This collection contains air-dried soil samples collected during periodic soil sampling at NEON terrestrial sites (NEON sample class: sls_bgcSubsampling_in.bgcArchiveID). Soil biogeochemical samples are collected once every 5 years, with three unique sampling locations per plot and ten plots per site. Soil sampling is conducted to a maximum depth of 30 ± 1 cm where possible. When organic (O) and mineral (M) horizons are present within a single profile they are separated prior to analysis and archiving. However, other sub-horizons are not separated. Soil from the O horizon is homogenized and non-soil material is removed by hand (no sieving), whereas soil from the M horizon is homogenized and sieved to 2 mm. Prior to archiving, all soil samples are air-dried, then placed into glass jars and stored at room temperature. See links below for NEON data products that provide various physical, chemical, and biological measurements (pH, moisture, carbon and nitrogen content and stable isotopes, inorganic nitrogen pools and net transformation rates, microbial community composition and biomass) for these same soils. In addition, a more detailed characterization of the dominant soil types at each site, including taxonomy, texture, bulk density, and geochemical properties, occurred during the construction period of NEON through two projects. These data are available in NEON data products Soil physical and chemical properties, distributed initial characterization (DP1.10047.001) and Soil physical and chemical properties, Megapit (DP1.00096.001).