Choosing the right cover crop to protect the soil

Date:
September 16, 2020
Source:
American Society of Agronomy
Summary:
Research helps farmers pick the best cover crops to keep their
soil and nutrients in the field.



FULL STORY ========================================================================== Farmers around the world are keen to protect their most important
asset: their soil. The soil supports and enriches their crops. But the relatively thin layer of topsoil can readily wash away into streams,
carrying unwanted nutrients with it.


========================================================================== Enter cover crops. Cover crops are inedible plants grown during the
off-season.

Their roots help keep soil in place, preventing erosion. Cover crops can
even absorb excess nutrients like nitrogen to keep them from polluting
streams.

Farmers are increasingly interested in using cover crops to help their
farms.

But with a dizzying array of plants to choose from and complex crop
rotations, making the right choice is no easy feat.

"I believe cover crops are a very important tool for both retaining soil
and keeping nutrients on the farm," says Mari'a Villamil, a researcher
at the University of Illinois and a member of the American Society of
Agronomy. "In the Midwest, we are very lucky to have high fertility soils, making us big providers of food worldwide. The protection of our soils
is critical." To help farmers in Illinois choose the right cover crop, Villamil and her team decided to test several potential cover crops. They planted different cover crops between the common Midwestern rotation of
corn and soybeans. The researchers worked closely with farmers to choose
which cover crops to test.

"They wanted to test different cover crops, especially ones that don't
generate extra work in the spring and others that will not compete with
the corn for resources," says Villamil.

Farmers preferred growing cereal rye as a cover crop before soybeans were planted. The rye captured the nitrogen remaining in the soil after the
previous year's corn crop season. But, when farmers were planning to grow
corn, they preferred using a vetch cover crop. Vetch is a legume crop,
which means it can provide nitrogen for the corn to use later in the
season. Vetch also uses less water than cereal rye, which means the corn
crop will not need to work as hard to compete for limited water resources.



========================================================================== Villamil's team set up experimental plots at six locations around
the state.

Toward the end of the growing season for corn or soybeans, researchers
walked through the crop fields to spread cover crop seeds among the
plants. This mimics seeding by airplane. Aerial seeding has been a
popular idea to plant cover crops in a timely manner over existing crops
in fields. The cover crops they tested included spring oats, red clover,
annual ryegrass and radishes, among others.

Then the researchers tracked how well the cover crops grew, how soil
properties changed over time, and the yield of future food crops.

Surprisingly, the cover crops didn't have a big effect on the soil. "There
was not much improvement of the soil properties with using a cover crop,
except for maybe the rotation using the annual ryegrass," says Villamil.

The biggest reason most of the cover crops didn't affect the soil very
much is that most of them died over the winter. That's largely because
of the weather.

Midwestern states like Illinois are subject to potentially harsh winters, especially in the northern part of the state. The broadcast seeding
the researchers did also meant that the seeds simply sat on top of the
soil. That meant the cover crops had a harder time germinating than if
the seeds had been buried in the ground.

But cover crops that die over winter can be a good thing. Dead cover
crops mean farmers will have less work killing them in the spring. But
they're also less effective at protecting the soil or absorbing nutrients.



========================================================================== Annual ryegrass and cereal rye, both grasses, largely survived the winter,
as did hairy vetch, a legume like soybeans. The grasses slightly reduced
future corn yields. That's probably because they compete with corn for
water in the spring.

"The yields of soybeans were not affected at all. Soybeans grow very well
with cover crops, so we need to take advantage of that," says Villamil.

The team also tested how tilling the fields affected the soil and yields,
but saw only modest effects.

"The lesson is that wringing benefits from cover crops requires a bigger commitment to using them to protect the soil," says Villamil. "That
means choosing cover crops that can survive the winter, grow a lot in
the spring, and hold onto soil that whole time. Some cover crops might
slightly decrease future crop yields, but in the long-term, protecting
our soil is worth it." "If we want to see benefits from cover crops,
we need to focus on managing our cropping systems for cover crops,
giving them room to grow, and using them strategically following corn
crops, or silage corn or even wheat, if we are lucky to have this crop
in the rotation" she says. "Our main goal when using cover crops should
be protecting the soil and leaving the soil nutrients in place."

========================================================================== Story Source: Materials provided by American_Society_of_Agronomy. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Gevan D. Behnke, Nakian Kim, Mari'a B. Villamil. Agronomic
assessment of
cover cropping and tillage practices across environments. Agronomy
Journal, 2020; DOI: 10.1002/agj2.20337 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200916090530.htm

--- up 3 weeks, 2 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)