An interesting source for information on recent sales of farm land is the University of Minnesota's "Minnesota Land Economics" site, which is available here:
http://landeconomics.umn.edu/MLE/landdata/FarmLandSale/RunReport.aspx?RI=3155
From the base page, you can select the jurisdiction you're interested in - in most cases it's most helpful to look at counties, but you might also be interested in watersheds, major river basins, or NASS districts - the specific county (or other geography) you want, and a set of other attributes. This can include years, acres, price per acre, or total sales price. From there, just click on "Generate Report" and you'll get the data you're looking for.
For this blog entry, I looked at Kandiyohi County's farm land sales from 2009, 2010, and 2011, and found a total of 60 sales, with average per acre prices ranging between $2,000 an acre and $6,135 an acre. The maximum price was $7,869 per acre, from a sale in Willmar township in 2011.
If you wanted any help in exploring the Minnesota Land Economics site, give me a call at 320-894-7528 or send me an e-mail at noah@farmlandman.com.
Sincerely,
Noah Hultgren
noah@farmlandman.com
320-894-7528