Agri News, MN
02/14/06
ISU researchers study winter habits of mice
for clues
AMES, Iowa -- Researchers at Iowa State University hope what they're
learning about the winter habits of mice may lead to better weed control with less
reliance on herbicides.
A new project that builds on work funded by the Leopold Center for
Sustainable Agriculture has received a three-year $499,500 grant from the
U.S. Department of Agriculture's Cooperative State Research, Education and
Extension Service (CSREES). It was one of 15 grants awarded to support a
national research initiative on the biology of weedy and invasive species that
cause environmental damage and losses adding up to more than $100 billion per
year.
"For the last four years, we've been keeping a detailed account of what goes into
and what comes out of the bank of weed seeds in the soil," said ISU agronomy
professor Matt Liebman, who leads the project. "We measure the number of
seeds in the soil at the start of every growing season, count the number of
emerged seedlings, and determine the number of new weed seeds produced and
shed back onto the soil. Using simple input-output accounting methods, we figure
that 70 to 90 percent of the weed seeds that should be in the soil aren't there."
So what happened to those "missing" weed seeds?
"We think most of the missing seeds have been consumed by insects and
rodents that live in crop fields," Liebman said. "This project attempts to get a
better picture of the effects of various cropping systems on deer mice and other
species in the seed-eating community. We're particularly interested in how these
animals can contribute to better control of weeds."
The prairie deer mouse, one of North America's most abundant vertebrates,
lives in the middle of fields. Its cousin, the white-footed mouse, lives near field
borders. The ISU team has found that both species are major consumers of
weed seeds during the summer, but little research has been done on the winter
habits of these mammals.
The research began in 2002 on 36 test plots at the ISU Marsden Farm in
eastern Boone County, and in larger fields on other ISU farms. The Marsden
farm plots compare the effects of three different crop management systems on
velvetleaf and giant foxtail:
--a conventional corn-soybean rotation,
--a three-year rotation for producers who use or market small grains (cornsoybean-triticale underseeded with red clover for soil improvement), and
--a four-year system for producers with livestock eating forage (corn-soybeantriticale underseeded with alfalfa-alfalfa for hay).
During the past two seasons, the researchers measured no tonly weed seed
longevity in the soil, weed seedling emergence and survival, and weed seed
production, but also weed seed loss to insect and animal predators. Losses to
predators were determined by lightly gluing weed seeds onto squares of
sandpaper and placing the seed cards throughout fields for 48-hour periods
between April and November.
Averaged over 27 measurement periods in two years, about one-third of the
velvetleaf seeds and half of the giant foxtail seeds were lost to predators within
two days. In 2003, the loss of velvetleaf seeds to predators was greater in the
four-year rotation than in the two-year rotation. Overall, seed predation patterns
in the different crops were complementary. For example, in triticale the largest
number of weed seeds was consumed in the spring, whereas weed seed
consumption in corn and soybean was greatest in late summer and early fall.
"Simple rotations require more herbicides than four-year rotations because you
do not have diverse weed control practices in place," Liebman said. "We're really
interested in the effects of different crop habitats and tillage practices on seed
predation so we can take advantage of it and other ecological processes."
The new project uses special cages to regulate access to seeds between
November and April so the researchers can measure rates of weed seed
predation that occur after the harvest of one crop and before planting another.
The researchers also will examine DNA in the feces of mice live-trapped during
the winter to determine what and where the animal has been eating.
The project represents a unique collaboration between two weed ecologists,
Liebman and Paula Westerman, both in the Department of Agronomy, and
an animal ecologist, Brent Danielson from the ISU Department of Ecology,
Evolution and Organismal Biology.
During the past two years, Liebman, Westernman and Danielson have offered
their research results as part of a field school on weed ecology and management
for farmers, funded by the Leopold Center. They also have been comparing the
related costs and income from the three cropping systems.