Look at the surface plants(50 cell trays bulk). When taking plastic pots and soils in the wild, you can look at the plants growing on the surface. The soils with pines and cedars are mostly acidic soils; the soils with millet and sorghum are mostly alkaline soils. By hand. Holding the acid soil by hand will have a very "soft" feeling. After releasing the hand, the soil will easily spread ...