Some good pH buffers for soil are greensand, peat moss, coco coir, cotton burr, and dolomite lime, not to mention the added micronutes they will add to the soil... And some vermiculite, and perlite are also good soil additives for not only water retention, but also helps to keep root systems a lil more oxygenated and all... These would all be good soil amendments to have just to help keep the pH in check, and aiding the water-retention and oxygenation, by way of "spacing out the rhyzosphere" over time...