Hydroponic Air Farms

Nutrient Solutions

The main keys to successful hydroponic gardening are pH level, nutrient concentration and lighting. There are a number of other factors including temperature among others, but if you take care of the "big three", the others will follow. I'll be adding articles on lighting, temperature and even others on pH and nutrient in time, but for now these are the two areas that we'll work on.

Most plants prefer slightly (6.8) to very (5.5 for tomatoes) acidic soil. In hydroponics, we provide them with an acidic solution.

Ideal nutrient concentration varies among plants and even in different cycles of each plant.

For seedlings, I'll use plain water or a very light nutrient mix (under 500 ppm), increasing the strength as the plants grow.

Evaporation and respiration will increase the strength of the solution and as the nutrients are mostly alkaline, the pH will also rise with evaporation.

So between complete replacement of the solution (about every two weeks) , I'll mix some very concentrated nutrient in one jug, but keep it to the side.

I'll top up the solution in the reservoir with plain water first. Then I'll measure the nutrient strength and add nutrient from the concentrated mix until that reads between 1200 on up to 1400 ppm for mature plants (parts per million) on my TDS (Total Dissolved Solids) meter.

With the nutrient strength taken care of, I'll adjust the pH, usually with pH Down, as it's almost certain to be above 8.5 after adding nutrient.

There are exceptions, such as high temperatures, plants exposed to wind or very large plants. In such cases, I'll go much lighter on the nutrient, as a mature tomato in warm weather and exposed to wind will go through nearly a gallon of water a day. You wouldn't want to dose it with all of that nutrient simply because it will consume the water to respire and the nutrient will make for a toxic buildup.

In cases like these, you'll want to provide a lighter nutrient solution with each topping so that over a two week period, it will receive two weeks worth of nutrient. We'll do this by mixing a one gallon solution at full strength, and adding portions of it when we top off the reservoir with plain water. This comes easier with practice and observation.
As to the water that you use, that will depend a great deal on what you have for water. We're still lucky enough to have a ground well, and though it does have some mineral content, it's adequate. Chlorinated or treated water will not be suitable, as the chlorine will affect the solution and many water treatments use salts to soften water. Well water that's been run through a simple filter only should work fine. Alternatives include bottled water or sterilized water.

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