Computing the Iowa Corn Suitability Rating for Your Farm

Knowing your farm’s Corn Suitability Rating index (CSR2) provides you with valuable insight into its potential productivity. The CSR2 system is unique to Iowa and originally created to equalize tax assessments on agricultural land based on soil types and their inherent properties. The information is one factor to consider in setting cash rental rates and computing a farm’s value along with other factors influencing the parcel, such as long-term yield and historical management practices. In 2013, the system for CSR was updated to CSR2 values. The new system brings greater transparency and consistency to the method of calculation. To learn more about CSR2, visit the Soil and Land Use website.

Most property tax statements for agricultural land will list details on the parcel’s soil types, including CSR2 points. Alternatively, you can compute the CSR2 for your farm by following the steps outlined below. The Natural Resources Conservation Service (NRCS) has an online program called "Web Soil Survey" that you can use to estimate the CSR2 for a tract of land in Iowa along with a multitude of other suitabilities and limitations. This is also a beneficial option to find soil maps or separate portions of a parcel for unique CSR2 calculations. Web Soil Survey is the nation’s official source of all soil survey information.

Steps in Computing Your CSR2

Follow the steps outlined below to compute the corn suitability rating for your farmland. Before you begin, you may want to print this file so that you can follow the directions from a paper version.

Start by bringing up the Web Soil Survey website. Then click the green button on the home page titled "Start WSS" (when the screen comes up you may need to adjust the size). On the screen that appears, there will be methods for finding a tract of land on the left side of the map and tools above the map that will allow you to zoom in, pan, measure distance, and define the "Area of Interest."

There are several methods to find a tract of land using the website; this article uses section, township, and range numbers. Other options allow you to search by address or state and county.

Initial screen view of Web Soil Survey

Finding Your Farmland – Section, Township, and Range Numbers

1. On the left side of the screen, under "Quick Navigation" click on "PLSS (Section, Township, Range)."
2. Click on "Iowa" from the drop-down state menu and then enter the "section number," "township number," and "range number" for the tract of land. Enter only numbers, not any letters. Click the "View" button and a map of the section that contains your land will appear.

Example of Section, Township, and Range values inserted in the search boxes.

Finding the section, township, and range numbers for your farmland:
If you don’t know this information for your farmland, use one of the methods below.

1. To find the township and range numbers for your county, use Information File C2-88 Iowa Township Names and Geographic Locations by County.
2. If you do not know the section number for your farmland, leave the value blank for now and click "view" in Web Soil Survey. A map of the township in which your farmland is located will appear. Using reference information such as towns, roads, farmsteads, railroads, and other factors, find your farmland on the map and identify the corresponding section number in which the land is located. Now enter the section number and left click "View" again and the map will zoom to the section in which your farmland is located.
3. The section, township, and range numbers may be given on the property tax statement that you received from the county. It may appear as "10 99 19," which means "Section/Township/Range."
4. This information also appears as part of the legal description on any legal papers associated with your farmland.
5. Consult a Farm Plat and Directory for the county. 

Another option is to select "State and County" under the "Quick Navigation" menu, choose Iowa, the county of interest, and click on "View." The map will show the entire county selected and you may then use the zoom buttons above the map (small magnifying glass button) to hone in on a particular area.

Map results from input of Section, Township, and Range.

Creating your Area of Interest (AOI)

Once the area is in view, you will need to define the "Area of Interest" (AOI), which is the specific land area for which you want to compute the CSR2.

1. Above the map are a series of icons. Although all of the icons can assist you, for our use, select one titled AOI that has an irregular shaped red box above it at the right end of the series of icons (you can use the rectangular shaped box if your AOI is a square or a rectangle).
   On the map, place the cursor over one of the corners of your farmland and click (down and up). Begin tracing around your farmland. A straight red line will appear. When you come to a corner of your farmland, click (down and up), continue to the next corner, repeating this process until you have come to the last corner of the property. At this point, double click the mouse. This double click will signal that you are finished tracing and the computer will automatically start computing your AOI.
   If you have made an error in defining your AOI, you can start over again by retracing the property using the steps above.
   Note: If you want to compute the CSR2 for your entire acreage, trace around the boundaries of your land. If you want to compute the CSR2 for just the cropland, trace around the cropland leaving out farmsteads, pastureland, etc.
2. After the AOI has been defined, you can see the number of acres and soil types you have selected by clicking on the "Soil Map" tab at the top of the screen. Check the “Total for Area of Interest” to see if you have selected the right number of acres for your farm or field. At any point, if needed, you can redraw your AOI by selecting the Area of Interest (AOI) tab and redrawing the area following the steps outlined above.

Selecting the 'Soil Map' tab shows the acres of each soil type in the selected tract.

Choices available under the "Soil Data Explorer" tab.

Identifying the Soil Types and Their Corresponding CSR2s

Once you have defined the area you’d like to find the CSR2 values for:

1. Click the "Soil Data Explorer" yellow tab above the soils map. The map will update to show the soil types in your AOI.
2. A menu will also appear on the left side of your screen titled "Suitabilities and Limitations Ratings." This is a long list of the information available in Web Soil Survey, but information specific to CSR2 can be found by clicking on "Vegetative Productivity" in the menu.
3. The menu will expand under Vegetative Productivity. Click on "Iowa Corn Suitability Rating."
4. Next click "View Rating."
5. The map of your AOI will update to show color-coded soil types. Also, a table will appear under the map titled "Iowa Corn Suitability Rating – Summary by Map Unit." It shows the Soil numbers (Map unit symbol), Soil names (Map unit name), CSR2 (Rating), Acres of each soil type (AOI), and Percent of this soil type in the field (Percent AOI).

Computing the Weighted Average CSR2 for Your Farmland

1. You want to know the Weighted Average CSR2 for the entire AOI. However, Web Soil Survey just provides the soil types and their CSR2 rating. To compute the CSR2, you can manually calculate the weighted average or use the Decision Tool "Calculating a Weighted Average CSR2."
2. To compute the weighted average CSR2, enter manually, or copy and paste the information from the table on the NRCS Website table into the Decision Tool.
1. To facilitate this process, highlight all of the information specific to the individual soil types (do not include column names at the top or the total at the bottom of the table). Then copy the information by simultaneously pressing the "Control (CTRL) and "C" keys on your keyboard.
2. Go to the Decision Tool and bring up the blank worksheet (tab at the bottom of the workbook). Place your cursor in the first yellow box below "Map Unit Symbol" (upper left-hand corner). Then simultaneously press the "Control" and "V" keys on your keyboard and the information will be pasted into the Decision Tool spreadsheet.
3. If the information is accurately placed in the spreadsheet, it will automatically compute the weighted average CSR2 at the bottom of the spreadsheet.

Additional Options

1. If you want a printed version of the Web Soil Survey analysis for your records, click on the "printable version" button at the top of your screen. Then click "view" on the screen that appears. Finally, print the map and table that appear (may need to disable pop-up blockers for the site to work properly). You can also print your information contained in the Decision Tool, Calculating a Weighted Average CSR2, for your records.
2. If you want to compute the weighted average CSR2 for another tract of farmland during this session, click on the "Area of Interest (AOI)" tab at the top left of your screen. When the new screen appears, click "Clear AOI". Now enter new information on section, township, and range numbers under Creating Your Area of Interest (AOI) and proceed as outlined above. Also, bring up a new version of the "Calculating a Weighted Average CSR2" Decision Tool.
3. For a visual walk through of Web Soil Survey to find Corn Suitability Rating information, view the Voiced Media file.

Handling Special Circumstances

1. You may have two tracts of farmland that are not contiguous, but you want to compute the composite CSR2 of both of them. To do this, compute the soil map and table for each of the tracts (separate AOIs) and enter both of them into the same "Calculating a Weighted Average CSR2" Decision Tool. The worksheet will merge the information from the two AOIs and provide a composite weighted average CSR2.
2. If your farmland is located in one contiguous piece, but a portion of it is not visible on the screen, you can choose the "zoom out" icon at the top (shaped like a magnifying glass with a dash in it) and click on the map. You can also use the "pan the map image" icon at the top (shaped like a hand), click down on the map, and drag the map in the direction you want.
3. While CSR2 is unique to Iowa, Web Soil Survey and the steps outlined above are similar to find productivity measures for other states.

 

Ann M. Johanns, extension program specialist, 515-337-2766, aholste@iastate.edu

Ann M. Johanns

extension program specialist
515-337-2766
View more from this author

Use this decision tool to find the weighted CSR2 based on information from the Web Soil Survey.