Caliche layers also prevent water penetration in the soil. Soils should have good aeration to allow roots to breathe and conduct physiological processes, primarily water and nutrient uptake. Sandy soils, however, can have excessive drainage which can cause water stress in the orchard. If the hole is empty in 48 hours, the soil has adequate internal drainage. If the holes still contain a static water level after 48 hours, the soil is not recommended for pecan orchards.
Good drainage can occur in sandy hills and in river bottoms.
However, some drainage problems may exist in some river bottom soils where clay and sand are layered. Soils adjacent to running streams can have higher moisture content in the subsoil most of the time, but will not have waterlogging problems because moving water contains oxygen. Deep, loose, permeable soils are needed. The water table should be at least 10 feet below the surface. Growth of pecan tree tap roots depends upon depth of the static water table.