Crop Rotation for Weed Suppression – Organic Weed Control


The crop rotation I kind of get a kick out
of because everybody wants to know what your crop rotation is. Well best made plans are just plans. It seems like every year our crop rotation
changes or maybe the weather is different and you have to be very very flexible and
open with a “rotation” because it seems more often than not it’s very hard to stick
to a set plan. For organic field crop farmers, weed control
starts with crop rotation. In this video, farmers share their strategies
for rotating crops to interrupt weed cycles and suppress weed growth and reproduction
through planting solid seeded-perennial crops like alfalfa; to incorporating cool season
spring-seeded crops like oats; to fall seeded small grains like winter wheat, rye or triticale. There’s probably as many different ways that
organic farmers look at this as there are organic farmers but it kind of all begins
with the crop rotation and it depends on a lot of things. You know, what you have for equipment, what
you have for markets. My go-to rotation is basically corn, soybeans
and a small grain and I have a cover crop, usually red clover, in with the small grain
so I can raise some of my own nitrogen for the following corn crop. Usually when I’m thinking about the rotation
I like to throw in that third year of oats or small grains, mainly to kind of break up
weed cycles. And a goal on our good soil, best laying fields
we really like Dick Thompson’s original rotation of corn, soybeans, corn, oats, hay and that
seems to work really well for both one, income and two, weed control. I do like corn, soybeans, corn and then it’ll
go to oats with an underseeding of like an organic plow down mix of clover and alfalfa. While many organic farmers plant corn after
alfalfa or clover, Nelson Smith of Brighton typically follows alfalfa with soybeans. At his 2018 field day, Nelson said that he
thinks the nitrogen credit is best achieved two years after killing the green manure crop which has been supported by a growing body of research. Also he likes planting soybeans after alfalfa
because the year after alfalfa is typically the year with the lowest weed pressure and
soybeans are more prone to weed pressure than corn due to later canopy closure. We’ll start out with oats and alfalfa and
then after the alfalfa, depending on how good the alfalfa crop is we may keep it two or
three years for hay production. We will go to soybeans after the alfalfa and
then corn following that and then on the basic rotation we’ll go back to the oats with the
alfalfa underseeding. Typically it’s always been corn, beans, corn,
beans and then a small grain and into hay for a year. And then after a year of hay it gets plowed
up and back into that corn-bean rotation. That’s typically been the norm anyway. Some years it might be a little bit different. I might do a corn-small grains rotation depending
on weed pressure in fields and how they work out. A lot of people think that you should put
your corn in right after the alfalfa so you get the nitrogen but the problem is, is we
don’t tear up the alfalfa until very late in the fall or we even wait until spring and
disc it in because we’ve been organic for so many years the ground is very mellow so
we can actually go out and tear up the alfalfa with a disc in the spring and still plant
and the soybeans go in the alfalfa because that’s the cleanest year is the first year
after the alfalfa so it’s much easier to get weed control so then we go with the soybeans
right after the alfalfa and then follow that with the corn because the corn makes a good
canopy for itself because of the height of the corn and the shading So we follow that
behind the soybeans is our rotation. The solid-seeded crops are typically cool
season crops and therefor you’re harvesting mid-summer and before the bulk of your weeds
go to seed you can either clip them, mow them off or till them under. Easier ways, different ways to control it
to break up that cycle of just plant in April-May harvest it in October-November. If you repeat that kind of six-month cycle
year after year nature just selects weeds that grow in that same cycle. Where if you can break up that cycle and say
plant a crop in March or April, harvest it in July there you’ve just interrupted that
weed’s natural life cycle and it gives you an opportune time to go in, mow it off before
it goes to seed, till it under, etc. Or with alfalfa or hay you’re mowing it three,
four times a year, constantly clipping that weed off before it gets a chance to grow seeds
or grow root reserves to spread etc. I do have some alfalfa periodically mainly
to help me control Canada thistle but I really can’t control any other way very well. A good stand of alfalfa for three years does
a pretty good job, maybe doesn’t eliminate them but it really cuts them back. You can’t go like a conventional crop rotation
is corn and soybeans and basically that’s not really a rotation it’s just a changing
of the crop. But with the alfalfa in there that gives you
the year that you had the oats and the nurse crop for the alfalfa and then the alfalfa
will hold your weed seed down because you’re clipping it to make hay hopefully three times
a year to get your three cuttings on it. Then when you disc that in and put your next
crop in you’ve held the weeds back and they are much easier to handle. The one thing that I do with my rotation is
my small grain hopefully is a winter annual like fall triticale for example and if you
can put a winter annual in your rotation that will help mess up the cycle of the summer
annual weeds and help you with your weed control. Whereas if you have all summer annual row
crops for example like just a corn-bean rotation. Particular weeds are going to be particularly
adapted to that system. Whatever your system is there will be weeds
that find that system advantageous. So you need to be willing to change things
up occasionally too if you have a particular weed that’s gaining ground, becoming more
populous you need to do something to mess up its growth cycles somehow. Mechanically, chemically, culturally, genetically,
something. We’ve started growing some winter wheat as
well on some of our weedier fields and what we’ve found is that gives you that time that
you can till the field in the late summer, break up that weed cycle and that crop then
has a head start for the next spring. It’s growing then in March and April and can
out-jump the weeds and out-compete the weeds hopefully and then you’re harvesting that
winter annual then in June or early July which is again off normal timing and then you can
go back in and mow those weeds and it just breaks up that weed cycle. If we need rye for a cover crop we’ll seed
the rye with an airplane in the standing corn and then we’ll harvest our corn and then we’ve
got our rye underneath that that’ll come on the next year. When the rye is harvested in the middle of
the next summer, then a lot of times we’ll put our buckwheat in to finish out because
buckwheat is a really short season 75-day growing season on that and then we can harvest
that at the killing frost because you need to get it out then once it’s dead it doesn’t
last through a killing frost. What we’ve started doing as well is growing
two cool season crops in a row followed by two warm season crops. So we’re growing oats followed by winter wheat
followed by corn followed by soybeans then in two years you get more time to break that
cycle so you’re breaking that cycle then two years in a row to kind of out-compete or break
that routine of the weeds if you just do one year, you’ll reduce some of them but there’s
still some that survive and then the next year they’ll come back or if you do it two
years in a row or leave alfalfa two years in a row or more you’re breaking that cycle
longer which can really help weed pressure. We’ve seen some really drastic declines in
weed pressure by going with a little bit longer rotation and doing more solid-seeded crops
and winter crops versus just the typical corn-bean-oat rotation or whatnot. The longer rotation you get the better off
you can control your weeds because the weeds don’t have a chance to come on, put on a seedbed
and then come the next year. You’ve changed it to a different crop so they’re
changing and you’re changing trying to stay ahead of them. If we can get to a three or a four or even
a five or a six year rotation that changes when we’re harvesting and when we’re cutting
weeds. So if we do a soybean year, generally we’re
just doing inter-row cultivation and killing weeds at a certain young point. Whereas with the oats if we can cut them before
our weeds go to seed that’ll king of break up their reproduction and keep those weeds
from setting a seed. The more consecutive years of row crops you
get, the harder weed control gets immensely. If you break up that row crop year with a
year or two of solid-seeded crops you can drastically see your weed pressure reduced.

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