“You
can’t be afraid to expose yourself to new ideas,”
John Biernbaum tells us whimsically as he presents a photograph
of the rear view of a barelegged man holding open his trench
coat to a facing sign reading “New Ideas.” Thus
begins a fun-filled day at Organic University, the pre-conference
program to the 16th annual Upper Midwest Organic Farming Conference
held January 24-27, 2005 in La Crosse, Wisconsin.
Biernbaum is professor of horticulture at Michigan State University,
where he is also the advisor to the Student Organic Farm,
a 48-week CSA developed and operated almost entirely by students.
Under his guidance, the Student Organic Farm is now in its
fourth season of research and second year as a CSA and serves
not only to produce food but also as a place to practice new
farming methods.
During the first CSA year, 40 percent of the Student Organic
Farm’s crop came from the greenhouses, which were only
20 percent of the farm’s first-year production area.
Greenhouse production has proven an important asset, and it
is to learn about year- round greenhouse production that we
are all seated before Biernbaum.
I am at Organic University, the prequel to the 16th annual
Upper Midwest Organic Farming Conference in La Crosse, Wisconsin.
While most of the 60-member, sold-out-in-advance audience
has either decided to build a greenhouse or is looking for
ways to improve their greenhouse crop production, the whole
concept of greenhouse vegetable production is fairly new to
me. I am a neophyte (a fancy way to call myself inexperienced)
to greenhouses, and just as Biernbaum advises, I am ready
to expose myself to this new idea in farming.
Fortunately for me, Biernbaum starts at the very beginning
by defining a greenhouse. For the sake of the workshop, he
explains, he will use the term greenhouse broadly, referring
to greenhouses, high tunnels and hoop houses, (though each
structure can be unique, he says). Greenhouses are gothic
or Quonset structures with end walls and a double-layer polyethylene
inflated roof. They are well sealed against winter weather
to encourage year-round growing, and they may be heated. High
tunnels are generally smaller, single-layer film covered cold
frame structures or multi-peak single layer structures, often
with limited structural end walls. Hoop houses are like greenhouses,
but they may be covered with single or double layer inflated
film, may have minimal end walls, and are usually unheated.
All three may have roll-up sides for summer ventilation.
With those distinctions made, we are ready to delve into
Biernbaum’s first topic of the day: site selection.
“The first step in effective greenhouse vegetable production
is selecting a greenhouse-friendly location,” Biernbaum
tells us. As I am about to discover, choosing a site requires
more than just finding enough room to build a structure. Biernbaum
describes four major components of a good greenhouse location.
Let it flow
First, Biernbaum tells us to think about drainage.
“Water removal is crucial! I can’t stress
that enough,” he says. The Student Organic Farm
had no drainage system its first winter, he says, and the
crops paid the price during the spring thaw. The lower end
of the greenhouse flooded and production there was weeks behind.
It is best to build your greenhouse on elevated ground so
runoff flows away from the structure, Biernbaum advises. Don’t
forget about the extra water coming off the roof either, he
says, especially if you have heavier soil.
If no slope can be achieved, he says, it is critical to provide
drainage pipes.
“To solve our flooding problem, we installed four inch
drain lines around each house,” Biernbaum explains.
The lines are covered with crushed gravel and have eliminated
flooding while also deterring tunneling rodents and preventing
grass from growing into the houses. Whaddya know. Solutions
to two challenges I never knew might exist.
Getting(and plugging) in
Next, Biernbaum tells us to consider the accessibility of
the greenhouse site—to both people and utilities.
Make certain, he says, that the roads leading to your greenhouse
are suitable for all seasons (remembering that they may be
used twice daily to manage frost fabric, to roll up the sides
of the house, or to open the end walls for ventilation).
Irrigation water is necessary in the winter, Biernbaum says;
so therefore are frost-free hydrants (in USDA Cold Hardiness
Zones where appropriate) and 4-feet-deep water lines. Remember
to backfill with gravel around the base of the hydrants so
they drain well, he says. The farther a water source, Biernbaum
says the more hose necessary to adequately drain at each irrigation.
You may also need electricity for the inflation of polyethylene
and/or for heat, he says, and will require a tank or line
for propane or natural gas (more about these choices later).
Also, Biernbaum says, make sure you build your greenhouse
where you will have easy access to a washing and processing
area and to your storage cooler or root cellar.
Shade and light
According to Biernbaum, if
you will be doing winter farming you want to orient the greenhouse
to maximize light interception during the winter months (orientation
refers to which way the ridge of the greenhouse runs). At
northern latitudes (above 40 degrees), he says, an east-west
orientation works best to catch maximum light during winter.
With an East-West orientation, Biernbaum explains, the winter
light will penetrate the length of the south side of the greenhouse
instead of shining through from the end.
“While an east-west orientation
works best in most northern latitudes, there may be some exceptions,”
Biernbaum says. “If heavy snow is an issue and wind
can help move the snow away, an alternative orientation might
be used.”
You should also consider the direction and strength of the
wind, he says, as wind may play a key role in the preferred
orientation of your structure. Wind blowing over a greenhouse
is like wind going over an airplane wing, Biernbaum says,
and while you can modify impact with windbreaks, wind is still
something to keep in mind. He adds that if your greenhouse
is in warmer or southern latitudes, a north-south orientation
may provide good light and the best ventilation.
It is also important to consider shadows and shade from trees,
hills and buildings, Biernbaum says, including the shadows
one greenhouse may cast on the next. Shade limits the amount
of sun your greenhouse receives, he says, thus limiting its
production. Remember, he advises, that shade lines differ
between summer and winter and that the longest shadow day
is December 21. When selecting a site, Biernbaum recommends
that the greenhouse be located at a distance equal to at least
twice the height of any potential shade source.
Know thy soil
And of course, you want your greenhouse site to have either
excellent soil quality or the potential to become so. If the
area is already cultivated and the soil is healthy, Biernbaum
says, little preparation is required.
If you have growing experience, he says, the easiest way to determine soil
quality is to let some crops do the analysis for you. Nutrient
and texture analysis are also possible if you don’t
have experience; while this gives you immediate answers regarding
the quality of your soil, you’ll have to invest $30
to $50.
“If you have the time and experience,
work up the ground and plant something and see how it grows,”
Biernbaum says.
Unless you find a site with exceptional soil quality and natural
drainage, Biernbaum recommends choosing a greenhouse site
at least one year before building the structure so you have
adequate time to improve land and reduce weed pressure.
“If the site is in sod or pasture and has not been
cultivated, it is particularly important to start in advance
so the sod has time to break down,” Biernbaum tells
the class. “Plowing or tilling is one way to break the
sod, although sheet composting [thick layers of mulch] without
cultivation is also an option. Regular cultivation and irrigation
will help reduce the weed seed bank, and additions of organic
matter from green manure or compost helps build soil organic
matter and nutrient availability.”
Biernbaum closes this section of his lecture with a final
site-selection consideration:
“Greenhouses with posts pounded into the soil are generally
considered temporary structures with regard to taxes, but
zoning ordinances are often done on a township level, which
means sometimes farmers need to be ready and able to explain
things.”
Whew! Lots of thought goes into just choosing and preparing
a site, and that is the easy part! Next, Biernbaum will talk
about constructing a greenhouse. I flip to a fresh new page
in my notebook, lean back in my chair, stretch my arms out
a little and prepare to expose myself to the next step.
Katie Olender is a senior majoring in agricultural communications
at Michigan State University.
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