September/October 2022 - 10

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Combining cover crops, fall manure boosts both
ZACK HAYDEN &
ALYSSA TARRANT
Michigan State University
growth, and tend to grow better when
soil N is high.
Combining fall manure applications
with an N-responsive fall cover crop
has the potential to maximize the
benefits of both.
Fall is often a practical time to
apply manure nutrients for many
growers. In the case of vegetables,
regulations associated with food
safety and organic certification can
further limit available windows to
apply raw manures in the spring.
However, fall application can leave
manure nutrients, especially nitrogen
(N), vulnerable to loss before a crop
can use them. This is especially true
when warm temperatures speed
manure decomposition and release
of available N, which can later be lost
with snowmelt or heavy rain.
Like manure, a good cover crop can
benefit both short-term crop fertility
and long-term soil health. Many fallplanted
cover crops, including those
in the brassica (mustard) family, are
good N scavengers. They prevent
N from being lost by taking up for
Poultry litter and brassica
cover crops
We conducted a two-year
experiment on a loamy sand soil in
Holt, Michigan, to evaluate how fallapplied
chicken litter impacts cover
crop performance and recycling of
nutrients to an organic acorn squash
crop. Four cover crop treatments
were planted in August of each year.
Cover crops included Defender
oilseed radish, Dwarf Essex rapeseed,
a radish-rapeseed mixture, and a no
cover crop control. In each case, cover
crop treatments received either no
manure or fall chicken litter applied
at about 1.5 ton per acre. Dwarf Essex
rapeseed is winter hardy in Michigan
while oilseed radish winterkills, so
these two cover crops were chosen
in part to see whether they differed
in their potential to recycle manure
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Overhead image of select acorn squash plots in July 2020 following fall applied
chicken litter and cover crop treatments. Orange = no cover, blue = oilseed radish,
purple = rapeseed, yellow = radish/rapeseed mixture. Solid outline = chicken litter,
dashed outline = no chicken litter. Both cover crops and fall manure increased squash
growth and yield in the summer. Photo: Hayden Lab, MSU
nutrients to the subsequent crop. A
bush-type acorn squash (Table Ace)
was grown the following summer. We
collected data on fall and spring cover
crop biomass production and quality,
soil available N from fall through
summer, and acorn squash growth, N
status and yield.
Synergistic benefits for crop
and soil health
In coarse-textured or otherwise
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10 | VegetableGrowersNews.com
low-fertility soils, cover crop
performance may be limited by
available nutrients. Applying
manure can improve cover crop
productivity, resulting in greater
organic matter contributions and
nutrient accumulation than could be
achieved through the applied manure
or cover crops alone. In our research,
the fall poultry litter addition more
than doubled cover crop biomass
and N accumulation compared to
unfertilized cover crops in some
cases. However, benefits were less
pronounced in a field with higher
initial available N, demonstrating that
cover crop response will be tied in
part to the fertility status of your soil.
All radish and rapeseed cover crop
treatments increased acorn squash
yield relative to not having a fall
cover crop. In addition, applying fall
The take-home message
If you already apply manure
nutrients in the fall, the right cover
crop may help you keep available
N in the plow layer to benefit cash
crops next season. If your rotation
allows, brassica family cover crops
can effectively scavenge N and store
it in residues likely to make that N
available again as they decompose.
Where soil fertility is low, fall manure
can improve growth and performance
of N-responsive cover crops.
Combining fall manure and cover
crops may be a win-win.
Zack Hayden is an assistant professor in
Michigan State University's Department
of Horticulture and a 2020 honoree of
Vegetable Growers News' 40 Under 40
Awards program. Alyssas Tarrant is a
Ph.D. graduate research assistant in
MSU's Department of Horticulture. VGN
chicken litter benefited squash yield
whether cover crops were planted
or not. However, the greatest yields
were achieved when fall manure and
cover crops were combined. We did
see some support that inclusion of
the winter hardy rapeseed in a cover
crop did a better job recycling N than
the winterkilled radish, but these
differences were not reflected in the
final yield.
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September/October 2022

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