My county has been buying up land for years for farm preservation. This policy is somewhat questionable to me. There are other ways to accomplish the same results without using scarce capital on land purchases.
For example, other counties nearby are offering huge tax breaks to those who set aside their farm land. When they do this, they are prohibited from subdividing or in any way developing their land for many years. If sold, it can only be sold as a complete farm and cannot be rezoned. Hence, the county accomplishes the same goal without huge outlays of cash. The folks I know who have signed up have locked their land into agriculture for a 30 year period. The tax breaks can be exceptional, and it's a good program. Owners just have to understand what they are signing up for. Kids looking to cash in on granddad's farm might be in for a shocker.