Fall 2020 - 43

CROP ROTATION
Left, crop rotation can be an important
part of the organic cultivation of
vegetables in hoophouses.
cover crop. In all of the three-year rotations, a winter green
or overwintering cover crop was also used.
KSU researchers also used published, enterprise budgets
to estimate the gross revenue per square foot of the
rotation crops in their studies.
Tomatoes topped the list at $3.66 per square foot. A
salad mix came in at $2.40 per square foot, bell peppers at
$2.30, beets at $1.92, cucumbers at $1.62, lettuce at $1.30
and spinach at $1.09.
Strawberries came in at $1.76 per square foot, seedless
watermelon at $0.89, and sweetpotato slips at $4.30 per
square foot.
" What we're really trying to do is document opportunity, "
Rivard said. " We're trying to give growers the data they
need to plan. We as researchers don't have a good way to
put a dollar value on the long term benefit to the soil. "
KSU also combined its crops grown in the three-year
rotations into a six-year rotation with tomatoes only grown
in one of the six years.
" If growers can put together a six-year crop rotation, that
will be more sustainable in the long term, " Rivard said,
with more diversified labor needs and less pest and disease
pressure.
" Be proactive, " Rivard said. " Think about structuring
your rotation for the long term and then tailor it to your
situation. "
Planned rotations must be across entire plant families
and not just species within a family.
There are several common vegetable families. The
Solanaceae family includes eggplant, peppers and
tomatoes. Beans and peas are in the Fabaceae family
and the Cucurbitacae family includes vine crops like
cucumbers, cantaloupe, watermelons, pumpkins and
squash. Lettuce is in the Asteraceae family and Brassicaeae
include crops like broccoli, cabbage, cauliflower, collards
and radish. " You want to follow some basic principles of
good rotation, " Rivard said.
Growing several crops in a high tunnel on a close spacing
and rotating them can be effective since soil pathogens
aren't typically spread by air movement. " Most of these
soil-borne pathogens don't move that far in the soil in a
high tunnel, " Rivard said.
A honeybee, with pollen attached to its hind leg, pollinating a
watermelon flower. Watermelon can be grown in hoophouses for crop
rotation but require pollination. Photo: Stephen Ausmus/USDA ARS
The most common way soil pathogens are spread in a
high tunnel is by contaminated tools which - as always -
makes sanitation an issue.
Cover crops fit in a rotation during fallow times of the
year. " Think about cover crops first as a partner for your
cash crop, " Rivard said. " Plan your cash crop strategy and
build your cover crop around the cash crop. " Cover crops
in high tunnels perform similarly to cover crops grown in
the field.
Growers targeting off season crops and the early season
market may have a fallow season in the summer - after
spring crops and before planting fall greens.
Millet, sorghum - sudangrass or buckwheat in
combination with cowpea as a legume are good options
for summer cover crops. " Have a termination plan, " Rivard
said. Sorghum-sudangrass and millet can get really tall.
" Buckwheat is good, " Rivard said. " It has a dense canopy
and has flowers that are good for beneficials. "
Oilseed radish, oats, spring barley or millet in
combination with cowpea are good options for a fall cover
crop and will all winterkill.
Rye, triticale, or wheat combined with hairy vetch or
Austrian winter pea are options for a cover crop that
will overwinter in the central U.S. Austrian winter pea is
probably a better choice for the winter legume because of
hairy vetch's growth habit and tendency to go dormant in
cold temperatures.
A mix of legumes and grasses is best for a cover crop.
" Grasses will pick up nitrogen in the soil and store it;
legumes are going to fix nitrogen from the air, " Rivard said.
" The big factor is being proactive, " Rivard said. " Find
your market, figure out something you can grow and sell,
and build your rotation from there. "
ORGANICGROWER.INFO 43
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Fall 2020

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