September - October 2002: Volume 57, Number 5
Table of Contents
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Features
Planning with Nature
By Brian Lavendel
The Soil Survey Report: New Forms for the 21st Century
By D.A. Miller, G.W. Petersen, P.J. Kolb, and J.J. Voortman
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Research
- Glyphosate effects on ground cover of tall fescue waterways and estimated soil erosion
W.W. Donald
- Streambank slumping and its contribution to the phosphorus and suspended sediment loads of the Blue Earth River, Minnesota
A.C. Sekely, D.J. Mulla, and D.W. Bauer
- Native American methods for conservation and restoration of semiarid ephemeral streams
J.B. Norton, F. Bowannier, Jr., P. Peynetsa, W. Quandelacy, and S.F. Siebert
- Cost effectiveness of agricultural BMPs for sediment reduction in the Mississippi Delta
Y. Yuan, S.M. Dabney, and R.L. Bingner
- Documenting no-till and conventional till practices using Landsat ETM+ imagery and logistic regression
R.S. Bricklemyer, R.L. Lawrence, and P.R. Miller
- Use of a submerged jet device to determine channel erodibility coefficients of selected soils of Mexico
K.N. Potter, J. de J. Velázquez-Garcia, and H.A. Torbert
- Continuous corn with moldboard tillage: Residue and fertility effects on soil carbon
D.C. Reicosky, S.D. Evans, C.A. Cambardella, R.R. Allmaras, A.R. Wilts, and D.R. Huggins
- Oral presentations given at the 2002 Soil and Water Conservation Society annual conference held July 13-17, 2002 in Indianapolis, Indiana
Morning Abstracts Afternoon Abstracts
- Poster presentations displayed at the 2002 Soil and Water Conservation Society annual conference held July 13-17, 2002 in Indianapolis, Indiana
Departments
- Home Front
- Viewpoint
- Raise Your Voice
- Notebook
- Conservogram
Glyphosate effects on ground cover of tall fescue waterways and estimated soil erosion
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
W.W. Donald
ABSTRACT: Glyphosate use for controlling weeds has increased in the Midwest, but drift or overspraying can damage tall fescue waterways. Farmers and conservation agents fear that glyphosate may reduce tall fescue ground cover in waterways and increase soil erosion. Glyphosate was applied in mid-May to tall fescue waterways at several rates from 0.14 to 2.24 kg ai/ha1 + ammonium sulfate (2% by volume) to simulate drift or direct overspraying. Percentage cover of live and dead tall fescue, broadleaf weeds, and bare soil was measured after treatment at two sites in Missouri, and annual erosion was estimated using revised universal soil loss equation (RUSLE) software. Total (live + dead) tall fescue ground cover remained greater than 88% even at 10 to 11 months after treatment. Enough live tall fescue remained to grow into gaps. Glyphosate drifts at low rates or single accidental incidents of overspraying glyphosate up to 2.24 kg ai/ha are unlikely to permanently damage tall fescue waterways.
Keywords: Erosion, glyphosate, grass waterways, tall fescue
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Streambank slumping and its contribution to the phosphorus and suspended sediment loads of the Blue Earth River, Minnesota
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
A.C. Sekely, D.J. Mulla, and D.W. Bauer
ABSTRACT: Suspended sediment transported in river systems has the ability to degrade water quality and impart negative impacts downstream as material is deposited. This study examines the significance of valley wall slumping as a source of both suspended sediment and phosphorus in the Blue Earth River. Several streambanks on the Blue Earth River in south central Minnesota were repeatedly surveyed from 1997 to 2000 to determine annual rates of streambank slumping. Volumetric changes between digital elevation models from successive topographic surveys were converted into changes in mass, and, subsequently, annual erosion rates were calculated based on surface area. An erosion rate constant was derived based on surface area of surveyed sites and applied to an inventory of eroding escarpments along the entire river to estimate the contribution of streambank slumping to the total suspended sediment (TSS) and total phosphorus (TP) loads in the Blue Earth River. Erosion rates for surveyed sites ranged from 544 to 3,995 t ha-1 yr-1 (242 to 1,782 tons ac-1 yr-1), with an average rate of 2,154 t ha-1 yr-1 (961 tons ac-1 yr-1). The derived erosion rate constant for slumping sites was 0.23 t m-2 yr-1 (0.024 tons ft-2 yr-1). Between 75,804 and 106,213 t (83,536 to 117,047 U.S. tons) of sediment is delivered to the river annually from all eroding escarpments inventoried, with between 28,047 and 39,299 t (30,908 and 43,307 U.S. tons) transported by flow as TSS. Streambank slumping accounts for 31% to 44% of the TSS load at the mouth of the Blue Earth River. The percentage of the TP load originating from streambank slumping is estimated to be from 7% to 10%, with annual contributions of 12 to 17 t P (14 to 19 U.S. tons).
Keywords: Phosphorus load, sediment load, streambank slumping, suspended sediment, topographic surveying
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Native American methods for conservation and restoration of semiarid ephemeral streams
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
J. B. Norton, F. Bowannie Jr., P. Peynetsa, W. Quandelacy, and S.F. Siebert
ABSTRACT: Combined effects of brush encroachment and channel entrenchment in the Southwestern United States threaten ecological, hydrological, and agricultural functions of ephemeral streams and associated alluvial surfaces. Restoration is difficult because entrenchment is widespread, and highly variable flow magnitudes defy standardized structural approaches. Methods developed by the Zuni Indians during more than 2,000 years of farming on dynamic alluvial fans combine brush removal with ephemeral channel-erosion control and show promise for effective watershed-scale conservation and restoration. Zuni utilize several types of simple brush structures that rely on hydraulic characteristics of woody material to modify erosive and depositional effects of both small seasonal and irregular storm-flow events. Zuni brush structures are inexpensive and quick to build, require no external material inputs, and avoid the extensive disturbance associated with conventional rigid check-dam construction. Successive surveys at three incised-headwater ephemeral channels on the Zuni Indian Reservation showed that Zuni techniques increased the incidence of overbank flow during small streamflow events (acting as permeable check dams) and large floods (moving downstream and forming debris jams) and thereby helped reconnect channels to alluvial fans. Zuni brush structures represent a potential alternative to capital- and labor-intensive approaches to semiarid watershed conservation and restoration.
Keywords: Arroyo cutting, conservation farming, discontinuous ephemeral streams, ecological restoration, local knowledge, permeable check dams, runoff agriculture, woody debris, woody species encroachment
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Cost effectiveness of agricultural BMPs for sediment reduction in the Mississippi Delta
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
Y. Yuan, S.M. Dabney, and R.L. Bingner
ABSTRACT: Sediment has been identified as the pollutant most limiting to fishery health in oxbow lakes in the Mississippi Delta. The Mississippi Delta Management System Evaluation Area (MDMSEA) project seeks to reduce the adverse agricultural impacts on water resources and ecological processes through the development and adoption of alternative best management practices (BMPs). However, resource limitations dictate that only a few combinations of BMPs can actually be physically tested over a few years at a limited number of locations. To extend results and better evaluate the effectiveness of alternative BMP combinations on sediment reduction, the Annualized Agricultural Nonpoint Source pollutant loading model (AnnAGNPS 2.1) was applied to a 12 ha (30 ac) MDMSEA subwatershed. BMPs considered included cover crops, filter strips, grade control pipes, and impoundments. Each BMP was considered in combination with three tillage systems: conventional tillage, reduced tillage, and no-till. Costs of BMPs were estimated using 2001 state average prices for Mississippi. Amortized fixed costs, using a 25 yr planning horizon and interest rates of both 5% and 10%, were combined with direct annual costs into total annual cost estimates. AnnAGNPS predicted that no-till alone, reduced tillage with winter cover and an edge-of-field pipe, or conventional tillage with a small permanent impoundment (covering less than 3% of the watershed) would all reduce sediment yield by at least 50%. The most cost-effective BMPs were management of volunteer winter weeds as cover crops and various types of edge-of-field grade-control pipes. The average marginal cost using BMPs for sediment yield reduction was about $8 MT-1 ($7.3 t-1) for conventional and reduced tillage. The cost was higher, about $10.7 MT-1, ($9.7 t-1) for no-till because the practice of no-till alone reduced sediment yield by half, and further marginal reductions were more expensive.
Keywords: Conservation tillage, cover crop, grade control, vegetated buffers, water quality
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Documenting no-till and conventional till practices using Landsat ETM+ imagery and logistic regression
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
R.S. Bricklemyer, R.L. Lawrence, and P.R. Miller
ABSTRACT: The ability of agricultural lands to sequester carbon from the atmosphere and help mitigate global warming has the potential to add value to farmland through the development of carbon-credit trading. Crucial to the creation of a market-based carbon credit trading system is the monitoring and verification of agricultural practices that promote carbon storage. Using remotely sensed images for this purpose could prove more efficient and cost-effective than traditional land-based methods. Landsat Enhanced Thematic Mapper Plus (ETM+) imagery and logistic regression had >95% accuracy in verifying no-till fallow fields. Further research is needed to investigate the potential for this low-cost technology to assist in the monitoring and verification of practices that sequester carbon. Development of an accurate, low-cost, efficient means of monitoring and verifying carbon sequestering practices will further the development of cropland carbon credits, thus helping to mitigate global warming, and will add value to U.S. farmland.
Keywords: Carbon credits, carbon sequestration, Landsat ETM+, logistic regression, no-till, remote sensing, tillage
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Use of a submerged jet device to determine channel erodibility coefficients of selected soils of Mexico
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
K.N. Potter, J. de J. Velázquez-Garcia, and H.A. Torbert
ABSTRACT: More than half of Mexico’s soil and water resources are considered moderately to severely degraded, primarily due to erosion and sedimentation. Characterization of soil susceptibility to erosion in the field is often hampered by difficulty in obtaining adequate water supplies. We tested a method to determine soil erodibility coefficients for concentrated water flow that had not been previously applied to agricultural soils. The submerged jet method of determining soil erodibility coefficients was tested on six soils in central Mexico of varying texture and predominant clay mineralogy near the end of the corn (Zea mays L.) growing season. The resulting erodibility coefficients generally segregated soils of similar texture and mineralogy. Soil silt plus very fine sand percentage and Plasticity Index were important soil properties affecting the Jet Index values. Moldboard plowed soils were more erodible at the end of the growing season than no-tilled soils at all sites except for two recent volcanic soils. The results of these tests, along with the relative ease of use and minimum labor and water requirements, suggest that the submerged jet device is a useful tool to determine soil erodibility coefficients of agricultural soils.
Keywords: Concentrated flow, erosion, submerged jet
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Continuous corn with moldboard tillage: Residue and fertility effects on soil carbon
(Full text appears in the Journal of Soil and Water Conservation, Vol.57, No. 5)
D.C. Reicosky, S.D. Evans, C.A. Cambardella, R.R. Allmaras, A.R. Wilts, and D.R. Huggins
ABSTRACT: Greenhouse gas emissions from soil depend on land use, cropping systems, and tillage methods. The impact of 30 years of continuous corn (Zea mays L.) with moldboard plow tillage was evaluated from four treatments and a control: silage removal versus grain removal, each with low [83 kg N ha-1 (74 lb N ac-1)] and high [166 kg N ha-1 (148 lb N ac-1)] fertility, and no added fertilizer with grain removal. Soil organic carbon (SOC) changes over a 30-yr period were measured, as well as tillage-induced CO2 loss immediately after moldboard plowing, in the spring of 1996. The 24 h cumulative tillage-induced CO2 loss was not significantly different among treatments (excluding the control). Total C, total N, and C:N ratio in the soil remained virtually unchanged after 30 yr in fertilized treatments. All four treatments produced the same SOC content [21.9 g kg-1 (2.2%)] in the 0 - 20 cm (0 - 8 in) depth. The cumulative total input of 241 Mg ha-1 (107 t ac-1) of aboveground stover from the high fertility grain treatment, compared to none from the high fertility silage treatment, yielded no differences in SOC. Fertilizer N rates of 83 and 166 kg ha-1 (74 and 148 lb ac-1) produced no difference in SOC or associated C:N ratios. Moldboard plow tillage caused rapid soil degassing that masked fertilizer and stover removal and/or return effects on SOC. This uncontrolled SOC decline agreed with other studies in this region, indicating that the soils were sources of CO2 regardless of other agronomic practices, as long as moldboard plow tillage was used.
Keywords: Biomass removal, carbon dioxide, plow tillage, soil organic carbon
