Indiana Soil Texture Samples

The Indiana Soil Texture Samples collection is a set of samples available to soil scientists, teachers, students, researchers, and others.  These samples are mainly used to calibrate the process of estimating soil texture in the field.  They can also be used to demonstrate soil properties to students, to evaluate field skills, and as laboratory standards.   The samples were collected in the state by soil scientists of the Indiana Association of Professional Soil Classifiers.  They were dried, crushed, and sieved by members of the Purdue Agronomy Club.  Sub-samples were analyzed by the National Soil Survey Laboratory of the Natural Resources Conservation Service in Lincoln, NE.  This lab determined particle-size distribution (the percent of eight size separates) on all samples.  On most samples, the lab also determined carbon (organic matter) nitrogen, sulfur, and carbonate content, and the water content at 15 bar suction (wilting point).  Soil properties such as contents of organic matter and carbonate minerals may influence how a sample feels when estimating texture.  Currently there are 42 samples in the set.
 
Soil properties
The texture class and soil judging class of each sample are shown on the USDA texture triangle (Figure 1). All data are shown in the data table (Table 1). Another table provides an explanation of the columns of the data table (Table 2). 

How to obtain samples
Samples are sold in units of five samples by the Agronomy Club for $5.00 for a one pound sample, plus shipping costs.  Prices are on the order form. (Figure 2)

Other soil information
Information on tags attached to the samples when they were collected is in the other information table (Table 3).  For most samples, it includes the name of the county in which the sample was collected and some information about the soil.   Purdue students determined the color and results of the HCl test for effervescence.  The table also lists the shelf on which the sample is stored, which is need by sample distributors. 

Collect more samples
There are gaps in the current sample set.  For example, there are no sandy clay loam, sandy clay, or silty clay samples as shown on the texture triangle (Figure 1).  Also, there are no samples with less than 40% sand and less than 15% clay (except for the silt sample).  We encourage those interested in maintaining and enlarging this sample set to collect samples to fill these gaps.  Collect about 10 gallons of soil, in two 5-gallon buckets.  Attach a sturdy label that gives the collector’s name, date, county, estimated texture, horizon and/or depth, and something about the soil (series, “calcareous till”. etc.).  Add “1 of 2” and “2 of 2” on the label so those processing the soil know which buckets are pairs.  You can contact Dr. Gary Steinhardt or Sherry Fulk-Bringman in the Agronomy Department at Purdue, or a member of IAPSC around the state about getting the samples to West Lafayette.  Future users of the sample set will appreciate your help.