Adding sodium carbonate—a harmless ingredient in soft drinks and some toothpastes—could be a practical and inexpensive method for treating dairy cattle manure to decrease Escherichia coli O157:H7 and other potential pathogens. Some cattle harbor E. coli: O157:H7 and other disease-causing bacteria that can persist in manure for long periods of time. But a team of ARS and Cornell University-Ithaca scientists found that adding sodium carbonate can kill many of these harmful microbes. Laboratory tests showed that although E. coli was resistant to alkaline pH and ammonia, it was very sensitive to carbonate if the pH was alkaline. Carbonate can be derived from urine when urease—an enzyme in feces—breaks down urinary urea, trapping some carbon dioxide as carbonate. Urinary carbonate alone can kill E. coli, but cows don't make enough urine to kill all the E. coli. The team made its discovery by mixing manure and urine. When the ratio was 1 to 1, virtually all of the E. coli bacteria were killed. But dairy cows typically excrete 2.2 times as much feces as urine, and E. coli persisted at that ratio—unless the cow manure samples were spiked in the lab with sodium carbonate. Laboratory experiments indicated that carbonate killed other bacterial pathogens, as well, such as Salmonella typhimurium, Streptococcus pyogenes, Klebsiella pneumoniae, and Staphylococcus aureus. The researchers also added some sodium hydroxide to ensure that the pH was at least 8.5. After only 5 days, the E. coli count was less than 10 cells per gram in manure samples—down from the original 100,000 to 100,000,000 counts per gram. Cattle manure is often stored outdoors in large tanks or ponds prior to spreading on fields, but a threefold dilution with water did not diminish the effectiveness of carbonate treatment. The estimated cost of this treatment would be only $10 per dairy cow per year. However, pilot and farm-scale testing will be needed before the technology can be recommended to the livestock industry.

U.S. Plant, Soil, and Nutrition Laboratory, Ithaca, NY
James B. Russell, (607) 255–4508, jbr8@cornell.edu

Using seismic/acoustic waves to describe important soil physical properties is relatively new to soil science. The description of how soil particles touch each other and are arranged in soil is also of great interest and can be deduced from these waves. The advantage of the seismic/acoustic technique over traditional methods is its ability to identify the magnitude of these properties without disturbing the soil. The key, ARS scientists say, is how well the soil absorbs these waves. They've developed a technique that lets them measure absorption of these waves, penetrating up to 4 inches of the upper soil profile. The seismic technique is especially useful for measuring the swelling or shrinking condition of soils, since the status of the soil can be changed by its water content. The scientists applied the seismic technique to a Mississippi Delta Sharkey clay soil, known for its high swelling/shrinking capacity. They found large changes in the velocity of seismic/acoustic waves in this soil as a result of its water content. From this information, scientists can determine the elasticity of the soil. When fully developed, this new technology could be used in agriculture and in highway and building construction. The technology could also be used someday to monitor the moisture content in fields so automated sprinkler systems would turn on only when the soil needed watering.

National Sedimentation Laboratory, Oxford, MS
Mathias J. Romkens, (662) 232–2927, romkens@sedlab.olemiss.edu

ARS scientists studying water quality in America's streams hope to find lots of healthy bugs. Scientists are finding that small aquatic invertebrates are excellent and inexpensive indicators of water quality. Some, like Hyalella azteca, can even be used to measure how much of any pollutant is acceptable in our surface water. The 1/8- to 1/4-inch crustacean, commonly found in lakes, ponds, and streams throughout North America, consumes decaying plant material. It can be found swimming in the water or burrowing into sediment. It's an important link in the aquatic food chain and a food source for several predators, such as fish and various invertebrates. Using Hyalella as an indicator of environmental quality has many advantages. It has been well studied; scientists know its life history, behavior, growth, reproduction, and the effect of different factors on its survival. It is easily raised and reproduces rapidly and is an inexpensive organism that is easy to work with. This crustacean provides researchers with a biological measurement of stream health, in addition to chemical and physical measurements.

National Sedimentation Laboratory, Oxford, MS
Charles Cooper, (662) 232–2935, cooper@sedlab.olemiss.edu

Cracking and swelling soils can have a profound effect on the hydrology of watersheds. ARS scientists studying the genesis, morphology, and underlying mechanisms of crack development found that, depending on the degree of dryness or size, cracks may absorb all incoming rainwater. Also, the presence of cracks will affect the absorption and deposition of surface-applied agrichemicals and rainfall-detached soil particles. This research showed that besides intrinsic soil characteristics, soil surface conditions, such as type of cover, also play a significant role in the manner of crack development. In this laboratory study, the breakdown and compaction of soil aggregate by raindrops falling on the unprotected surfaces led to a stratification in the upper 0.4 inches of the soil profile. The surface seal had different mechanical properties than the substrate and therefore affected crack development. Most of the water infiltration and soil movement took place in and through those cracks. On protected soil surfaces, such as those covered with mulch, cracks developed as well, but infiltration was more uniform.

National Sedimentation Laboratory, Oxford, MS
Matt. J. Romkens, (662) 232–2927, romkens@sedlab.olemiss.edu

An increased demand for rapid extraction and analysis of pesticide residues has led ARS scientists to develop a new analytical chemistry technique. Their fast and sensitive gas chromatographic method uses sonication (sound agitation) for extracting atrazine (triazine herbicide) and lambda-cyhalothrin (pyrethroid insecticide) from sediment and aquatic plant samples. This method requires less chemical solvent and smaller samples than standard U.S. Environmental Protection Agency methods. Since newer analytical equipment is not always available, the researchers reevaluated and updated older methods that use more traditional equipment. They discovered that, for optimal pesticide recovery, sediment and plant samples should be wetted with water prior to the addition of extracting solvents. Analytical chemists studying herbicide and other pesticide residues in sediment and plant samples will use this information.

National Sedimentation Laboratory, Oxford, MS
Sammie Smith, Jr., (662) 232–2936, smith@sedlab.olemiss.edu