Describing Soil Morphology and Identifying Soils

Colby J Moorberg

7 Describing Soil Morphology and Identifying Soils

Acknowledgement and Recommended Reading

This laboratory was designed to help you correlate the soils on your site to known soil series based on data for the site in the SSURGO data set. This will be done with the assistance of the the Field Book for Describing and Sampling Soils (Schoeneberger et al. 2012), the SoilWeb web app (California Soil Resource Lab 2018), and/or the LandPKS app (LandPKS 2022). Videos are provided below to guide you through describing soil morphology, SoilWeb, and the Web Soil Survey. A series of videos are also provided if you prefer to use the Land Info module of the LandPKS app to complete this laboratory activity.

Learning Objectives

By the end of the laboratory you will:

Describe the soil morphology at your site
Correlate the soil morphology to a known soil series

Materials

Materials required to complete this laboratory activity include the following:

Shovel, spade, soil probe, or soil auger
Water in a spray or squirt bottle
Soil knife
Field Book for Describing and Sampling Soils or the LandPKS app
Munsell Soil Color Chart or the LandPKS app and a 3M canary yellow Post-It note or other color reference
Pedon description form (available on page 2-93 and 2-94 of the Field Book for Describing and Sampling Soils) or the LandPKS app
Optional items
- 10% hydrochloric acid
- 2 mm sieve

Introduction

Identifying the specific soil series on site is useful for providing context for soil management decisions. In the US the USDA-NRCS and the National Cooperative Soil Survey (NCSS) have extensive soils data that covers most of the country. Most map units used by the soil survey include one or two dominant soil series and often include several other soil series as map unit components or inclusions. By describing basic soil morphology, such as soil color and texture, combined with the soils expected to be present based on work by the soil survey, the soil series that are present can be accurately determined.

Two methods are presented below. The first uses a traditional soil pedon description card followed by manually correlating your soil description to the properties of soil series mapped at the site within the SSURGO database and accessed via the SoilWeb app. The second method uses a similar approach, but has you record your soil color and texture within the LandPKS app which also helps you identify the soil series present.

Identifying the Soil Onsite Using a Pedon Description and SoilWeb

Identify the soil on site by digging a soil pit as deep as you are able. For safety it’s recommended to keep the pit shallower than 1.4 m (4.5 ft). Alternatively, you can use a soil probe, an auger, or even a fence post digger to collect a core to use for describing the soil. Identify the horizon breaks then describe the soil texture, color, and structure of each horizon. Refer to the Field Book for Describing and Sampling Soils, Version 3.0 (Schoeneberger et al. 2012) for information about describing soil morphology, or watch the videos below for step-by-step directions. Record your results in the soil profile description sheet provided in Schoeneberger et al. (2012).

Describing Soil Profiles

Watch the following four videos to learn how to describe a soil profile; identify horizons; and describe soil texture, color, and structure.

Once you’ve described the soil texture, color, and structure, compare the description to the data available for soil series listed for the mapping unit at that location as described in SoilWeb. Note: this information is also available in Web Soil Survey, but SoilWeb is preferred for field use due to the ease of use in a mobile browser. Each mapping unit will likely contain a list of soil series likely to be present, and a percentage of the area within the mapping unit represented by each series. The soils that have the highest percentages are the soils most likely to correspond to the soil you described, so review those soils first. Once you find a soil series with similar soil textures, colors, and structure by depth to your soil record the name of the soil series and the taxonomic classification on the pedon description sheet. Also, make a note of the land capability classification and the limitation listed with the land capability classification.

Overview of SoilWeb

Watch the video below for an overview of SoilWeb, including how to review data for each of the soil series present withing a soil mapping unit.

Identifying the Soil Onsite Using LandPKS

The LandPKS app LandInfo module is targeted specifically towards identifying the soil series that most closely corresponds to the soil you have a your site. Describe and record the soil texture and color using the LandPKS app. Then use the app to identify the soil series that most closely match what you observed. From the report portion of the app note the land capability classification and the potential land capability classification limitations. Generate a PDF of the report by clicking on the green “Generate PDF Report” button within the LandInfo tab and submit that report with your laboratory report. Watch the LandPKS videos below for further directions.

Using the LandPKS LandInfo Module

Watch the five videos below to learn how to use the Land Info module within LandPKS to identify soil series that are the closest match to the soils onsite.

Questions

The following questions directly relate to this lab activity and will be answered as part of the Site Evaluation and Soil Health Assessment Report.

What soil series was the closest match to the soil(s) at your site? Explain why you thought that series was the best fit.
Was the soil series you identified one of the primary map unit components or was it a minor map unit component?
What was the land capability classification limitation(s), and how can that limitation(s) be addressed through your conservation plan for this site?
Based on the surface textures you observed, are water or wind erosion a concern at this site? Explain why or why not.

References

California Soil Resource Lab. 2018. SoilWeb. https://casoilresource.lawr.ucdavis.edu/gmap/.

KStateAgronomy. 2017. Soil Horizons. https://www.youtube.com/watch?v=b1VcCc0co78.

K-State Research and Extension. 2010. Eye on Agriculture Today: Soil Texture By Feel. https://www.youtube.com/watch?v=IOyaBxj767s.

K-State Research and Extension. 2011a. Soil Profiling: Color. https://www.youtube.com/watch?v=2cmJa8dQ5_I.

K-State Research and Extension. 2011b. Soil Profiling: Structure. https://www.youtube.com/watch?v=UKT9RBIkeKc.

LandPKS. 2020. LandInfo Training, Part 1: Introduction and General Site Classification. https://www.youtube.com/watch?v=YD49kck6dpI.

LandPKS. 2020. LandInfo Training, Part 2: Soil Texture. https://www.youtube.com/watch?v=OgYZMsFkoEc.

LandPKS. 2020. LandInfo Training, Part 3: Soil Color. https://www.youtube.com/watch?v=OwfkMXWP1Ls.

LandPKS. 2020. LandInfo Training, Part 4: Soil Limitations. https://www.youtube.com/watch?v=1G7gd8epGlA.

LandPKS. 2020. LandInfo Training, Part 5: Interpreting Your Reports. https://www.youtube.com/watch?v=bYpiZyrbdRI.

LandPKS. 2022. LandPKS. https://landpotential.org/.

Schoeneberger, P. J., D. A. Wysocki, E. C. Benham, and Soil Survey Staff. 2012. Field Book for Describing and Sampling Soils, Version 3.0. Lincoln, NE: USDA-NRCS. https://www.nrcs.usda.gov/resources/guides-and-instructions/field-book-for-describing-and-sampling-soils.

USDA-NRCS. 2021. Cropland In-Field Soil Health Assessment Guide. USDA-NRCS. https://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/soils/health/?cid=nrcs142p2_053869.