March 2007, Vol. 19, No.3

Research Notes

Testing Poultry Litter for No-Till Farming

Injecting liquefied manure into the soil may be the key to reducing phosphorus runoff at poultry and other animal farms. Peter Kleinman, a soil scientist with the U.S. Agricultural Research Service (ARS), has been studying this method of injection on Delmarva Peninsula, according to an ARS news release.

The 15,400-km2 (5950-mi2) peninsula encompasses parts of Delaware, Maryland, and Virginia. There, Kleinman will investigate an experimental method of injecting chicken litter into the soil to keep this natural fertilizer from running off into Chesapeake Bay.

Each year, Delmarva’s approximately 2700 poultry farms raise about 571,141,000 chickens. The 544,000 tonnes (600,000 tons) of litter they produce is an ideal fertilizer for corn, soybeans, and other Delmarva crops, according to ARS. However, spreading it over the soil surface exposes nutrients, such as phosphorus, to runoff that can drain into the bay’s surrounding waters, triggering algal blooms that block sunlight and deprive fish, crabs, and other forms of aquatic life of oxygen.

The increasingly popular use of no-till farming compounds the problem, according to Kleinman, who works at the ARS Pasture Systems and Watershed Management Research Laboratory in University Park, Pa.

Since 2005, Kleinman has been researching fertilizer-application equipment called injectors, which squirt liquefied manure below the soil surface. Tom Way, a collaborator at the ARS Soil Dynamics Laboratory in Auburn, Ala., developed the new litter-injector technology. Now, in collaboration with the University of New Hampshire’s Cooperative Institute for Coastal and Estuarine Environmental Technology (Durham) and the National Oceanic and Atmospheric Administration, they’re exploring equipment modifications that could enable the injection of chicken litter into the Delmarva Peninsula’s sandy soils.

Their onsite efforts will draw from prior research in which Kleinman and colleagues from ARS, The Pennsylvania State University (State College) and the University of Maryland–Eastern Shore (Princess Anne) used a combination of rainfall simulators, runoff monitoring technology, and other equipment to examine how well four types of cow-manure injectors curbed runoff and odors emanating from fertilized fields.

Contact Kleinman at for more information.

Research Seen To Improve Chesapeake Bay

Chesapeake Bay has undergone a lot of stress from animal and crop production, as well as regional development. U.S. Agricultural Research Service (ARS) scientists and others have been investigating ways to mitigate or prevent harm from farming practices, and there has been progress.

An ARS news release states that the bay’s total estimated levels of phosphorus fell from 12.3 million kg (27.1 million lb) of phosphorus in 1985 to 8.8 million kg (19.5 million lb) in 2002. The nitrogen level fell from 153.3 million kg (338 million lb) in 1985 to 126.1 million kg (278 million lb) in 2002.

To further reduce runoff into the bay, soil scientist Greg McCarty at the ARS Hydrology and Remote Sensing Laboratory in Beltsville, Md., has done extensive research on the use of riparian buffer zones to reduce the amount of nutrients getting into waterways. These buffer zones — wooded or grassy areas in wetlands and along streambanks — help filter out pollutants and excess nutrients.

Unfortunately, the nutrient reductions made to date may still be insufficient, because in summer 2005 there was almost no oxygen in 3% of the bay’s waters, and 21% had low levels, according to the multiagency Chesapeake Bay Program. This was the lowest oxygen level detected in the bay’s central region since the program began monitoring in 1984.

Now, in addition to scientific studies by state and federal agencies to improve the bay, there is a U.S. Department of Agriculture effort under way called the Conservation Effects Assessment Project (CEAP), which taps watershed researchers nationwide to assess the benefits and value of conservation efforts. As part of CEAP, the researchers use historical data and monitor current conditions to estimate the impact of conservation practices, such as riparian zones and cover crops, on environmental issues, such as the quality of the water entering the bay.

For more information, see the November issue of Agricultural Research magazine at

Rubber From Scrap Tires Might Filter Wastewater

A professor at Pennsylvania State University at Harrisburg may have found an innovative method for reusing rubber tires that normally clog landfills — to filter wastewater.

Yuefeng Xie has found that crumb rubber can be used to filter wastewater, according to a university news release. Xie said the crumb rubber — produced by chopping up and grinding up waste tires to a desired size, cleaning the rubber, and removing any metal particles — could be used for treating wastewater, ship ballast water, and stormwater.

Crumb rubber is currently being used in highway pavement, athletic track surfaces, playgrounds, landfill liners, energy recovery, and even as artificial reefs for aquatic life, according to the news release.
For traditional wastewater filtration, gravity downflow granular filters using sand or anthracite as a medium are commonly used. One major problem with these filters is that upon backwashing the particles, the larger ones settle at a greater rate than the smaller ones.

The Penn State researcher explains that this causes the top of the filter bed to hold the smallest-medium particles and the bottom to hold the largest, with the small-medium particles or top layer of the filter tending to become clogged quickly.

Through his research, Xie has found that crumb rubber is not a rigid material; instead it can be easily bent or compressed. Through the crumb rubber method, the larger solids are removed at the top layer of the filter and the smaller solids at a lower level. This reduces clogging, which, according to Xie, may happen with gravity downflow granular filters that use sand or anthracite as a medium.

Also, because of the higher water filtration rates and lighter weight of the crumb rubber filters, they may be a good choice in a mobile treatment unit for disaster relief operations, Xie said.

Another benefit to crumb rubber is that it’s compressible — the porosity of the particles is decreased, resembling an ideal filter medium configuration, the press release states. It can then be used at higher filter rates while performing similarly to other media, Xie explained.

Contact Xie at