Agronomic Soil Chemistry – Analytical Lab Analysis



Surface (0-25 cm) soil samples are typically collected in the fall, composited by plot, and sent to an analytical laboratory for analysis and for nutrient and liming recommendations for field crops. Analyses include pH, lime index, phosphorus, potassium, calcium, magnesium, and cation exchange capacity. Samples collected in the fall provide liming and fertilizer recommendations for the following year.

Deep cores (0-100 cm) are collected every 5-10 years and samples are analyzed separately by depth interval to monitor longer-term changes in composition with depth.

Sampling frequency: Depends on experiment and research objective.


The number and location of surface cores taken for agronomic soil chemistry varies by experiment. For the LTER Main Cropping System Experiment (MCSE), 25 surface cores (0-25 cm) are taken post-harvest in a 5-by-5 grid expanding the entire treatment plot. Samples are composited by plot and sieved. Depending on analytical lab, soils are either left fresh or air-dried before placing 1-2 cups fresh or 300-500 grams dried subsamples in labelled ziplock bags and sending for analyses.

For the GLBRC Biofuel Cropping System Experiment (BCSE), two soil cores are taken around each of the 3 established sampling stations per plot, with an equal number of cores taken within and between rows for row crops and are composited by plot and processed as above. Soils from annual treatments are analyzed every year; starting in 2018, soils from perennial treatments are analyzed every three years.

Starting in 2022, samples are sent to and analyzed by A&L Great Lakes Laboratories in Fort Wayne, IN.

Soil samples from the KBS LTER and Michigan sites of the GLBC were sent to the MSU Soil and Plant Nutrient Lab until their closure in December 2022. Soil test procedures and interpretation of results of/by the MSU Soil and Plant Nutrient Lab are outlined in Extension Bulletin E2904: Nutrient Recommendations for Field Crops in Michigan: phosphorus was analyzed with a colorimeter using a dip probe, K and Ca using a flame photometer, and Mg with a colorimeter on a segmented flow analyzer. BrayP1 was used to extract the P and 1N Ammonium Acetate to extract the K, Ca and Mg.

Samples from GLBRC sites in Wisconsin were sent to the University of Wisconsin Soil and Forage Analysis Lab through 2014 when the BCSE at Arlington WI was decommissioned and the management and sampling of the Marginal Land Experiment was transferred to KBS.

Date modified: Thursday, Jan 04 2024