Michigan State University - US Forest Service Soil Drainage Index

Welcome to the Michigan State University - US Forest Service Soil
Drainage Index and Productivity Index web page

This page is designed to help you calculate the Drainage Index (DI) and Productivity Index (PI) of any soil in the world, as long as it is classified within the US system of Soil Taxonomy. For help with this taxonomic system, please go to the official NRCS page or to the Pedosphere page. This work was performed under the supervision of Dr. Randall Schaetzl, Department of Geography, Michigan State University, under contract with (and supported by) the US Forest Service. Special thanks go to Frank Sapio and Frank Krist of the USFS, who have long been supporters of this project, and to the USFS for research support.

The Drainage Index
What is the Drainage Index? The DI, originally named the "natural soil wetness index" (Schaetzl 1986), is a measure of the wetness of a soil. It is designed to represent, as an ordinal number, the amount of water that a soil contains and makes available to plants under normal climatic conditions. It is not meant to mimic the concept of "plant available water", which is mostly dependent upon soil texture. The DI only loosely/secondarily takes soil texture into consideration. The main factor affecting the DI is the depth to the water table and the soil volume available for rooting, for a plant can get at this form of water readily. The DI concept was first initiated by Hole (1978) and Hole and Campbell (1985), and expanded upon by Schaetzl (1986).

The DI ranges from 0 to 99. The higher the DI, the more water the soil can and does, theoretically, supply to plants. Sites with DIs of 99 are, essentially, open water. A soil with a DI of 1 is so thin and dry as to almost be bare bedrock. The DI is derived from the soil's taxonomic subgroup classification in the US system of Soil Taxonomy, and (optionally) its soil map slope class. Because a soil's taxonomic classification is not (initially) affected by such factors as irrigation or artificial drainage, the DI does not change as soils become irrigated or drained (unless the long-term effects of this involve a change in the soil's taxonomic classification). Instead, the DI reflects the soil's NATURAL wetness condition. Each soil SERIES has, in theory, its own unique DI. Some soil series span two or more drainage classes; in this case the DI that is used is the one that would normally be used for a soil with that subgroup classification.

The Productivity Index
What is the Productivity Index? Like the DI, the PI is an ordinal measure, but of the productivity of a soil. The PI uses family-level Soil Taxonomy information, i.e., interpretations of taxonomic features or properties that tend to be associated with low or high soil productivity, to rank soils from 0 (least productive) to 19 (most productive). The index has wide application, because, unlike competing indexes, it does not require copious amounts of soil data, e.g., pH, organic matter, or CEC, in its derivation. GIS applications of the PI, in particular, have great potential. For regionally extensive applications, the PI may be as useful and robust as other productivity indexes that have much more exacting data requirements. As with the DI, users may choose to download the join file from this web site and join it to their SSURGO data. After the join is completed, the PI shows up as a field in the SSURGO data attribute table.

To determine the DI of a soil, you must know one or two facts about it:
(1) its taxonomic subgroup, e.g., Typic Hapludalf, or Vitrandic Torripsamment,
(2) the slope class within which it is mapped, e.g., 0-2% slopes, or 12-18% slopes. Slope class is an optional entry.
Once this information is known, you may choose one of three ways to determine its DI, within this web-based platform

If you only know the taxonomic subgroup of the soil series you are concerned with, type it into the box that follows and click on 'Search Database'. Spelling must be exact or your search will return an error.

Please enter subgroup:

If you only know the taxonomic Great Group of the soil series you are concerned with, type it into the box that follows and click on 'Search Database'. Spelling must be exact or your search will return an error.

Please enter great group:

If you would rather pick from a list of options, starting with order and progressing down to great group, subgroup and then to slope class, make your selection below.

Soil Order	Suborder	Great Group	Subgroup

You may also perform a 'reverse look-up' of a subgroup if you know the Drainage Index. In many cases there may be more than on subgroup that corresponds to a particular drainage index.

USING THESE DATA IN ArcGIS

Join our master DI - PI database (table) to your SSURGO table (SSURGO soils data are the county-level soil survey data that can be downloaded from the NRCS directly, from their Soil Data Mart web page). The join should be made on the MUKEY variable. Once the join has been made you will notice columns in the joined table called DI and PI, which will then provide the DI and PI values for each of your soil map units, by MUKEY. By joining the tables in this way, not only are the DI and PI tallied for each taxonomic subgroup in your data file, but slope class is also taken into account automatically.

Download the Master DI - PI join table, in Excel format, HERE
And HERE is the same file in csv format.

For more details about the DI and/or PI workings and theory, or to have questions answered, feel free to contact Randall Schaetzl at Michigan State University. For a detailed listing of all the various taxonomic modifiers and how they affect the DI value, please follow this link. Follow this link for similar data for the PI. We welcome suggestions and additions to help make the DI and PI better.

This link will take you to an Excel file that lists all the DI and PI values by subgroup or family (as appropriate), in Soil Taxonomy.

Links to research using the DI and PI

Please contact Randy Schaetzl for a more detailed copy of any of these posters.

Poster 1 | Poster 2 | Poster 3 | Poster 4 | Poster 5

The DI has been published; a link to the paper is here: DI Paper

U.S. Forest Service

References::

Hole, F.D. 1978. An approach to landscape analysis with emphasis on soils. Geoderma 21:1-13.

Hole, F.D. and J.B. Campbell. 1985. Soil Landscape Analysis. Rowman and Allanheld, Totowa, NJ 196 pp.

Schaetzl, R.J. 1986. A soilscape analysis of contrasting glacial terrains in Wisconsin. Annals Assoc. Am. Geogs. 76:414-425.

PDF of the DI manuscript (In Physical Geography): LINK

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