Couple tips from doing significant work in rural land (row crop farms for conversion to vineyards) deals in TX....
1) 90% (making that # up, but it's high) of the time when rural land is sold, it never ever hits the market or even a broker and is sold to someone who also owns land within a few miles that the current owner knows. If you can network with the local landowners some and let them know you're looking and why, it can go a long way. Become a known quantity and "part" of the community you're looking to buy in.
2) Most of the best land deals are pocket listings, IE they never hit the MLS or other website. In our case, we see about 10X or more pocket listings than MLS listings. Reach out to all the land brokers that do advertise on the MLS occasionally and let them know exactly what your "buy box" is (parameters of a property that you will say "yes" to and buy). Ask that they bring you deals that fall in those parameters first. Most/many land brokers shop properties as pocket listings long before it ever hits the MLS, unless it's and ultra-high-end property. As the song goes, "If you've got the money, honey, (they've) got the time!"
3) If there are any major crops or livestock grown on the type of property you are looking for, go to wherever the processing center or aggregation point is and chat with the manager (gin, grain elevator, market, auction yard, etc). Let them know who you are and what you're looking for and how to contact you. Reach out a couple times to keep top-of-mind for them. They often know someone who is going to sell before that person even decides! For us it's cotton gin managers.