Figure 17.—Indicator A12, Thick Dark Surface.
This photo accompanies Figure 17.—Indicator A12, Thick Dark Surface. [Field Indicators of Hydric Soils in the United States].
Preparing to describe the soil (Tonka) soil series. To observe and document a hydric soil, first remove from the soil surface any woody material larger than 2 cm in cross section that cannot be crushed or shredded when rubbed. Do not remove the organic surface layers of the soil, which generally consist of plant remains in various stages of decomposition. Dig a hole and describe the soil profile. In general, the hole should be dug to the depth needed to document an indicator or to confirm the absence of indicators. For most soils, the recommended excavation depth is approximately 20 inches (50 cm) from the soil surface, although a shallower soil pit may suffice for some indicators (e.g., A2, Histic Epipedon). Digging may be difficult in some areas because of rocks or hardpans. Use the completed profile description to determine which hydric soil indicators have been met (USDA, NRCS, 2006a).
Whenever possible, excavate the soil deep enough to determine if there are layers or materials present that might restrict soil drainage. This determination will help to indicate why the soil may or may not be hydric. After a sufficient number of exploratory excavations have been made to determine the soil hydrologic relationships at the site, subsequent excavations can be limited to the depth needed to identify hydric soil indicators. Consider taking photographs of both the soil and the overall site, including a clearly marked measurement scale in pictures of soil profiles.
Figure 17.—Indicator A12, Thick Dark Surface.
This photo accompanies Figure 17.—Indicator A12, Thick Dark Surface. [Field Indicators of Hydric Soils in the United States].
Preparing to describe the soil (Tonka) soil series. To observe and document a hydric soil, first remove from the soil surface any woody material larger than 2 cm in cross section that cannot be crushed or shredded when rubbed. Do not remove the organic surface layers of the soil, which generally consist of plant remains in various stages of decomposition. Dig a hole and describe the soil profile. In general, the hole should be dug to the depth needed to document an indicator or to confirm the absence of indicators. For most soils, the recommended excavation depth is approximately 20 inches (50 cm) from the soil surface, although a shallower soil pit may suffice for some indicators (e.g., A2, Histic Epipedon). Digging may be difficult in some areas because of rocks or hardpans. Use the completed profile description to determine which hydric soil indicators have been met (USDA, NRCS, 2006a).
Whenever possible, excavate the soil deep enough to determine if there are layers or materials present that might restrict soil drainage. This determination will help to indicate why the soil may or may not be hydric. After a sufficient number of exploratory excavations have been made to determine the soil hydrologic relationships at the site, subsequent excavations can be limited to the depth needed to identify hydric soil indicators. Consider taking photographs of both the soil and the overall site, including a clearly marked measurement scale in pictures of soil profiles.