If insects or weather could negatively effect your ancestor, it could have a financial impact. Did your ancestor only mortgage the farm once–right after a year of drought or an infestation of locusts? Did your ancestor move because there were several years of extremely uncooperative weather in a row? Newspapers and county histories may mention such events and they could be timed to documents that indicate your ancestor was under financial stress.
In severe cases your ancestor may have moved, lost the farm, or both.
Always keep an open mind for things outside your relative’s control that may have impacted his behavior.