Oops, not going to bed yet I guess :)
Yes, farm land can be depleted of good soil and nutrients. You can get the soil tested, generally by the extension agent too. If it's not been used for farming, it may just need whatever your soil in that area needs for the type of grass you pick - like nitrogen, etc.
It would be great if she and her husband could look at it for you.
Most of our farmland across the country has been depleted of its nutrients. There was a reason God instructed the Israelites to rest the fields every 7th year. The need for supplemental vitamins is greater than ever because our land isn't providing them any longer.