By
Kimberly Warren
Managing Editor
Winter isn’t just
a time where fields lie fallow and growers wait for the snow to melt.
With careful planning and good timing, cover crops can make winter
just as productive as spring and summer.
“Growers should first think about each rotation sequence with
what they’re trying to solve,” said Sieglinde Snapp, a
horticulture assistant professor at Michigan State University (MSU).
“Cover crops prevent soil erosion. Do you have nematode issues?
Are fertility or yield not what it’s supposed to be? There are
different crops for different problems.”
MSU researchers currently are looking at three different options:
cereal grasses, legumes and brassicas.
The rye, wheat and other cereal grasses are used most often for soil
erosion and is the most inexpensive option.
“If it’s late in the season, they’re (cereals) one
of the best options,” Snapp said. “Round-up after rye
is a good way to make sure you have maximum biomass from the rye with
fast decomposition.”
Snapp said some worry about rye growing too vigorously, but Round-up
speeds decomposition and won’t harm any of the next season’s
crops. However, Snapp said, organic growers should use oats as the
cover crop because the crop kills itself.
So when should someone plant a cereal cover crop? Snapp said as early
as possible in August, but they can be planted as late as into early
October and still have beneficial effects.
For growers looking to improve soil fertility rather than stop soil
erosion, the cover crop best suited to the task is legumes. Legume
options include red clover and hairy vetch. Like cereals, legumes
should be planted early, but they can survive the winter when planted
in early October.
Combining a legume crop with rye will make the cover crop cheaper,
but Snapp said it has shown positive results in research trials.
“Mix a bushel and a half of rye with 15 to 20 pounds of hairy
vetch,” Snapp said. “It’s cheaper, plus it gives
it some protection from the wind. Together, they do better than either
alone.”
However, if wheat is grown in rotation, growers shouldn’t mix
these two cover crops because hairy vetch winds around grasses.
“But if you’re growing vegetable after vegetable, it’s
great,” Snapp said.
For those growing wheat, red clover is the best cover crop option.
Cereals and legumes are the classic options, but for the past two
years Snapp and other MSU researchers have been looking at brassicas,
or mustards.
“In Washington state, there are a lot of potato and vegetable
growers using mustards specifically,” Snapp said. But Snapp
has seen difficulties with brassicas in her research.
Last year, they had establishment problems with the brassicas. To
have better establishment, brassicas should be rye-cast on the surface
and irrigated in – especially in a sandy soil.
“It (brassica cover crop) does work as a biofumigant,”
Snapp said. “If you have nematode problems, that will not only
improve your soil but give you good root health.”
Though the team is seeing positive results with brassicas, it recognizes
brassicas are expensive, including transport costs . Snapp’s
brassicas are coming from Idaho – these cover crops can cost
about $30 per acre.
“We’re also trying mixtures of mustard with rye to cut
the costs, but that research is just starting,” Snapp said.
For those still wondering whether a cover crop is a good option, Snapp
said her research has shown that they are getting a 5 to 10 percent
yield increase in potatoes and snap beans just from using a rye cover
crop. In addition, she said they’re also getting nitrogen credit.
“Growers should try to get rye on all their fields,” Snapp
said. “Don’t leave any fields bare. We can’t fully
explain it, but you just see better root vigor and health where there’s
been a cover crop.”
For more information on cover crops, there will be a session at the
Great Lakes Fruit, Vegetable and Farm Market EXPO, which will be Dec.
7-9. Or, visit MSU’s Vegetable Information Network at http://web4.msue.msu.edu/veginfo/
