By Don Comis
July 8, 2003
An experimental feedlot in Bushland,
Texas, is one of a very few fitted with devices that measure runoff flow from
the cattle pens and sample it for nitrogen, phosphorus and pathogens.
Commercial feedlots store runoff in holding ponds that normally prevent it from
The study, by Agricultural Research
Service animal scientist Andy Cole and colleagues at the ARS Conservation
and Production Research Laboratory in Bushland and
Texas A&M University, is aimed at
finding ways to minimize the amount of nutrients in runoff and eliminate
pathogens. The excess nutrients are a waste of money to feedlots and pose a
risk if the holding ponds should fail. The scientists are also concerned that
feedlot dust, runoff and manure might carry pathogens to nearby crops.
Cole is monitoring how much nitrogen is escaping from manure into the air as
ammonia gas. Ammonia washed from the atmosphere in rain can harm natural
ecosystems by overfertilizing them with nitrogen. Also, it can combine with
others gases to produce particles small enough to be inhaled, potentially
causing human health problems.
To study ammonia emissions from manure, ARS soil scientist Richard Todd of
the Bushland lab simulates feedlot surfaces by packing manure in 8-inch-deep,
33-foot-diameter circles outdoors. He places a 10-foot-tall tower in the center
of each circle, with collectors at various heights to capture ammonia.
Initial results show that decreasing the protein fed to cattle in feedlots
from 13 to 11.5 percent might decrease daily ammonia emissions by about 20
percent. But that may be possible only near the end of animals' feedlot stay,
to preserve weight gains.
Future studies will look at methane emissions from manure. The objective of
the experimental feedlot is to find cost-effective ways to improve feedlots
More information about this research can be found in the July 2003 issue of
Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.