Indicators of Hydritic Soils

(upper 10-16" in soil column)

Because of differences in the parent soil material not all of these indicators will be found in any given hydritic soil. Any one of these indicators is sufficient to classify the soil as hydritic.

Non-Sandy Soils:

• Organic Soils (at least 50% organic content) - peats and mucks - The organic matter accumulates because the soil is anoxic during enough of the growing season to retard the breakdown of organic materials.
• Histic Epipedons - A 8" to 16" layer above the mineral soil that contains at least 20-30% organic matter. The organic matter accumulates because the soil is anoxic during enough of the growing season to retard the breakdown of organic materials.
• Sulfide - The odor of hydrogen sulfide (rotten eggs) indicates a low redox potential.
• Aquatic or Periaquatic Moisture Regime - Soil innundated or groundwater near surface more than 12.5% of the growing season.
• Reducing Soil Conditions - The redox potential of the soil can be measured directly or indirectly (indicator dye).
• Soil Color: Gleyed Soil - When anaerobic conditions reduce manganese and iron the soil develops a gray to blue/green gray color (gley) just under the organic layer of recently fallen plant material.
• Soil Color: Prominent Mottles and/or Low Matrix Chroma - When the anaerobic conditions are not sufficient to produce gleying, these are still indicators of hydritic soils: Prominent mottles means there are patches of color in the soil that contrast with the background matrix. Low matrix chroma means that the background color of the soil is a fairly pure gray.

Sandy Soils:

• High Organic Matter Content in the Surface Horizon - The organic matter accumulates because the soil is anoxic during enough of the growing season to retard the breakdown of organic materials.
• Streaking - Surface organic matter moves down into the sand in a streaky pattern; caused by periodic fluctuations of the water table.
• Organic Pans - Organic matter accumulates just above the average depth of the water table and becomes cemented together into a "pan" by aluminum.