Interpretive Maps

Preface    Introduction    Geology    Soil Descriptions    Mapping    Interpretive Maps    References

Soil Series Capability Table    Agricultural Capability Classes Map    On-Site Waste Disposal Map    Building Site Map    Woodland Capabilities Map    Pond Site Capabilities Map

    The main purpose of a soil map is land use projects.  The map should serve as a basic reference to the soil series found in the area proposed for development or use.  These maps are not a substitute for field data, but allow general planning.  Actual boundaries may vary, but it is nearly impossible and illogical to find and map the exact soil boundaries. 

    Based upon the soils layer, one can determine different types of uses for these soils.  Common types of interpretive maps include, agricultural capability map, septic tank suitability, and building capability.  These maps can then serve specific purposes for land use managers.  A location with poor drainage may need an alternative septic system.  A series with a shallow depth may not be able to support buildings with basements.  Using interpretive maps may make all of these decisions simple.

    The basis for these maps is data performed in laboratories and fieldwork.  A Soils 5 sheet is produced from this data.  The maps then utilize a stop light system for the color-coding of the maps.  A green area means there are slight limitations and you may freely use this land for the specific type of planned use.  A yellow colored polygon denotes a cautious method of use.  Mainly there are moderate limitations with this area including, slope, drainage, or stoniness.  Red areas should not be used for the specific type of use.  There are severe limitations on these soils and a land manager should stray from these soils.  Although a soil may have a severe rating for one type of map, it may have a slight rating for another.  This is because the soil may have certain characteristics that are favorable for one use and not another.

    The Agricultural Capability Map is one of the most basic interpretive maps.  The system has 8 classes ranging from I to VIII.  Class I and Class II are prime farmland, but the arable lands continue up to Class IV.  Class V is a wet soil.  Class VI through Class VIII are soils most suitable for recreational land, forested areas, and rubble lands.  With each class, a subscript may be added.  A w indicates that there is an excess amount of water present in these soils.  e denotes an erosion problem, while an s dictates soil limitations such as fragipans.  These are the main subscripts used in PA, but there is another subclass.  The c subscript means climate has effects in the soil’s suitability in agricultural activities.  PA is situated in the Udic climatic area.  This means that there is enough rainfall to provide plants with sufficient water needed for survival.

    Waste disposal is a large problem of Pennsylvania.  Only 13% of the soils in PA are suitable for standard on-site waste disposal systems (Petersen, 1999).  45% may use alternative methods such as an elevated sand mound.  Since septic tank systems are common in PA, an on-site waste disposal suitability map is a good idea.  The soils at the Agronomy Farm vary with their limitations.  The Murrill soils are very suitable for on site waste disposal.  The upper footslope and ridge soils are severely rated.  This is due to fragipans formed in the colluvial soils.  Drainage problems come with the fragipans, and the slope is also a problem.  Septic tank system may be placed on slopes as steep as 12%, but a special trench system must be used. Limitations also include depth to bedrock, sink holes, and severely steep slopes. 

    The current population of the United Sates is 274,049,141 (U.S. Census Bureau 1999).  With all these people come housing problems.  The soils we build homes and other living areas must be appropriate for building.  If not, foundation cracking problems, wet basements, and even shifting may occur.  This map is well suited for any area due the United States’ rapidly expanding population of 1 person per 13 seconds (Census Bureau 1999).  Depth to bedrock and drainage problems once again causes most of the soils at the farm to be in the severe of moderate limitations range. 

    Woodlands makeup a majority of Pennsylvania’s landscapes.  For this map, a rating system was used instead of the limitations.  This was done because almost all soils can produce trees.  From the map, one may see the soils best suited for agriculture are also those soils receiving and excellent woodlot rating.  Approximately 90% of the farm received a Good rating indicating they are well suited for woodlots. 

    Water is essential for all plant growth.  Many times the amount of rainfall is simply not enough water to keep the plants alive (Summer of 1999).  A pond was constructed for the irrigation system at the Agronomy Farm.  Most of the surrounding soils were moderate in their limitations for a pond, but the limestone valleys received a severe rating.  This is due to the fact that the water will seep from the pond slowly eroding the limestone forming huge cracks.  These cracks will then drain the pond.  This is not a good thing to have happen.