I have three suggestions: 1. Try a local realtor. That is always the first place to start.
2. Google "land", "acreage" or something similar for Manhattan KS or Fort Riley. You might find people like me who specialize in that product. 3. Talk to a local community bank and ask them for references.
Professionals answering your questions here is a good place to start, but go get the list of questions to use in evaluating who to use.
Best of luck!
Best of luck.
Tierra Antigua Realty
Try, Loopnet. They have search features that allow you to look for Farms and other agricultural land.