bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Soil Quality in Conservation Reserve Program and Wheat‐Fallow Soils
Authors: Staben M. L. , Bezdicek D. F. , Fauci M. F. , Smith J. L. 
Published: July 2010

AbstractChemical and microbial aspects of soil quality are an important consideration when evaluating the benefits of soil conservation efforts such as the Conservation Reserve Program (CRP). The objective of this study was to evaluate the quality of CRP and wheat‐fallow (W‐F) soils using soil biological and chemical parameters and C and N mineralization processes. The study was conducted on 20 CRP/W‐F paired sites in eastern Washington, on Ritzville silt loam (coarse‐silty, mixed, mesic Calciorthidic Haploxerolls). Soils collected from the paired fields were analyzed for chemical and biological parameters that have been suggested as indicators of soil quality. Potential enzyme activities and soil N were higher in the CRP soil than the W‐F soil. Although there were no significant differences in total organic carbon (TOC) or microbial biomass carbon (MBC) the C mineralization potentials and C pools were significantly different between the CRP and W‐F soils. Soil biota measurements showed there was greater active bacterial biomass in the CRP soil but greater fungal‐feeding nematodes, flagellates, and amoebae in the W‐F soil. The C mineralization study suggests that there is a significant increase in the secondary C pool of the CRP soil, which may indicate a buildup of higher quality soil organic matter and the potential for higher enzyme levels. When grass or straw was added to each soil type, the W‐F soil produced more CO2 with either substrate than the CRP soil, indicating C limiting conditions in the W‐F soil. Since it is unknown what constitutes good soil quality, these shifts in chemical and biological parameters may seem subtle. However, in general, trends in the data indicated that soil quality in the CRP was improved after 4 to 7 yr, compared with its previous management in W‐F cropland.
Soil Zinc Map of the USA using Geostatistics and Geographic Information Systems
Authors: White J. G. , Welch R. M. , Norvell W. A. 
Published: July 2010

AbstractThe geographic distribution of soil Zn is important to agriculture, nutrition, and health. A map illustrating the total Zn content of soils of the conterminous USA was developed using geostatistics and geographic information systems. Data were combined from a U.S. Geological Survey study targeting nonagricultural soils in 47 states, and a U.S. Department of Agriculture‐U.S. Environmental Protection Agency‐U.S. Food and Drug Administration study targeting agricultural soils in 33 states. Semivariograms indicated spatial correlation at distances up to 470 km. A significant quadratic trend was modeled, but detrending had little effect on the semivariogram or on interpolation via kriging. The data exhibited some anisotropy, but it had little effect on kriging. An exponential semivariogram model was fit using least squares and used to krige a grid covering the conterminous USA. The resultant map depicted soils north of about 37°N latitude or west of about 109°W longitude as generally having more Zn than the average of 55 mg kg−1. Soils southeast of this boundary tended to contain less Zn than average, with exceptions of soils developed on Mississippi alluvium and in Piedmont valleys and ridges. High estimate standard deviations occurred where data were sparse. The map will be useful in future research to determine the geographic distribution of plant‐available soil Zn, regional patterns of plant, animal, and human Zn deficiencies, the relationship of Zn to soil parent material, genesis, and surficial geology, and in considering the consequences of land disposal of Zn‐laden wastes.
Factors Influencing Heavy Metal Distribution in Six Oklahoma Benchmark Soils
Authors: Lee B. D. , Carter B. J. , Basta N. T. , Weaver B. 
Published: July 2010

AbstractSix contrasting benchmark Oklahoma soils underlain by sedimentary rock were selected and sampled by horizon to parent material or a 2‐m depth. Total Co, Cu, Ni, Pb, and Zn concentrations by horizon in total soil and clay fractions were determined by x‐ray fluorescence. Total concentration of heavy metals in these soils is dependent on clay content. There are fivefold more Cu, twofold more Zn and Ni, and 1.5‐fold more Co and Pb in the clay fraction than in the total soil. The clay fraction of surface horizons contains a greater concentration of Cu, Zn, and Co than subsoil horizons due to biogeochemical cycling of these micronutrients from the subsoil to the surface during melanization. Biogeochemical cycling reduces the total amount of heavy metal loss from surface to subsoil horizons by clay translocation but doesn't offset the illuviation of total heavy metals sorbed to clay. Higher levels of total heavy metals in each profile for each element are found in the B horizons than the A horizons (77% of the samples). Characterization of soil for total heavy metal content should include a sample from the B horizon especially in soil with higher clay content in the B than the A horizon. Soil parent material discontinuities cause changes in concentration of several heavy metals within two of the six soil profiles. Identification of soil parent material discontinuities is not a consistent factor causing change in heavy metal concentration within the soils studied.
Effectiveness of Organic Matter Incorporation in Reducing Soil Compactibility
Authors: Zhang Haiquan , Hartge K. H. , Ringe H. 
Published: July 2010

AbstractIncorporation of organic matter (OM) into soil can reduce its susceptibility to compaction. However, the significance of incorporated OM for different soil and soil water conditions is not well documented. We investigated the effectiveness of incorporated OM at different soil and soil water conditions and the OM effect on strength and structure recovery of compacted soils. A sandy soil (sandy Orthod), a silt loam (loamy Udalf), and a clay soil (clayey Umbrept) were amended with up to 80 g kg−1 of highly and slightly humified peat. The peat‐soil mixtures were compacted at different water contents using the standard Proctor procedure. Soil strength was determined with a penetrometer. Structure recovery was determined by bulk density changes and disintegration of clods through wetting‐drying cycles. For the cohesive silt loam and clay soils, OM was most effective at reducing compactibility at water contents lower than those for maximum Proctor compaction. For the sandy soil, OM was most effective at the Proctor‐optimum water content. The slightly humified peat had a greater effect than the highly humified. We found that OM is most effective for soils with high compactibility. The maximum penetration resistance, Pmax, of the clay soil was reduced from 0.49 to 0.30 MPa, and that of the sandy soil increased from 0.64 to 1.08 MPa. For the silt loam, 30 g kg−1 peat content had the highest Pmax. After five wetting‐drying cycles, bulk densities showed no significant differences among treatments. Clod disintegration was hindered by the OM incorporation. Although soil compactibility was reduced by OM incorporation, OM was more effective as soil compactibilty increased and at water contents lower than or close to the Proctor‐optimum water content. Structure recovery of compacted soils was not improved. The penetration resistance after compaction is not consistently related to the incorporated OM.
Incorporating Spatial Trends and Anisotropy in Geostatistical Mapping of Soil Properties
Authors: Crawford Carol A. Gotway , Hergert Gary W. 
Published: July 2010

AbstractThe spatial variation in soil parameters often differs with direction. These differences may occur naturally or may be due to management practices. Regardless of their origin, they present a challenge in geostatistical mapping of soil parameters. Recommendations pertaining to the selection of an appropriate geostatistical method based on the current literature are often incomplete or contradictory. The purpose of this investigation was to provide a unified description, comparison, and discussion of different geostatistical methods for handling trend and anisotropy that may be present in measured soil properties. Soil organic matter content of the 0‐ to 20‐cm depth from a field in continuous ridge‐tilled corn (Zea mays L.) was used to compare five geostatistical methods: ordinary kriging with an isotropic semivariogram (OKI); ordinary kriging with an anisotropic semivariogram (OKA); ordinary kriging within local neighborhoods (OKN); universal kriging (UK); and median polish kriging (MPK). Organic matter maps produced from the five methods showed similar large‐scale features but marked differences in the finer features. A comparison of percentage of total area in each organic matter range among mapping methods also showed strong similarities; however, the proportion of the field assigned to each range differed by as much as 7%. Larger differences would be expected at large sample spacing. Although the five methods produced similar maps, selection of the “best” technique should be based on selection of an associated model that best accounts for and describes the nature of the cause of the variation.
Wetland Denitrification: Influence of Site Quality and Relationships with Wetland Delineation Protocols
Authors: Groffman Peter M. , Hanson Gay C. 
Published: July 2010

AbstractDenitrification, the microbial conversion of NO3‐ to N gases, is important to wetland biogeochemistry and water quality maintenance functions. We measured denitrification along toposequences from forested upland‐wetland transition zones to red maple wetlands in Rhode Island. The sites were located on different soil parent materials derived from different geomorphic features including glacial outwash, granitic glacial till, basaltic glacial till, and alluvium. Each toposequence contained four or five different natural soil drainage classes. We assessed spatial and temporal variation in denitrification relative to site quality (parent material), water table dynamics, hydric soil and hydrophytic vegetation status, and a “growing season” defined as soil temperature >5°C. Denitrification rate was measured by intensive sampling during a 2‐yr period using an acetylene‐based intact soil core method. Annual estimates of denitrification were produced by extrapolating measured rates over the intervals between sample dates. Soils that were very poorly drained or that had developed on nutrient‐rich parent materials had higher denitrification than more well‐drained and/or less fertile soils. Nitrogen inputs from adjacent ecosystems also appeared to be a key regulator of denitrification rates. Annual denitrification ranged from 1 to >130 kg N ha−1 yr−1 and was lower in Year 2 than in Year 1 in all soils. There were poor relationships between spatial and temporal patterns of denitrification and patterns of hydric soils and hydrophytic vegetation within the wetlands. Wetland delineation and classification protocols based on soils, vegetation, or hydrology do not appear to encompass the capacity of a wetland to support denitrification.
A Two‐Stage Procedure for Determining Unsaturated Hydraulic Characteristics using a Syringe Pump and Outflow Observations
Authors: Wildenschild D. , Jensen K. Høgh , Hollenbeck K. J. , Sonnenborg T. , Butts M. B. , Illangasekare T. H. , Znidarcic D. 
Published: July 2010

AbstractA fast two‐stage methodology for determining unsaturated flow characteristics is presented. The procedure builds on direct measurement of the retention characteristic using a syringe pump technique, combined with inverse estimation of the hydraulic conductivity characteristic based on one‐step outflow experiments. The direct measurements are obtained with a commercial syringe pump, which continuously withdraws fluid from a soil sample at a very low and accurate flow rate, thus providing the water content in the soil sample. The retention curve is then established by simultaneously monitoring the capillary pressure. The measured retention curves were compared with those obtained by static methods and found to agree closely. Subsequently, a transient outflow experiment is carried out on the same soil sample, in the same apparatus, and the information is obtained on a time‐scale of days. The one‐step outflow data and the independently measured retention data are included in the objective function of a traditional least‐squares minimization routine, providing unique estimates of the unsaturated hydraulic characteristics by means of numerical inversion of Richards equation. As opposed to what is often assumed in practical applications, we found it necessary to allow the exponent (γ) of van Genuchten's hydraulic conductivity expression to vary to obtain satisfactory estimates. Optimized hydraulic conductivity estimates were ultimately compared with directly measured values, and visual agreement was quite satisfactory. However, we encountered numerical instabilities of the optimization code used (SFIT), a flaw that may constitute a potential problem when using this code for the optimization.
Steady‐State Funnel Flow: Its Characteristics and Impact on Modeling
Authors: Ju S.‐H. , Kung K.‐J. S. 
Published: July 2010

AbstractPreferential flow could dictate the leaching of contaminants in unsaturated soils. The objectives of this study were to: (i) numerically determine the characteristics of steady‐state funnel‐type preferential flow and how would it be influenced by infiltration rate, soil layer density, and textural combinations; and (ii) explore the validity of several basic assumptions used in different models to incorporate pesticide leaching through preferential flow paths. Water movement and pesticide transport in 12 two‐dimensional hypothetical profiles were numerically simulated. Results showed that there was an induction zone where water was gradually congregated into preferential flow paths and its movement could be conceptualized as a network of tributaries merging into rivers. Beneath the induction zone, water moved through several distinct flow domains without lateral interaction. The frequency distribution of normalized water fluxes would spread out when the layering density increased or the pore discontinuity across a textural boundary increased. There existed a critical number beyond which any further increase in layer density would not influence the frequency distribution of normalized water fluxes. Frequency of water fluxes in the stationary region was not lognormally distributed. Pesticide leaching depended primarily on the last 20% of the water flux distribution. If a profile was made of regions with different layer densities, the water fluxes of the entire unsaturated profile might be neither spatially stationary nor vertically invariant. It was possible to numerically derive the worst‐case scenario (i.e., the widest spreading of the water fluxes). Because it is impossible to measure the frequency distribution of normalized water fluxes in a field, it is prudent to predict pesticide leaching according to this worst‐case frequency distribution.
Nitrogen Contribution of Pea Residue in a Hummocky Terrain
Authors: Stevenson F. C. , van Kessel C. 
Published: July 2010

AbstractTopography influences the distribution of soil water and inorganic N, which could affect the availability of N from legume residue to the subsequent crop. A study assessed the landscape‐scale variability of the N contribution by pea (Pisum sativum L.) to the soil (N2 fixation in residue minus seed N derived from the soil) and the subsequent wheat (Triticum aestivum L.) crop. In situ 15N‐labeled pea residue was used to monitor the contribution of pea residue to the succeeding crop. A 100‐point sampling grid, with 10‐m spacings, was established in a field with hummocky terrain. Each sampling point was classified as a shoulder or a low‐catchment or high‐catchment footslope. The N contribution by pea to the soil was 45 kg ha−1 in the shoulders and 63 kg ha−1 in the footslopes. Recovery of 15N in the microbial biomass was greater in the footslopes (71%) vs. the shoulders (51%), and related to greater soil water content in the footslopes. The N contribution by pea to wheat, as assessed by the 15N that wheat derived from the residue of the preceding wheat crop, was 11% and similar among landform complexes. Therefore, the N contribution of pea to wheat did not explain the greater N accumulation by wheat in the high‐catchment areas than the other landform complexes. The N contribution of pea to a succeeding wheat crop apparently will be a small component of the rotation benefit by pea in a hummocky terrain.
Evaluation of an In Situ Net Soil Nitrogen Mineralization Method in Dryland Agroecosystems
Authors: Kolberg R. L. , Rouppet B. , Westfall D. G. , Peterson G. A. 
Published: July 2010

AbstractDirect quantitative measurement of soil net N mineralization in agricultural soils under field conditions has not been widely used. A potential method of in situ net N mineralization was investigated in the fallow phase of a 3‐yr no‐till crop rotation at two sites. Undisturbed soil cores (5 by 15 cm) with anion‐ and cation‐exchange resins (Sybron Ionac ASB‐1P and C‐249) at the bottom were incubated in situ. Nitrate‐N plus NH4+‐N extracted from soil was added to extracted amounts from resin bags to determine net N mineralized during each of three incubation periods (3–4 wk each). Total net N mineralization was 33.7 and 26.5 kg N ha−1 during 84 and 75 d of incubation at Sterling and Stratton, respectively. Relative amounts of resin did not affect N captured but cores placed midway between old corn (Zea Mays L.) rows tended to accumulate more (P > F = 0.13) N than cores placed in rows. This in situ method appears to be a reliable method for measuring net N mineralization in the field; however, variation is large and many observations are required to obtain net N mineralization rates within an acceptable confidence interval.
Spatial Patterns of Carbon and Texture on Drumlins in Northeastern Wisconsin
Authors: Kabrick J. M. , Clayton M. K. , McSweeney K. 
Published: July 2010

AbstractThe objective of the study was to determine if there is a consistent and pervasive spatial pattern to organic C and particle‐size distribution for drumlin summits of the Nicolet National Forest, Wisconsin. Accordingly, a method for estimating confidence intervals was developed and used to assess variogram similarity and variation. Organic C and particle‐size distribution were determined for the upper 20 cm of mineral soil at nodes of sampling grids on each of six drumlin summits. The aeolian cap thickness was also measured at each node. Variograms and confidence intervals were constructed for each attribute on each drumlin. A systematic comparison of variograms and their confidence intervals revealed that C and clay content each had similar variograms from drumlin to drumlin. Thus, composite variograms for each C and clay content were then constructed. Organic C appeared to be nearly spatially random, while clay content is spatially dependent. Sand and silt variograms each varied from drumlin to drumlin and thus were not combined into composite variograms. Variogram dissimilarity for sand and silt appeared to be related to aeolian cap thickness; greater sill variances occurred on drumlins with thinner aeolian caps. The approach and methods described here have utility for identifying attributes that have similar patterns on a particular landform and show promise for more rigorously quantifying soil attribute patterns for soil surveys and related land information systems.
Anthraquic Conditions in Nonagricultural Soils: A Proposal and Case Study
Authors: Evans C. V. 
Published: July 2010

AbstractAs soil scientists develop recommendations for the classification and interpretation of anthropogenic soils, many altered soils will need to be described and classified, probably at a variety of taxonomic levels. One agent of alteration may be the application of liquid wastes to soils for extended periods of time, with the potential of creating aquic conditions in those soils. Although such conditions could logically be termed anthraquic, no provision exists for recognizing anthraquic conditions in nonagricultural soils. As these morphological characteristics may be reversed if the spraying were discontinued, it is important that future land‐use planners be given such information. The most logical venue is to include anthraquic designators at appropriate levels of classification that may also be applied to nonagricultural soils. An example is given of a wooded plot in New Hampshire that has received secondary Cl‐treated wastewater for >15 yr.
Rapid Laboratory Calibration of Time Domain Reflectometry Using Upward Infiltration
Authors: Young M. H. , Fleming J. B. , Wierenga P. J. , Warrick A. W. 
Published: July 2010

AbstractWe propose an upward infiltration method to calibrate a time domain reflectometry (TDR) system. The method is rapid, allows the soil to remain unchanged during the experiment, and provides hundreds of data points. Three experiments were conducted using 18.7‐cm‐long probes in soils of three textures (nine experiments total). Calibrations also were performed by packing soil cores with soil at progressively higher water contents. The data from the two methods were fitted using regression techniques to two published models of the dielectric constant‐water content relationship. The results show that the calibration curves of all three soils, fitted simultaneously to replicate experiments, were similar in shape and statistically the same. A single calibration curve, fitted simultaneously to the replicate experiments of the three soils, was compared with Topps equation and was statistically the same. The results support the conclusion that the upward infiltration method provides a fast and repeatable calibration method, consistent with conventional calibration.
Uniform Separation of Concentric Surface Layers from Soil Aggregates
Authors: Santos D. , Smucker A. J. M. , Murphy S. L. S. , Taubner H. , Horn R. 
Published: July 2010

AbstractIt is well accepted that soil organic matter improves soil structure; however, current methods limit our knowledge of the many physical‐chemical mechanisms that control the temporal processes of soil aggregation. A soil aggregate erosion (SAE) apparatus was designed to uniformly remove concentric surface layers of soil aggregates in an enclosed erosion chamber. The SAE was used to test for the presence of concentration gradients within aggregates of different soil types. The SAE method generally improved the separation of ion concentrations between the external and internal layers. Concentrations of C, Ca, and Mg were 8 to 19, 20 to 21, and 29 to 33% lower, respectively, at the external layers of aggregates for Haplaquoll and Hapludalf soils. Removal of surface layers had no effect on the tensile strength of soil aggregates. Therefore, we concluded that the SAE apparatus improves the separation of ion gradients within natural soil aggregates. Identification of the mineralogical, physical, chemical, and biological properties of this improved separation of concentric layers from soil aggregates should lead to further advancements in our knowledge of the functional mechanisms associated with the development and stability of soil aggregates.