Soil water nitrogen composition is measured using porous cup lysimeters. Measurements include nitrate, ammonia, phosphate, and organic nitrogen and phosphorus. Variables of interest are rainfall patterns, vegetation types, and time since burning.
To measure NO3, NH4 and organic-N in soil water collected at two depths (20 cm and 80 cm) using porous cup lysimeters.
Location of Sampling Stations: Lysimeters were installed on one sampling site on each of the following four watersheds in March of 1982: 001C, 001D, N01B, and N04D. In October of 1982, additional sites on 020B and 004B were established. All sites were in Tully soil, about 10-20 m from main stream channels. Each site had five porous cup lysimeter collectors buried to a depth of 20 cm and four collectors buried at a depth of 80 cm. Lysimeters were spaced ca. 3 m apart. This study was terminated in fall 1990 and the lysimeters were removed.
Frequency of Sampling: All collectors were pumped to a vacuum of about -60 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 concentrations in individual samples. Concentrations of organic-N, organic-P, and phosphate were determined on composite samples, prepared by volume-weighing the individual samples into a single monthly composite.
Installation of lysimeter:
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.
Summary of All Changes: Methods of chemical analysis were modified in 1984. Samples collected in 1982-83 were analyzed according to the methods outlined in Appendix A of the 1983 LTER Methods Manual.
For additional metadata information see: http://lter.konza.ksu.edu/sites/default/files/DC.pdf
For additional methods information see: http://lter.konza.ksu.edu/sites/default/files/MM.pdf