July - August 2004: Volume 59, Number 4
Table of Contents
Features
Rented Land: Barriers to Sustainable Agriculture
by Michael S. Carolan, Diane Mayerfeld, Michael M. Bell and Rick Exner
Research
- Integration of SSURGO maps and soil parameters within a GIS-NPS model system
M.D. Luzio, J.G. Arnold, and R. Srinivasan
- Assessing regional impacts of conservation reserve program-type grass buffer strips on sediment load reduction from cultivated lands
C. Das, W.J. Capehart, H.V. Mott, P.R. Zimmerman, and T.E. Schumacher
- Water balance of a dairy loafing lot using geotextile and its impact on water quality
K.A. McVay, D.E. Radcliffe, M.L. Cabrera, and G. Hoogenboom
- Effect of water table depth and irrigation application method on water use for subirrigated fresh market tomato production in Florida
C.D. Stanley
- Runoff, erosion, and nutrient losses from compost and mulch blankets under simulated rainfall
L.B. Faucette, L.M. Risse, M.A. Nearing, J.W. Gaskin, and L.T. West
- Soil erosion following forest operations in the Southern Piedmont of central Alabama
J.M. Grace III
- Factors influencing the implementation of best management practices in the dairy industry
N.C. Rahelizatovo and J.M. Gillespie
- Water use and depletion by diverse crop species on Haplustoll soil in the northern Great Plains
S.D. Merrill, D.L. Tanaka, J.M. Krupinsky, and R.E. Ries
- Geospatial assessment of agricultural lands critical to air quality on the Columbia Plateau, Washington State
D.G. Chandler, S. Blaesing-Thompson, and A. Busacca
Departments
- Home Front
Viewpoint
- Raise Your Voice
- Notebook
- Conservogram
Integration of SSURGO maps and soil parameters within a GIS-NPS model system
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
M. Di Luzio, J.G. Arnold, and R. Srinivasan
ABSTRACT: Computer based frameworks, including geographical information systems (GIS), associated digital data sets and integrated hydrological models, have become essential tools for the practical deployment of watershed assessment projects and ultimately for providing support for water quality protection and conservation. Within these frameworks digital soil information and data sets play a key role in defining the spatial distribution of important hydraulic variables and consequently of fundamental hydrologic functions connected with NPSs (Nonpoint Sources) and their modeling. This paper illustrates background and results from the development of a GIS based tool required for the use of Soil Survey Geographic (SSURGO) data sets (an undergoing development and delivery effort of digital soil maps by the Natural Resources Conservation Service) and primarily designed in specific support of the Soil and Water Assessment Tool (SWAT) model and its applications in the United States. The tool is developed as an addition or extension to the model companion, the ArcView GIS interface in its latest version (AVSWAT-X) which is designed to define watershed hydrologic features; store, organize, and manipulate the related spatial and tabular data; and analyze management scenarios. Within this framework the tool expedites the otherwise complex inclusion operations of the SSURGO data, such as: (1) downloading, via the Internet, up-to-date SSURGO data sets (version I or II); (2) processing and managing variously formatted data sets in order to create the needed digital soil maps; (3) generating and/or storing the required soil physical and hydraulic model input parameters derived from pedo-transfer functions; and (4) seamlessly including them in any watershed modeling framework. Besides the operational advantages, the tool addresses the trend of employing soil maps with increasing detail in order to improve the landscape representation and reduce the modeling drawbacks involved with the aggregation of the spatial input. Soil map features with unprecedented detail along with the elaborated attributes have a potential for enhancing modeling assessments in support of water quality programs (i.e. Total Maximum Daily Load) at the watershed as well as stream reach scale, as indicated in basic yet important highlights in the paper.
Keywords: ArcView, AVSWAT, geographical information systems, GIS, nonpoint source pollution, soil hydraulic properties, soil maps, SSURGO, SWAT
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Assessing regional impacts of conservation reserve program-type grass buffer strips on sediment load reduction from cultivated lands
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
C. Das, W.J. Capehart, H.V. Mott, P.R. Zimmerman, and T.E. Schumacher
ABSTRACT: A methodology of determining regional estimates of Conservation Reserve Program (CRP) areas required to achieve a given percentage reduction of localized agricultural sediment yield is introduced. Using South Dakota as a test domain, a collection of regional-scale databases was used to compile a statewide erosion vulnerability map based on Universal Soil Loss Equation (USLE) factors. This was then arranged into climate, erosion risk, soil and topographic zones. Statistical procedures were then employed to extract predominant input values required for the U.S. Department of Agriculture (USDA) Water Erosion Prediction Project (WEPP) model applicable to each of these zones. WEPP simulations using these inputs provided estimates of grass buffer strip areas required to achieve targeted percentage reductions of sediment yield in each of these zones. The response of each of these zones towards employment of grass buffer was found to vary considerably. Comparison with small-scale field studies suggest that the WEPP model can be used to measure efficiency of grass buffer strips in different zones. This approach demonstrates how regional analyses using factor-based erosion models can be combined effectively with process-based field-scale erosion models to provide viable estimates of sediment reduction due to adoption of CRP-type grass buffer strip practices.
Keywords: CRP grass buffer strips, GIS, sediment load, USLE, WEPP
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Water balance of a dairy loafing lot using geotextile and its impact on water quality
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
K.A. McVay, D.E. Radcliffe, M.L. Cabrera, and G. Hoogenboom
ABSTRACT: To lessen soil erosion due to high animal stocking rates on small Georgia dairies, the Natural Resources Conservation Service (NRCS) recommends a system that utilizes geotextile material covered with crusher run gravel as a soil cover in high animal traffic areas. Our objective was to determine the runoff and leachate characteristics of a typical system. At a 60-cow dairy in Oglethorpe County, Georgia, a loafing lot was constructed on a Pacolet sandy loam soil (clayey, kaolinitic, thermic, Typic Kanhapludult). Tile drains were installed at 0.65 m (26 in) depth on 7.5 m (25 ft) spacing. Approximately 18 percent of the rainfall became surface runoff. Surface runoff water typically contained levels of NH4-N and PO4-P that exceeded the Environmental Protection Agency (EPA) guidelines for surface water. Approximately 32 percent of the rainfall became drainage water that moved below the top 1.5 m (60 in) soil profile and had nitrate levels ranging from 10 to 40 mg NO3-N L-1. Our results indicate that surface water running off of these sites should be impounded in a lagoon or similar structure and these systems should not be located in areas where groundwater contamination is a concern.
Keywords: Cattle, chloride, groundwater, manure, nitrate, phosphorus, surface water
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Effect of water table depth and irrigation application method on water use for subirrigated fresh market tomato production in Florida
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
C.D. Stanley
ABSTRACT: Conventional seepage subirrigation (Seep) where water is applied via irrigation furrows to achieve water table depth management is a common irrigation method for field production of vegetables on high water table flatwoods soils in southwest Florida. The fully enclosed subirrigation system, utilizing microirrigation tubing to distribute water and manage a target water table position, has been designed for water conservation and increased water table depth control throughout a production area. A three-year study (1999-2001) was conducted to compare these two subirrigation systems for water use and the effect that water table depth had on subirrigated fresh market tomato fruit production. Results for a 45 cm (18 in) water table depth showed that significant water savings (>60 percent) were measured by using the fully enclosed subirrigation system compared to the seepage subirrigation system, primarily due to elimination of irrigation runoff with the fully enclosed subirrigation system. No significant fruit yield and quality differences were detected as a result of irrigation system. Using water table depths of 45 and 60 cm (18 and 24 in, respectively) with the fully enclosed subirrigation system showed a 40 percent water savings at the lower 60 cm (24 in) depth with no statistically significant reduction in fruit yield or quality due to water table depth.
Keywords: Fully enclosed subirrigation, seepage subirrigation, tomato production, water table management
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Runoff, erosion, and nutrient losses from compost and mulch blankets under simulated rainfall
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
L.B. Faucette, L.M Risse, M.A. Nearing, J.W. Gaskin , and L.T. West
ABSTRACT: Control of soil erosion and associated nonpoint source pollution is essential to improving water quality. The use of compost or mulch blankets as a soil cover can help control soil erosion and provide sustainable alternatives to disposal for many biomass resources. The objective of this study was to investigate the amounts of runoff, erosion, and nutrient losses obtained under simulated rainfall using a variety of compost and mulch materials. Treatments included aged poultry litter, two different types of poultry litter compost, municipal solid waste compost, biosolids compost, food waste compost, yard waste compost, three different types of wood mulch, and bare soil. Results indicated that all of the treatments except for aged poultry litter were effective at reducing total solids loss in the runoff. Nutrient losses from most of the compost treatments, however, were higher than those from bare soil or mulch treatments. Treatments with lower respiration rates and nitrate-nitrogen concentrations tended to have less erosion and transport of solids. Nitrate-nitrogen content, respiration rates, soluble salt, sodium, and potassium contents were good indicators of ammonium and phosphorus losses.
Keywords: Compost, erosion control, mulch, nutrient loss, runoff, water quality
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Soil erosion following forest operations in the Southern Piedmont of central Alabama
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
J.M. Grace III
ABSTRACT: In recent years, nonpoint source pollution (NPS) has been recognized as one of the major threats to the nation’s water quality. Clearly, forest operations such as harvesting and site preparation have the potential to have degrading impacts on forest water quality. However, there exists a gap in the understanding of the nature and extent of NPS pollution problems related to forest operations. The study presented here was performed in Lee County, Alabama to investigate the impact of clear-cut harvesting and mechanical site preparation on a 20-year-old loblolly pine (Pinus taeda L.) plantation on sediment and runoff yield. Sediment and runoff yield responses on treated areas were compared to that of undisturbed areas. Impacts were evaluated by monitoring isolated small plots, 2 m (6.6 ft) by 5.5 m (18 ft), over a two-year period following the harvest prescription. Sediment yield from the control treatment was 0.11 t/ha (0.30 ton/acre) over the study period. Sediment yield increases of 0.11 t/ha (0.30 t/ac) and 1.3 t/ha (3.5 t/ac) were observed from clear cut harvest/site prep/plant (H-SP-P) treatment and clear cut harvest /plant (H-P) treatment, respectively. However, erosion losses from the most erosive treatment, clear cut harvest /plant, was still very low at less than 1 t/ha/yr. Runoff yield results were similar to those observed with sediment yields from treatments in the investigation. Differences in the two treatments were likely due to the differences in surface roughness, which affects infiltration and surface flow velocity.
Keywords: Forest operations, harvesting, site preparation, soil erosion, surface runoff
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Factors influencing the implementation of best management practices in the dairy industry
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
N.C. Rahelizatovo and J.M. Gillespie
ABSTRACT: Best management practices (BMPs) are promoted to reduce water pollution from agricultural activities. This study investigates the likely determinants of Louisiana dairy farmers’ decisions to voluntarily implement BMPs. Adoption rates of 21 BMPs ranged from 28 to 83 percent, with “not applicable to my farm” as the most often cited reason for non-adoption. Larger, more productive farms with greater financial resources were the most frequent adopters of BMPs. Use of sources of information such as seminars and the Cooperative Extension Service were associated with greater adoption, underscoring the importance of information in encouraging adoption. Younger, more educated farmers who had been in business a shorter time, as well as those who had a family member planning to take over the farm upon the farmer’s retirement were more likely to adopt BMPs.
Keywords: Best management practices, dairy, Louisiana, probit, technology adoption
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Water use and depletion by diverse crop species on Haplustoll soil in the northern Great Plains
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
S.D. Merrill, D.L. Tanaka, J.M. Krupinsky, and R.E. Ries
ABSTRACT: In a semiarid-to-subhumid region, water use by crop species can have a considerable impact on both crop production and soil landscape hydrology. Crop production following high water-using crops can be decreased while ephemeral streams and wetlands can be increased by growing lower water-using crops. Water use and soil water depletion were determined with neutron moisture meters in ten crop species (barley, canola, crambe, dry bean, dry pea, flax, safflower, spring wheat, soybean and sunflower) for two years, and measurements are presented for four of these species for one additional year. The observations were made in various species which were grown after spring wheat during crop sequence experiments. Sunflower was the greatest water user, followed by safflower and soybean. Dry pea was the lowest water user, followed in order by barley, crambe, and spring wheat. During an above average precipitation year, the depth distribution of soil water depletion among canola, dry pea, spring wheat, and sunflower was similar. In contrast, during a year of relatively low seasonal precipitation, differences were evident among the four crop species. Sunflower and canola extracted 49 percent and 45 percent of their soil water depletion, respectively, from soil depths greater than 60 cm, while spring wheat and dry pea extracted 33 percent and 27 percent of their soil water depletion from below 60 cm depth. Using a three-year dataset, it was found that water use and soil water depletion were highly correlated with seasonal precipitation, significantly correlated with median depth of water depletion and days from seeding to harvest, but not correlated with root growth parameters. As a general guide to water use by crop species, length of active growing season appears to be the most important factor.
Keywords: Alternative crops, differential water depletion, diverse soil-crop production systems, northern Great Plains, soil water depletion, water use
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Geospatial assessment of agricultural lands critical to air quality on the Columbia Plateau, Washington State
(Full text appears in the Journal of Soil and Water Conservation, Vol.59, No. 4)
D.G. Chandler, S. Blaesing-Thompson, and A. Busacca
ABSTRACT: The soils and landscape of the Columbia Plateau in eastern Washington and northeastern Oregon have developed primarily as a result of redistribution of glacial outwash sediments by wind. Contemporary agricultural disturbance of regional soils facilitates wind erosion that impairs downwind air quality by the introduction into the atmosphere of large quantities of particulate aerosols less than 10 microns in aerodynamic diameter (PM10). Reducing these agricultural contributions to PM10 concentrations in urban areas has been identified as a critical component of regional compliance under the Clean Air Act. We designed a sampling and analysis scheme to develop empirical relationships first between total mass flux during wind tunnel erosion trials and soil aggregate size distributions; and second between soil PM10 emission potentials and primary particle size distributions. We then applied those empirical relationships to predict potential total soil erodibility and potential PM10 emissions at a larger set of field soil sample sites. The resultant point predictions were interpolated spatially using geostatistical methods to generate a prediction map of PM10 emissions hazard, which is similar to the U.S. Department of Agriculture (USDA) Farm Services Agency map of air quality conservation priority areas for the Columbia Plateau.
Keywords: Air quality, erosion mapping, loess soils, PM10, wind erosion
