- By: Larry Gray
- Posted on: February 17, 2014
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.
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.
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