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Asked by Ryan to Keegan on 25 Apr 2016.
Question: Do you think hydroponics also have to do with soil?
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Keegan Cooke answered on 25 Apr 2016:
Interesting question! Hydroponics, by definition, means that soil is not used. But hydroponics is all creating nutrient cycles that mimic the nutrient cycles that happen in soil, to make plants healthy and happy. So they are very much related in that way.
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Clay commented on :
In hydroponics, people are trying to provide everything plants need in an environment without soil. But in nature, 14 of 17 plant essential nutrients are provided by soil. Plants only get hydrogen and oxygen from water, while they get carbon (and some oxygen) from the atmosphere.
That means other nutrients needed in relatively large amounts (5 to 200 kg/ha, including nitrogen, phosphorus, potassium, calcium, magnesium, sulfur) and those needed in small amounts (a few mg/ha to 5 kg/ha, including iron, manganese, zinc, copper, nickel, chlorine, boron, molybdenum) are obtained from the soil.
Hydroponics has to find ways to mimic this process.
Plant roots also need oxygen to be healthy.
So hydroponics systems have to
1) pump air through the water to keep enough oxygen in the water for the plant roots to respire and remain healthy, and
2) provide those 14 nutrients in the right proportions. Plants do not grow to their full potential if the nutrient supply is limited, while some nutrients can be toxic if they are present in large amounts.
All the nutrients obtained from the soil are charged, either acidic or basic cations or anions, and remember that an acid and a base form a salt. This leads to two other major challenges, hydroponics systems have to
3) maintain the proper pH range (6.5 to 7.2) so that the nutrients remain in solution, and
4) manage the salt balance because hypertonic solutions can pull water out of plant roots. This means a plant can become dehydrated and die for lack of water while its roots are growing only in water!
Plants need some way to be anchored or supported, which is a function the soil naturally provides. So, hydroponics systems also have to
5) provide a physical support system for the plants. In order to accomplish this, some add expanded perlite or expanded vermiculite as a rooting media to provide some anchor for the roots. These minerals also help keep some oxygen in the water. Others have a trellis system in which they tie the plants to the trellis and train the branches along the strands of the trellis.
In all soils, No. 2 must be managed.
In some soils, No. 3 must be managed.
In most soils, No. 1, 4 and 5 require no additional management.