re: work from home?
19 oct 2000
>i wouldn't exactly call it lucrative work. more like a lot of work,
>sweat, and hope to be lucky enough to make a profit.
>...39.3k lb/year from a $1,000 14'x96' greenhouse...
...sounds a little too good to be true. my farmer partner and i have
a couple of 14x96' tomato hoophouses with roll-up sides for natural
ventilation now, and we are adding a third this fall... about $750 for
the materials for each structure, plus another $200 for a single layer of
4-year plastic film. the plants are in the ground, with black plastic
mulch over drip irrigation tube. last year we got 4,000 pounds of fruit
between the two houses, 20x less than this book suggests is possible,
so it seems we have a lot to learn.
>my father grows greenhouse tomatoes commercially. he has been for
>about 50 years. when i was growing up in the 60's there were several
>hundred acres of greenhouses in my home town. now my father is the
>last one still in operation growing tomatoes. the cost of heating
>a greenhouse in the winter, the price of labor to cultivate and harvest,
>maintenance, insurance, taxes, and marketing commissions have made it
>just too difficult to make a living doing it.
the cost of heating can be dramatically reduced by automatically filling
the space between two layers of plastic film with tiny cold soap bubbles
at night vs air during the day. a 12k ft^2 greenhouse like this in calgary
used 82% less seasonal heat than double poly, with lots of -20 f nights.
>it's cheaper for the stores to purchase the tomatoes shipped from
>california and mexico or the government subsidized greenhouse growers
our local warehouse market (redners) was selling canadian hydroponic
tomatoes for about $2.50/lb in august, and paying $1.82/lb for them,
when the local wholesale price was $1.25 for a 20 pound box (the price
of the standardized box was 55 cents :-) the local price was about
$60 for the same 20 pound box in early spring.
eliot coleman's calculations show that the energy needed to grow
vegetables in a low-energy greenhouse is a lot less than growing them
in far-away places and shipping them to markets by truck. the dollar
cost is still lower by truck, but that may change.
>the market price is good for a few months in the winter and early spring,
>then it falls to where it barely covers the cost of harvesting.
we got an average of about 80 cents per pound at our roadside stand.
amish people with large unpaid families can barely cover the cost of
harvesting in august. drying tomatoes could help smooth out the large
seasonal price variation, but dried tomatoes seem very cheap in stores,
given the 15:1 or so weight reduction, and they have less vitamin c.
>the only tomatoes that will sell are the #1 large and select grades.
they do seem more popular than cluster tomatoes. we also raised grape
tomatoes, but the labor to pick them is higher, and i've heard that
seed is soon to be monopolized.
>if you want quality fruit you need to purchase quality seed that is
>hybridized to be grown in greenhouse conditions and is resistant to
so far, we've used plants started by others, at about 20 cents each
for good disease-resistant varieties, eg mountain spring. some people
say that outdoor varieties grown indoors have a better flavor than
varieties bred for indoor growing.
>at several hundred dollars per ounce, it is a good deal more
>expensive than pot.
but it goes further :-)
>if you want good pollination you must either purchase fresh hives of
>bumblebees at various times in the growing season or hand pollinate the
>plants with electrical or battery operated wands at least every 2 days.
we've done alright with the roll-up sides, when they are open. i like
the idea of walking down rows and whacking the strings with a 2x4 in
february, if internal air circulation fans won't work, vs this kinky-
sounding labor-intensive individual electrical pollination...
when hand pollinating using a vibrator (figure 2.1), the open flower
must be vibrated several times over several days to ensure complete
pollination. the vibrator probe is placed on the underside of the
truss stem next to the main stem as pictured in figure 2.2. if pollen
is ready to be released, a small cloud of yellow pollen will be seen
falling from the open flower when vibrated [with a small gasp?] great
care needs to be taken to keep the vibrating probe from hitting the
flower or any small developing fruit because contact will scar the fruit.
from tomato plant culture by j. benton jones, jr.
1999, crc press, $64.95, 199 pages.
>you will need to remove any small or deformed blossoms leaving just
>3-4 per cluster and the plants need to be suckered and wound around
>the twine at least every 2 weeks.
doesn't sound too labor-intensive. can small or deformed blossom removal
also be done every 2 weeks? we used plastic clips to hold vines on twines.
>many diseases are spread through the soil and wet growing conditions, so
>you will want to keep water and soil from splashing on the leaves of the
>plants. watering can be done with a drip irrigation system with fertilizer
we haven't fertilized either. just rototilled in a couple of pickup loads
of horse manure and shavings per greenhouse... the plants start fast...
>supplement co2 levels with a natural gas burning co2 injection fans to
>maintain optimum co2 levels during the day.
like 1000 ppm? who makes controllers that measure co2 concentration?
i'd also like one for automatic watering. maybe a rebar pounded into
the ground at each end of the greenhouse, with a current flow and
a sensitive relay and a solenoid valve for the drip tube. i've read
that sudden increases in soil moisture cause fruit cracking.
>maintain temperature between 60-90 degrees, humidity 70-80%, and
>provide adequate ventilation.
again, what's "adequate"? how can that be automatically measured and
controlled? a condensing air-air heat exchanger could save lots of
heating energy in the winter, since 65% of the water that enters the
plant is evaporated into the air by the leaves. one main reason for
ventilation is dehumidification, about a pound of water vapor (1000 btu)
per square foot per day, i've read. it's wasteful to allow this to leave
the greenhouse as vapor in wintertime. it's also wasteful to turn on
the big ventilation fans to blow solar heat out of the greenhouse at dawn
on a sunny winter day, and turn on the propane heaters at dusk. better
to save some of the heat of the day for the night.
>the fruit can be picked as soon as it begins to show color. it will be
>fully ripe within 3-7 days and will stay fresh and firm for 10-14 days
>under ideal conditions. once the fruit is fully ripe the taste is
>identical to a tomato that is picked fully red ripe...
i've read the flavor gets better the longer it stays on the vine...
>this means that you will need to pick the tomatoes every 2 days
>to allow maximum time to pack and market the fruit.
>there are no days off. no vacation until the season is finished.
>then its time to start getting ready for the next season.
this could work better as a continuous year-round process, only
replacing plants as they get diseased, and cutting them back to
the ground when they get too tall...
>fixing the things that broke and maintaining the greenhouse - scraping,
>painting, fixing broken glass, etc.
we don't need to do any of that with our plastic film houses.