July-August 2005: Volume 60, Number 4
Table of Contents
Features
The Iraqi Drain
By Pat Hemminger
Nitrate Leaching Hazard Index Developed for Irrigated Agrigulture
By Laosheng Wu, John Letey, Christine Fench, Yvonne Wood, and David Birkle
Research
C.J. Henri and J.D. Johnson
W.F. DeBusk, B.L. Skulnick, J.P. Prenger, and K.R. Reddy
Full Text
R. Shepard
M.M. Wagner
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S.A. Hayes, R.A. McLaughlin, and D.L. Osmond
A.B. Leytem and D.L. Bjorneberg
R.C. Brandt and H.A. Elliott
Departments
- Homefront
- Raise your voice
- Notebook
- Going Retro – Celebrating 60 Years of the JSWC
- Conservogram
Riparian forest buffer income opportunities: A hybrid poplar case study
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
C.J. Henri and J.D. Johnson
ABSTRACT: Forested buffers are frequently recommended to protect agricultural watercourses. However, little is known about their contribution to farm economy. We investigated the income potential of a riparian buffer located on a western Washington blueberry farm by inventorying the trees in the buffer, developing several management scenarios for the trees, and evaluating the economic potential of each scenario. The issue weather or not a harvested buffer could adequately maintain its environmental function was beyond the scope of this research.
Results show that a positive net present value can be achieved in the buffer by harvesting 50 percent of the timber volume and selling half as veneer logs. Net present value was slightly negative when only one third of the harvestable timber was sold. Harvest and sale of only pulpwood was not found to be profitable. Achieving a positive net return depended greatly on harvest volume. How much timber volume can be removed from a buffer without jeopardizing its water protection function is currently unknown in western Washington. Poplar wood production returns are comparable to lower-end local crops such as hay and green peas.
Environmental credits, such as carbon, water quality and habitat credits are potential future sources of income from riparian buffers. The use of alternative species and extension of the harvest age are also potential means of enhancing buffer net income on smaller acreages.
Keywords: Buffer, crops, farm, income, management, poplar, riparian, water
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Response of soil organic carbon dynamics to disturbance from military training
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
W.F. DeBusk, B.L. Skulnick, J.P. Prenger, and K.R. Reddy
Abstract: A field study was conducted at Fort Benning, Georgia (USA) to evaluate changes in soil organic carbon storage and partitioning in response to site disturbance from ground-based military training. Our primary goal was to investigate the utility of selected soil biogeochemical parameters for monitoring and assessment of land condition in conjunction with restoration and other management activities. Soil was sampled at sites representing a wide range of intensity of land disturbance due to mechanized training, foot and light vehicle traffic, and related activities. Soil chemical and microbial analyses included total carbon (C), total nitrogen (N), dissolved organic C, microbial biomass C, and soil respiration. All of these, with the exception of dissolved organic C, showed relatively consistent decreasing trends (significant at P?0.05) with increasing site disturbance, consistent with increased loss of topsoil in uplands and sedimentation in bottomlands. Concomitant increases in dissolved organic C:total C and microbial biomass C:total C appear to indicate that the relative bioavailability of soil C increased with soil disturbance despite a decrease in C storage.
Keywords: Microbial biomass, military lands, nitrogen, soil erosion, soil organic carbon
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Nutrient management planning: Is it the answer to better management?
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
R. Shepard
ABSTRACT: Agricultural nutrient management is an important part of water resources protection strategies, especially in the upper Midwest. In Wisconsin, nutrient management plans are thought to reduce the excess application of agrichemicals, such as nitrogen and phosphorus, on cropland. A survey of 127 farmers, representing 90 percent of the farmers in two northeastern Wisconsin watersheds where nutrient management plans had been extensively promoted documented the application of nitrogen (N) and phosphorus (as P2O5) and the extent to which those farmers follow nutrient management plans. Results indicate that farmers with nutrient management plans do apply lower rates of total N and P2O5 compared to farmers without plans, however, the existence of a plan does not necessarily lead to the elimination of excess nutrient applications. Furthermore, there is minimal difference between public agency plans and those supported by the private sector in Wisconsin. Results from this study are useful in developing more effective public policy, and especially conservation programs that encourage the adoption of nutrient management plans.
Keywords: Farmer adoption, fertilizers, nitrogen, nutrient management planning, phosphorus, water quality
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Watershed-scale social assessment
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
M.M. Wagner
ABSTRACT: Effective watershed-scale planning integrates place-based social information with physical landscape data to create solutions appropriate for local communities. Implicit in this integration is an understanding of the differences between planners and residents. This research utilized a multi-disciplinary social assessment to obtain information about these differences and how they might impact planning and decision-making for a polluted water supply reservoir. The assessment was structured to compare assumptions in technical understanding and social dynamics among the planning team, watershed residents, and local public officials. Results were integrated into planning efforts affecting how potential landscape changes to enhance water quality were approached, communication strategies between planners and residents, and the structure of project planning and decision-making. Given the large numbers of planning projects that require effective public participation for decision-making and implementation to meet objectives, this type of information and methodologies to collect and integrate it early in a project will be essential.
Keywords: Multidisciplinary, social assessment, technical understanding, water quality, watershed planning
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Erosion control materials used on construction sites in California
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
L. Raskin, A. DePaoli, and M.J. Singer
ABSTRACT: Variable conditions on active construction sites make erosion and sediment control a necessity and a challenge. A large number of non-structural products and materials are available to help prevent storm water runoff and control sediment movement to streams. The objective of this study was to determine what materials were available in California, what materials were used and how much of the most used products were applied to the soil. Data are from four mail surveys of Certified Erosion Control Specialists, contractors, consultants, and product manufacturers. Response to the surveys was 15 percent from the contractors and erosion control professionals and 23 percent from the manufacturers. From the surveys, we gathered data on 493 materials used by 155 respondents. Wattles, logs and rolls were used by the largest percentage of respondents (83 percent), followed by blankets (63 percent), mulch
(56 percent), dust suppressants (36 percent), tackifiers (30 percent), soil drying agents
(18 percent), and soil binders (14 percent).
Keyword: Dust suppressants, soil binders, tackifiers, water quality, wattles
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Polyacrylamide use for erosion and turbidity control on construction sites
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
S.A. Hayes, R.A. McLaughlin, and D.L. Osmond
ABSTRACT: Streams and lakes adjacent to construction sites are often heavily impaired by sediment and turbidity coming from areas of exposed soil. A study was conducted to determine if the application of polyacrylamide (PAM) can reduce erosion and runoff turbidity on moderate to steep slopes at construction sites. The test sites were three North Carolina Department of Transportation construction sites in the Piedmont and Coastal Plain. Two PAM products were applied at recommended rates (10.5 and 1.5 kg ha-1; 9.3 and 1.3 lb ac-1) and one half the recommended rates (5.2 and 0.76 kg ha-1; 4.6 and 0.68 lb ac-1) with and without grass seeding and straw mulching. Runoff volumes, turbidity levels, and eroded sediment data were collected after natural rain events. On a 50 percent fill slope, turbidity and sediment loss were significantly decreased with application of seed/mulch but not PAM alone. PAM applied on the seed/mulch treatment did not have statistical effects compared to the seed/mulch alone. Erosion rates of up to 43 t ha-1 were recorded for one storm on bare soil; seed/mulch reduced this by 83 percent. On a 20 percent cut slope, PAM significantly (P < 0.10) reduced turbidity only during one of six storms but did reduce the average turbidity over all storms. No other PAM effects were found. The third site was comprised of a sandy soil on a 20 percent slope and PAM did not have any effect on any parameters, probably due to the low runoff rates on that soil. Overall, the results suggest that PAM application rates of 10.5 kg ha-1 (9.3 lbs ac-1) or less may not have significant benefits on moderate to steep slopes in the Piedmont. This may be at variance with state requirements or manufacturer recommendations, which can be as low as 0.56 kg ha-1 (0.5 lb ac-1).
Keywords: Construction sites, erosion, mulch, polyacrylamide, sediment, turbidity
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Removing soluble phosphorus in irrigation return flows with alum additions
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
A.B. Leytem and D.L. Bjorneberg
ABSTRACT: Phosphorus (P) losses from irrigated cropland transferred to surface waters via irrigation return flows, can impair regional water quality. Best management practices to reduce soil erosion on fields and sediment concentration in return flows do little to reduce soluble P concentrations, which can exceed total maximum daily load (TMDL) limits for total P. Laboratory and field tests were conducted to evaluate the effect of alum on soluble P concentration in return flow water from an irrigation tract in southern Idaho. The laboratory study used two water sources (tap and irrigation), three sediment concentrations (0, 100 and 1000 mg L-1), two added
P concentrations (0 and 1 mg L-1), and five alum concentrations (0, 5, 10, 20 and 40 mg L-1). Field tests were conducted at sediment ponds on two irrigation drains with 20 to 500 mg L-1 sediment and 0.09 to 0.19 mg L-1 dissolved P in inflow water. Regression analysis of laboratory data showed a 53 percent reduction in soluble P concentration with 20 mg L-1 alum, which was similar to field data. Applying 40 mg L-1 alum to irrigation water reduced soluble P concentrations up to 98 percent in the field. Achieving 50 percent soluble P reduction would cost about $0.007 m-3 ($8.25 per ac ft) at the current alum cost of $0.33 kg-1 ($0.15 lb-1). Although alum effectively reduced soluble P in irrigation return flow, the cost of applying alum may be too high for routine use in many irrigation districts.
Keywords: Alum, irrigation, phosphorus, return flow, water quality
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Sensitivity analysis of the Pennsylvania phosphorus index for agricultural recycling of municipal biosolids
(Full text appears in the Journal of Soil and Water Conservation, Vol. 60, No. 4)
R.C. Brandt and H.A. Elliott
ABSTRACT: Forty-nine states are developing phosphorus (P) site indices to assess vulnerability of agricultural fields to P loss. When a P index has multiple variables and mathematical operations, it is often difficult to predict the sensitivity of the final site rating to individual input variables. Sensitivity analysis is a powerful diagnostic technique for assessing the behavior of a P index, prioritizing data collection and research efforts to improve its predictive capabilities, and for focusing management efforts. In this study, nominal range sensitivity analysis was used to determine the effect of input factor perturbations on the final P index score for agricultural biosolids recycling. Baseline conditions (P index score = 116) for the sensitivity analysis were established from a detailed evaluation of representative Pennsylvania sites targeted for biosolids application in 2003. The base condition was evaluated for Sensitivity Coefficient and Swing to identify the importance of individual input factors on final P index rating. For biosolids sites, P loss vulnerability forecast by the Pennsylvania P index was found to be relatively insensitive to subsurface drainage and mineral fertilizer application rate and method (with Swing values of 23, 18, and 4 respectively). Accordingly, uncertainty in these Low Impact P index variables will have little adverse effect on the reliability of index scores for biosolids land application. For sites receiving biosolids, the Pennsylvania P index is most sensitive to the biosolids application rate and method, organic P source coefficient, and nature of the site buffer strip. Remarkably, varying the P source coefficient (alone) over its full range of plausible input values resulted in a P index rating Swing of 167 points. Thus, beyond changing biosolids application rates and methods, the greatest potential to reduce the P index score is in establishing riparian buffer zones and reducing biosolids P source coefficients. It is important to note that the differential sensitivities of fertilizer P source rate and organic P source rate in the Pennsylvania index do not imply that organic P sources are inherently more susceptible to off-site P export than chemical fertilizers. Research efforts should focus on High-Impact factors for improving the predictive capability of the P index.
Keywords: Biosolids, P index, phosphorus, sensitivity analysis, spider plot, tornado diagram
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