Determination of field-effective soil properties in the tidewater region of North CarolinaThis article is part of a larger document. View the larger document here.
Soils vary spatially in texture, structure, depth of horizons, and macropores, which can lead to a large variation in soil physical properties. In particular, saturated hydraulic conductivity (Ksat) and drainable porosity are critical properties required to model field hydrology in poorly drained lands. These soil-property values can be measured by several methods; however, larger scale, “field-effective” values may be needed in developing, calibrating, and validating models, such as DRAINMOD. In this investigation, field-effective soil-property values were estimated from water table and outflow measurements from a 3-year field experiment on poorly drained loblolly pine (Pinus taeda L.) plantation watersheds in eastern North Carolina and tested against two additional estimation methods. Field estimates for Ksat were compared to estimates determined using the auger-hole method and estimates determined from soil cores by the constant-head method. The fieldeffective Ksat of the surface layer was estimated at 140 and 90 cm/hour for the unthinned and thinned condition, respectively. These values are greater than values obtained from soil cores and not different from values obtained from the auger-hole method which had mean conductivities of 100 and 80 cm/hour for unthinned condition, respectively. The thinned condition had Ksat values of 32 and 17 cm/hour based on soil cores and the auger-hole method, respectively. The differences between the field-based values and the constant-head method and auger-hole method may be a result of heterogeneity of soils or overestimations in the field-effective results.