Eliminating Weeds Could Put More Cows on the
By Don Comis
April 28, 2010
An online weed calculator developed by
an Agricultural Research Service (ARS)
scientist tells ranchers the number of additional cows they could raise if they
eliminated one or two widespread exotic invasive weeds.
Rinella at the ARS
Keogh Livestock and Range Research Laboratory in Miles City, Mont., created
a computer model that predicts weed impacts on forage production.
Data for developing the model came from 30 weed researchers working
throughout the western United States. In addition to developing the calculator
so that ranchers can calculate what weeds are costing them on any given site,
Rinella used the data to estimate what weeds are costing ranchers in a 17-state
region. He calculated that if leafy spurge were eliminated, ranchers in that
entire region could graze up to 200,000 or more cows a year and save tens of
millions of dollars.
Spotted knapweed is another exotic invasive weed whose elimination would
greatly increase the number of cows ranches could support, and the calculator
also predicts its impacts.
All the rancher needs is a datasheet, a clipboard, a pencil, a yard stick,
and homemade sampling frames of any size, rectangular or circular. Ranchers can
download datasheets for recording weeds. They tally weeds in each frame,
grouping them by their heights. The necessary data can be gathered in about 30
When the numbers are entered into the calculator, the ranchers learn how
many pounds of weed they are producing per acre and how many more cattle they
could raise per acre if those pounds of weeds were replaced by forage plants.
It is important to quickly spray or hand-pull small weed infestations before
they expand. But with large weed infestations, the calculator reflects a
fundamental principle of integrated pest management: It is only worth
controlling a pest if the profits from doing so outweigh the costs.
Interested parties can access the calculator at:
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture (USDA). This
research supports the USDA priority of promoting international food security.