Buying a home is often conditional upon a satisfactory home inspection. Investing in farmland is also a very expensive venture, and although we have many avenues of establishing value (assessment, local market recent sales, crop productivity ratings), none of them give us a clear indication of how the land has been taken care of. In my years in the Agricultural Sector, I often explained the notion of crop fertilization to that of a bank account. If you start with a good, strong fertility program and at minimum, your putting in each year what your taking out, you will be maintaining your fertility level. However, if you are only applying 60 lbs of N, while you lose 10 lbs to de-nitrification and volatilization during the growing year, and the crop you harvest removes 70 lbs worth of N, you just asked the soil bank account to pick up the other 20.That can be done occasionally, but a continuation of a fertility program that under fertilizes will leave soil reserves low.
While Soil Testing is an imperfect science, it will still give you insight to how the land has been taken care of. Rough estimates of fertility and organic matter percentages are important indicators of productivity.
Including a satisfactory Soil Test as a condition to purchase may be the right call in land that you may not be as familiar with.