My guess would be a lot of composted material, maybe some sorta composted forestry products. Or maybe some liquid gypsum- not sure if that would make your soil too acidic though. Hard for me to say, as I live in alkaline land.
If the goal is to improve soil aggregation, increase porosity and permeability, and improve aeration and drainage then fibrous amendments like peat, wood chips, tree bark or straw are most effective in this situation. Perlite works well too.