How to Use Straw Bale Culture Growing for Indoor Crops

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PHOTO: C. DONALD KNIGHT AND BETSY TAYLOR
Tomatoes thrive in a straw bed, where the presence of higher-than-average CO2 levels promote plant growth.

How to use straw bale culture growing for indoor crops, a similar method to hydroponics without the special equipment or the twice-daily soakings necessary in many water-growing methods.

How to Use Straw Bale Culture Growing for Indoor Crops

I think I’ve discovered the perfect compromise method for
growing tomatoes (and other garden produce) indoors . . . a
Golden Mean between the high-tech effectiveness of
hydroponic cultivation and the simplicity–and lower
cost–of raising plants in soil. I’m talking about
straw-bale culture, a technique I heard of only after
hauling some 300 cubic feet of pumice, gravel, and dirt to
fill the planting beds of my new solar-heated greenhouse.

As I paused in the middle of that task to contemplate (and
curse) the necessity of trucking still more earth to my
conservatory, some sympathetic friends came to my rescue
with tales of “soilless” hothouse gardening. Needless to
say, the idea caught my fancy immediately. After all, who
wouldn’t exchange the transfer of tons of terra firma for
the lifting of a little straw?

Bale culture, as noted above, is similar to hydroponics in
many respects . . . but it does not require the
special equipment or the twice-daily soakings necessary in
many water-growing methods. In fact, plants raised in straw
seem to need even less water than do those rooted in soil.
And unlike the almost inert growing medium of the
hydroponic system, the constantly composting environment of
straw-nurtured plants provides some “bonus” nutrients for
the vegetables . . . as well as a source of gentle heat for
their roots and for the greenhouse.

Nor do the advantages of growing vegetables in straw end
there. Tomatoes, in particular, seem to fairly leap at the
chance to form huge nurturing root systems amidst the
stalks .. . and such formations are (within limits) very
productive of healthy plant tops. The composting straw also
produces some CO2 gas, the presence of which in more than
usual amounts tends to improve the growth rate and general
health of all the vegetation in the greenhouse.

GETTING OFF THE GROUND
Because a typical straw bale is about 24 inches wide, I set aside
room–in my conservatory–to accommodate a 2 foot by
20 foot bed of the material. After putting down a layer of
plastic sheeting (to help the straw retain water), I simply
set the bales end to end. (You could use loose straw held
in place by barrier walls . . . but the unpacked stalks sink
rather drastically in the course of time, displacing the
plants. It’s also somewhat difficult to stake tomatoes that
are growing in unbound straw.)

After the bales are in place, you’ll have to undertake a
three-week period of preparation before setting out your
plants. First, each bale needs to be soaked with a gallon
of water daily for two weeks. (It’s also a good idea to
keep the straw covered with plastic sheeting between
waterings.) Once the bundles have been thoroughly drenched
for 14 consecutive days and organic decomposition is
underway, you can apply the fertilizer that will nurture
your vegetables.

Commercial tomato food (for example) contains everything
necessary for the successful growth of a crop of love
apples . . . providing nitrogen, phosphate, and potassium
represented in a ratio of about 5/10/10. For the initial
fertilization of your straw bed, you’d need about 2-1/2
pounds of such augmentation per bale.

In contrast, many hydroponic fertilizers have a
nitrogen/phosphate/potassium ratio of 8/8/22 (they also
supply calcium, manganese, magnesium, cobalt, iron, and
molybdenum). Though I’ve had no personal experience in
using those products, I’d imagine
that–again–feedings of 2-1/2 pounds per bale
would be suitable . . . though you may want to cut down on
the amount of potassium later– in the growth cycle.
[EDITOR’S NOTE: It’s a good idea to check with your local
fertilizer dealer–or county agricultural
agent–before using plant foods in growing mediums
other than those intended by the manufacturer.]

If you prefer to mix your own growth inducer, you’ll find
blood meal to be an excellent source of nitrogen. It also
has some phosphate content, and more of that substance can
be obtained from rock phosphate. Wood ash will provide
potassium . . . iron is present in the blood meal . . . and
magnesium can be supplied by seaweed or Epsom salts (at a
dosage of one tablespoon per plant). Finally,
well-composted manure is generally an adequate source of
many of the minerals necessary to healthy plant growth.

Any good book on gardening will suggest ways to supply your
plants with the essential nutrients. I’ve found Frank
Allerton’s Tomatoes for Everyone (available for $7.50
postpaid from the publisher: Faber & Faber, Dept. TMEN,
Winchester, Massachusetts) to be
an excellent guide to all kinds of productive
tomato-growing methods, including straw bale culture.

Whatever fertilizer you use, first spread
it–dry–on top of the straw, then water the bed
daily for about a week (use a gallon per bale). If the
growing medium is too densely packed or the plant food
seems insoluble, you can work it into the tightly bound
bundle with a trowel.

The introduction of the fertilizer will rapidly increase
the rate of bacterial action in the decomposing straw,
raising the bed’s internal heat. An effort should be made
to retain this warmth (by continuing to cover the planting
medium with plastic) to aid in the generation of the
nutrients needed for plant growth.

During the period of intense composting, any seeds in the
straw are likely to sprout. It’s possible that the heat of
decomposition will kill the shoots . . . if not, you’ll
want to weed them out prior to transplanting your tomato
seedlings.

Within a week following fertilization, the temperature in
the interior of the bales will have begun to subside. Once
it drops below 100 degrees Fahrenheit, you’ll be
able–finally–to plant your crop. (If you don’t
have an appropriate thermometer for monitoring the internal
temperature of the straw, just push a stick into the
bedding and leave it there for an hour. If the wood is only
slightly warm to the touch when you withdraw it, you’re
ready to bring on the plants!)

SWING YOUR PLANTER
While I’d imagine you could grow just about any variety of
tomato in a composted straw bed, I’ve had very good luck
with Tuckcross 520 . . . which was developed specifically
for greenhouse cultivation. I’ve also achieved excellent
yields from such standbys as Marglobe, Rutgers, and Red
Cherry. In short, straw-bale culture seems to reward the
gardener on a fairly consistent basis, regardless of the
kind of plant raised . . . as long as each seedling’s
feeding requirements are recognized.

You’ll get the best results from your straw bed by
transplanting tomatoes that are six to eight weeks old.
Allow five plants for every two bales. To hold each
young’un in place and give it a start, set a 4 inch- to
6 inch-high, 6 inch-diameter ring of cardboard or metal (a
one-pound coffee tin with both ends removed works well)
directly on top of the bedding . . . fill the cylinder with
compost or soil . . . and plant one of your infant tomatoes
in it.

This is also the best time to stake the young plants. The
job will be easy if you’re using bales . . . but if you’ve
opted for loose straw, it’ll be necessary to devise a
supporting frame.

As the seedlings begin to sink their roots into the
fertilizer-enriched straw, they’ll rapidly use up the
nutrients. Therefore, approximately two weeks after
planting–and every other week thereafter–you
should replenish the beds with about one-quarter of the
amount of nitrogen fertilizer you used in the first
feeding. On alternate weeks, refortify the potassium
content of the straw with one-quarter of the dosage
initially spread on the bales . . . and always keep a sharp
eye out for signs of nutrient deficiencies.

I’ve occasionally varied my feeding routine by serving each
tomato a gallon of manure tea. And I’ve also tried a
solution of water and fish emulsion . . . a mixture which had
the unexpected and pleasant side effect of filling my
inland greenhouse with the faint but unmistakable aroma of
the sea.

THE JOY OF STRAW-BURYING
Aside from their need for regular nutritional supplements,
tomatoes planted in straw are cared for pretty much as more
traditionally cultivated crops would be. Soon after my
initial planting, I was able to harvest succulent red
fruit, and I did so for months before the plants began to
give out. Of course, there are a few things to be
considered prior to opting for the bundled stalk method . .
. including the cost of the straw itself, fertilizer
prices, and the possibility of plant burnout if you
overfeed your tomatoes (or of the production of giant
stalks with more leaves than fruit if you overdo the
nitrogen).

All things considered, though, I’m convinced that
straw-bale culture’s advantages far outweigh any drawbacks.
In fact, I plan to use the method with other crops, and try
it for outdoor planting as well. Meanwhile, I believe I’ve
discovered an important secret: When it comes to growing
tomatoes in a greenhouse, straw–the Golden
Mean–is the happy medium!