Hydric soil color and Redoximorphic features
A hydric soil is a soil that formed under conditions of saturation, flooding or ponding long enough during the growing season to develop anaerobic conditions in the upper part.
Hydric soil indicators are formed predominantly by the accumulation or loss of iron, manganese, sulfur, or carbon compounds under saturated and anaerobic conditions.
In an anaerobic environment, soil microbes reduce iron from the ferric (Fe3+) to the ferrous (Fe2+) form and manganese from the manganic (Mn4+) to the manganous (Mn2+) form. Of the two, evidence of iron reduction is more commonly observed in soils characteristic bluish gray or greenish gray colors known as gley colors with value of 4 or more. Ferric iron is insoluble, but ferrous iron enters the soil solution, where it may be moved or translocated to other areas of the soil. Areas that have lost iron typically develop characteristic gray or reddish gray colors and are known as redox depletions. If a soil reverts to an aerobic state, iron that is in solution will oxidize and become concentrated in patches as soft masses and along root channels or other pores. These areas of oxidized iron are called redox concentrations.
Since water movement in these saturated or inundated soils can be multidirectional, redox depletions and concentrations can occur anywhere in the soil and have irregular shapes and sizes. Soils that are saturated and contain ferrous iron at the time of sampling may change color upon exposure to the air, as ferrous iron is rapidly converted to ferric iron in the presence of oxygen. Such soils are said to have a reduced matrix (Vepraskas, 1994).
Redox concentrations, depletions, and reduced matrixes are collectively referred to as redoximorphic features. While indicators related to iron or manganese depletions and/or concentrations are most common in hydric soils, they cannot form in soils with parent materials that are low in Fe or Mn content. Soils that formed in such materials may have low-chroma colors that are not related to saturation and reduction. Such soils may have hydric soil morphological features that formed through accumulation of organic matter.
FIELD INDICATORS OF HYDRIC SOILS
For more information about Hydric Soils and their Field Indicators, visit Field Indicators of Hydric Soils in the U.S.
Hydric soil color and Redoximorphic features
A hydric soil is a soil that formed under conditions of saturation, flooding or ponding long enough during the growing season to develop anaerobic conditions in the upper part.
Hydric soil indicators are formed predominantly by the accumulation or loss of iron, manganese, sulfur, or carbon compounds under saturated and anaerobic conditions.
In an anaerobic environment, soil microbes reduce iron from the ferric (Fe3+) to the ferrous (Fe2+) form and manganese from the manganic (Mn4+) to the manganous (Mn2+) form. Of the two, evidence of iron reduction is more commonly observed in soils characteristic bluish gray or greenish gray colors known as gley colors with value of 4 or more. Ferric iron is insoluble, but ferrous iron enters the soil solution, where it may be moved or translocated to other areas of the soil. Areas that have lost iron typically develop characteristic gray or reddish gray colors and are known as redox depletions. If a soil reverts to an aerobic state, iron that is in solution will oxidize and become concentrated in patches as soft masses and along root channels or other pores. These areas of oxidized iron are called redox concentrations.
Since water movement in these saturated or inundated soils can be multidirectional, redox depletions and concentrations can occur anywhere in the soil and have irregular shapes and sizes. Soils that are saturated and contain ferrous iron at the time of sampling may change color upon exposure to the air, as ferrous iron is rapidly converted to ferric iron in the presence of oxygen. Such soils are said to have a reduced matrix (Vepraskas, 1994).
Redox concentrations, depletions, and reduced matrixes are collectively referred to as redoximorphic features. While indicators related to iron or manganese depletions and/or concentrations are most common in hydric soils, they cannot form in soils with parent materials that are low in Fe or Mn content. Soils that formed in such materials may have low-chroma colors that are not related to saturation and reduction. Such soils may have hydric soil morphological features that formed through accumulation of organic matter.
FIELD INDICATORS OF HYDRIC SOILS
For more information about Hydric Soils and their Field Indicators, visit Field Indicators of Hydric Soils in the U.S.