Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
Soil Science
Non Technical Summary
Hydropedologic studies related to seasonal saturation and hydraulic conductivity add to our knowledge to make accurate land use interpretations, particularly as related to land application of waste (liquid and solids) and many urban land uses. Soils mapped in the Carolina Slate Belt in the southeastern region of the United States, including the benchmark Tatum and Chewacla Series, are no exception to this and proper identification of seasonal saturation in these soils is critical as urban and suburban development increases in this region. Soils related to the Tatum Series may lack the typical 2 chroma redox depletions commonly used to identify seasonal saturation even though high water table is often directly observed in these soils. When a seasonal high water table is determined, the soil may be classified as oxyaquic. However, if 2 chroma depletions are absent (or present at deeper depths than seasonal saturation) local or state land use codes may misidentify the depth to saturation. Therefore, even when a soil is classified as oxyaquic, local and state codes do not always interpret this as a limitation for waste treatment and dispersal purposes. The result is that soils in this region?s toposequence (particularly Georgeville-Tatum-Lignum-Chewacla) may be inappropriately used for waste disposal and other purposes. Along with proper identification of saturation, soil hydraulic conductivity measurements are needed. The soils listed above all have similar hydraulic conductivities listed in their current interpretations, yet anecdotal field data from consultants indicate a wide range in measured values. Possible reasons for the wide range in hydraulic conductivity values have not been well researched. This proposal specifically seeks to provide information for improved interpretations of soil and land use for this toposequence that include the benchmark series listed above. The toposequence will be investigated following a hydropedologic approach, including water table and hydraulic conductivity assessments. The data attained can then be used to improve urban land use interpretations (e.g., septic systems, land application for waste treatment, storm water BMP design). In addition to the above benefits of this project data will also provide supporting data for the initial soil survey in Caswell County, North Carolina and provide basis for MLRA Soil Survey projects in the Carolina Slate Belt, including completion of the extensive revision of Alamance County, North Carolina.
Animal Health Component
70%
Research Effort Categories
Basic
30%
Applied
70%
Developmental
(N/A)
Goals / Objectives
1. Morphology and related soil properties of selected soils in the toposequence (Georgeville-Tatum-Lignum-Chewacla) will be determined and used in subsequent objectives. 2. The relation of saturation (frequency and duration) to morphology (redoximorphic features and/or pattern) will be investigated. 3. By using redox electrode the Eh of the soil water will be determined on a weekly basis and related to both saturation levels and redoximorphic patterns. 4. Hydraulic conductivity both in-situ and lab will be measured at multiple depths for each soil and related to the soil morphology
Project Methods
The project area is in the thermic, Carolina Slate Belt Soil System and is located approximately 8 miles north of Hillsborough in Orange County, NC.. The site, Breeze Farm, is owned by North Carolina State University. It consists of approximately 250 acres of hay, pasture, row crop and forested land. The site contains uplands to flood plains adjacent to several creeks that run through the property. Based on the soil survey and Orange County GIS the soils on the site include Georgeville, Tatum, Lignum, Cid, and Chewacla. Preliminary investigation on the site have confirmed these series as well as unclassified soils with a moderately well and somewhat poorly drained drainage classes. In addition, several areas on the site have been observed where oxyaquic conditions are likely to occur. Transects will be located to cross from the well drained Georgeville and Tatum through the less well drained soils and terminate in the flood plain where Chewacla soils occur. A minimum of two transects will be located in the forest or inactive pasture/forest edge. Specific site locations for wells, piezometers and redox probes (as applicable) will be determined through reconnaissance boring. Observation well, piezometers, and redox probes will be installed on each transect following standard procedures. Wells will extend to approximately 80 cm, to the depth of seasonal low water table, or to a lithic contact whichever is shallower. Piezometers will be placed at several depths spanning the range of expected seasonal high water table. Redox probes will be installed at depths similar to the piezometers. In addition to wells with water level recorder, a check well will be installed. A recording rain gauge will also be installed on site. Observation pits will be dug at least 3 meters away from the transects to avoid disturbing the instrumentation. Soil profile descriptions will be made with the assistance of MLRA Soil Scientists. Samples will be taken from each horizon for analysis by the USDA, NRCS-NCSS laboratory. In addition, soil cores will be taken at each major horizon for laboratory determination of hydraulic conductivity (see subsequent section). In-situ hydraulic conductivity will be measured in triplicate in each major horizon. Procedures and data analysis will follow the standard methods (Amoozegar, 2004; Amoozegar and Wilson, 1999). Soil samples taken from the pits will be analyzed following standard methods as described in the USDA-NRCS Soil Survey Laboratory Methods Manual (Burt, 2004). At a minimum each horizon will be analyzed for particle size distribution, bulk density, cation exchange capacity (CEC), base saturation, extractable Fe, Al, and Mn, and clay mineralogy. If possible samples will also be taken for micromorphologic investigation. For laboratory measurement of saturated hydraulic conductivity a minimum of 30 intact soil cores will be collected from three different horizons/depths (10 samples each) of the soils at two to three different sites. Hydraulic conductivity will be measured by the constant head method (Amoozegar and Wilson, 1999).