Been re-watching Downton Abbey, season 3. What does it tell us about British agriculture, or at least farming on the Earl's estate? (Caution: We probably can't assume Julian Fellowes is an expert on early 20th century agriculture.)
It appears that the estate includes a substantial acreage of farmland, divided into farms held by tenant farmers. Remember that when Daisy the assistant cook visits Mr. Mason's (father of her late husband) farm, he tries to entice her to live with him by offering to make her his heir, inheriting all he has. He describes that as essentially equipment and livestock, but not the land. We've no clue how much land he's farming, but he's obviously done well. I'm not sure whether Mason is one of the Earl's tenants, but it indicates the pattern that existed, or Fellowes thinks existed, in Yorkshire.
When Matthew and Tom work out a plan to modernize the running of the estate, it includes offering the tenants a buy-out, so the land they are farming can be reworked into bigger estates. Though there's no discussion of why bigger is better, season 2 did include scenes of Lady Edith driving a tractor. Presumably that tractor was the farmer's, not the estate's, but being able to afford such modern labor-saving devices would require the tenant to farm more acreage.