Soil chemical and physical characteristics are quantified on selected LTER watersheds adjacent to LTER vegetation sampling plots. Sampling was initiated in 1982, and is repeated every five years. A subset of variables (e.g., pH, Bray extractable P, total C, exchangeable cations) is measured on all sample dates, while additional specific variables (e.g., bulk density, soil texture, CaCO3 content, trace metals, extractable inorganic N) are measured less frequently. Methods for C and N analysis have changed over time. C content of samples from 1982, 1987 and 1997 was derived from Walkley-Black measurements of % soil organic matter (OM) content, using a conversion factor of 1.72 (%C = %OM / 1.72). Soil C content of samples from 1992, 2002 and later were determined by dry combustion and gas chromatography (i.e., Carlo-Erba C/N analyzer). N content of samples prior to 1992 was based on Kjeldahl digeston. N content of samples from 1992 on were determined by dry combustion and gas chromatography (i.e., Carlo-Erba C/N analyzer). Additional details regarding sampling protocols and analytical methods are available in the Konza LTER Methods Manual.
Location of Sampling Stations: Soil are sampled along the LTER vegetation transects.
Frequency of Sampling: Cores were obtained for analysis once from each site during the first week of October 1982. Sites are now scheduled to be sampled in the non-winter seasons of every 5th year.
Variable Measured: Bulk density, pH, cation exchange capacity, concentrations of Ca++, Mg++, and Na+, extractable phosphorous, and total Kjeldahl nitrogen. In 1987, the following additional variables were measured: K, Zn, Cu, Fe, Mn, NH4-N, and NO3-N.
Methods: An Oakfield Soil Sampler, with a coring diameter of 3/4" (19.05 mm) is used to obtain soil.
Litter is scraped off of the surface prior to inserting the tube. Soils are sampled to a depth of 5 cm at all sites, and additional samples to a depth of 25 cm are obtained at all Tully soil sites. A composite sample is obtained by taking ten 5 cm cores along each of the vegetation transect and mixing these together in plastic zip-closed bags. Similarly, four 25 cm cores are combined to form a single sample at each Tully site. Occasionally, it is not possible to get all the 25 cm samples. Samples were taken as deeply as possible and notes about actual depths were made on the plastic sampling bag.
All samples were stored at 5-10oC until they could be processed. The samples were sieved through a #5 U.S.A. Standard Testing sieve (4 mm opening). All visible rocks and large root fragments are subsequently removed from the sieved soil. Sorting takes approximately 20 minutes for each composite sample. Sieved soil is returned to the plastic sampling bag and submitted to the K.S.U. Soils Testing Laboratory for chemical analyses. Upon completion of analysis, any remaining soil is returned to KSU Biology for archival storage.
Bulk density data are obtained from the individual cores placed in soil tins. These are air-dried and weighed, sieved (as above) and reweighed, then dried at 105oC and weighed a final time. No chemical analyses are performed on these samples. Locations of Archived Soil Samples: 1982, 1987, 2002, 2010 -Bushnell Annex 121. Other years are missing or were not returned from Soils Testing Lab.
Procedures for Chemical: KSU Soils Testing Laboratory used their standard test procedures. Details about their
various procedures may be found through their website: www.agronomy.ksu.edu/soiltesting/
Many of the original methods used may be found in the following reference: 1998. Recommended Chemical Soil Test Procedures for the North Central Region-North Central Regional Publication No. 221 (revised). University of Missouri Agricultural Experiment Station, Columbia, MO.
Summary of All Changes:
1982: Watersheds: 001c, 001d, 004b, 020b, N01b, N04a. N20b
1987: Watersheds: 001c, 001d, 002c, 002d, 004a, 004b, 004d, 004f, 020b, N01a, N01b, N04d, N20a, N20b. Samples were taken July to September.
1992: Watersheds: 001c, 001d, 002c, 002d, 004a, 004b, 004d, 004f, 004g, 020b, N01b, N02a, N04c (bench), N04d, N20a, N20b, irrigation transect. Samples were taken May to June. Twelve 5cm cores taken at all sites.
1997: Watersheds: 001a, 001c, 001d, 002c, 002d, 004a, 004b, 004f, 020a, 020b, N01a, N02a (N, S and W), N04a (N and S), N04c (bench), N04d, N20a, N20b, irrigation transect. Samples were taken in July. Twelve 5 cm cores taken at all sites
2001: Fire reversal project began. 001a became R20a, 001c became R20b, 020a became R01a and 020d became R01b.
2002: Watersheds: 001d, R01a, R01b, 002c, 002d, 004a, 004b, 004f, 020b, R20a, R20b, N01a, N01b, N02a (N, S and W), N04a, N04c (N and S), N04d, N20a, N20b, irrigation. Samples were taken in September. Slopes are no longer sampled. 5cm cores reduced to 10 per site.
2010: Watersheds: 001d, R01a, R01b, 002c, 002d, 004a, 004b, 004f, 020b, R20a, R20b, N01a, N01b, N04a, N04d, N20a, N20b, irrigation, Texas Hog pasture, 00SA, 00SB, 00SC, C03A, C03B, C03C, C01D. Samples were taken September to October. Texas Hog pasture, 00SA, 00SB, 00SC, C03A, C03B, C03C, C01D are part of the new patch burn study.
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