Clay or organic matter has most important effect on soil. A mixed soil like this is called a loam . It is the percentage of holes. If soil has too low a porosity it cannot hold water or provide air to plant roots. Ideally, half of pores should hold air while half should hold water.
Poor drainage can cause flooding and starve plant root for oxygen.
Best if 5-8. Pine forest soils and bog soils have low pH while desert soils are alkaline. Decayed plant materials, bugs, worm casings, dead relatives, etc. Form humic acids. Lower pH. Produce dark colored soil.