DEAR NEW FARM:
We're in our fourth year of organic CSA farming, and we've
managed to really wear out the soil in our oldest set of rows.
We have incorporated composted cow manure every year and cover
cropped with oats twice. It's also had a thick layer of hay
mulch incorporated through tillage in most places. What's
the best cover crop we could put on it this winter to improve
matters? We're considering putting it to rest for all of next
year as well, so we could till something in next spring and
crop again with something else. Vetch? Rye? I worry about
something that doesn't winter kill or easily till becoming
a weed problem, as these rows are hard to get our bigger equipment
Any advice would be appreciated!
We know from our own research and from stories from other
farmers that carefully managed organic farming regenerates
the soil year over year. For some specifics on your situation,
we asked The Rodale Institute’s own research agronomist,
Dave Wilson. Here’s what Dave had to say:
First determine if you need to produce nitrogen with your
cover crop for the subsequent crop in your rotation. If
the next crop to be planted in the rotation is a legume
(peas, beans), you don't need to produce nitrogen (they
will fix their own nitrogen). If you want to add nitrogen
with your cover crop, then you want to grow a legume. If
you have plenty of nitrogen from manure or compost, you
may not need to use a legume; you can use a cereal-grain
cover crop that overwinters, such as winter rye, winter
wheat, winter barley or a brassica.
Hairy vetch and spring oats or hairy vetch and winter
cereal rye are good options. Hairy vetch is a winter annual
legume. Spring oats or winter rye planted with the hairy
vetch will act as a nurse crop for the legume. Both the
spring oats and rye will germinate quickly and grow until
the first killing frost; spring oats will winter kill but
the winter rye won't (the spring oats will die and still
leave some residue over winter). Hairy vetch seed will take
longer to germinate than the oats and will grow slower initially
in fall compared to small grain until the killing frost;
then the vetch will go dormant over the winter. Hairy vetch
should be planted at least 40 days before the first killing
frost, and it will make it through the winter better. Starting
about mid April and through May, the vetch will grow prolifically,
producing a lot of biomass and fixing nitrogen. In June
the vetch can be tilled under as a green manure, or it can
be flail mowed, or, if you have the equipment. it can be
rolled down (tomato sets can then be planted into the mulch).
Another option is to plant winter cereal rye with the
hairy vetch. Cereal rye is also a winter annual and will
overwinter and grow more in the spring along with the hairy
vetch (the vetch tends to grow up the rye tillers in the
spring). Grown in combination, the two cover crops produce
more biomass than the vetch alone.
Winter cereal rye is usually the most inexpensive and
available winter grain to use as a cover crop. Winter wheat,
winter barley, winter spelt, or triticale can all be substituted
for winter rye. Rye typically produces the most biomass,
then triticale, spelt, wheat and barley.
Some seed companies have cover crop mixtures designed
for green manure plow down, or you can mix your own (such
as 60-percent red clover, 20-percent yellow-blossom sweet
clover and 20 percent ryegrass). Another good combination
is yellow-blossom sweet clover, red clover and white clover
in a 2:2:1 ratio by volume.
Another option is to plant a brassica cover crops, oilseed
/forage radishes, rapeseed or mustard. These cover crops
do not fix nitrogen like the legumes do, but they will take
up excess nitrogen left in the field and help prevent it
from leaching over the fall-winter-early spring months.
They grow tenacious taproots that penetrate the soil deeper
than the cereal crops or legumes.
Hope this helps,
us with comments, suggestions and questions.