Hydroponic Greenhouse Gardening

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Plants in the author's highly successful hydroponic greenhouse.
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A flourishing tomato plant.
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Nutrient solution in plastic buckets is fed through hoses to plants rooted in beds of pebble gravel.
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New plant starts.
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Wife and son help with maintenance and harvesting.
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An abundance of hydroponically-grown pickled cucumbers.

In “Build an Ecosystem: The Earth-Sheltered Solar Greenhouse” I described a homemade
ecosystem, an underground hydroponic greenhouse and
aquaculture tank which I recently built on my small New
Mexico homestead. In that article I discussed the
construction procedure and philosophical rationale of the
project. Now I’d like to expand on some of the details: in
this installment, specifically, the subject of hydroponic

The American Heritage Dictionary of the English
defines “hydroponics” as follows:

hy-dro-pon-ics (hi’ dre-pon’iks) n. Plural in form,
with a singular verb. The cultivation of
plants in water containing dissolved inorganic nutrients,
rather than in soil ….

Most plants grown hydroponically are raised in greenhouses
under carefully controlled conditions. Gravel is usually
used as a medium for root support, and a balanced mixture
of all the necessary nutrients is periodically fed to the
crops in a liquid form. This method is called
“sub-irrigation culture.” In large commercial greenhouses
it’s been refined to such a degree that–once the
seedlings have been planted–almost all the work is
done by automation. Delicate sensors in the gravel “decide”
when the plants need more solution and turn on pumps which
meter out the correct dosage.

The biggest advantage of the hydroponic method is that crop
yields are increased many times over those of conventional
agriculture. For example, the yield per acre of tomatoes
grown in soil is from five to ten tons. With hydroponics,
the harvest is from 60 to 300 tons! For cucumbers, the
equivalent figures are 7,000 pounds compared with 28,000
pounds … for lettuce, 9,000 pounds and 21,000 pounds.

For years I’d heard about hydroponic gardening, but had
never given the subject more room in my thoughts than a
quickly contemptuous dismissal. After all, hydroponics is
the quintessential form of chemical agriculture. To a dyed-in-the-wool organic gardener like me, the thought
of feeding my vegetables with a pure chemical solution was
blasphemy. Then one day about two years ago, I was browsing
in a bookstore and came upon a thin newsprint pamphlet with
the title Hydroponics!. My first reaction was an
almost irrational disgust: “What kind of propaganda are the
big chemical companies putting out now?” But the
work had the aura of a counterculture publication: large
format, cheap paper, and on the cover a reproduction of
Buckminster Fuller’s Dymaxion map of the world. I picked up
the booklet, gingerly leafed through it, and then bought it
on the spot.

Hydroponics!– by Steve Fox of Albuquerque,
New Mexico–is definitely not a big business promotion
for chemical fertilizers. On the contrary, it is the
enlightened vision of a man who sees hydroponic agriculture
as one solution to the coming world famine, and an
alternative to the destruction of our once fertile
soil with chemicals. Fox proposes that extensive use of
hydroponic greenhouses, with their greater yields of
produce, would actually free our cropland for organic
agriculture! In other words, instead of poisoning our soil
with chemical fertilizers which eventually destroy the
micro-organisms that make natural plant growth possible, we
would keep these chemicals in the controlled environment of
a greenhouse where they couldn’t “poison” anything more
valuable than the gravel beds which serve as the
root-support medium for hydroponically grown plants.

“But wait a minute!” you’re probably saying. “What about
the plants themselves? I’m not going to eat any vegetables
that were grown in a chemical solution!” A good point, and
one which used to bother me, until I did some research on
the subject. A report in the March 11, 1974
Newsweek on the annual meeting of the American
Association for the Advancement of Science quoted the
following opinions expressed by the nation’s top

… the organic nutritionists’ basic error is their
assertion that organically grown foods are more nutritious
than others because they receive all their nutrients from
“natural” rather than synthetic inorganic sources. “A basic
fact of plant nutrition is that plant roots absorb the
nutrients elements from the soil only in an inorganic
explained plant physiologist Daniel I. Arnon
of the University of California. “Plant nutrients in
organic manures and composts become available to plants
only after they are converted into inorganic form by the
activity of soil microorganisms …”

The experts at San Francisco were at pains to point out
that they were not disparaging so-called natural foods …
that is, products free of additives,
preservatives, artificial coloring, and other chemicals
added after the food has been harvested. “The health food
advocates may be on legitimate ground when they attack a
number of additives found in foods,” conceded Allentown,
Pennsylvania psychiatrist Stephen Barret, a prime critic of
the organic-growth industry. “However, they tend to lump
together arguments for organic gardening and against food
additives as though one is naturally linked to the
other–when, in fact, they are entirely different
(Copyright Newsweek, Inc., 1974,
reprinted by permission.)

Another article, entitled “Nutritional Value of Organically
Grown Foods Same As That Using Commercial Products”,
appearing in the March 10, 1974 Sante Fe New
had this to say about the subject:

“Promoted and accepted by many people is the theory
that foods grown “naturally” provide greater nutrition …

But absolutely no scientific evidence that this is so
was gleaned by the Michigan Experiment Station in a 10 year
study, or by the U.S. Plant, Soil and Nutrition Laboratory
in Ithaca, New York in a 25 year program, or in a
34-year-long study on an experimental research farm in

These studies found that while soil improvement can
increase the yield and size of crops, the nutrition factors
of the food grown in such soil aren’t altered …

All food scientists agree that all fertilizer elements
have to be in a soluble form before any plant can use them … Once converted into the soluble form, the plant
neither knows the difference nor does it make different use
of them.

Now, before anyone takes me to task for advocating the use
of chemical fertilizers–as these quotes seem to
do–let me explain my position further. There’s an
adage in organic gardening that goes like this: “When
fertilizing, always remember that the objective of the
organic method is to feed the soil, not necessarily the
plant.” In other words, if you build your soil with organic
material, you will eventually provide enough nutrients to
grow healthy produce.

The spreading of chemical fertilizers, however, does just
the opposite: It feeds the crops and not the land. The
result is that the micro-organisms which break down organic
material into the chemical form that plants can use are
starved out, and the soil literally dies.

Purely and simply, to put raw chemical fertilizer on the
soil is not unlike giving hard narcotics to a human being.
A man on a steady maintenance dose of heroin, for example,
can live a completely “normal” life as long as he
receives that dose.
If the drug is taken away from
him, he suffers withdrawal symptoms and can no longer
function. It’s the same with the land. Once the natural
micro-organisms have been destroyed by artificial
fertilizers, the soil is to all intents a “junkie.” Nothing
will grow on it unless it receives its dose of chemicals.

In hydroponic gardening, however, there is no soil, so the
plants can be fed the exact nutrients they need for rapid
growth and volume production. Does this sound like a
typical agribusiness statement? Maybe so … but bear in
mind that the earth is already unable to feed its
continually growing population. That’s one reason why
chemicals are being used: “Natural” methods can no longer
keep up with the tremendous demand for food. The situation
is bad, and getting worse. Doesn’t it make more sense to
solve a part of our problem with hydroponic methods rather
than poison our cropland beyond the point of recovery?

Even if agricultural chemicals didn’t destroy the
soil–and even if they didn’t wash into our lakes and
streams and seep into the water table as
pollutants–the use of artificial fertilizers on
cropland would still be bad ecology. Petroleum is one of the major sources of such products, and it
doesn’t take an Einstein to see what is bound to happen to
farmers who continue to rely on them. With our petroleum
resources rapidly vanishing, what will those producers do
with soil that’s hooked on chemicals? And what will happen
to the world’s food supply?

“But,” you might ask, “what about the chemicals used to
make up the hydroponic solution? Aren’t they derived from
petroleum? Even if hydroponic gardening, properly done,
doesn’t cause pollution, won’t it create a needless drain
on a finite resource?”

To be quite frank, I don’t know how the commercially
available hydroponic chemicals are manufactured, or what
raw materials they are derived from. And, while it’s true
that I’m using a conventional product in my tanks at the
present time, my objective is to develop a hydroponic
solution which is derived from organic materials.
Fox, in his pamphlet, gives us a hint as to how an organic
hydroponic solution might be created:

the end product of… regular composting, or
itself, can be put into a burlap bag which,
in turn, is put
into solution. The proper mixture
consists of 1/2 bushel
of manure for fifty gallons
of water. This solution
which is very rich, and
should be used about once every ten
days–could be used daily if the solution is
weaker ….

In all my research into the available literature, this is
the only reference I have found to an organic hydroponic
solution. Obviously, most hydroponic gardeners rely on the
commercially prepared product. Perhaps the time has come
for some basic research into an organically derived formula
which can be duplicated by anyone with reasonable accuracy.

The Complete Book of Composting (Rodale Press,
1971) gives the nitrogen (N), phosphorus (P) and potassium
(K) percentages of most common organic materials. (For
example, rabbit manure has NPK percentages of 7.0, 2.4 and
0.6.) The method I intend to explore in my greenhouse is to
mix the proper proportions of organic materials, compost
them, feed the compost to earthworms, and then leach the
earthworm castings with water to get my hydroponic

The reason for using earthworms is twofold: [1] the worms
can be used as fish food (remember, the greenhouse contains
an aquaculture tank!) and [2] earthworm castings are known
to be just about the richest organic material around.
Rodale’s The Complete Book of Composting quotes
Dr. Ehrenfried Pfeiffer’s opinion that “The earthworm
excrements, the so-called castings, are the richest and
purest humus matter in the world,” and adds the following
from the writings of Sir Albert Howard: “The casts …
contain everything the crop needs–nitrates,
phosphates and potash in abundance and also in just the
condition in which the plant can make use of them.”

I don’t expect this project to be quite as easy as it may
sound. For one thing, there are many micro-nutrients and
trace elements which plants require for good growth
and finding natural, readily available sources of such
chemicals may be difficult. Meanwhile, the greenhouse has
been in existence just one year and–so far–I’ve
concentrated on learning this new method of agriculture by
using “conventional” methods.

As I mentioned briefly in the first article of this series,
my hydroponic tanks are made from four 55-gallon drums
(each one cut in half lengthwise to make a total of eight
tanks). At the bottom front of every trough is brazed a
three-inch piece of 1/2″ O.D. brass tubing. A length of
ordinary garden hose (1/2″ I.D.) is clamped to this tube,
and the other end attached to a similar tube which has been
brazed onto a five-gallon can. The insides of both the tank
and the can are painted with a thick coating of an
asphalt-based paint. (This is necessary to prevent the
metal surfaces from rusting, since they are constantly
exposed to moisture.) The tank itself is filled to within a
few inches of the top with pea-sized gravel. It’s essential
that a small piece of galvanized or fiberglass screen be
placed over the inlet tube inside the container before
gravel is installed, to prevent pebbles from clogging the

My procedure for planting the tanks is to start seedlings
in paper cups full of vermiculite, with the bottoms of the
containers perforated enough to allow the hydroponic
solution to enter. Once the plants are well started, it’s a
simple matter to place the entire cup in the gravel.

The five-gallon can is filled with the hydroponic solution.
When it’s time to feed the plants, the container is lifted
so that it’s higher than the tank. The fluid runs down the
hose and into the gravel, irrigating the plant roots from
below. (That’s why they call this method “sub-irrigation”
culture.) As soon as the can is empty, it’s placed back
down on the floor and the liquid flows out of the gravel,
down the hose and back where it came from. I do this three
times a day–morning, noon and evening–so that
the roots of my crops are always moist but never actually
flooded with solution for more than a few moments.

The hydroponic solution I’m using at present–until I
can develop an organic substitute–is called Hyponex and is
readily available in most nurseries. It comes in a powder
form, with complete directions on the box for mixing and
use. I’ve found it both inexpensive and effective.

I can attest that this method really works. At this writing
(April 1974), we have growing in the greenhouse the
healthiest, largest lettuce, spinach and cabbage we’ve ever
raised. I’ve seen radish and lettuce plants become
measurably larger from one day to the next! We find that
lettuce, especially, grows like a weed and almost takes
over the greenhouse if we don’t trim it regularly for
salads every evening.

Per Acre Soil Yield vs. Hydroponic Yield Comparison           

 Soil        Hydroponics

Soybeans    600 lbs       1,550 lbs
Beans         5 tons     21 tons
Peas          1 ton       9 tons
Wheat       600 lbs       4,100 lbs
Rice      1,000 lbs        6,000 lbs
Oats      1,000 lbs       2,500 lbs
Beets         4 tons     12 tons
Potatoes      8 tons     70 tons
Cabbage       6.5 tons    9 tons
Lettuce       4.5 tons   10.5 tons
Tomatoes     5-10 tons  60-300 tons
Cucumbers     3.5 tons   14 tons

Hydroponics Offers These Advantages

To sum up, let me quote once more from
Hydroponics! by Steve Fox:


1. Greater yields
2. Extension of growing season
3. No insecticides
4. Weeding is eliminated
5. No heavy labor required
6. No need to change greenhouse soil
7. Ease of transplanting


1. Greater rural densities
2. Possibility of letting land lie fallow
3. Less labor to harvest
4. Methods could be standardized
S. Maintains hydrological cycles


1. Permits establishment of earlier ecologies
2. Oxygen production in urban areas
3. Autonomous self-contained optimum environment
4. Space travel 

With the world facing a food shortage of unimaginable
proportions (read The Population Bomb by Paul
Ehrlich), hydroponic agriculture could provide a viable
alternative to starvation–if not for the whole world,
then at least for those individuals who can read the
handwriting on the wall.

In the next installment I’ll describe how wind-generated
electricity provides the power to heat my greenhouse and
aerate the fish tank.

Books on Hydroponics

Hydroponics! Steve Fox, Station A,
Albuquerque, New Mexico 87106, 1971.

Hydroponics as a Hobby: Growing Plants
Without Soil, Circular 844, College of Agriculture, University of Illinois, Urbana,

A Final Thought on Hydroponics

Taken from: Hydroponics! by Steve Fox

. . . (when people) are unemployed, as millions have
been during the last decade, they cannot buy their food but
still must be fed. One way of lightening the burden of
relief expenditures is to alter the ratio of agricultural
to nonagricultural laborers. The unemployed must become
farmers themselves, and produce their own subsistence …
The answer lies in hydroponics, which can operate
wherever climate is available and produce on a small plot
the same amount of food as can agriculture on a large farm.
It offers the most feasible method of removing the
unemployed from towns and cities where private employment
for all of them may never again be available and of
allowing them to support themselves. Nations such as Italy
and Japan which are worried by crowded populations and
inadequate agricultural land could easily use it to
multiply their production of foodstuffs manifold. Once
their hunger is satisfied from within their own boundaries,
the reasons for seizing the rolling wheatfields of the
neighbors might be swept away ….

W.F. Gericke, Complete Guide to Soilless
(PrenticeHall, Inc., 1940) (emphasis