Freeland J.D.,NRCS |
Bass A.G.,State Office |
Burns A.D.,U.S. Department of Agriculture
Association of State Dam Safety Officials - Dam Safety 2011 | Year: 2011
More than 11,000 dams have been constructed nationwide in the last 62 years by local project sponsors with assistance from the Natural Resources Conservation Service (NRCS). With this many dams in service, it is inevitable that many will require repair or rehabilitation due to physical deterioration or changes in hazard classification. It is also certain that the costs required to bring some of these dams into compliance with current safety criteria would be so great that the only economically viable option is decommissioning. Dam decommissioning primarily involves the physical removal of the embankment and associated works in a manner that leaves the landscape in a condition as close to its natural state as practical. As easy as this may sound, the environmental, social, and possible economic impacts of the removal are complicated. Some of these dams have been in place for more than 60 years. Upstream and downstream channels have adapted to their presence over this period and have usually reached equilibrium. Removal of the dam may result in the physical impacts of increased downstream flooding, release of sediment with possible toxins or excessive nutrients from the sediment pool and stream channel or secondary erosion. There are also social impacts to consider; such as the loss of recreational use, agricultural water, and wildlife benefits. This paper looks at three flood control dams in Oklahoma that have been or are in the process of being decommissioned. This study focuses on practical planning, design, and construction considerations for dam removal that help to mitigate all of the impacts of decommissioning.
Sigua G.C.,U.S. Department of Agriculture |
Coleman S.W.,U.S. Department of Agriculture |
Albano J.,U.S. Department of Agriculture |
Nutrient Cycling in Agroecosystems | Year: 2010
Characterizing and assessing spatial distribution of soil phosphorus and herbage mass in relation to landscape properties, land use, or landscape positions is important for understanding how pasture sustainability can be managed and improved properly. Our reason for conducting this study was to determine the effects of different slope aspects and slope positions on spatial distribution of soil phosphorus and herbage mass in subtropical pastures. Soil and forage samples were collected from contiguous south-, north-, east-, and west-facing slopes across different landscape positions (top slope, middle slope, and bottom slope) in 100 ha of bahiagrass (Paspalum notatum)-based pastures from 2003 to 2006 in subtropical region of southeastern USA. Averaged across years, soils on the north-facing slope contained the greatest amount of soil phosphorus (12.4 ± 2.7 mg kg-1) when compared with other slope aspects. Slope aspect may be acting as an important topographic factor influencing local site microclimate mainly because it determines the amount of solar radiation received. The greatest herbage mass (averaged across year) of 2,967 ± 980 kg ha-1 and the highest phosphorus accumulation of 7.7 ± 3.0 kg ha-1 for bahiagrass were from the top slope position. There was a significant (P ≤ 0.05) decrease in the average herbage mass and phosphorus accumulation with decreasing slope (top to middle slope). Between the top slope and the bottom slope, herbage mass declined from 2,967 ± 980 to 1,805 ± 370 kg ha-1 while phosphorus accumulation was reduced by approximately 40% (7.7-4.6 kg ha-1). Results of our study may increase awareness on how the arrangement of food, water, and shelter and their interactions with topographic and landscape features can significantly influence the movement of animals and utilization of different pastures' resources. While our study supports our hypothesis that slope aspect and slope position could be of relative importance in controlling spatial distribution of soil phosphorus and herbage mass, broad knowledge of cattle movement in pasture situations is as critical to understanding their impact on agro-ecosystems. © 2010 Springer Science+Business Media B.V.
Davy J.S.,Range Resources |
Roche L.M.,University of California at Davis |
Robertson A.V.,University of California at Davis |
Nay D.E.,NRCS |
Tate K.W.,University of California at Davis
California Agriculture | Year: 2015
Invasive weed species in California's rangelands can reduce herbaceous diversity, forage quality and wildlife habitat. Small-scale studies (5 acres or fewer) have shown reductions of medusahead and yellow starthistle using prescribed grazing on rangelands, but little is published on the effects of pasture-scale (greater than 80 acres) prescribed grazing on weed control and plant community responses. We report the results of a 6-year collaborative study of manager-applied prescribed grazing implemented on rangeland that had not been grazed for 4 years. Grazing reduced medusahead but did not alter yellow starthistle cover. Medusahead reductions were only seen in years that did not have significant late spring rainfall, suggesting that it is able to recover from heavy grazing if soil moisture is present. Later season grazing appears to have the potential to suppress medusahead in all years. In practice, however, such grazing is constrained by livestock drinking water availability and forage quality, which were limited even in years with late spring rainfall. Thus, we expect that grazing treatments under real-world constraints would reduce medusahead only in years with little late spring rainfall. After 10 years of grazing exclusion, the ungrazed plant communities began to shift, replacing medusahead with species that have little value, such as ripgut and red brome.
American Society of Agricultural and Biological Engineers Annual International Meeting 2010, ASABE 2010 | Year: 2010
An Amish landowner in southeastern Pennsylvania asked NRCS to help him improve his existing manure management system. He had an existing concrete-block storage tank that held about 1.5 months of manure from his dairy herd, consisting of 45 Holstein cows. The landowner was interested in decommissioning the existing storage to build a larger one. In addition, he wanted to modify the barn for a Virginia-style heifer facility, rework the barnyard, and tie the entire system together. Manure will gravity flow from the gutters in the tie-stall barn, through a cross gutter and into the slatted storage of the heifer facility. A gated pipe will allow manure to flow out of the heifer barn and into the 56' diameter by 10' deep concrete liquid manure storage tank. Barnyard runoff and lot scrapings will be pushed over the side of the tank. Various challenges to the site included working in and around an existing barn, decommissioning the existing block-wall manure storage, capturing spring flow, non-encroachment on surface water, equipment access over a buried gas pipeline, and working with the special needs of the Plain Sect landowner. Ensuring that the manure management design was compatible with the planned construction was also critical.
Peterson D.,NRCS |
Brownlee M.,Brownlee Ranch |
Kelley T.,Kelley Ranch
Rangelands | Year: 2013
On the Ground Stocking density is a powerful tool to manage grazing land resources, as demonstrated on prairie and pasture in Missouri. Utilizing different stock densities, we can achieve different goals, including affecting diet selection, weed and brush control, improving utilization and manure distribution, and even improving seed-to-soil contact. We allow sufficient recovery periods between grazing events to increase plant diversity and develop as much above- and below-ground biomass as possible. During grazing periods we use stocking density to manipulate the amount of forage trampling that occurs. Trampling can have a very positive impact on water and mineral cycles, building soil and increasing fertility in our perennial grasslands. © 2013 The Society for Range Management.