Computing the Iowa Corn Suitability Rating for Your Farm
NOTE: As of September 2012, CSR information is temporarily not available through the Web Soil Survey. When that option is made available again, this Information File will be updated with new instructions on finding a CSR rating. It is not yet known when the information will be up again.
Knowing your farm’s Corn Suitability Rating (CSR) provides you with valuable insight into its productivity. CSR is useful in setting cash rental rates and computing a farm’s sale value. To learn more about CSR, go to Information File C2-86 Understanding Corn Suitability Ratings.
You can compute the CSR for your farm by following the steps outlined below. The Natural Resources Conservation Service (NRCS) has an on-line program called “Web Soil Survey” http://websoilsurvey.nrcs.usda.gov/app/ that you can use to do the computation. Also, most Iowa counties have a CD/DVD available for purchase that provides information just for that county. http://www.extension.iastate.edu/soils/county-soil-surveys.
Steps in Computing Your CSR
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 of this file.
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 enlarge it). Although there are several ways to do the analysis using the website, we will lead you through the way that’s easiest to navigate the site.
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. Just enter the numbers, not any letters. Use the buttons to designate north, south, east and west. Click the “View” button and a map of the section that contains your land will appear.
Finding the section, township and range numbers for your farmland
a. To find the township and range numbers for your township, use Information File C2-88 Iowa Township Names and Geographic Locations by County. If you do not know the section number for your farmland, leave blank for now and click “view”. 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 a map of the section in which your farmland is located will appear.
b. 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”.
c. This information also appears as part of the legal description on any legal papers associated with your farmland.
d. Consult a Farm Plat and Directory for the county.
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 CSR.
1. Above the map are a series of icons. Although all of the icons can assist you, for our use select the one titled AOI that has a little oddly 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).
Using the map, place the cursor over one of the corners of your farmland and click (down and up) and then press down again and hold it down. While holding it down, begin tracing around your farmland. A straight red line will appear. When you come to a corner of your farmland, stop, lift your finger up and press it down once again and hold it down while you trace another straight boundary line of your farmland (this procedure signals to the compute that you are changing directions). When you have traced all the way around the farmland and are back to the starting point, lift your finger and then click (up and down). This click will signal that you are finished tracing and the computer will automatically start computing your AOI.
If you have made an error in designating your AOI, you can start over again by returning to the AOI of Interest page by clicking on “Area of Interest (AOI)” at the top of the page and then clicking on “Clear AOI”.
If you want to compute the CSR for your entire acreage, trace around the boundaries of your land. If you want to compute the CSR for just the cropland, trace around the cropland leaving out farmsteads, pastureland, etc.
2. After the AOI has been computed, the number of acres you have selected will appear under “AOI Information” in the left hand column. Check this number to see if you have selected the right number of acres for your farm or field.
Identifying the soil types and their corresponding CSRs
- Next, click the “Soil Data Explorer” yellow tab at the top of the screen. A new map will appear showing the soil types in your AOI.
- A menu will also appear on the left side of your screen titled “Suitability and Limitations Ratings”. Click on “Vegetative Productivity” in the menu
- A new menu will appear under Vegetative Productivity. Click on “Iowa Corn Suitability Rating”
- Next click “View Rating”
- A new map of your AOI will appear where the soil types are color coded. Also, a table will appear under the map titled “Iowa Corn Suitability Rating – Summary by Map Unit”. It shows the Soil Numbers (Map Unit Number), Soil Names (Map Unit Name), CSR (Rating), Acres of each Soil Type (AOI), and Percent of this Soil Type in the Field (Percent AOI).
Computing the weighted average CSR for your farmland.
- You want to know the Weighted Average CSR for the entire AOI. However, the map just provides the soil types and their CSR rating. To compute this, you will need to use the Decision Tool “Calculating a Weighted Average CSR”.
- To compute the weighted average CSR, enter the information from the table on the NRCS Website table into the Decision Tool.
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 to compute the weighted average CSR 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 CSR” Decision Tool.
- If you want a printed version of the 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. You can also print your information contained in Decision Tool, Calculating a Weighted Average CSR, for your records.
Handling special circumstances
- You may have two tracts of farmland that are not contiguous but you want to compute the composite CSR 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 CSR” Decision Tool. The worksheet will merge the information from the two AOIs and provide a composite weighted average CSR.
- If your farmland is located in one contiguous piece but a portion of it is not visible on the screen, you can depress and “zoom out” icon at the top (shaped like a looking glass with a dash in it) and click on the map. You can also use the “drag 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.