RELEASE-2022

At each site, up to 4 Tower and 30 Distributed plots are sampled, with number of plots determined by NRCS based on site variability and number of soil map units present. In most Distributed base plots, a single 1 m x 1 m x 1 m soil pit is excavated. In Tower plots and sites where pit sampling is not permitted, several 10 cm diameter, 1 m deep cores are collected from within a 1 m x 1 m square (where possible). Upon excavating a pit or collecting cores, NRCS describes the profile and all major horizons, assesses coarse fragment volumes, collects bulk density samples (most often by the clod method), then collects enough material to conduct all physical and geochemical laboratory analyses. Field sampling and descriptions follow the methods outlined in the NRCS Field Book for Describing and Sampling Soils, version 3.0. Laboratory analyses are conducted at the Kellogg Soil Survey Laboratory in Lincoln, Nebraska following the standard operating procedures outlined in the Soil Survey Laboratory Methods Manual, Report No. 42, Version 5, 2014. Some horizons do not have bulk density measurements - this includes plots and sites where cores were taken instead of pits and horizons where the bulk density sample was destroyed, lost, or of poor quality.