PRODUCTION AND MARKETING OF
ORGANIC VEGETABLE CROPS
submitted by Lynn Oliphant
THIRD GENERATION STRAWBALE GREENHOUSE
1) Design and build low-input greenhouses and offer workshops that would
encourage entry into greenhouse production by minimizing capital expenditures.
2) Produce an instruction booklet on building a low-input greenhouse.
3) Develop a small scale CSA model utilizing produce from these greenhouses and
conduct initial market tests.
4) Train a construction crew that is capable of commercial construction of low-
input, energy efficient greenhouses.
Observations and Conclusions:
A number of workable designs were built and tested that showed the
feasibility of inexpensive, low input, greenhouses that can be constructed by the
producer. Workshops were conducted in which participants built modest sized
greenhouses (~360ft2) in an 8 hour period with minimal instruction. A small scale
CSA model demonstrated a market for produce as did a survey of interest in locally
produced organic vegetables. A Worker's Cooperative capable of helping producers
design and construct alternative greenhouses was formed.
Greenhouse production offers a number of advantages to the producer
including extension of growing season, warmer growing temperatures throughout
the season and protection from wind, hail, and desiccation. There are, however
disadvantages that must be taken into consideration including cost of construction
and maintenance, energy costs for heating and cooling, need for a watering source
and potential for large scale crop loss if overheating occurs.
The Saskatchewan greenhouse industry is in its infancy compared to the rest
of Canada and the U.S. Over two-thirds of the potential greenhouse market is
currently imported. Using conventional greenhouses and marketing techniques, the
profit margin is low requiring 100,000 ft2 of greenhouse space to be economically
viable (Wayne Craig, pers.comm.). Therefore, while the production of vegetable
crops as well as other products has been shown to be feasible under greenhouse
conditions in Saskatchewan, the high capital and operational costs of conventional
greenhouses has made it difficult for many potential growers to enter into this
market or expand their current operations. Financing is a particular problem since
assets have almost no economic value should the operation encounter financial
difficulties (Marketing Development Branch, Regina, 1992).
If it can be done economically, the production of a wide range of high quality
greenhouse products over all or most of the year in Saskatchewan could provide a
significant income and diversification for prairie farmers and result in a decrease in
money currently leaving the province. Experience in marketing locally in the
Lanigan area suggests a high demand for quality produce (S. Leach, pers. comm.)
and vegetable crops offer one of the highest rates of return ($15/ft2). Salad greens
produced by the "Mesclun Method" sell for $16/lb. in the United States (A. Edey,
Production is labour intensive providing jobs in rural areas and utilizes
relatively little land. The production of high quality, pesticide-free food crops for
local consumption eliminates the tremendous energy costs of packaging and
transportation. In contrast, the purchase of imported produce by Saskatchewan
consumers incurs great costs to the environment elsewhere on the globe in terms of
soil degradation, and often high rates of biocide usage. It also perpetuates poor
working conditions of farmers who themselves have often been displaced from the
land associated with the emphasis on production of crops for export.
Saskatchewan farmers may well be in for the most difficult period they have
ever faced with the loss of the crow rate and the collapse of world export markets
and economies. We desperately need economically viable alternatives for people in
rural communities as well as jobs for our young people. The information contained
in this report will help farmers or rural cooperatives initiate greenhouse production
on a small scale with minimum capital outlay and maximum potential profit while
they learn the techniques necessary for this type of production. The techniques and
greenhouse designs developed could be used in other areas of greenhouse
production such as flowers and bedding plants.
The potential for direct market application is virtually immediate. This is
especially true of greenhouse vegetable production where only two million dollars
worth of the 21 million dollar market is produced in the province. It has been
estimated that only three acres were devoted to greenhouse vegetable production in
Saskatchewan in 1991 while an additional 29 acres were needed to satisfy the
province's demand (Marketing Development, 1992). The public's interest in
healthy, uncontaminated, locally grown food is high. Steep Hill and Spring Creek
Markets in Saskatoon have indicated a large demand for organic produce throughout
the year (pers.comm.). By reducing capital and operating costs and developing
more direct links between producer and consumer, start-up operations can be made
more financially viable and circumvent the problems of financing.
Greenhouse construction and performance:
The greenhouse designs described in this report can lower capital costs from
$10-$20/ft2 to around$1/ft2 for a conventional hoop style, uninsulated greenhouse.
This low capital outlay has the potential for allowing new producers to gain
experience in greenhouse production techniques. The construction of this type of
greenhouse, which is recommended as the first step in developing a greenhouse
operation, is described in detail in the accompanying manual.
The more advanced, insulated greenhouse designs were built with an aim to
minimizing the total embodied energy in construction and utilize materials (straw)
obtained from the local farming community wherever possible. They were designed
based on the following criteria: 1) low capital costs, 2) energy efficiency using
insulated strawbale walls and 3) ease of construction and maintenance.
The basic designs of the various greenhouses that were built are hybrids of
the rebar quonset covered with reinforced poly pioneered by Bob Davis (Northern
Greenhouse Sales, Altona, Manitoba), the insulated, energy efficient greenhouse
pioneered by the Brace Research Institute (MacDonald College, Quebec), the
Solviva Greenhouse (The Growing Edge) and straw bale construction techniques
that have recently been 'rediscovered' and improved by groups in the southwest US
(Matts Myhrman, Out on Bale Ltd., Tucson, Arizona).
FIRST GENERATION GREENHOUSES:
A major improvement in the design of the simple rebar hoop style greenhouse
was the covering of the rebar with white plastic 'shelf edging'. This provides a
smooth, non-heating surface over which the plastic is stretched. The area of contact
between the rebar and woven poly has been a problem in terms of abrasion and
degradation due to heat which is only partially solved by painting or wrapping the
rebar. The use of the shelf edging significantly increases the life span of the woven
poly resulting in considerable savings of capital and labour.
Temperature monitoring in the simple quonset greenhouses indicated a
modest level of frost protection. Overheating during mid-summer was an occasional
problem and is best solved by ensuring adequate sized openings are present in both
ends and the total length of the greenhouse is not excessively long (we recommend a
30 foot maximum). In greenhouses 30ft long or less, there was no problem with
overheating without a need for exhaust fans as long as the end doors were opened
by mid-morning on hot sunny days. Overnight temperatures averaged just over 3
degrees centigrade higher than outside temperatures as measured at midnight. Some
additional moderation of overnight temperatures was obtained with two 50 gallon
barrels of water and covering the crop.
Three hoop style greenhouses were dismantled and rebuilt at other locations.
The frames, rebar and plastic were all in good enough shape that they could be
reused, demonstrating the potential for moving the greenhouse or reusing the
materials in a new design. Examination of greenhouses that remained up over
winter indicate that the design is capable of withstanding normal snow loads even
with a five foot spacing of rebar. Little or no wear was observed where the woven
poly contacted the white plastic shelf edging used to cover the rebar. One of the
greenhouses suffered minor damage to one endwall where the one inch screws had
pulled out in places due to buffeting by the wind. No other damage was evident.
Several first generation greenhouses constructed of rebar hoops failed during
the exceptionally heavy snow load experienced in early October 1998. Some of
these greenhouses had survived at least three winters with no problems in terms of
structural damage. At least one actually held up under the entire snow load until an
attempt was made to brush off the snow with a broom at which time it collapsed
starting at one end and rapidly proceeding to the other. Although this was a "once
in a hundred year" snow load, we feel that the hoops should be supported by
temporary 2x4 braces at their mid points over winter unless the plastic is removed.
Plastic life using the superstrong reinforced poly from Northern Greenhouse
Sales in Altona, Mb. has been excellent. Plastic from a collapsed greenhouse that
was examined in detail did not tear even though the rebar was completely collapsed
and the plastic was over three years old.
The primary crops grown were several tomato and pepper varieties, melons,
eggplant, okra, celery, basil and corn. Good yields and quality were obtained from
all crops except the celery and corn. The corn, which is not generally thought of as
a greenhouse crop, was planted as an experiment due to the late date at which the
project got underway the first year (our corn wasn't in the ground until June). It
responded very well to greenhouse conditions and grew at twice the rate of corn
planted on the same date outside the greenhouse. The greenhouse corn developed
small but high quality ears while the corn planted outside produced virtually nothing.
With reasonable fall weather, tomato, pepper and eggplant production can continue
up to early October. Late fall sowing of salad greens and spinach produced an
excellent crop well into November in one year.
SECOND GENERATION GREENHOUSES:
Four "second generation" greenhouses with insulated north walls were built
over the tenure of the project. Two of these utilized straw bales for the construction
of the north wall and the other two were constructed against the south facing walls
of existing buildings.
The "Keet" greenhouse was our most advanced second generation
greenhouse. It was built on the south side of an existing chicken barn and utilized a
buried straw bale foundation. The foundation was constructed by digging a two foot
wide trench about four feet deep into which straw bales wrapped in superstrong
poly were placed and embedded in concrete. An initial 4-6 inch layer of concrete
was poured in the trench and the plastic wrapped straw was then placed on top.
Additional concrete was then poured around both sides of the bales and a 4-6 inch
cap of concrete pored on top. Bolts were placed in the wet concrete to attach a sill
plate. The framing for the poly was 2x6 dimensional lumber wrapped with opaque
white plastic. The existing roof was extended and an "attic" space for the placement
of straw bale insulation was constructed (see accompanying photos).
THIRD GENERATION GREENHOUSE:
The "Marysburg Greenhouse" was a complete "third generation" design with
buried strawbale perimeter insulation, strawbale walls and roof, and glass and
polycarbonate glazing. This 24ftx35ft greenhouse was built in Marysburg, Sk. for
Earthcare Connections, a non-profit group devoted to sustainable agriculture
alternatives which provided the bulk of the funding. The design was based on a
"boxbeam" construction technique that utilized two 2x4"s with plywood gussets 14
inches wide (the width of strawbales on edge) for posts. These were placed on
concrete pillars seven feet deep spaced at approximately 11 foot centres around the
periphery of the building. A four foot deep trench dug between the pillars was filled
with two layers of strawbales placed on a gravel base and wrapped in reinforced
poly. The walls were then filled in with strawbales. The roof was supported with
2x4 trusses spaced the width of a strawbale laid flat and slab lumber was attached to
the underside of the trusses to support a layer of straw bales for the roof which was
then covered with metal roofing. The southern exposure was framed in
conventionally and large, used double pane windows were installed vertically to a
height of about eight feet. The southern slope of the roof was then covered with
sheets of polycarbonate (see photo on cover). The building is designed to dry herbs
in the north portion and grow greenhouse crops in the south portion.
We were responsible for the design, initial construction and organization of
the workshop associated with this building. Finishing work, including stuccoing and
instillation of glazing and doors was the responsibility of Earthcare Connections.
Unfortunately time and money ran out and the doors were not installed before
winter so data on temperature performance of the building could not be obtained.
Temperature performance of a similarly constructed garage/shop was
monitored over the winter and suggest an extremely low energy demand to maintain
adequate temperatures over winter. The building that was monitored did NOT have
any peripheral insulation and had only the equivalent of the vertical glazing (none on
the roof portion). There was NO source of heat other than that provided by the
passive solar design. The insulation value of the north and east/west end walls and
roof is ~R-40. It has a four inch thick concrete floor outfitted with piping for radiant
floor heating with solar panels although this was not operational during the
temperature monitoring period. Temperatures were read daily from a
maximum/minimum thermometer and compared with reported daily highs and lows.
The lowest temperature recorded during the December- February monitoring period
was minus 12C. High temperatures varied from ~20-35 degrees above ambient
(depending on sun intensity during the day) and overnight lows were ~10-15
degrees above ambient. Overnight lows seemed to depend at least to some degree
upon the amount of heat stored in the floor from previous day(s).
Based on the thermal performance of this building we predict that a very
minor heat input in the Marysburg greenhouse should be adequate to maintain
adequate growing temperatures throughout most of the winter. The installation of
lights for plant production may provide adequate heating although current plans are
to pour a concrete floor with radiant floor heating. The cost to date for construction
(labor and materials) is $16,000 (~$19/ft).
Among the design modifications which we feel are worthy of consideration
in the construction of alternative greenhouses are the following:
1) The use of rainwater collection trenches lined with the ends of the woven poly
covering the greenhouses. This water is diverted to channels inside the greenhouse
where the water acts as a large thermal mass, stabilizing temperatures. It acts as
well to increase the humidity, reducing watering requirements and allowing the
plants to be watered directly from the water channels.
2) Underground closable air vents on the north side combined with large end vents
that will allow for increased ventillation.
3) The use of additional solar heating panel to provide hot glycol that can be
circulated under the soil in the greenhouse. This provides an inexpensive source of
heat where it is needed the most. This can be accompanied by thermal covers on
especially cold nights, trapping the heat stored in the soil.
4) Extended straw bale endwalls to protect the poly surface from wind to reduce the
5) Building without foundations or insulated foundations that incorporate strawbales
(see descriptions of Keet and Marysburg greenhouses and photos.)
7) Perimeter insulation using straw bales laid directly on the ground around the
perimeter of the greenhouse.
8) The use of chickens and/or active composting as a source of heat for the
9) The use of opaque white poly as both a reflecting layer and covering for the
interior side of the north wall increasing light levels and furnishing a "northern" light
direction to keep plants growing upright.
The greenhouses were in general remarkably free of any significant pest or
disease problems during the first three years of operation and no control was found
to be necessary. This may be due to the fact that the placement of the greenhouses
was in areas not previously used for growing vegetables and the enclosed space
provided a physical barrier to the entrance of many insects. Some grasshopper
damage was noticed in the summer of 1997 and flea beetles were a particular
problem in 1998 (see photos).
A total of fourteen workshops were presented between spring of 1995 and
spring of 1998. Total attendance exceeded 150 people. Nine of the workshops
involved the construction of simple rebar greenhouses, four were "second
generation" models utilizing some form of insulated north wall and/or buried straw
insulation. The last was the "third generation" Marysburg greenhouse.
A small scale CSA model utilizing produce from the hoop greenhouses built
the first year was successful in showing the consumer interest in direct connections
with local producers of organic vegetables (see attached "newsletters" that were
provided to subscribers). This was followed by a modest market survey with 40%
of the respondents indicated that organically grown produce was important to them,
although they were unwilling to pay more than a 10% premium for the product.
Complete survey results are as follows:
MARKET SURVEY AUG/SEPT 1996
The purpose of this survey was to determine the level of awareness of
organically grown produce in the province and the marketability of specific crops.
The survey was based on replies from 50 individuals who agreed to participate in
the survey which was conducted over the phone. Note: In some cases there was no
response to the question and in other cases individuals may have given multiple
responses; numbers indicate total number of positive responses.
1) Is organically grown produce important to you and your family?
very important: 8
somewhat important: 12
not important: 30
2) Reasons why organically grown produce is important to you.
other (better taste, garden failure): 3
3) Reasons why organically grown produce is not important to you.
too expensive: 10
lack of information: 11
other (own garden): 4
4) Where do you currently get the majority of your produce?
grocery store: 15
farmer's market: 5
own garden: 4
5) Is the where organic produce is grown important to you?
6) If place is important, rank the following in order of preference.
Saskatchewan: 9 first, 1 second, 1 third
Other prairie provinces: 1 first, 9 second, 1 third
Canada: 1 first, 1 second, 9 third
Other: 11 fourth
7) Is the availability of organically grown produce in your area (50km radius)
don't know: 9
8) Where do you get the majority of your information about organically grown
word of mouth: 10
books, magazines, articles: 2
9)Would you be willing to pay more than grocery store prices for organically grown
10) If yes, how much more would you be willing to pay?
other: (based on taste and quality) 1
11) Indicate your age group.
under 25: 6
over 65: 0
12) Respondents were asked to indicate the 5 organically produced vegetables they
would eat most often in order of preference. Five points were awarded for first place
choice, four for a second, etc.
Although our sample size is small and may be biased by the non-
respondents, a number of useful conclusions can be made with a reasonable degree
1) A reasonably large proportion of people appear to be interested in locally
produced organic produce.
2) Perceived higher prices and lack of information are major reasons for people not
being interested in organic produce.
3) Both health and environmental concerns are major reasons for wanting organic
4) Even people who think organic produce is important are mostly unwilling to pay
more than a slight (5-10%) premium for organically produced food.
5) There appears to be much room for improvement in advertising and information
6) Standard vegetables are the most popular choices with carrots, lettuce, tomatoes
and potatoes ranking far above most other choices.
Note: The results of our limited survey mirror the results of a more extensive
survey of consumer trends in the United States as summarized in Vol. 15 No. 1 of
the Alternative Agriculture News.
Publicity and public education:
A number of articles were published by both project personnel and
professional writers in the following publications- Synergy Magazine, The Western
Producer, Whole Life, The Humbolt Journal. Four open houses/field days were held
with over 800 people attending. A display table was set up at the Saskatoon
Farmer's Market. Several interviews with project personnel were aired on CBC
1) The Keet family have begun a greenhouse business (1700 ft2), growing
flowers, strawberries, tomatoes and lettuce. They market directly to the Coop food
stores in Saskatoon.
2) A Worker's Cooperative has been formed that will help design and build
low-input greenhouses. The founding members got their start working on this
project (see appended brochure).
3) Several of the student's employed by this project are now working in
other agricultural areas.
Edey, Anna 1994. Solviva Greenhouse. The Growing Edge.
Leach, Sharon 1994. Building Your Hobby Greenhouse. Extension Division, UofS
MacDonald, Steve 1993. Straw-Bale Primer. Out on Bale, Tucson, Arizona
Greenhouse and Nursery Products Industry and Market Study. March 1992.
Prepared by: Marketing and Development Branch, Regina, Sk.
Hobby Greenhouses in Alberta. 1989.Alberta Agriculture, Edmonton, Alberta
Plans for the Construction of a Brace Greenhouse. Brace Res. Inst., MacDonald