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Hydroponics for the Homestead


When I think of Hydroponics I also think of Aquaponics. Aquaculture is the raising of fish and Aquaponics is using fish waste water to fertilize a hydroponics bed. But also there is Aeroponics, which is the spraying or misting of roots and plants with nutrient solutions. Hydroponics is generally thought of as the growing of plants in a water solution alone, which is called water culture. However, some plants are better grown in a sterile medium of some kind like sand, gravel, saw dust, peat, straw, etc. In those cases it is called sand culture, or gravel culture, or peat culture, etc. The basics are the same, which is that nutrient rich water is pumped and gravity fed though the medium and around the roots.

As it turns out, all plant nutrients in the form of ions of various salts can be suspended in water. These "nutrients" are all basic elements. Of the 100 or so elements in the chart of elements table about 60 have been found in plants. And, of that, only a few are considered to be essential. To be exact 16 (wikipedia says 14, different sources vary) are essential and, of those, some are more essential in greater quantity. Those are called macro-nutrients. Those needed in less quantity are called micro-nutrients.

Hydrogen, carbon and oxygen are the main elements and guess what? Plants get most of that from air and water. Of those three, carbon and oxygen are 45% each with hydrogen at 6%. Yes we have all heard that plants breath co2, giving off oxygen, and we animals breath oxygen, exhaling co2. Of the macronutrients we also have the famous NPK or nitrogen, phosphorus and potassium (the primary macronutrients). The other three secondary macronutrients that most of us don't think about are calcium, magnesium and sulfur. Micronutrients needed can be chlorine, boron, iron, manganese, zinc, copper and, strangely, molybdenum. Of those, we might have thought of iron, manganese, zinc and copper, but not the rest. And there are a few elements outside that which some plants might need, such as selenium or nickel. There was one plant, a tree, found recently where they discovered gold in its leaves. There was not enough gold to try to get rich getting gold from its leaves; however, the tree might be used as an indicator that there is gold in the ground beneath it. As far as they could tell, the plant has no use for the gold, it just happened to draw it up with other nutrients.

About 15% of a plant's mass is dry weight. 90% of that dry weight is hydrogen, carbon and oxygen, and it gets much of that from the air and water. This means that 1.5% of a plant's weight are nutrients. Of 100 pounds of plant matter, 1.5 pounds are nutrients. The point being the nutrients you buy for hydroponics are very compact compared to the plants they will produce. Or to say it another way, a little plant nutrient will go along way.

If you research you might find information similar the following.

Carbon 45%
Oxygen 45%
Hydrogen 6%
Nitrogen 1.5%
Potassium 1.0%
Calcium .5%
Magnesium .2%
Phosphorus .2%
Sulphur .1%
Chlorine .01%
Iron .01%
Manganese .005%
Boron .002%
Zinc .002%
Copper .0006%
Molybdenum .00001%

Aside from plant nutrients, another major factor which is to be considered is the pH. 7 is neutral pH. Less than 7 is acidic. More than 7 is alkaline. PH of 6 to 7 is best for plants to properly convert the salts to something they can use. The pH is different for various elements, however. So a plant requiring one element more than others might want a pH that is suited more for that element.
With all but aeroponics, air is needed, as well. This can be achieved with aquarium air pumps and air stones. If you think about it, soil has air in it, and that air  is more carbon dioxide rich than the atmosphere. The rotting plant matter and humus and manures help to provide a looseness which gives the soil more air. In aeroponics, the roots are sprayed or misted so air is a constant. In hydroponics, water levels need to be raised and lowered to to help with aeration.

Some advantages of growing with hydroponics versus soil are:

  • The growing medium can be totally sterilized. This means no diseases, fungus, weeds, bugs, etc. to bother your plants while they are growing. One interesting method for this is using steam, though I'm not totally sure how well this would work out on the homestead.
  • No weeds.
  • No bugs (probably indoors only), at least it reduces bugs outdoors.
  • Lower chance of diseases.
  • Plant nutrition and pH can be controlled precisely at each stage of plant growth and evenly to all plants at the same time.
  • You can space plants closer together and get more yield per square foot.
  • You can automate the watering more precisely and there is less water loss due to evaporation versus flooding or other typical irrigation methods.
  • More sanitary because you are not using manures, which could transmit human diseases to fruit.
  • Plants mature faster.
  • Plants are not stressed as much during transplanting. Transplant shock is not as severe. Start your plants in, say, sand or vermiculite, then transplant to the growing medium.
  • Pesticides and herbicides are not necessary. Pesticides are not necessary if grown indoors, but some may be if grown outdoors. Herbicides won't be necessary at all; however, you might have to protect the nutrient solution from sun light so that algae won't grow in it.

What might some possible disadvantages be?

  • Cost and labor in designing and setting up the system, containers, pumps, etc.
  • If using a medium (sand,gravel, saw dust, etc.), a change, or at least cleaning of the medium, is necessary after so many cycles.
  • Roots clog the medium.
  • The nutrients needed probably come totally from industry byproducts. Yes nutrients are terrible dangerous chemicals (satire alert). What? Not organic? If a bag of sulfur can be labeled organic, I'd say these nutrient solutions are organic, too. My concern here is that we are dependent on the systems of support for the nutrients.  (Nutrients would be a good prepper item to stock up on with possibly an infinite shelf life).

In soil, apparently we have nutrients as ions, meaning basic molecules that contain any of the 16 nutrient elements. There are different molecules for different elements. We generally call this chemical fertilizers. Organic is where plant and animal matter have been decayed or broken down to the point that it has become these chemical molecular ions. Some of these elements also come from rock, gravel, clays, and sands that have been broken down to where the roots can grab them and use them. Much of the soil is not usable by the plant and is simply good for aeration and supporting the plant structurally while it lives.

Plants roots absorb nutrients via chemical magnetism between molecules.  Soil nutrients are - ions which are attracted by + molecules inside the plant cells. Water is pulled into the plant via a suction created by evaporation of water from plant leaves. Nutrients move to the leaves where they are turned into food for the plant and its parts by photosynthesis. Strangely, plants can take in water and nutrients through their stems and leaves, as well as roots. The point is that nutrient solution in contact with plant parts makes plants grow.
I say all the above to give you an introduction to hydroponics. I myself have yet to try this method of growing food. But I'd like to try it for some staple items. Corn, beets, carrots, potatoes and rice come to mind as staples. About the grains, such as wheat, oats and such, I'm not sure on how easy it would be or how to go about it.  You may have heard of fodder systems for feeding livestock. This is a form of hydroponics. I would think root crops would be nicely grown in a sand culture. Corn might be best grown in a gravel culture, I would probably support corn with string as it grew. Other plants such as tomatoes, melons, squash, lettuce, greens, etc. might be good grown in water culture.
The basics should all be about the same. You will need some kind of containment for the air, water or medium culture. This container will need to be water tight. Solution will flow from one end to another through it and the medium. Pumps will be needed to circulate the solution. Alternatively, if your setup doesn't actually flow, then changing out the solution will have the same effect.  So, on the small scale, pumps are not absolutely necessary. However, aeration will be using the fish tank pumps and stones.

For plants where roots will hang down into the water, something will be needed to support the plant itself. Anything with a funnel shaped hole might suffice. And this might be one good reason to raise your own cotton. After you have sprouted your plants in perlite, vermiculite or sand, or whatever, you can transplant it to the bed by stuffing its roots down through the hole then supporting the plant with cotton. Alternatively, peat or rockwool (an insulation) might be used, as well. Could recycled fiberglass insulation work? For making holes you could get a cone shaped bit from the hardware store and drill the cone shape hole into 1" plywood. If using styrofoam, one might just cut the hole the proper shape with a pocket knife. And styrofoam will float in the water solution.

Alternatively, one might make cone shaped pieces from any plastic material and insert that into a flat hole in flat material. Have you ever made a paper funnel for pouring oil into your car? Same concept. The thing is that you need to have this cone shape to allow the roots to be lowered below into the solution and to hold the stem. Again, some material needs to be packed into the cone to hold the stem in place.

Hydrogen 1.0079
Carbon 12.0107
Oxygen 15.9994
Nitrogen 14.0067
PHosphorus 30.9738
Potassium 39.0983
Sulphur 32.065
Magnesim 24.305
Calcium 40.078
Iron 55.845
Chlorine 35.453
Manganese 54.938
Boron 10.811
Zinc 65.39
Copper 63.546
Molybdenum 95.94
Nickel 58.6934
Selenium 78.96
Aluminum 26.9815

The above table is the atomic mass of each nutrient (element). Atomic mass is defined as 1/12th the mass of a carbon 12 atom. This gives us a ratio for figuring atomic mass of molecules. We can then determine what percentage of the molecule is our nutrient. Using this, we can figure ppm mg/l. That is parts per million milligrams per liter. A good digital scale, such as a scientific or scale used to measure gun powder, might be used to weight out a fertilizer salt to be added to a solution. Just as percent means out of one hundred, ppm means out of one million. One microliter is one ppm of a liter. 1,000 microliters would be a milliliter. PPM, though, is a ratio that is used with any measuring system. PPM for gallons would be 1 millionth of a gallon. And one ounce of a gallon is 7,812.5 ppm.

Sources for plant nutrients

  • Dry fertilizer compounds
  • Liquid fertilizer solutions
  • Teas (manure tea, compost tea)
  • Home mixed liquid fertilizer solutions

The last one, of course, will be made from the first three. Some compounds are more soluble in water than others. This means they dissolve well and stay suspended. Solubility ratios might be 1:1, 1:2, 1:3, 1:4, 1:5, 1:15, 1:60, 1:300, 1:500. Compounds that are less soluble tend to be better for gravel and sand cultures and anything but pure water culture. The end result is that you mix up something liquid that can be added to your tank of water at a nutrient level, which will feed the plants and yet not burn them with too much nutrient. This is called a nutrient formulation.  Nutrient formulations are like recipes for nutrient solutions.

Fertilizer compounds should give you amounts of each compound (molecule). It should give you the name of the compound and possibly the molecule itself. You will need to calculate a ratio for each compound. First, you will need to figure the molecular weight of a compound. A nutrient will be one atom in that molecule. You will need to figure the total weight for that element. A molecule may have more than one atom of the nutrient. Online Molecular weight calculator. You could try to calculate molecular weight yourself and then check it with an online molecular weight calculator.

1 mg/l is one ppm. You will divide the nutrient weight by the molecule weight to get a ratio. This ratio will be .2358, for example, or .4231 or .1258. Let's say you need 150 ppm of the nutrient in the solution. This means 150 mg/l. By the way, it's probably best to just calculate this in mg/l and later convert to ounces per gallon if you must. So we divide 150 ppm by a ratio, say, .3092 and get 485 mg of your fertilizer compound to get the proper ppm in your 1 liter solution.

Compounds are usually not 100% pure and may be, for example, 40% up to 98% purity. I would assume the impurities are not harmful to plants and they should tell you what they are. Let's say in the above example the compound was 85% pure. 85% is .85. We divide 485 by .85 and get 570 mg. I made up the numbers above, but you get the point. Now we multiply 570 by the total number of liters of water in our system. Say, 100 liters, which would give 5,700 mg or 5.7 grams.

Factors that affect the formulation might be the following.

  • Plant species and variety
  • Stage of plant growth
  • Part of plant being harvested (stem, root, leaves, fruit etc. )
  • Hours of sunlight
  • Intensity of sun
  • Temperatures

You will most likely be mixing your solutions from solid fertilizer compounds or from liquid solutions or both. In order for you to use some manure or compost tea, you would have to test your tea solution for nutrient content. This is not cheap or fast. Though there may be some general data already established  for popular manure teas. For example, fish waste for a given type of fish in aquaponics. Or for a given compost recipe. Local county extension offices would probably test a tea solution for you and maybe for free. However, most people probably wouldn't bother unless you are wanting to find non-industrial organic solutions.

You may experience nutrient deficiencies. This can be a complicated issue. Testing can be time consuming or expensive. You can get strip test kits from the hardware store. But you, as a homesteader, will basically have to watch for symptoms and then change out or amend your water. I won't really go into talking about symptoms in this article. Conversely, having a toxic nutrient level is usually not a problem. And, again, there might be differing nutrient requirements at different stages of growth.  That means there may not be a single generic one size fits all nutrient solution. Some further research and study here will be necessary.

As preppers we might simply experiment with hydroponics, aquaponics, and aeroponics. We might have a small system setup so that, if needed, we could fire up the hydroponics system for a few months and produce some staples.  Or one might live off the produce day in and day out. In the case of a greenhouse or poly tunnel, we could live off of some of it year round. Hydroponics is not without work, however. It is merely another way to skin the cat.

If you wanted to try aeroponics  you might check out www.dripworks.com Drip Works for some drip and spray emitters and other components. However, I don't have a clue if these will clog or stop up due to the solution not being pure water.



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Guest bhoutl


Nice summary Larry. You really need to try doing a small scale version of this. I did some experimenting with a desktop aquaponics system. It still needs some work but you are welcome to take it over if you want. You may even be able to make it work in a truck. Kind of like a pet.

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Just now, Guest bhoutl said:

Nice summary Larry. You really need to try doing a small scale version of this. I did some experimenting with a desktop aquaponics system. It still needs some work but you are welcome to take it over if you want. You may even be able to make it work in a truck. Kind of like a pet.

Thanks, well I’ve thought about starting plants in the truck actually. But with a student it wouldn’t work all the space is taken up. It would be difficult for me to try this without a partner who is there to do the actual monitoring and work,. I’d have to be the partner that funds the project and shows up once a month to assist a little.

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