Many users wonder if they can generate a baseline without knowing historic management information such as (a) pre-1980 and pre-2000 management and tillage information or (b) if the land was enrolled in Conservation Reserve Program (CRP) at anytime before 2000. We encourage you to try your best! You may also consider reaching out to your local extension office or resource conservation districts for information.
Not knowing those data creates additional uncertainty in foretasted model runs, however we are not able to quantify the extent of that uncertainty at the moment.