August 2006, Vol. 18, No.8

Research Notes

Research Notes - Potatoes Help Reduce Nitrogen in Groundwater

Deep-rooted cover crops can help potato farmers prevent erosion and protect groundwater by reducing nitrate leaching, according to U.S. Agricultural Research Service (ARS) scientists.

Heavily fertilized crops with shallow roots, such as potatoes, are more susceptible to nitrate leaching, according to Jorge Delgado, a soil scientist in the ARS Soil Plant Nutrient Research Unit in Fort Collins, Colo. However, nitrogen recovery can be significantly improved — and leaching minimized — by using a deep-rooted cover crop, such as winter rye, malting barley, or winter wheat.

Deep-rooted cover crops reduce wind erosion, sequester carbon, cycle nutrients, and draw nitrate from deeper in the soil than crops with shallow roots, according to an ARS news release. Crops like winter cover rye and wheat can even be used for grazing.

Complementary potato research is being conducted in ARS labs at Prosser, Wash., and Orono, Maine. At Prosser, scientists measured how much nitrogen Brassica cover crops contributed to the soil and how much was taken up by subsequent potato crops. The studies found that about 30% of the nitrogen on the surface of the crop field was cycled back to the soil. Planting Brassica cover crops could save growers $15 to $20 per acre at current fertilizer prices, according to ARS.

Orono researchers modeled the influence of temperature on crop residue decomposition and nitrogen availability in order to predict the best time to apply additional fertilizer to meet the crop’s needs and potentially reduce the amount of nitrate lost to groundwater.

Read more about the research in the May 2006 issue of Agricultural Research magazine at www.ars.usda.gov/is/AR/archive/may06.  

Water Cycle Intensifies, No Increase in Storms or Floods

 The U.S. Geological Survey (USGS) on March 15 announced the publication of a study showing that many aspects of the global water cycle, including precipitation and evaporation, have intensified. The report is quick to point out, however, that the data do not indicate that this trend has resulted in an increase in the frequency or intensity of tropical storms or floods during the past century, according to a USGS press release.

“A key question in the global climate debate is if the climate warms in the future, will the water cycle intensify and what will be the nature of that intensification,” said USGS scientist Thomas Huntington, who authored the study. “This is important because intensification of the water cycle could change water availability and increase the frequency of tropical storms, floods, and droughts, and increased water vapor in the atmosphere could amplify climate warming.”

For the report, Huntington reviewed data presented in more than 100 peer-reviewed scientific studies. Although the data are incomplete and sometimes contradictory, the weight of evidence from past studies shows on a global scale that precipitation, runoff, atmospheric water vapor, soil moisture, evapotranspiration, growing season length, and wintertime mountain glacier mass are all increasing, the press release states.

“This intensification has been proposed and would logically seem to result in more flooding and more intense tropical storm seasons,” Huntington said. “But over the observational period, those effects are just not borne out by the data in a consistent way.”

Huntington notes that the long term and global scale of this study could accommodate significant variability, for example, the last two Atlantic hurricane seasons.

“We are talking about two possible overall responses to global climate warming: first an intensification of the water cycle being manifested by more moisture in the air, more precipitation, more runoff, more evapotranspiration, which we do see in this study; and second, the potential effects of the intensification that would include more flooding and more tropical storms, which we don’t see in this study,” Huntington said.

The research report was published in the March 16 issue of the Journal of Hydrology.

U.S. EPA Releases First-Ever Assessment of U.S. Wadeable Streams

By knowing the condition of streams, the U.S. Environmental Protection Agency (EPA) is hoping citizens will have a better idea of the overall health of their local watershed and take appropriate action. EPA is providing such information through its Wadeable Streams Assessment (WSA), a sampling of 1392 streams conducted between 2000 and 2004.

Called a “scientific report card on America’s streams” by Benjamin Grumbles, EPA assistant administrator for Water, the study was conducted by more than 150 field biologists, according to an agency news release.

Noted by EPA as the first consistent evaluation of U.S. streams that feed rivers, lakes, and coastal waters, the report includes assessments of streams that are shallow enough to be sampled adequately without a boat.

The survey found that stream conditions vary widely across the diverse ecological regions of the country and that streams in the West were in the best condition. Humans, the researchers found, have a significant impact on wadeable streams. A majority of streams showed evidence of human influence, such as dams, pavement and pastures.

WSA measured key chemical and physical indicators that reveal stress or degradation of streams. The most widespread stressors observed are nitrogen, phosphorus, and streambed sediments, which smother aquatic habitat and degrade conditions for fish. Nitrogen and phosphorus are nutrients that can increase the growth of algae, decrease levels of dissolved oxygen, and cloud the water.

WSA is part of a series of surveys to evaluate all U.S. waters. Coastal condition has already been evaluated. During the next 5 years, EPA will sample the condition of lakes, large rivers, and wetlands. Then the process will be repeated to provide ongoing comparisons of the state of the waters and point to possible future action.

For more information on WSA, see www.epa.gov/owow/streamsurvey.  

Technology Turns Contaminated Sediment Into Useful Product

The soil used to landscape lawns someday may come from contaminated river and harbor sediments, according to a news release issued by the U.S. Environmental Protection Agency (EPA).

The technology uses water under high pressure and biodegradable detergents to strip away contaminants and leave behind soil that can be blended with compost or yard waste to produce high-quality topsoil. It is patented by BioGenesis Enterprises Inc. (Oak Creek, Wis.) and is being used in a Woodbridge, N.J., facility to treat more than 3440 m3 (4500 yd3) of contaminated sediment from the lower Passaic River.

The new technology is part of a demonstration program to decontaminate dredged materials from the Port of New York and New Jersey, the news release states. The program is being funded and implemented by EPA and the New Jersey Department of Transportation. In addition to sediment washing technology, the two agencies are evaluating a technology that heats the sediment to 1427°C (2600°F) and blends it with cement. This technology — patented by Endesco Clean Harbors, a GTI (Des Plaines, Ill.) company for marketing waste-treatment technologies — will be used at the International Matex Tank Terminal in Bayonne, N.J., to treat sediment currently stored in the Valgocen, a large cargo vessel docked on the Raritan River at Bayshore Recycling.

Sediment washing and thermal destruction may be among the technologies available for treated dredged sediments from the New York–New Jersey Harbor and large aquatic Superfund sites, such as the lower Passaic River, with an ultimate goal of creating a self-sustaining industry that uses treated dredged sediments as building material, the news release says.

The technology strips contaminants — including PCBs, dioxins, heavy metals (such as mercury and arsenic), and petroleum-related compounds — from sediment particles using a specially developed biodegradable detergent and high-pressure water jets. Manufactured soil can be produced from the decontaminated sediment and could be used in a number of land-based applications, such as remediation and landscaping. Beneficial-use products also include construction-grade cement, lightweight aggregate, composite bricks, and structural fill, according to EPA.

Information and technical reports on EPA’s sediment decontamination program can be found at www.bnl.gov/wrdadcon. Information on the agency’s national dredged materials management program is available at www.epa.gov/owow/oceans/regulatory/dumpdredged/dredgemgmt. For information on beneficial uses of treated sediments, see el.erdc.usace.army.mil/dots/budm.  

Phages Eyed as New Way To Control Salmonella in Swine Waste Lagoons

U.S. Agricultural Research Service (ARS) scientists and university collaborators have collected and partially characterized beneficial viruses, called bacteriophages, that could help control Salmonella bacteria in swine waste lagoons.

Disease caused by Salmonella costs pork producers an estimated $100 million annually, according to an ARS news release. The U.S. Centers for Disease Control and Prevention estimates that foodborne outbreaks of salmonellosis affect 1.4 million consumers annually.

Mike McLaughlin, a virologist in the ARS Waste Management and Forage Research Unit at Mississippi State University (Mississippi State, Miss.) and collaborators from the Western Kentucky University (Bowling Green) biology department have devised and adapted methods to collect, isolate, and identify bacteriophages that attack and kill Salmonella strains. Salmonella causes illness in livestock, pets, and people, but its hosts often show no signs of disease, complicating detection and control efforts.

Bacteriophages — or “phages” — invade bacteria, multiply and eventually rupture bacterial walls, releasing multiple copies of new phages capable of invading more bacteria, according to the news release. Most phages only attack specific species and strains of bacteria. Knowledge of this host-specificity allows specialists in agriculture, medicine, and food safety to apply specific phages to help identify, track, and even treat or prevent bacterial infections. McLaughlin and his team examined the bacterial host-specificity of the phages found in swine manure and, using electron microscopy, classified the phages according to their unique sizes and shapes.

Information from the study will enable scientists to understand better the microbial ecology within swine effluent lagoons, according to ARS. This research, part of the ARS national program on manure and byproduct utilization, is reported in the March issue of Journal of Environmental Quality, online at jeq.scijournals.org.