimeter cap.

Further details on how to pump the lysimeter and collect samples are located in Bushnell Rm 209 in the 'Copy of Field Notes' file.

Chemical analyses: Procedures for measuring soil water nitrogen and phosphorus were the same as are used for stream water nitrogen, bulk precipitation nitrogen, and throughfall nitrogen.

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