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 productivity. CSR2 is a tool used in setting cash rental rates and computing a farm’s sale value. 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.
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.
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 by clicking the link http://websoilsurvey.nrcs.usda.gov/app/. 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.”
Initial screen view of Web Soil Survey
There are several methods to find a tract of land using the website; we will lead you through using section, township, and range numbers. Other options allow you to search by address or state and county.
Finding Your Farmland – Section, Township, and Range Numbers
- On the left side of the screen, under “Quick Navigation” click on “PLSS (Section, Township, Range).”
- Click on “Iowa” from the pull-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:
Map results from input of Section, Township, and Range. Icons for defining “Area of Interest” are circled above the map.
Creating your Area of Interest (AOI)
You will need to create the "Area of Interest" (AOI), which is the specific land area for which you want to compute the CSR2.
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 simply 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.
- After the AOI has been computed, 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 this number to see if you have selected the right number of acres for your farm or field. At this 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
If you have selected the area you’d like to find the CSR2 values for:
- Next, if you have selected the area for which you’d like to find CSR2 values, click the “Soil Data Explorer” yellow tab at the top of the screen. The map will appear showing the soil types in your AOI.
- A menu will also appear on the left side of your screen titled “Suitabilities and Limitations Ratings.” Click on “Vegetative Productivity” in the menu
- A menu will appear under Vegetative Productivity. Click on “Iowa Corn Suitability Rating.”
- Next click “View Rating.”
- The map of your AOI will show the 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.
- 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.” (https://www.extension.iastate.edu/agdm/wholefarm/xls/c2-87compositecsr.xlsx)
compute the weighted average CSR, enter or copy and paste the
information from the table on the NRCS Website table into the Decision
- 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 depressing the “Control” and “C” keys on your keyboard.
- 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 depress the “Control” and “V” keys on your keyboard and the information will be pasted into the Decision Tool spreadsheet.
- If the information is accurately placed in the spreadsheet, it will automatically compute the weighted average CSR at the bottom of the spreadsheet.
- 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.
- 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.
- For a visual walk through of Web Soil Survey to find Corn Suitability Rating information, view the Voiced Media file.
Handling special circumstances
- 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.
- 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) and click down on the map and drag the map in the direction you want.
Ann M. Johanns, extension program specialist, 641-732-5574, firstname.lastname@example.org