🌱Intro to Soil Science Unit 13 – Soil Surveys and Land Use Analysis

What's a Soil Survey?

• Comprehensive inventory of the soil resources within a specific area
• Classifies soils according to a standardized system (Soil Taxonomy)
• Includes detailed descriptions of soil properties (texture, structure, color, pH, etc.)
• Maps the geographic distribution of different soil types
• Provides information on soil suitability for various uses (agriculture, engineering, etc.)
• Typically conducted at a county or state level
• Involves both field work (soil sampling, description) and lab analysis
• Final product includes detailed soil maps and accompanying reports

Why Soil Surveys Matter

• Provide essential information for land use planning and management decisions
• Help farmers and ranchers optimize crop production and grazing practices
  • Identify soils best suited for specific crops
  • Guide fertilizer and irrigation management
• Inform engineering projects (road construction, building foundations, septic systems)
  • Identify soils with high shrink-swell potential or poor drainage
• Support conservation efforts by identifying areas at risk of erosion or degradation
• Assist in land valuation and tax assessment
• Guide environmental regulations and policy development
• Facilitate scientific research on soil genesis, ecology, and management

Key Players in Soil Surveying

• Natural Resources Conservation Service (NRCS) - primary federal agency responsible for soil surveys in the US
• Soil scientists - trained professionals who conduct field work and classify soils
  • Typically have a degree in soil science or related field
• Soil survey project leaders - coordinate and oversee the survey process
• Cooperative Extension Service - provides education and outreach to help land managers use soil survey information
• State and local government agencies (e.g., state geological surveys, county planning departments)
• Universities and research institutions - conduct research to improve soil survey methods and applications
• Private consulting firms - may be hired to conduct soil surveys for specific projects

How Soil Surveys Are Done

• Begin with preliminary research and planning
  • Review existing maps, reports, and other relevant data
  • Develop a sampling plan based on landscape features and project goals
• Conduct field work to describe and sample soils
  • Dig soil pits to expose soil profiles
  • Describe soil horizons (layers) in terms of color, texture, structure, etc.
  • Collect samples for laboratory analysis
• Perform laboratory analyses to determine soil properties
  • Particle size distribution (% sand, silt, clay)
  • pH, organic matter content, nutrient levels
  • Engineering properties (Atterberg limits, shear strength)
• Classify soils according to Soil Taxonomy
  • Based on field descriptions and lab data
  • Assign soil series names and map units
• Create soil maps using GIS software
  • Delineate map unit boundaries based on field observations and landscape features
• Prepare final reports and documentation
  • Describe soil properties, interpretations, and use limitations
  • Include tables, charts, and other supporting information

Reading and Using Soil Maps

• Soil maps show the geographic distribution of different soil types
  • Each map unit is labeled with a unique symbol and name
• Map unit descriptions provide detailed information on soil properties and interpretations
  • Found in accompanying reports or online databases
• Soil properties important for land use decisions include:
  • Texture (affects water holding capacity, workability, erosion potential)
  • Depth to bedrock or restrictive layers (limits root growth, excavation)
  • Drainage class (indicates wetness, suitability for septic systems)
  • Slope (affects erosion potential, equipment operability)
• Soil interpretations rate soils for specific uses (e.g., building site development, cropland, pasture)
  • Based on soil properties and landscape features
  • Expressed as classes (e.g., slight, moderate, or severe limitations)
• Users can overlay soil maps with other data layers (topography, land cover) using GIS
  • Helps visualize relationships between soils and other landscape features

Land Use Analysis Basics

• Process of evaluating the suitability of land for different uses
  • Agriculture, forestry, urban development, recreation, etc.
• Considers both natural factors (soils, topography, climate) and socioeconomic factors (land ownership, zoning, market demand)
• Typically involves a multi-criteria analysis
  • Assign weights to different factors based on their relative importance
  • Combine factor layers using GIS to create a suitability map
• Soil properties are a key input to land use analysis
  • Affect the productivity, management needs, and environmental impacts of different land uses
• Other important factors include:
  • Accessibility (distance to roads, markets)
  • Water availability (precipitation, irrigation sources)
  • Existing land use and land cover
  • Biodiversity and habitat value
• Land use analysis can inform:
  • Land use planning and zoning decisions
  • Environmental impact assessments
  • Conservation prioritization
  • Infrastructure development

Connecting Soils to Land Use Decisions

• Soil surveys provide essential information for land use decisions
  • Help identify opportunities and constraints for different land uses
• Agricultural land use decisions:
  • Select crops based on soil fertility, water holding capacity, and climate
  • Determine irrigation and drainage needs based on soil properties
  • Identify areas at risk of erosion and implement conservation practices
• Forest management decisions:
  • Select tree species based on soil type and site index
  • Plan harvest and regeneration methods based on soil properties and topography
• Urban development decisions:
  • Identify areas with soil limitations for buildings, roads, and septic systems
  • Plan stormwater management based on soil infiltration and drainage properties
• Recreational land use decisions:
  • Identify soils suitable for trails, campgrounds, and other facilities
  • Assess soil suitability for off-road vehicle use and potential for erosion
• Soil information can help balance competing land use objectives
  • Identify areas where multiple uses are compatible or conflicting
  • Inform trade-offs between economic development and environmental protection

Real-World Applications

• Precision agriculture:
  • Use soil maps to vary fertilizer and irrigation rates within fields
  • Increases efficiency and reduces environmental impacts
• Septic system design:
  • Use soil properties to determine appropriate system type and size
  • Ensures proper treatment of wastewater and protects groundwater
• Wetland delineation:
  • Use soil indicators (color, texture, redox features) to identify wetland boundaries
  • Important for regulatory compliance and conservation planning
• Habitat restoration:
  • Use soil maps to identify areas with suitable conditions for target species
  • Guide site preparation, planting, and management practices
• Watershed management:
  • Use soil information to model water quality impacts of land use changes
  • Prioritize areas for conservation practices (buffers, cover crops)
• Transportation planning:
  • Use soil maps to identify areas prone to landslides or subsidence
  • Inform road and bridge design, maintenance, and safety
• Real estate transactions:
  • Use soil information to assess land value and development potential
  • Disclose soil limitations to buyers and inform land use restrictions