Searching around for fertile soil and forest soil of high quality can be a pain. Especially since gathering in a spot can damage forest soil with each attempt! I wish there was a farmer-craftable item that was... the COMPOST HEAP! You feed it with food items, vegetables, rotting meat, dung, etc and that decays over time. As the perishable items are eaten up by the heap, they add to the harvest meter (similar to gathering eggs from chickens, wool from sheep or milk from cows) and the farmer can harvest... fertile soils! The quality of the soil can be based on the skill of the farmer and the quality of the rotting things he tosses into it. The end result is nice fertile soils of either type that can be used in terraforming farms and tree farms.