Michael Vepraskas - Academia.edu (original) (raw)

Papers by Michael Vepraskas

Acta Physiologica, 2013

Next month, it will be 50 years since Bob Dylan released this song. Conspiracy theories have it t... more Next month, it will be 50 years since Bob Dylan released this song. Conspiracy theories have it that he died only three years later in a motorcycle accident. The times they are a-changin’ for Acta Physiologica as well. Far from dying, Acta Physiologica enhanced all its performance parameters this year, as for the previous years before (Persson 2012a,b). Submissions surge in parallel to the impact factor. Having an impact factor of 4.4 places Acta ahead of most topnotch journals in the field. Of course, this development only mirrors your publications in Acta. Thank you and congratulations! What makes Acta so special? It is a recipe with several ingredients. Today’s reader often needs a quick scan of a certain research field and wishes original articles to be put into context of state-of-the-art science. Acta takes these needs into account by publishing numerous editorials, which readers download at a remarkable rate (the top two for 2011/2012 (Park et al. 2012, Persson & Persson 2012)). More than 30 editorials appeared in 2013, some highlighting our very best work and others providing a broader picture of a field that has progressed, thanks to deeper understanding provided by the articles in Acta. When was actually the last time you held the printed copy of Acta Physiologica in your hands, physically leafing through it, article by article? Cannot remember? This monthly routine for editors is probably a very unusual event for our readers. In fact, almost all of our subscriptions are online only. The libraries simply do not have space to deposit all the hard copies, and the reader prefers to scan groups of publications and then assess them immediately online. This has led to a situation in which our printed copies are primarily being distributed to our editors and editorial board members, a thank you for their endless work they dedicate to the Journal. However, you may ask, ‘Is the effort of print setting and binding the copies together with the posting really worth the hassle?’ After all, every one of our editors and editorial board members do have free access to the Journal online. Thus, we have decided to go along with modern developments in publishing science (Anon 2007, Perham 2013) and will now make Acta Physiologica a free to publish journal, online only. Saving the printing and postage costs, we can guarantee yet another period of reviewing and publishing your best work without any cost on your side.

SSSA Special Publications, 1997

Wetlands, 2016

Carolina Bay wetlands are common in the southeastern US Coastal Plain and important to water qual... more Carolina Bay wetlands are common in the southeastern US Coastal Plain and important to water quality, carbon sequestration, and habitat. Only South Carolina and Georgia have statewide inventories. We developed and evaluated a novel way to identify and delineate Bays using Baydense Bladen County, NC as a testbed. We posited that Bay land use had changed in the past 40 years and that Bays comprise a small subset of their surrounding soils. We classified decadal Landsat images as forest, agriculture, urban, and water. We used 812 previously delineated Bays to identify common Bay soils. From areas with common Bay soils and landuse change, we identified 548 new Bays and delineated them using a semi-automated on-line digitization tool. We saved new Bays to a Google Fusion Table for download and integration within a GIS. To gauge accuracy, Bays were scored on soils, land-use change, wetland delineation, and landscape position. Potential errors included omission of some small Bays (3.3-14.6 % of total Bay area) and commission of misclassified Bays (11 % of 1360 Bays), an estimated overall accuracy of 74 to 86 %. With 1360 delineated Bays, we estimated that as many as 478 have not yet been identified. These are most likely <5.76 ha.

Soil Micromorpohlogy: Studies in Management and Genesis, 1993

ABSTRACT Aquic moisture regimes have been redefined in Soil Taxonomy and are now called aquic con... more ABSTRACT Aquic moisture regimes have been redefined in Soil Taxonomy and are now called aquic conditions. The new system uses micromorphological concepts to define macroscopic indicators that show that a soil has been saturated and reduced. Aquic conditions are defined on the basis of three criteria which must be documented separately: saturation, reduction, and redoximorphic features. Low (&lt;2) chroma-colours and mottles have been replaced in Soil Taxonomy by redoximorphic features which are features formed by the reduction, translocation, and oxidation of Fe and Mn compounds. Three major groups of redoximorphic features have been identified: redox concentrations, redox depletions, and reduced matrices. Additional research is needed in order to utilize more fully redoximorphic features in defining aquic conditions. -from Authors

Genesis, Hydrology, Landscapes, and Classification, Second Edition, 2015

Hydric soils are described in Chapter 2 as soils that formed under anaerobic conditions that deve... more Hydric soils are described in Chapter 2 as soils that formed under anaerobic conditions that develop while the soils are inundated or saturated near their surface. These soils can form under a variety of hydrologic regimes that include nearly continuous saturation (swamps, marshes), short-duration flooding (riparian systems), and periodic saturation by groundwater. The most significant effect of excess water is isolation of the soil from the atmosphere and the prevention of O 2 from entering the soil. The blockage of atmospheric O 2 induces biological and chemical processes that change the soil from an aerobic and oxidized state to an anaerobic and reduced state. This shift in the aeration status of the soil allows chemical reactions to occur that develop the common characteristics of hydric soils, such as the accumulation of organic carbon in A horizons, gray-colored subsoil horizons, and production of gases such as H 2 S and CH 4 . In addition, the creation of anaerobic conditions requires adaptations in plants if they are to survive in the anaerobic hydric soils. This chapter discusses the chemistry of hydric soils by focusing on the oxidation–reduction reactions that affect certain properties and functions of hydric soils and form the indicators by which hydric soils are identified (Chapter 7). Both the biological and chemical functions of wetlands are controlled to a large degree by oxidation–reduction chemical reactions (Mitsch and Gosselink 1993). The fundamentals behind these reactions will be reviewed in this chapter along with methods of monitoring these reactions in the field, and the effects of these reactions on major nutrient cycles in wetlands. In our experience, soil chemistry is probably the subject least understood by students of hydric soils and wetlands in general. Therefore, the following treatment is intended to be simple, and to cover those topics that can be related to the field study of hydric soils. Students wishing more detailed treatments are encouraged to consult the work of Ponnamperuma (1972) in particular, as well as the discussion of redox reactions in McBride (1994) and Sparks (1995).

Genesis, Hydrology, Landscapes, and Classification, Second Edition, 2015

Genesis, Hydrology, Landscapes, and Classification, Second Edition, 2015

Water in the capillary fringe (CF) moves horizontally with the groundwater, but the biogeochemica... more Water in the capillary fringe (CF) moves horizontally with the groundwater, but the biogeochemical reactions in it may be more like those in the vadose zone above it than the groundwater below. A series of laboratory studies were conducted to assess the redox conditions and the fate of nitrate (NO3), and bromide (Br) within the vadose zone-groundwater continuum. Two different sizes of columns (90- and 240-cm long), each with its front face constructed of clear polycarbonate sheet, were packed with different soils. Two 2.5-cm wide chambers on the sides of each column allowed solution application/drainage. In one experiment, four different soil materials were packed in small (90-cm long) columns and a water table (WT) was established at 38 cm below the soil surface. A series of redox probes were installed at 5 cm below and 5, 15 and 25 cm above the WT at 20, 42.5 and 65 from the inlet, and distilled water was passed through each column horizontally at different velocities. A redox gra...

Soil Science Society of America Journal, 1990

Chisel plowing loosens dense root-restricting layers within 0.25 m of the soil surface, while sub... more Chisel plowing loosens dense root-restricting layers within 0.25 m of the soil surface, while subsoiling can be used to routinely loosen dense layers down to a depth of approximately 0.45 m. Selecting one tillage method over the other to maximize yield is problematic because the lower depth of a root-restricting layer is often difficult to determine precisely if the layer contains structural aggregates. We hypothesized that the ability of roots to penetrate dense soil layers is related to the size of aggregates in the dense layers. Therefore, this study compared root distributions for chisel plowed and subsoiled tillage treatments and related them to soil properties and corn (Zea mays L.) grain yield for soils having dense layers that varied in their aggregate size. Yields and root distributions were determined for the two tillage treatments on eight Typic and Arenic Paleudults. Each site had a dense, high-strength soil layer below the depth of chiseling. Subsoiling significantly (P = 0.10) increased yields over chisel plowing at five sites. At four of these sites, the proportion of roots between depths of 0.3 and 1.0 m in the chiseled treatment was low (<0.20) due to the root-restricting layer extending below the depth of chiseling. Although all sites had pan-like layers, which were characterized on the basis of bulk-density and cone-index measurements, only layers whose ped meanweight diameter was <1.2 mm resulted in root proportions being <0.20 in the chiseled treatment. These virtually nonaggregated layers also tended to have low amounts of plant-available water (<0.12 m 3 m 3). To adequately characterize root-restricting layers that reduced yield in these soils, some measure of subsurface aggregation or a correlated property such as plant-available water or texture had to be evaluated along with bulk density or cone index. D ENSE SOIL LAYERS such as tillage pans are commonly found in the coarse-textured, welldrained Udults of the southeastern USA (Campbell et al., 1974; Cassel, 1981; NeSmith et al., 1987). These dense layers often restrict root development and reduce yields, particularly during dry years (Kamprath

Wetlands, 2006

Wetland hydrology can be restored to soils that have been drained by plugging ditches to return t... more Wetland hydrology can be restored to soils that have been drained by plugging ditches to return the water table to its original elevation. Organic soils subside after drainage, and when ditches are plugged the restored water table may rise above the soil surface, killing newly planted vegetation. This study developed a method to estimate amounts of primary (settling) and secondary (oxidation) subsidence that could be applied to any organic soil. Primary subsidence was estimated from differences in bulk density between the drained and representative undrained sites. Secondary subsidence was estimated from accumulation of sand in the surface (Oap) horizons and changes in bulk density between oxidized and unoxidized organic horizons. Total subsidence was the sum of primary and secondary subsidence. Bulk density, particle size, and organic carbon data were gathered from one drained (Juniper Bay) and three undrained Carolina bay wetlands. Juniper Bay was drained with a network of ditches in three stages, 15, 20, and 30 years ago. Mean total subsidence was not significantly different (0.10 level) over time and averaged 121 cm for the three drainage periods. The mean rate of primary subsidence across the three drainage periods was 4 cm yr Ϫ1 , while secondary subsidence was approximately 2 cm yr Ϫ1. Subsidence values were variable across Juniper Bay and were not related to distance from a field ditch. Restoration of the hydrology in Juniper Bay to predrainage water-table elevations could result in a water table that is Ͼ1 m above the existing soil surface.

Soil Science Society of America Journal, 2007

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Soil Science Society of America Journal, 2000

Field indicators are used to identify hydric soil boundaries and to delineate wetlands. The most ... more Field indicators are used to identify hydric soil boundaries and to delineate wetlands. The most common field indicators may not be seen in some soils with thick, dark, mollic epipedons, and do not form in Fe-poor soils. This study evaluated magnetic susceptibility (MS) meter as a field tool to determine hydric soil boundaries. Five Mollisol-dominated sites formed in glacial deposits in Illinois were evaluated along with one Ultisol-dominated site formed in Coastal Plain sediments of North Carolina. Measurements of volumetric MS were made along transects at each site that extended from wetland into upland areas. One created wetland was evaluated. Field indicators were used to identify the hydric soils. Results showed that volumetric MS values were significantly (P 0.15) differences in MS were found for Coastal Plain hydric and nonhydric soils where MS values were low (<10 x 10 -5 SI). Critical MS values that separated hydric and nonhydric soils varied between 20 x 10 -5 and 30 x 10 -5 SI for the loessal soils evaluated in Illinois. Such critical values will have to be determined on site using field indicators until specific values can be defined for hydric soils within a given parent material. With a critical MS value in hand, a wetland delineator can make MS measurements along transects perpendicular to the envisioned hydric soil boundary to quickly and quantitatively identify it.

Soil Science Society of America Journal, 2002

approach for assessing seasonal saturation is to use hydrologic models to estimate daily water ta... more approach for assessing seasonal saturation is to use hydrologic models to estimate daily water table levels across Seasonal saturation in soils is expensive and time consuming to long (e.g., 40-yr) periods. The water table data can be document, but the information is needed for land use assessments. correlated to soil color patterns, and the colors then used Hydrologic models can be used to assess saturation occurrence quickly if the models are calibrated for individual sites. This study determined to extrapolate the water data to other sites containing whether a drainage model (DRAINMOD) could predict water table similar soils. Such an approach was used by Boersma levels in soils with and without a perimeter ditch. Water table levels et al. (1972) and Simonson and Boersma (1972) with were monitored for up to 3 yr at two toposequences that contained limited success. a total of 21 soil plots (3 m by 3 m). Soils included Typic Paleudults, Hydrologic modeling can be used to predict long-Aquic Paleudults, and Umbric Paleaquults. Each plot was instruterm historic water table fluctuations on a day-today mented with a recording well to monitor daily water table levels. basis for a soil (Skaggs, 1999). The required input data DRAINMOD was calibrated for each soil plot using measurements for model calibration can be acquired in a short period of in situ saturated hydraulic conductivity, soil water characteristic, (e.g., 6 mo) and the long-term simulations using historic depth to impermeable layer, depth of rooting, and rainfall. A plot's rainfall data can be done on a desktop computer rapidly. water table fluctuation was simulated by a system of virtual drains whose distance and depth were adjusted to produce simulated water Once the long-term daily water table data are obtained, table fluctuations in line with those actually measured. Further calibraprobability values for a specific duration of saturation tion adjusted drainable porosity in the upper 20 cm of the soil, deprescan be computed for any soil depth. The major advansional storage, evapotranspiration rate, and depth to impermeable tage of using simulation models is that the effects of layer. Adjustments were made by iteration to minimize the absolute annual and seasonal variability of weather can be conaverage deviation between simulated and measured water table levels. sidered in the analysis. Calibration had to be done by plot. Average absolute deviations were The hydrologic model DRAINMOD has been extengenerally Ͻ20 cm for periods ranging from 1 to 3 yr. The results sively used in the USA to analyze the long-term effects showed that DRAINMOD could be adapted to simulate water table of drainage on water table fluctuations (Skaggs, 1980; levels in landscapes that do not contain a network of parallel drains.

Soil Science Society of America Journal, 2004

... that the recording wells were monitoring daily water levels accurately, a manual check well .... more ... that the recording wells were monitoring daily water levels accurately, a manual check well ... describe soil horizons and the redoximorphic features without affecting the hydrology near the ... a temperature-dependent conversion factor to the voltages measured in the field (Patrick et ...

Soil Science Society of America Journal, 1987

Sand grain roundness and sphericity were evaluated for 50 soil samples from Atlantic Coastal Plai... more Sand grain roundness and sphericity were evaluated for 50 soil samples from Atlantic Coastal Plain soils to determine relationships of sand grain roundness and sphericity to the soils' cone index (mechanical impedance), bulk density, and the dense soil angle of repose. A previous investigation collected undisturbed cores from 50 tillage-induced pans in the Atlantic Coastal Plain, and determined cone index, bulk density, and the dense soil angle of repose. One hundred sand grains were isolated from each of the 50 soil materials. Roundness was determined for each grain by comparing the grain's projected image to standard images in published roundness charts. Sphericity was also determined for the 100 grains per soil by measuring selected grain axes. Mean values for roundness and sphericity were determined for each soil sample. Mean roundness values ranged from 0.44 to 0.57 across sites, but 74% of the sites had mean roundness values between 0.45 and 0.49 inclusive. Mean sphericity values ranged from 0.74 to 0.81, but 72% of the sites had mean sphericities between 0.78 and 0.81 inclusive. Correlation coefficients for relations of cone index, bulk density, and dense soil angle of repose to roundness and sphericity were generally and not significant (0.10 level). Sphericity and roundness were not significant variables in regression models describing variations in cone index and the dense soil angle of repose. Roundness was not a significant variable in regression models describing variations in bulk density among sites, but sphericity was a significant variable in models that were based on particle size characteristics alone. Additional Index Words: bulk density, cone index, dense soil angle of repose, particle size distribution, texture, tillage pans. View complete article To view this complete article, insert Disc 5 then click button8

Soil Science Society of America Journal, 1985

ABSTRACT Tillage-pans occur in many soils of the southeastern United States and usually decrease ... more ABSTRACT Tillage-pans occur in many soils of the southeastern United States and usually decrease crop yields. Relative yield increases from subsoiling (deep tillage) as compared to a nonsubsoiled treatment have been variable among soils due to differences in soil properties. The primary objective of this investigation was to relate soil physical properties to relative yield increases of corn (Zea mays L. ) due to subsoiling. Corn yields were measured for subsoiled and nonsubsoiled (disked twice) treatments during 1978, 1979, and 1980 at 12 locations in the North Carolina Coastal Plain region. Soil physical properties of the Ap and E or B horizons were characterized for each site, and included air-filled porosity, cone index, saturated hydraulic conductivity, bulk density, ped mean weight-diameter, and texture.

Soil Science Society of America Journal, 1983

ABSTRACT Significant periods of seasonal waterlogging in some soils of the Texas Coastal Plain ha... more ABSTRACT Significant periods of seasonal waterlogging in some soils of the Texas Coastal Plain have gone unrecognized because the soils lack low chroma colors. A study was conducted in two soils along a forested toposequence of Alfisols to identify morphological features other than color that are indicative of groundwater saturation and Fe reduction. It is suggested that albic neoskeletans be used as diagnostic criteria for water saturation and Fe reduction despite their moist color chromas of four or less. It is proposed that albic neoskeletans be used, when low chroma colors are absent, to identify aquic intergrades in Paleudalfs.-from Authors

Acta Physiologica, 2013

Next month, it will be 50 years since Bob Dylan released this song. Conspiracy theories have it t... more Next month, it will be 50 years since Bob Dylan released this song. Conspiracy theories have it that he died only three years later in a motorcycle accident. The times they are a-changin’ for Acta Physiologica as well. Far from dying, Acta Physiologica enhanced all its performance parameters this year, as for the previous years before (Persson 2012a,b). Submissions surge in parallel to the impact factor. Having an impact factor of 4.4 places Acta ahead of most topnotch journals in the field. Of course, this development only mirrors your publications in Acta. Thank you and congratulations! What makes Acta so special? It is a recipe with several ingredients. Today’s reader often needs a quick scan of a certain research field and wishes original articles to be put into context of state-of-the-art science. Acta takes these needs into account by publishing numerous editorials, which readers download at a remarkable rate (the top two for 2011/2012 (Park et al. 2012, Persson & Persson 2012)). More than 30 editorials appeared in 2013, some highlighting our very best work and others providing a broader picture of a field that has progressed, thanks to deeper understanding provided by the articles in Acta. When was actually the last time you held the printed copy of Acta Physiologica in your hands, physically leafing through it, article by article? Cannot remember? This monthly routine for editors is probably a very unusual event for our readers. In fact, almost all of our subscriptions are online only. The libraries simply do not have space to deposit all the hard copies, and the reader prefers to scan groups of publications and then assess them immediately online. This has led to a situation in which our printed copies are primarily being distributed to our editors and editorial board members, a thank you for their endless work they dedicate to the Journal. However, you may ask, ‘Is the effort of print setting and binding the copies together with the posting really worth the hassle?’ After all, every one of our editors and editorial board members do have free access to the Journal online. Thus, we have decided to go along with modern developments in publishing science (Anon 2007, Perham 2013) and will now make Acta Physiologica a free to publish journal, online only. Saving the printing and postage costs, we can guarantee yet another period of reviewing and publishing your best work without any cost on your side.

SSSA Special Publications, 1997

Wetlands, 2016

Carolina Bay wetlands are common in the southeastern US Coastal Plain and important to water qual... more Carolina Bay wetlands are common in the southeastern US Coastal Plain and important to water quality, carbon sequestration, and habitat. Only South Carolina and Georgia have statewide inventories. We developed and evaluated a novel way to identify and delineate Bays using Baydense Bladen County, NC as a testbed. We posited that Bay land use had changed in the past 40 years and that Bays comprise a small subset of their surrounding soils. We classified decadal Landsat images as forest, agriculture, urban, and water. We used 812 previously delineated Bays to identify common Bay soils. From areas with common Bay soils and landuse change, we identified 548 new Bays and delineated them using a semi-automated on-line digitization tool. We saved new Bays to a Google Fusion Table for download and integration within a GIS. To gauge accuracy, Bays were scored on soils, land-use change, wetland delineation, and landscape position. Potential errors included omission of some small Bays (3.3-14.6 % of total Bay area) and commission of misclassified Bays (11 % of 1360 Bays), an estimated overall accuracy of 74 to 86 %. With 1360 delineated Bays, we estimated that as many as 478 have not yet been identified. These are most likely <5.76 ha.

Soil Micromorpohlogy: Studies in Management and Genesis, 1993

ABSTRACT Aquic moisture regimes have been redefined in Soil Taxonomy and are now called aquic con... more ABSTRACT Aquic moisture regimes have been redefined in Soil Taxonomy and are now called aquic conditions. The new system uses micromorphological concepts to define macroscopic indicators that show that a soil has been saturated and reduced. Aquic conditions are defined on the basis of three criteria which must be documented separately: saturation, reduction, and redoximorphic features. Low (&lt;2) chroma-colours and mottles have been replaced in Soil Taxonomy by redoximorphic features which are features formed by the reduction, translocation, and oxidation of Fe and Mn compounds. Three major groups of redoximorphic features have been identified: redox concentrations, redox depletions, and reduced matrices. Additional research is needed in order to utilize more fully redoximorphic features in defining aquic conditions. -from Authors

Genesis, Hydrology, Landscapes, and Classification, Second Edition, 2015

Hydric soils are described in Chapter 2 as soils that formed under anaerobic conditions that deve... more Hydric soils are described in Chapter 2 as soils that formed under anaerobic conditions that develop while the soils are inundated or saturated near their surface. These soils can form under a variety of hydrologic regimes that include nearly continuous saturation (swamps, marshes), short-duration flooding (riparian systems), and periodic saturation by groundwater. The most significant effect of excess water is isolation of the soil from the atmosphere and the prevention of O 2 from entering the soil. The blockage of atmospheric O 2 induces biological and chemical processes that change the soil from an aerobic and oxidized state to an anaerobic and reduced state. This shift in the aeration status of the soil allows chemical reactions to occur that develop the common characteristics of hydric soils, such as the accumulation of organic carbon in A horizons, gray-colored subsoil horizons, and production of gases such as H 2 S and CH 4 . In addition, the creation of anaerobic conditions requires adaptations in plants if they are to survive in the anaerobic hydric soils. This chapter discusses the chemistry of hydric soils by focusing on the oxidation–reduction reactions that affect certain properties and functions of hydric soils and form the indicators by which hydric soils are identified (Chapter 7). Both the biological and chemical functions of wetlands are controlled to a large degree by oxidation–reduction chemical reactions (Mitsch and Gosselink 1993). The fundamentals behind these reactions will be reviewed in this chapter along with methods of monitoring these reactions in the field, and the effects of these reactions on major nutrient cycles in wetlands. In our experience, soil chemistry is probably the subject least understood by students of hydric soils and wetlands in general. Therefore, the following treatment is intended to be simple, and to cover those topics that can be related to the field study of hydric soils. Students wishing more detailed treatments are encouraged to consult the work of Ponnamperuma (1972) in particular, as well as the discussion of redox reactions in McBride (1994) and Sparks (1995).

Genesis, Hydrology, Landscapes, and Classification, Second Edition, 2015

Genesis, Hydrology, Landscapes, and Classification, Second Edition, 2015

Water in the capillary fringe (CF) moves horizontally with the groundwater, but the biogeochemica... more Water in the capillary fringe (CF) moves horizontally with the groundwater, but the biogeochemical reactions in it may be more like those in the vadose zone above it than the groundwater below. A series of laboratory studies were conducted to assess the redox conditions and the fate of nitrate (NO3), and bromide (Br) within the vadose zone-groundwater continuum. Two different sizes of columns (90- and 240-cm long), each with its front face constructed of clear polycarbonate sheet, were packed with different soils. Two 2.5-cm wide chambers on the sides of each column allowed solution application/drainage. In one experiment, four different soil materials were packed in small (90-cm long) columns and a water table (WT) was established at 38 cm below the soil surface. A series of redox probes were installed at 5 cm below and 5, 15 and 25 cm above the WT at 20, 42.5 and 65 from the inlet, and distilled water was passed through each column horizontally at different velocities. A redox gra...

Soil Science Society of America Journal, 1990

Chisel plowing loosens dense root-restricting layers within 0.25 m of the soil surface, while sub... more Chisel plowing loosens dense root-restricting layers within 0.25 m of the soil surface, while subsoiling can be used to routinely loosen dense layers down to a depth of approximately 0.45 m. Selecting one tillage method over the other to maximize yield is problematic because the lower depth of a root-restricting layer is often difficult to determine precisely if the layer contains structural aggregates. We hypothesized that the ability of roots to penetrate dense soil layers is related to the size of aggregates in the dense layers. Therefore, this study compared root distributions for chisel plowed and subsoiled tillage treatments and related them to soil properties and corn (Zea mays L.) grain yield for soils having dense layers that varied in their aggregate size. Yields and root distributions were determined for the two tillage treatments on eight Typic and Arenic Paleudults. Each site had a dense, high-strength soil layer below the depth of chiseling. Subsoiling significantly (P = 0.10) increased yields over chisel plowing at five sites. At four of these sites, the proportion of roots between depths of 0.3 and 1.0 m in the chiseled treatment was low (<0.20) due to the root-restricting layer extending below the depth of chiseling. Although all sites had pan-like layers, which were characterized on the basis of bulk-density and cone-index measurements, only layers whose ped meanweight diameter was <1.2 mm resulted in root proportions being <0.20 in the chiseled treatment. These virtually nonaggregated layers also tended to have low amounts of plant-available water (<0.12 m 3 m 3). To adequately characterize root-restricting layers that reduced yield in these soils, some measure of subsurface aggregation or a correlated property such as plant-available water or texture had to be evaluated along with bulk density or cone index. D ENSE SOIL LAYERS such as tillage pans are commonly found in the coarse-textured, welldrained Udults of the southeastern USA (Campbell et al., 1974; Cassel, 1981; NeSmith et al., 1987). These dense layers often restrict root development and reduce yields, particularly during dry years (Kamprath

Wetlands, 2006

Wetland hydrology can be restored to soils that have been drained by plugging ditches to return t... more Wetland hydrology can be restored to soils that have been drained by plugging ditches to return the water table to its original elevation. Organic soils subside after drainage, and when ditches are plugged the restored water table may rise above the soil surface, killing newly planted vegetation. This study developed a method to estimate amounts of primary (settling) and secondary (oxidation) subsidence that could be applied to any organic soil. Primary subsidence was estimated from differences in bulk density between the drained and representative undrained sites. Secondary subsidence was estimated from accumulation of sand in the surface (Oap) horizons and changes in bulk density between oxidized and unoxidized organic horizons. Total subsidence was the sum of primary and secondary subsidence. Bulk density, particle size, and organic carbon data were gathered from one drained (Juniper Bay) and three undrained Carolina bay wetlands. Juniper Bay was drained with a network of ditches in three stages, 15, 20, and 30 years ago. Mean total subsidence was not significantly different (0.10 level) over time and averaged 121 cm for the three drainage periods. The mean rate of primary subsidence across the three drainage periods was 4 cm yr Ϫ1 , while secondary subsidence was approximately 2 cm yr Ϫ1. Subsidence values were variable across Juniper Bay and were not related to distance from a field ditch. Restoration of the hydrology in Juniper Bay to predrainage water-table elevations could result in a water table that is Ͼ1 m above the existing soil surface.

Soil Science Society of America Journal, 2007

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or b... more All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Soil Science Society of America Journal, 2000

Field indicators are used to identify hydric soil boundaries and to delineate wetlands. The most ... more Field indicators are used to identify hydric soil boundaries and to delineate wetlands. The most common field indicators may not be seen in some soils with thick, dark, mollic epipedons, and do not form in Fe-poor soils. This study evaluated magnetic susceptibility (MS) meter as a field tool to determine hydric soil boundaries. Five Mollisol-dominated sites formed in glacial deposits in Illinois were evaluated along with one Ultisol-dominated site formed in Coastal Plain sediments of North Carolina. Measurements of volumetric MS were made along transects at each site that extended from wetland into upland areas. One created wetland was evaluated. Field indicators were used to identify the hydric soils. Results showed that volumetric MS values were significantly (P 0.15) differences in MS were found for Coastal Plain hydric and nonhydric soils where MS values were low (<10 x 10 -5 SI). Critical MS values that separated hydric and nonhydric soils varied between 20 x 10 -5 and 30 x 10 -5 SI for the loessal soils evaluated in Illinois. Such critical values will have to be determined on site using field indicators until specific values can be defined for hydric soils within a given parent material. With a critical MS value in hand, a wetland delineator can make MS measurements along transects perpendicular to the envisioned hydric soil boundary to quickly and quantitatively identify it.

Soil Science Society of America Journal, 2002

approach for assessing seasonal saturation is to use hydrologic models to estimate daily water ta... more approach for assessing seasonal saturation is to use hydrologic models to estimate daily water table levels across Seasonal saturation in soils is expensive and time consuming to long (e.g., 40-yr) periods. The water table data can be document, but the information is needed for land use assessments. correlated to soil color patterns, and the colors then used Hydrologic models can be used to assess saturation occurrence quickly if the models are calibrated for individual sites. This study determined to extrapolate the water data to other sites containing whether a drainage model (DRAINMOD) could predict water table similar soils. Such an approach was used by Boersma levels in soils with and without a perimeter ditch. Water table levels et al. (1972) and Simonson and Boersma (1972) with were monitored for up to 3 yr at two toposequences that contained limited success. a total of 21 soil plots (3 m by 3 m). Soils included Typic Paleudults, Hydrologic modeling can be used to predict long-Aquic Paleudults, and Umbric Paleaquults. Each plot was instruterm historic water table fluctuations on a day-today mented with a recording well to monitor daily water table levels. basis for a soil (Skaggs, 1999). The required input data DRAINMOD was calibrated for each soil plot using measurements for model calibration can be acquired in a short period of in situ saturated hydraulic conductivity, soil water characteristic, (e.g., 6 mo) and the long-term simulations using historic depth to impermeable layer, depth of rooting, and rainfall. A plot's rainfall data can be done on a desktop computer rapidly. water table fluctuation was simulated by a system of virtual drains whose distance and depth were adjusted to produce simulated water Once the long-term daily water table data are obtained, table fluctuations in line with those actually measured. Further calibraprobability values for a specific duration of saturation tion adjusted drainable porosity in the upper 20 cm of the soil, deprescan be computed for any soil depth. The major advansional storage, evapotranspiration rate, and depth to impermeable tage of using simulation models is that the effects of layer. Adjustments were made by iteration to minimize the absolute annual and seasonal variability of weather can be conaverage deviation between simulated and measured water table levels. sidered in the analysis. Calibration had to be done by plot. Average absolute deviations were The hydrologic model DRAINMOD has been extengenerally Ͻ20 cm for periods ranging from 1 to 3 yr. The results sively used in the USA to analyze the long-term effects showed that DRAINMOD could be adapted to simulate water table of drainage on water table fluctuations (Skaggs, 1980; levels in landscapes that do not contain a network of parallel drains.

Soil Science Society of America Journal, 2004

... that the recording wells were monitoring daily water levels accurately, a manual check well .... more ... that the recording wells were monitoring daily water levels accurately, a manual check well ... describe soil horizons and the redoximorphic features without affecting the hydrology near the ... a temperature-dependent conversion factor to the voltages measured in the field (Patrick et ...

Soil Science Society of America Journal, 1987

Sand grain roundness and sphericity were evaluated for 50 soil samples from Atlantic Coastal Plai... more Sand grain roundness and sphericity were evaluated for 50 soil samples from Atlantic Coastal Plain soils to determine relationships of sand grain roundness and sphericity to the soils' cone index (mechanical impedance), bulk density, and the dense soil angle of repose. A previous investigation collected undisturbed cores from 50 tillage-induced pans in the Atlantic Coastal Plain, and determined cone index, bulk density, and the dense soil angle of repose. One hundred sand grains were isolated from each of the 50 soil materials. Roundness was determined for each grain by comparing the grain's projected image to standard images in published roundness charts. Sphericity was also determined for the 100 grains per soil by measuring selected grain axes. Mean values for roundness and sphericity were determined for each soil sample. Mean roundness values ranged from 0.44 to 0.57 across sites, but 74% of the sites had mean roundness values between 0.45 and 0.49 inclusive. Mean sphericity values ranged from 0.74 to 0.81, but 72% of the sites had mean sphericities between 0.78 and 0.81 inclusive. Correlation coefficients for relations of cone index, bulk density, and dense soil angle of repose to roundness and sphericity were generally and not significant (0.10 level). Sphericity and roundness were not significant variables in regression models describing variations in cone index and the dense soil angle of repose. Roundness was not a significant variable in regression models describing variations in bulk density among sites, but sphericity was a significant variable in models that were based on particle size characteristics alone. Additional Index Words: bulk density, cone index, dense soil angle of repose, particle size distribution, texture, tillage pans. View complete article To view this complete article, insert Disc 5 then click button8

Soil Science Society of America Journal, 1985

ABSTRACT Tillage-pans occur in many soils of the southeastern United States and usually decrease ... more ABSTRACT Tillage-pans occur in many soils of the southeastern United States and usually decrease crop yields. Relative yield increases from subsoiling (deep tillage) as compared to a nonsubsoiled treatment have been variable among soils due to differences in soil properties. The primary objective of this investigation was to relate soil physical properties to relative yield increases of corn (Zea mays L. ) due to subsoiling. Corn yields were measured for subsoiled and nonsubsoiled (disked twice) treatments during 1978, 1979, and 1980 at 12 locations in the North Carolina Coastal Plain region. Soil physical properties of the Ap and E or B horizons were characterized for each site, and included air-filled porosity, cone index, saturated hydraulic conductivity, bulk density, ped mean weight-diameter, and texture.

Soil Science Society of America Journal, 1983

ABSTRACT Significant periods of seasonal waterlogging in some soils of the Texas Coastal Plain ha... more ABSTRACT Significant periods of seasonal waterlogging in some soils of the Texas Coastal Plain have gone unrecognized because the soils lack low chroma colors. A study was conducted in two soils along a forested toposequence of Alfisols to identify morphological features other than color that are indicative of groundwater saturation and Fe reduction. It is suggested that albic neoskeletans be used as diagnostic criteria for water saturation and Fe reduction despite their moist color chromas of four or less. It is proposed that albic neoskeletans be used, when low chroma colors are absent, to identify aquic intergrades in Paleudalfs.-from Authors