SOIL-HORIZON USE BY THE UNITED-STATES SOIL SURVEY

The mission of the soil survey is to assist mankind in understanding and wisely using soil resources in achieving a sustainable and desirable quality of life. The soil survey in the U.S. is founded on the precept that the soil forming factors and their interactions are distributed geographically in a sufficiently systematic manner that the relationships of soil properties and recognizable landscape features can be mapped and described consistently enough to satisfy the purposes of the survey as stated above. There are many more possibilities for designating horizons and layers in field descriptions than there are when applying the defined diagnostic horizons that are used in Soil Taxonomy. The first set are based on qualitative judgements, the latter are based on quantitative measurements. The Soil Survey in the United States has found it useful in meeting our objectives to keep the two kinds of horizon designations separate. Designations of genetic horizons by field scientists is in keeping with the application of the scientific method of developing concepts and hypothesis about how and why soils form and axe distributed in landscapes. The measurement of properties and designation of quantified diagnostic horizons is in keeping with the desire to have standards and definitions for a consistent hierarchical system of soil classification that can be applied more universally. Both systems are open and subject to change as knowledge and experience prevail.