![Photo: Angus cattle on pasture. Link to photo information](/peth04/20041101001833im_/http://ars.usda.gov/is/graphics/photos/jun04/k4148-10i.jpg) Angus cattle on pasture.
Click the image for more information about it.
Read the
magazine
story to find out more. |
Continual Fertilizing, Not Cows, Is the
Problem on Sensitive Pastures By
Don Comis June 8,
2004
Although cattle add some nitrogen to pastures via their feces
and urine, it isn't enough to warrant removing them from a pasture, according
to an Agricultural Research Service
scientist, even if the pasture is above groundwater contaminated by high levels
of nitrate-nitrogen.
A study by Lloyd Owens, a soil scientist at the ARS
North Appalachian Experimental
Watershed Laboratory in Coshocton, Ohio, has shown that it doesn't make any
difference in groundwater nitrate levels whether cattle are on the pasture or
not.
What does make a difference is fertilization. Pastures with high
nitrate levels can't be fertilized for at least a few years, until the levels
drop sufficiently. U.S. Environmental Protection
Agency guidelines for drinking water stipulate 10 parts per million (ppm)
nitrate-nitrogen as the maximum allowable safe level for drinking water.
Owens studied problem pastures with groundwater nitrate-nitrogen
levels of 13 to 26 ppm, caused by heavy experimental fertilization for 11 years
before the study. He stopped fertilizing for a seven-year study to see if that
would bring nitrate levels down to safe levels. For comparison, he let cattle
graze on two pastures, and fenced them out and made hay from two other
pastures.
In the groundwater underneath three pastures, the
nitrate-nitrogen levels dropped below 10 ppm within three years; after five
years, the levels below all four pastures fell to 2 to 4 ppm.
Because of soil conditions, some fields are more prone to high
nitrate levels. Fertilizing every year can eventually turn them into problem
fields. The finding is good news for farmers because they don't have to remove
cattle from these problem fields, as long as they stop fertilizing for a while.
Letting cattle graze saves the time and labor of baling hay for feed, which is
what was done on the two test pastures where cattle couldn't graze.
The withholding of fertilizer caused only a slight decrease in
grass growth, so it doesn't seem to be a serious disadvantage to farmers,
especially compared to the environmental benefit.
More
information about nitrate research can be found in the current issue of
Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency. |