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Can refuse from starch-based plastics be converted into compost for
America's farms and gardens? Not until the current biodegradable
formulations change. Researchers with ARS and the Rodale Institute in
Kutztown, PA, found that only plastic golf tees work. They added the tees
along with forks and other starch-based plastics--as well as the pellets
used to manufacture them--to a compost pile. After 11 weeks, only the
golf tees were indistinguishable from the decayed leaves, used paper
plates and poultry litter with which they were composted. All the other
items, made with a different plasticizer, failed to decompose
sufficiently, even after a year. The researchers concluded that these
items had been made with too high a percentage of the wrong type of
plasticizer to make acceptable compost for farmers and gardeners. They
plan to test other biodegradable formulations as they become available.
The work is part of an overall testing of various industrial, urban and
rural wastes as possible ingredients in a low-cost commercial compost.
Soil-Microbial Systems
Research Laboratory, Beltsville, MD
Don Kaufman, (610) 683-6383 (at the Rodale Institute)
A slightly heavier, but naturally occurring, form of nitrogen acts as a
yardstick in identifying the source of nitrate pollution in cave water,
springs and streams. Nitrate is a form of nitrogen available to
plants. ARS researchers have been measuring the nitrogen form, N-15, in
nitrate removed from soil, water and mineral deposits in caves. Tracing
nitrate back to its source helps the researchers understand nitrate
pollution and recommend solutions to farmers. A year's data confirms
earlier studies showing that nitrate with high N-15 levels comes from
animal waste, while nitrate with low levels comes from commercial
fertilizer. Medium levels come from soil microbes. Also, the first
year's data indicate that during the winter, the main source of nitrate
pollution is animal waste. Summer's main sources are commercial
fertilizer and soil microbes.
Appalachian Soil and Water
Conservation Research Laboratory, Beckley, WV
Doug Boyer, (304) 252-6426
Compost can reduce fertilizer needs by one-third. When scientists
replaced a third of a nitrogen fertilizer with a blend of composts from
sewage sludge and municipal trash, they found that tall fescue grass
didn't miss the fertilizer. That's because compost nitrogen is a
slow-release form that the grass uses more efficiently with less waste.
So grass fertilized with compost took in as much nitrogen as more heavily
fertilized grass. An added long-term benefit: The compost continues to
supply nitrogen in the following years--half as much as in the previous
year. Similar results have been seen in corn grown this summer for a
sustainable agriculture demonstration.
Soil-Microbial Systems
Laboratory, Beltsville, MD
Larry J. Sikora, (301) 504-9384
Mixing shredded newspapers with poultry manure makes soil microbes more
active, cutting down on the chance of nitrogen polluting surface and
ground water. The mixture adds carbon, which boosts the activity of
soil microbes that trap nitrogen before it washes away. In preliminary
studies, ARS scientists filled eight-inch diameter columns with the
newspaper/manure mixture above a six-inch hard pan soil, typically found
on the southeastern Coastal Plains. Scientists added four grams of
nitrogen in two forms--commercial fertilizer and poultry manure--to
separate columns. Then they leached water through the column, measuring
nitrogen in the water filtering out the bottom. Only two percent of the
nitrogen from poultry manure leached out, compared to 25 percent from the
commercial fertilizer. Preliminary field studies show that nitrogen
losses are reduced by half when newsprint and poultry litter are used
instead of commercial nitrogen fertilizer to enrich soil. Scientists are
planning more field and lab studies to confirm their findings.
Coastal Plain Soil, Water and
Plant Research Laboratory, Florence, SC
Warren J. Busscher, (803) 669-5203
Last updated: October 30, 1996
Return to: Quarterly Report
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