HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Hayes, W.A. Articles by Vepraskas, M.J. Search for Related Content PubMed Articles by Hayes, W.A., Jr. Articles by Vepraskas, M.J. GeoRef GeoRef Citation Agricola Articles by Hayes, W.A. Articles by Vepraskas, M.J.

Morphological Changes in Soils Produced When Hydrology Is Altered by Ditching

North Carolina State Univ., Dep. of Soil Science, Box 7619, Raleigh, NC 27695-7619 USA

View larger version (19K): [in a new window]   Fig. 1 Schematic map of the study site. One ditch occurred along a portion of the perimeter of the site. The four transects were at differing distances from the ditch. Each transect consisted of at least three soil plots, with a plot in the Goldsboro, Lynchburg, and Rains series. Soil boundaries approximate topographic changes, with the Goldsboro plots lying at an elevation approximately 1 m higher than the Rains plots

View larger version (111K): [in a new window]   Fig. 2 Profile photographs showing the development of Fe masses in the Rains plots at 7 m (A) and 60 m (B) from the ditch. Approximately twice as many Fe masses (40- to 100-cm depths) were found at 7 m than at 60 m from the ditch

View larger version (18K): [in a new window]   Fig. 3 Iron to clay ratios with depth for the Goldsboro, Lynchburg, and Rains soils at 7 m from the ditch (A) and 60 m from the ditch (B). Prior to ditching the soils may have had a depth function like that shown in B. Following ditching, the increase in Fe found near the ditch apparently caused an increase in Fe:clay, particularly at depths below 50 cm

View larger version (18K): [in a new window]   Fig. 4 Water table fluctuations in Rains plots at 7 m (A) and 60 m (B) from the ditch. The water table in A showed greater fluctuation for the periods indicated, and allowed some oxygen to penetrate to depths of 50 cm

View larger version (17K): [in a new window]   Fig. 5 Concentrations of Fe(II) in groundwater samples extracted at a depth of 60 cm in Rains soils at 7 and 60 m from the ditch in 1997 (A) and 1998 (B). The soils at 7 m from the ditch developed higher Fe(II) levels over time, which were maintained in 1997 even after periods of drainage and resaturation. Concentrations estimated visually by dye reaction in the field are shown as circled symbols

View larger version (15K): [in a new window]   Fig. 6 Concentrations of Fe(II) in groundwater samples extracted at a depth of 60 cm from the Lynchburg soils at 30 and 60 m from the ditch in 1997 (A) and 1998 (B). The soils at 60 m from the ditch developed higher Fe(II) levels over time, which were maintained in 1997 even after periods of drainage and resaturation. Concentrations estimated visually in the field are shown as circled symbols. Water samples collected at 7 m from the ditch contained only trace levels of Fe(II)

View larger version (25K): [in a new window]   Fig. 7 Redox potential measurements for Rains soils at 7 m and 60 m from the ditch at a depth of 60 cm. Data are means of five replicate measurements. Saturation occurred on the same day in both plots, but a redox potential of 500 mv was reached 20 d later in the plot 7 m from the ditch compared with the plot at 60 m from the ditch. This is explained by influxes of aerated water occurring frequently at 7 m from the ditch. The "spikes" in redox potential found at 7 m coincide with large rainfall events and show that some aerated rainfall apparently reached the 60 cm depth. An earlier fall of the water table also caused redox potentials at 7 m from the ditch to rise earlier than at 60 m. A redox potential of 500 mv was selected for reference because at this point and lower Fe(II) was detected in water samples. The range in Eh values for both distances from the ditch was approximately 150 mv, but increased to 350 mv when the mean Eh values decreased after saturation. Soil pH's ranged from 4.5 to 5.2 during the study

View larger version (24K): [in a new window]   Fig. 8 Theory explaining why Fe masses develop in soils within 7 to 30 m of the ditch. A: the frequent water table fluctuations and earlier decline of the water table keep this zone oxidized for a longer period during the year than is found further from the ditch. B: the oxidized zone is not saturated for shorter periods because rainfall penetrates to depths of 60 cm and deeper, and this introduces aerated water into the soils. C: the ditch serves as a discharge point for groundwater. Iron(II) that has been reduced further upslope, possibly beneath the Goldsboro (G) or Lynchburg (L) soils is carried toward the ditch in moving groundwater. When the Fe(II) encounters the oxidized zone a portion of it is oxidized in the form of Fe masses