Usda Soil Taxonomy
USDA Soil Taxonomy
The USDA Soil Taxonomy is an intricate system developed by the United States Department of Agriculture (USDA) along with the National Cooperative Soil Survey. This classification system is a pivotal tool for understanding soil science and for differentiating soil map units, providing a comprehensive framework for soil classification used globally.
Evolution
The genesis of the USDA Soil Taxonomy dates back to 1938 when soils were first systematically categorized into orders based on dominant soil-forming factors. This initial framework has undergone substantial revisions over the decades, leading to a sophisticated hierarchical system used today.
Structure
The USDA Soil Taxonomy classifies soils into several hierarchical levels:
- Orders: The highest categorical level, which includes distinctive soil-forming processes. Examples include Vertisols and Gelisols.
- Suborders
- Great Groups
- Subgroups
- Families
- Series
Each level provides increasingly specific information regarding the soil's characteristics and behavior.
Classification Criteria
The criteria for the classification are based on distinctive soil properties such as soil horizons, texture, and organic content. Some soils, like Histosols, are identified primarily by their organic material composition. Others, such as Entisols, are distinguished by lacking clearly defined horizons.
Global Influence
Though the USDA Soil Taxonomy originated in the United States, its influence extends globally. Systems like the World Reference Base for Soil Resources (WRB) and the FAO Soil Classification have drawn from its methodologies, ensuring a more unified global approach to soil classification.
Applications
The taxonomy is essential for various applications, including:
- Agricultural Planning: Assisting in determining the suitability of soils for different crops.
- Environmental Management: Facilitating the assessment of land for conservation purposes.
- Urban Development: Helping to guide infrastructure projects by understanding soil stability and drainage capabilities.
Ongoing Developments
The Natural Resources Conservation Service (NRCS) maintains and continuously updates the taxonomy to incorporate advances in soil science. This includes the contributions from international committees and the experiences of pedologists worldwide, ensuring that the system remains relevant and accurate.