Horizon: Root restrictive layers in semi-consolidated marine sediments
Depth to a root limiting or restrictive layer is important because it determines the amount of soil material favorable for plant rooting. A shallow soil limits the amount of water the soil can supply plants. A root limiting layer impeds the vertical movement of water, air, and growth of plant roots. If cracks are present, areas that roots can enter are 10 cm or more apart. Examples are: densic materials, hardpan, claypan, fragipan, caliche, or some compacted soils, bedrock and unstructured clay soils.
Consolidation of Sediments. When deposited on a sinking sea-bottom, sediments often accumulate in masses of great thickness, and in such cases the lower portions tend to consolidate from the weight of the overlying masses. We may safely infer that this weight is not without effect. These materials my be affected by one or more cycles with or without intervening soil formation dependent on time of surface exposure as with fluctuating sea levels.
If these sediments are affected by soil genesis, they may develop diagnostic horizons or features such as soil structure, areas of translocated clay, fragic soil properties, and/or redoximorphic features. If unaltered (or relatively unaltered), these consolidated sediments meet the criteria for densic materials if they are root limiting.
The area of difficulty for soil scientists is determining if the materials are geogenic (altered by geologic processes) or pedogenic (soil forming processes). For example: densic material (C horizon) versus a fragipan (B horizon). Both layers are non-cemented, dense, compact, and root limiting. A subjective determination as to their origin and development must be made to consistently describe and classify the soils.
In plinthic soils, these underlying layers act as an aquitard restricting water movement, facilitating the formation of plinthite.
For more information about describing and sampling soils, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
or Chapter 3 of the Soil Survey manual:
www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...
For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:
www.youtube.com/watch?v=e_hQaXV7MpM
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...
Horizon: Root restrictive layers in semi-consolidated marine sediments
Depth to a root limiting or restrictive layer is important because it determines the amount of soil material favorable for plant rooting. A shallow soil limits the amount of water the soil can supply plants. A root limiting layer impeds the vertical movement of water, air, and growth of plant roots. If cracks are present, areas that roots can enter are 10 cm or more apart. Examples are: densic materials, hardpan, claypan, fragipan, caliche, or some compacted soils, bedrock and unstructured clay soils.
Consolidation of Sediments. When deposited on a sinking sea-bottom, sediments often accumulate in masses of great thickness, and in such cases the lower portions tend to consolidate from the weight of the overlying masses. We may safely infer that this weight is not without effect. These materials my be affected by one or more cycles with or without intervening soil formation dependent on time of surface exposure as with fluctuating sea levels.
If these sediments are affected by soil genesis, they may develop diagnostic horizons or features such as soil structure, areas of translocated clay, fragic soil properties, and/or redoximorphic features. If unaltered (or relatively unaltered), these consolidated sediments meet the criteria for densic materials if they are root limiting.
The area of difficulty for soil scientists is determining if the materials are geogenic (altered by geologic processes) or pedogenic (soil forming processes). For example: densic material (C horizon) versus a fragipan (B horizon). Both layers are non-cemented, dense, compact, and root limiting. A subjective determination as to their origin and development must be made to consistently describe and classify the soils.
In plinthic soils, these underlying layers act as an aquitard restricting water movement, facilitating the formation of plinthite.
For more information about describing and sampling soils, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
or Chapter 3 of the Soil Survey manual:
www.nrcs.usda.gov/sites/default/files/2022-09/The-Soil-Su...
For additional information on "How to Use the Field Book for Describing and Sampling Soils" (video reference), visit:
www.youtube.com/watch?v=e_hQaXV7MpM
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...