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Home » Journal of Soil and Water Conservation » Abstracts and Archives » Third Quarter 2001
Third Quarter 2001

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Third Quarter 2001 Table of Contents

Features

  • A hierarchical evaluation of soil quality
    S.J. Langley-Turnbaugh and C.V. Evans

Research

Departments

  • Book Review by Dr. J. Laflen

  • Letters to the Editor

  • Upcoming

Managing nitrate and bacteria in runoff from livestock confinement areas with vegetative filter strips
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

J.J. Fajardo, J.W. Bauder, and S.D. Cash 

ABSTRACT: A documented source of nitrate-nitrogen contamination of surface water is livestock waste and storage facilities.  A vegetative filter strip (VFS) is effective in reducing some nutrients, sediment, and suspended solids in surface runoff from feedlots; however, results are variable in controlling water-soluble nutrients and bacteria in runoff. This study assessed the role of tall fescue (Festuca arundinacea Schreb.) as a VFS in reducing contaminants from stored animal wastes. The study evaluated the extent to which livestock manure stockpiles potentially contribute to nitrate-nitrogen (NO3-N) and coliform bacteria contamination of surface water resources. The experiment was conducted on Amsterdam silt loam (fine-silty, mixed, superactive Typic Haploboroll) soil. Tall fescue and bare soil (fallow) strips were established on a 4% slope. Treatments consisted of manure applications in the upland position for the strips. For comparision, vegetated and bare control (non treated) strips without manure in the upland position were also studied. Manure was applied annually (approximately 2 t fresh weight per strip). Runoff was achieved by applying water at the head of the treatments and forcing the applied water to pass through the manure stockpiles and into the VFS and fallow strips. Runoff water samples were collected and analyzed for NO3-N and coliform. Concentration of NO3-N in surface runoff from VFS with manure stockpiles in the headland was reduced up to 97% in 1997 and 99% in 1998 where a VFS was present. Coliform populations in runoff were reduced significantly by VFS in two runoff events, a 64% reduction in July 1997, and an 87% reduction in August 1998. However, the coliform counts in runoff, even from VFS treatments not receiving manure, remained substantially elevated. Dilution and residence time of water passing through the VFS appeared to be the most significant factors affecting reductions in NO3-N and bacteria in runoff. 

Keywords: Coliform bacteria, nitrate, runoff, vegetative filter strips, water quality

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Soil quality of harvested and grazed forest cutblocks in Southern British Columbia
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

M. Krzic, K. Broersma, R.F. Newman, T.M. Ballard, and A.A. Bomke 

ABSTRACT: This study evaluated soil chemical and physical properties as affected by timber harvesting and cattle grazing on cutblocks planted to lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.). Soil conditions on the ungrazed exclosures (representing disturbance by harvest only) and pastures grazed over 10 years to achieve 50% forage utilization (representing disturbance by harvest and grazing) were compared to the nearby forest without harvest and cattle grazing. Soil chemical properties showed no detrimental impacts from harvesting and/or livestock grazing. In fact, greater CEC, Ca, C, and N values on disturbance treatments should improve these soils as rooting media. Soil physical properties, although less favorable for tree growth on the two disturbance treatments than the mature forest, showed that a majority of the soil profile was not compacted above root-restricting threshold conditions. Results obtained from this study support the integrated use of forested rangelands in southern British Columbia. 

Keywords: Cattle grazing, forest soil, lodgepole pine, soil compaction, soil quality


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Vertical accuracy of two differentially corrected global positioning satellite systems
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

D.P. Johansen, D.E. Clay, C.G. Carlson, K.W. Stange, S.A. Clay, D.D. Malo, and J.A. Schumacher 

ABSTRACT: Farmers and scientists are using topographic maps resulting from data collected by differentially corrected global positioning systems (DGPS) to identify management zones and characterize the influence of conservation practices and landscape position on soil productivity, erosion, and agricultural sustainability. To develop accurate topographic maps, watershed managers must know positional errors associated with the different types of differentially corrected global positioning systems (DGPS). The objective of this study was to determine under field conditions, the vertical errors associated with real time kinematic (RTK) and real time stop-and-go (RTSG) sampling approaches using a single frequency carrier phase DGPS and RTK using C/A code DGPS. Research was conducted with and without selective availability. This experiment showed that elevation information determined by: 1.) a single frequency carrier phase DGPS receiver using RTK and RTSG sampling approaches, measured prior and post selective availability, had consistent results with standard deviations of less than 3.5 cm; 2.) a C/A code DGPS receiver, measured prior and post selective availability, had inconsistent results with relatively large standard deviations (83–100 cm); and 3.) GPS, measured post selective availability, had inconsistent results with relatively large standard deviations (100–200 cm). Results suggest that caution should be used in using elevation information collected from C/A code DGPS or GPS. 

Keywords: DGPS, GPS, landscape position, precision farming, selective availability, topography

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Phosphorus risk assessment index evaluation using runoff measurements
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

B. Eghball and J.E. Gilley 

ABSTRACT: An index to evaluate the phosphorus (P) pollution potential of agricultural fields was proposed by Lemunyon and Gilbert in 1993. Data from three rainfall simulation studies were used to evaluate the relative importance of the variables in the P index. These studies included plots containing sorghum (Sorghum bicolor L.), winter wheat (Triticum aestivum L), and corn (Zea mays L) residues on which chemical fertilizer and composted or noncomposted beef cattle feedlot manure were applied under no-till and disked conditions. The factors of erosion, runoff, soil P level, P application source, and method, and rate of P addition were weighted and considered in the index calculation. Measured soil erosion accounted for 78% and 88% of the variability in total and particulate P losses, respectively, indicating the importance of erosion in the loss of sediment bound P. Bioavailable and dissolved P losses were unrelated to measured soil erosion but were influenced by tillage, runoff amount, and P source. The P index of Lemunyon and Gilbert was modified based on the results of these experiments. The correlation coefficient value (r) between total P loss and the modified P index values, was 0.74 as compared to 0.52 for the Lemunyon and Gilbert’s P index. Additive index values were more closely correlated with total P loss than the index values calculated by multiplying the weight of each factor. If erosion and runoff are accurately predicted, the P index can serve as a useful tool for identifying sites where transport of P to surface water can be a potential concern. 

Keywords: Animal waste, erosion, eutrophication, fertilizer, P loss, runoff, water quality

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Assessing uncertainty of erodibility factor in national cooperative soil surveys: a case study at Fort Hood, Texas
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

P. Parysow, G. Wang, G. Gertner, and A.B. Anderson 

ABSTRACT: Soil erodibility is the inherent susceptibility of soil to be lost to erosion. The Universal Soil Loss Equation (USLE) is an erosion model that predicts soil loss as a function of soil erodibility (known as K-factor), as well as topographic, rainfall/runoff, cover, and support management factors. The National Cooperative Soil Survey (NCSS) has assigned each soil series (minimum mapping unit) one value of K representing classes of soil erodibility. Information contained in those surveys implies that K-factor values are free of estimation errors, and remain unchanged not only across whole soil series but also over time. However, evidence provided by soil science literature challenge those assumptions. The objective of this study was to evaluate variability and uncertainty in K-factor as reported by the NCSS at Fort Hood, Texas. We obtained one K value from each of 524 soil samples collected in the late summer of 1998 following a 10 m square grid. For each soil series, sampled K means were significantly different than K values proposed by NCSS, and intraseries coefficients of variation showed variability of up to about 20%. Sampled K values disregarded NCSS soil series boundaries and departed from NCSS K values as the distance from the soil series boundary increased. The USLE estimates of soil loss using sampled K versus NCSS K were also significantly different. Limitations in K estimation from typical pedons of original soil surveys, soil misclassification, as well as changes in surface soil structure may have contributed to the differences found. 

Keywords: Erodibility, geostatistics, K-factor, soil loss, spatial uncertainty, USLE

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An evaluation of wind erosion hazard in fallow lands of semiarid Aragon (NE Spain)
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

M.V. López, R. Gracia, and J.L. Arrúe 

ABSTRACT: Long fallowing (16 to 17 months), in the cereal/fallow rotation, may favor soil losses by wind erosion in agricultural soils of semiarid Aragon (NE Spain). With the objective of evaluating the risk of wind erosion in this area, soil losses for the most critical period of fallow (February-April) were estimated from a total of 67 fallow fields by using the Wind Erosion Equation (WEQ). All soils were medium textured, with this loam the most frequent textural class (45%). The CaCO3 content in the soil was higher than 200 g kg-1 in 90% of the fields. Mouldboard plough, chisel plough, and disk harrow were the main primary tillage tools used by farmers during fallow. Soil cover by crop residues was negligible (< 1%) in 76% of the fields, and only 20% tilling was done perpendicularly to dominant wind direction. The highest erodibility values corresponded to soils with a sandy loam texture and traditionally tilled with mouldboard plough. Predicted wind erosion was high to very high in 30% of the fields (> 20 Mg ha-1). The WEQ estimated erosion reductions to tolerable levels if reduced tillage, with chiseling as the primary tillage, is adequately adopted in the dryland cereal production areas of semiarid Aragon. 

Keywords: Crop residues, dryland farming, fallowing, reduced tillage, surface roughness, wind- erodible fraction, wind erosion

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Factors affecting nutrient application rates within three Midwestern watersheds
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

T.L. Napier and M. Tucker 

ABSTRACT: Data were collected in the winter of 1998 and spring of 1999 from 1,011 agriculturalists who were operating farms within watersheds in three Midwestern states to examine the merits of a social learning theory-farm structure model for explaining variability in fertilizer applications rates. Study findings revealed that the theoretical perspective used to guide the investigation had limited utility for predicting nutrient application rates at the farm level. Variables commonly purported to predict fertilizer use were shown not to be useful for explaining fertilizer application rates when nutrient rates were measured as bushels of grain produced per pound of nutrient applied per acre. Study findings are discussed in the context of existing intervention programs designed to reduce fertilizer application rates at the farm level. 

Keywords: Adoption, application rates, Midwest, watershed

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Potential changes in rainfall erosivity in the U.S. with climate change during the21st century
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3) 

M.A. Nearing 

ABSTRACT: The erosive power of rainfall can be expected to change as climate changes. Such erosive changes are likely to have significant impacts on local and national soil conservation strategies. This study uses results of climate change scenarios from two coupled Atmosphere-Ocean Global Climate Models to investigate the possible levels and patterns of change that might be expected over the 21st century. Results of this study suggest the potential for changes in rainfall erosivity across much of the continental United States during the coming century. The magnitude of change (positive or negative) across the country over an 80 year period averaged between 16–58%, depending upon the method used to make the predictions. Some areas of the country showed increases and others showed decreases in erosivity. Spatial distributions of calculated erosivity changes indicated areas of both consistency and inconsistency between the two climate models. 

Keywords: Atmosphere-ocean global climate models, precipitation, RUSLE, soil erosion

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Stocking rate effect on soil carbon and nitrogen in degraded soils
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3) 

K.N. Potter, J.A. Daniel, W. Altom , and H.A. Torbert 

ABSTRACT: Stocking rate (SR) effects on soil organic carbon (OC) and nitrogen content resulting from 10 year continuous management were determined. Treatments were rotational grazing with four SR levels: light, moderate, heavy and non grazed. Two soils, a Durant loam (Udertic Argiustolls) and a Teller silt loam (Udic Argiustolls) located within common paddocks were sampled. Total OC mass in the surface 60 cm of the Durant soil, averaged across treatments, was 95.7 t ha-1 compared to 56.7 t ha-1 in the Teller soil. In the Durant soil, OC decreased as SR increased, with the non grazed exclosure having the greatest amount of soil OC. In contrast, the Teller soil had similar amounts of OC in the soil profile with all grazing treatments, but less without grazing. Total soil nitrogen followed similar trends as the soil OC. Soil properties should be considered to accurately assess the potential of grazing lands to sequester carbon. 

Keywords: Grazing, organic carbon, sequestration

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CQESTR: a model to estimate carbon sequestration in agricultural soils
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

R.W. Rickman, C.L. Douglas, Jr., S.L. Albrecht L.G. Bundy, and J.L. Berc 

ABSTRACT: The PC-based model for predicting tillage and crop rotation effects on organic carbon decomposition and storage in the soil as organic matter (OM) uses crop residue and root biomass production, tillage type and timing, and average temperature from existing c-factor files, created with the Revised Universal Soil Loss Equation (RUSLE). Residue nitrogen content and soil layering information—including layer thickness, organic matter content, and bulk density— complete the input requirements for the model. Short-term trends of surface and remaining buried residue and long-term trends in soil organic matter content, are computed for individual fields and cropping practices. The model was calibrated with soil organic carbon observations (converted to equivalent OM values) from plots with over 60 years of recorded management history including wheat/fallow with manure additions and wheat/fallow with stubble removal. Computations have a 95% confidence interval of +/- 3.3 g OM kg-1 soil (0.33% OM). Comparison of OM calculations from the calibrated model with observed values from Lancaster, Wisconsin, and Lexington, Kentucky, produced mean residual errors ranging from -3.0 to + 0.2 g OM kg-1 soil (- 0.3 to + 0.02 % OM). 

Keywords: Carbon storage, crop residue, greenhouse gasses, organic matter, soil amendments

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A phosphorus budget for Wisconsin cropland
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

L.G. Bundy and S.J. Sturgul 

ABSTRACT: Phosphorus budget information for Wisconsin cropland was compiled between 1970 and 1995 in order to identify changes and trends in budget parameters through time. The main P inputs were animal manure and commercial fertilizer, and the major P removals were crop uptake and loss through runoff and erosion. The difference between inputs and removals was accounted for as a change in the amount of P stored in the soil. Phosphorus inputs from manure have decreased from a high of 120 million lbs (54.5 million kg) in 1975 to about 98 million lbs (44.5 million kg) in 1995. Since 1985, inputs from P fertilizers have decreased by about 30% . Phosphorus removals through crop uptake have increased since 1970 due to increased crop yields. Estimated annual P losses in runoff and erosion represent about 1.4% of the P applied each year or an average loss of about 0.32 lb P ac-1 (0.36 kg P ha-1) of  cropland. Excess P additions to cropland have decreased by 74% since 1975, with the 1995 excess amounting to 31 million lb (14.2 million kg) of P, or 3.3 lb  of P ac-1 (3.7 kg of P ha-1)of cropland. Most of this decrease is due to reduced use of P fertilizers and increased crop removal of P due to higher yields. Most of the excess P input contributes to increased amounts of P stored in soils. This change in storage of soil P is confirmed by the increasing average soil test P values for the state. 

Keywords: Budget, cropland, fertilizer, manure, phosphorus, Wisconsin


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Slope length effects on runoff and sediment delivery
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

C.C. Truman, R.D. Wauchope, H.R. Sumner, J.G. Davis, G.J. Gascho, J.E. Hook, L.D. Chandler, and A.W. Johnson 

ABSTRACT: Lab studies provide an opportunity to isolate processes influencing water, sediment, and agrichemical transport under standard conditions. However, extending this information to field or watershed scales is often difficult. We compared runoff (R) and sediment (E) losses from a lab study with field data from a Tifton loamy sand (3% slope). Three plot scales/length-rainfall simulator methodologies were used: 1.) 0.32 m2 lab pan (L = 0.6 m) under an oscillating nozzle rainfall simulator; 2.) 5.5 m2 field plot (L = 3 m) under a Wobbler nozzle rainulator, and 3.) 600 m2 field plots (L = 43 m) under the same rainulator used in method 2. For field plots (methods 2 and 3), R and E losses were measured from six simulated rainfall events (I = 25.4 mm hr-1, 2 hr duration) during two corn growing seasons (five days before agrichemical application and 1, 14, 29, 49, and 108 days after agrichemical application). Similar rainfall intensity and duration were used in the lab study. R and E losses from lab pan (method 1) and 5.5 m2 field plots (method 2) were measured at 5 minute intervals, whereas R and E delivery for 600 m2 plots (method 3) were measured continuously and at selected times, respectively. R and E rates from all methods generally increased during each event with similar maximum rates. Total R and E for method 2 was at least an order of magnitude greater than those for method 1, and total R and E for method 3 were at least 1 order of magnitude greater than those for method 2. R and E were related to slope length (R2 = 0.94-0.99). Exponents (b) for R and E were 0.50–1.63. Detachment and transport processes varied spatially. Once a critical slope length was exceeded, rilling occurred. Rilling was non existent in method 1 and was present but not dominant in method 2. For method 3, slope length was sufficient to cause rilling, therefore E was greater than that for methods 1 and 2. 

Keywords: scaling, rainfall simulation, transport capacity 

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Comparison of two electromagnetic induction tools in salinity appraisals
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

J.Doolittle, M. Petersen, and T. Wheeler 

ABSTRACT: Electromagnetic induction (EMI) is a relatively low cost and rapid method for measuring and mapping soil salinity over broad areas. This study compares apparent conductivity (ECa) data obtained with single-frequency (EM38 meter) and multi-frequency (GEM300 sensor) EMI instruments and relates apparent conductivity measured by these instruments with the more conventional conductivity of saturated extract (ECe). Correlation coefficients between the ECa data sets obtained with the two instruments were 0.80 and 0.86 in the horizontal and vertical dipole orientations, respectively. Although the GEM300 sensor produced higher apparent conductivity measurements and also predicted somewhat less accurately the conductivity of soil samples, spatial patterns of apparent and electrical conductivity produced by the two instruments were similar and reasonable. Multifrequency sounding with the easier-to-operate GEM300 sensor was found to provide no additional information and did not improve interpretations over single frequency sounding. 

Keywords: Apparent conductivity, electrical conductivity, electromagnetic induction, salinity, salinity mapping, soil conductivity, soil salinity

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Variability of total and dissolved elements in stormwater runoff
(Full text appears in the Journal of Soil and Water Conservation, Vol.56, No.3)

R.E. Zartman, R.H. Ramsey III, and A. Huang 

ABSTRACT: Stormwater runoff may contribute to groundwater pollution. This study evaluated seasonal influence on runoff water quality and compared urban runoff water quality with U.S. Environmental Protection Agency (EPA) drinking water standards. Stormwater from sixteen playa lakes were evaluated for total and dissolved elements during a 32-month period. Twenty elements were monitored to determine if concentrations posed a potential groundwater pollution problem. Eleven of the elements evaluated were temporally correlated with season of the year for both total and dissolved concentrations. Seasonal significances of the total and dissolved elemental concentrations were explained by natural or anthropogenic causes. The majority of the elements considered hazardous to human health, appeared in low concentrations in these urban stormwater fed lake waters during the study period. Concentrations of total and dissolved Al and Fe exceeded the U.S. EPA’s secondary drinking water standards (cosmetic and aesthetic, not health). No significant health risk would seem to be posed by this urban stormwater runoff percolating to groundwater.  

Keywords: Playa lakes, primary drinking water regulations, secondary drinking water regulations, urban stormwater runoff


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