• The Dirt on Phytoremediation
• Lessons from the National Water-Quality Assessment

Research

• Using empirical erosion models and GIS to determine erosion risk at Camp Williams, Utah
  K.P. Bartsch, H. Van Miegroet, J. Boettinger, and J.P. Dobrowolski
• Modeling wind and water erosion in northern China under climate and land use changes
  Q. Gao, L. Ci, and M. Yu
• A mail survey approach to watershed condition assessment
  G. A. Lomnicky, J.R. Barker, and S.A. Bryce
• Runoff of 1,3-dichloropropene from field plots exposed to simulated and natural rainfall
  L.G. Heim, N.J. Snyder, and I.J. van Wesenbeeck
• Runoff and soil-loss responses to changes in precipitation: a computer simulation study
  F.F. Pruski and M.A. Nearing
• Using soil properties to predict forest productivity in southern Illinois
  M. E. Woolery, K.R. Olson, J. O. Dawson, and G. Bollero
• An investigation of spatial variation in soil erosion, soil properties, and crop production within an agricultural field in Devon, United Kingdom 
  T.A. Quine and Z. Yusheng
• Clod Movement and Tillage Tool Characteristics for Modeling Tillage Erosion
  D. Torri and L. Borselli  

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Using empirical erosion models and GIS to determine erosion risk at Camp Williams, Utah
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

K.P. Bartsch, H. Van Miegroet, J. Boettinger, and J.P. Dobrowolski

ABSTRACT: Soil erosion was assessed at Camp Williams Army National Guard Training Facility by creating an erosion risk classification map. The map was created by applying empirical erosion models including the Revised Universal Soil Loss Equation (RUSLE) with GIS and then grouping the quantitative erosion estimates into erosion risk classes. The assessment indicated where problem areas occurred and showed relative erosion risk, but its lack of quantitative accuracy should be noted. Soil erosion does not appear to be a problem for most of the facility except in areas with little or no protective vegetation such as roads. Analysis of each factor showed that the cover-management factor (C) contributed most of the variability to the erosion risk classification map. A comparison of three GIS derived factors (K, S, and C) to factors derived from field data indicated mixed results for accuracy.

Keywords: Military installation, military training, rangeland, RUSLE, semi-arid, USLE.

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Modeling wind and water erosion in northern China under climate and land use changes
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

Q. Gao, L. Ci, and M. Yu

ABSTRACT: We developed a semi-empirical model of soil erosion by wind and water for sandy grassland areas in northern China (east of Erdos Plateau, Inner Mongolia). The model was partially validated against a recently compiled soil erosion map and was shown to accurately represent soil erosion. Simulations were then run for increased temperature and altered land use patterns. Increasing air temperature by 1°C increased average wind erosion by 31 t km-2 yr-1 (79 ton mi-2 yr-1), but decreased average water erosion by 5 t km-2 yr-1(12.7 ton mi-2 yr-1). Converting grasslands to dry crop fields increased wind and water erosion, with increases being about the same order and range. Each 1 km2 (0.386 mi2) of grasslands converted to dry crop fields resulted in an increase of 0.38 t km-2 yr-1 (0.98 ton mi-2 yr-1) in average soil erosion. No statistically significant interaction was found between temperature and land use. Converting grasslands into dry crop fields was about eight times as detrimental to soil conservation as increased temperature for the sandy grassland areas in northern China. Simulated results suggested that anthropogenic activity, especially changed land use, rather than climatic change was probably the major causal factor of desertification that occurred during the past century.

Keywords: Desertification, sandy grasslands, simulation, soil erosion.

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A mail survey approach to watershed condition assessment
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

G. A. Lomnicky, J.R. Barker, and S.A. Bryce

ABSTRACT: Aquatic resource monitoring attempts to assess the condition of aquatic habitat and organisms. Assessments require that disturbances from human activities be identified, quantified and ordered along a gradient for interpreting biological response. An index of relative risk to aquatic systems was developed based on identifying and prioritizing stream-reach and watershed stressors. Mail surveys were sent to natural resource experts (county extension agents, NRCS employees) familiar with the targeted watersheds, to collect data for assessment of 25 watersheds in the Mid -Appalachian region of the United States. A 56% correspondence was found between this method and another approach when scoring identical sites. Scoring differences resulted from discrepancies in available data between the two methods. Scores were consistent with water chemistry and benthic macroinvertebrate measures of stream condition and required less time to develop for ranking watersheds than the second method. The mail survey approach is readily transferable to other regions.

Keywords: Aquatic monitoring, biological integrity, mail surveys, risk assessment, water quality, watershed management.

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Runoff of 1,3-dichloropropene from field plots exposed to simulated and natural rainfall
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

L.G. Heim, N.J. Snyder, and I.J. van Wesenbeeck

ABSTRACT: Runoff potential of a subsurface soil-injected volatile compound, such as the soil fumigant 1,3-dichloropropene (1,3-D), that diffuses rapidly through the soil profile has not been studied for potential to contaminate surface water bodies through edge-of-field runoff. The objective of this study was to measure the runoff of 1,3-D, a soil fumigant and nematicide, under severe rainfall conditions at a field study site near Blacksburg, Virginia. 1,3-D was injected into the Groseclose clay loam (clayey, mixed mesic Typic Hapludults) at a 30 cm (12 inch) depth on three replicate 0.04 ha test plots. Special considerations for 1,3-D were required to make a uniform application to each plot and maintain worst-case conditions (rainfall timing and plot conditions). The measured application rate was 367-kg/ha (32.4 gallons/acre), which is greater than the typical maximum rate for Telone II® uses on crops grown in the Southeastern United States. The study was conducted on a hydrologic group C soil with a 5% slope. The 2-hour simulated rainfall water input was 9.4 cm (4.7 cm/h), which is about a 1-in-50-year storm for Blacksburg, Virginia. Concentrations of 1,3-D measured in soil and air prior to the simulated rainfall event suggested that 1,3-D was present at the soil surface and available for runoff. An average of 0.002% of the applied 1,3-D was observed in runoff. Maximum 1,3-D concentration (sum of both isomers) observed in runoff was 17.2 ppb, which is more than one order of magnitude below the lowest aqueous toxicological level of concern (280 ppb).

Keywords: 1,3-D, fumigant, irrigation, surface water

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Runoff and soil-loss responses to changes in precipitation: a computer simulation study
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

F.F. Pruski and M.A. Nearing
ABSTRACT: Changes in precipitation have occurred over the past century and are expected to continue over the next century. These changes will have significant implications for runoff, soil erosion, and conservation planning. This study was undertaken to investigate how runoff and soil erosion by water can be expected to be altered as a function of changes in the average number of days of precipitation per year and changes in the amount and intensity of the rain that falls on a given day. The Water Erosion Prediction Project (WEPP) model was used to simulate erosion for three locations, three soils, three slopes, and four crops. Average annual precipitation was changed ±10% and ±20% by changing either a) the number of wet days per year, b) the amount and intensity of precipitation per day, or c) a combination of the two. Results indicated that, on average, each 1% change in average annual precipitation induced a 1.28%, 2.50%, and 1.97% change in runoff and a 0.85%, 2.38%, and 1.66% change in soil loss for the three types of precipitation changes, respectively. Comparisons of the results of the soil-loss simulations to published relationships for Revised Universal Soil Loss Equation (RUSLE) R-factors in the United States suggest that the third option of changing both the number of wet days per year and the amount and intensity of precipitation per day is the most realistic scenario for representing changes in precipitation for hydrologic studies.

Keywords: Climate change, erosion, global change, hydrology

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Using soil properties to predict forest productivity in southern Illinois
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

M. E. Woolery, K.R. Olson, J. O. Dawson, and G. Bollero

ABSTRACT: The purpose of this study was to help explain and extrapolate expert site index value estimates for important tree species of southern Illinois soils. Statistical models were used to quantify the relationship between soil properties and expert-derived values for tree growth. Sixteen physical and chemical soil properties of 64 soils found in southern Illinois were used, along with published site index values, in a multivariate stepwise multiple regression analysis. The tree species selected for estimated site index regression were white oak (Quercus alba L.), yellow poplar (Liriodendron tulipifera L.), and northern red oak (Quercus rubra L.). These tree species were chosen based on availability of site index data, the site conditions required by the species, and ability to allow the prediction of tree growth for all soil series in the area. Stepwise regression procedures were used to select the most important soil parameters for each species productivity estimate from 16 original physical and chemical soil properties. The most important soil parameters in models to extrapolate site index predicting were total rooting depth, thickness of the A horizon, bulk density of the A and E horizon, bulk density of the subsoil, and percentage clay found in the B horizon. The parameter estimates were used to construct site index prediction equations. The soil property equations explained 61% of the variation in white oak site index estimates, 70% of northern red oak site index estimates, and 80% of the variation in site index estimates of yellow poplar. The projected productivity estimates will be useful to land managers who wish to allocate time and other resources to land based on the potential productivity of the site. Use of this method resulted in tree height growth projections for many soils published in regional soil surveys, including soils that currently lack forest cover and have high seasonal water tables or are subject to flooding.

Keywords: Forest productivity, multiple regression, multivariate statistics, soil properties, timber site indices

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An investigation of spatial variation in soil erosion, soil properties, and crop production within an agricultural field in Devon, United Kingdom
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

T.A. Quine and Z. Yusheng

ABSTRACT: This paper explores the role of tillage erosion and water erosion in the development of within-field spatial variation in soil properties and their contribution to variation in crop production. Data sources include spatial distributions of: plow soil concentrations of total N, total C, total and inorganic P; soil texture; grain yield and aboveground biomass; topographic attributes, derived from a detailed digital terrain model (DTM); net soil redistribution, derived from 137Cs measurements; tillage erosion, derived from simulation; and rill erosion, mapped in the field and simulated. Soil properties were found to be non-normally distributed and systematically related to slope curvature. Tillage erosion was found to be the dominant soil redistribution process on the basis of the close correlation between its distribution and that of the pattern of net soil redistribution. Tillage erosion also correlated closely with the soil properties, suggesting that soil redistribution by tillage is a major contributor to the spatial variation in soil properties. Relationships between crop production and soil properties and erosion rates were complex. Eroded and nutrient-depleted locations exhibited low rates of crop production, but low production was also found in some areas of high aggradation. Simulation of a further 40 years of tillage erosion suggests that spatial variation in soil properties will become more extreme and is likely to have a deleterious impact on crop production.

Keywords: Crop variation, erosion modeling, GIS, precision farming, soil variation, tillage erosion

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Clod Movement and Tillage Tool Characteristics for Modeling Tillage Erosion
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No.1)

D. Torri and L. Borselli

ABSTRACT: Soil erosion caused by tillage is proportional to the local slope curvature. The value of the coefficient of proportionality (tillage transport coefficient) depends on the interaction between tillage tool and soil. These interactions have been modeled as a three-phase motion: drag (depending only on tool characteristics), when the soil is in contact with the instrument; jump (not necessarily present for all tools), when the soil loses contact with the tool and is ejected; and rolling, when the clods roll and jump in relatively close contact with the soil surface. Three sets of equations have been proposed and assembled into a computer program (SETi, from Soil Erosion by Tillage). The model simulates the 3D behavior of the transported soil. The performance of SETi is illustrated for the case of the moldboard plow. The simulated trends closely resemble those observed in experimental studies of tillage translocation. The major improvement with respect to previous models is that tool characteristics are explicitly taken into account. Tillage erosion is one of the major soil redistributing processes within the field border. Recent research has shown that that tillage erosion is often proportional to the local slope curvature (i.e., the rate at which slope gradient varies per unit of length). In present-day models, the proportionality coefficient is considered to be a black-box coefficient, depending on tillage tool and soil characteristics. To make the relationship between tillage translocation, soil, and tool characteristics more explicit the process of soil translocation must be better understood. We have found that there are three phases of motion, each described by its own set of equations, namely, drag, jump and rolling. Each phase depends on measurable characteristics of the tillage tools and of the soil. These equations have been implemented in the SETi computer model. At present, the model has been parameterized for a moldboard plow. The simulated soil transport reproduces the trends shown in the literature, indicating that the model behaves realistically. In its present form it can already be used for calculating the tillage transport coefficient needed by the existing tillage erosion models, as well as for designing less erosive tillage tools.

Keywords: Clod movement, modeling tillage erosion, soil erosion, soil translocation, tillage erosion