Hydroponics basics

by Elizabeth Beavis
Lately we have been growing tomatoes in a hydroponic system. They are growing stronger and taller than any tomatoes in my garden. I thought you might be interested to know more about hydroponics, the system that we use and the pros and cons of hydroponics in general.

eight acres: hydroponics basics - is it sustainable?
Tomatoes day 1

What is hydroponics?
Hydroponics is a method of growing plants using a nutrient solution, in water, without soil. There are a number of different types of systems, depending on how the plants are supported and how the water drains. See Wikipedia for more detail about all the different systems.

Why use hydroponics?
When you live in a hot, dry climate with sporadic rainfall, a system that consistently delivers water and nutrients to plants naturally results in better produce compared to growing the same plants in soil. It all sounds great in theory, but there are a few issues which I’ll discuss below.

What system do we use?
We have a flood and drain system that Pete set up years ago. He built a trough the right size for a grow tray to sit on top. On the tray we place nine pots filled with media (we are currently using clay balls and vermiculite, and have used find gravel in the past). A small pond pump is submerged in the trough and feeds water through plastic tubing to each pot. We currently have this running continuously as the pump is a bit small, so its just a trickle to each pot. We then plant seedlings in the media, and add nutrient solution to the water. We use an electrical conductivity meter and a pH meter to monitor the nutrient levels and add more nutrient or water as required. The water is continuously recirculated, so water consumption is very low compared to gardening in soil.

eight acres: hydroponics basics - is it sustainable?
Tomatoes week 2

Why did we stop using it for several years?
We haven’t set up our hydroponics system since we moved to Nanango five years ago. There are a few reasons for this:

  • We have never been comfortable with buying nutrients, they are expensive, most are imported, we’re not sure what they are made from, and its hardly self-sufficient to be buying nutrients all the time.
  • We bought an aquaponics system just before we bought Cheslyn Rise, which solves most of the above problems, but we haven’t had a chance to set it up yet, its just not high on the to-do list! (but its safe in a corner of the shed for when we’re ready).
  • The electricity requirements of the pump (which will actually be higher for aquaponics, because it needs a larger pump), there is probably a solar option, but we haven’t had a good look so far.

Is hydroponics organic?
Hydroponics is excluded from organic status by most certifying agencies simply because it doesn’t use soil. There is some controversy around this. Obviously producers of hydroponic produce would benefit from organic certification, and many do not use pesticides anyway (as it can contaminate the nutrient solution). However, from everything I’ve read about soil microbes and their interaction with plants, I can’t help but agree with the certifiers. Hydroponic growing is not natural and requires additional input of balanced nutrients that could be provided by soil microbes, so I don’t think it should be recognised as organic. However, hydroponic growers could establish their own standards to certify for best practice (free from pesticides, organic nutrients used, energy efficiency of the operation etc). Whether consumers can cope with yet another system confusing their food choices is another issue!

However these considerations for commercial hydroponics growers should not discourage the backyard grower. There are certainly things that can be done on a small scale to improve the hydroponics system, and if growing in the soil is not working for you, this may be worth a try.

eight acres: hydroponics basics - is it sustainable?
Tomatoes week 4

What other options do we have for providing nutrients?
Aquaponics is the ultimate closed system, it is a combination of hydroponics and aquaculture. This means that you grow fish in a tank and feed the waste water to the hydroponics system. Nutrients are removed from the water by the plants and the clean water is returned to the fish tank. The only problem is feeding the fish. You can buy commercial fish pellets, but again, that is not self-sufficient. I am experimenting with growing meal worms and compost worms for the fish (and chickens) and there are some other options for plants that can be grown as part of the system and fed to the fish. If this is successful in providing the fish with 100% of their nutrition, then we will have achieved a hydroponics system that is entirely self-sufficient with no outside inputs.

At the moment its not the right time for us to be growing fish, so we have been buying commercial nutrients again (we had some left, so we used that up first and then I popped into a hydroponics shop to get some more). Fortunately now there are some better options for commercial nutrients. The standard nutrients are made from soluble fertilisers, exactly the same as the ones used in conventional agriculture, that’s why the plants grow so big so quickly. You can buy completely organic nutrients, made from plant material and guano only. You can also get hybrid nutrients, which contain the soluble fertilisers as well as organic nutrients such as fulvic acid.

Even if we were to buy the fully organic nutrients, we would still be stuck BUYING something. I can grow plants in the garden without buying anything, and even if they don’t grow as well, at least they are virtually free. I discussed this with my friendly hydroponics nutrient retailer and she said that some people do run their system entirely on compost or wormfarm tea. She said that the system would not be as balanced, and the plants won’t grow as well (she also said that about the organic nutrients I could buy, this sounded just like what a conventional fertiliser salesperson would say about organic growing). She did say that I could start adding some compost tea to the water and reduce the nutrients and see what happens. (I bought this brand of hybrid, and even better its made in Australia).

The tomato plants are doing really well at the moment, so it would be silly to jeopardise their development by fiddling around with nutrients at this stage, but Pete did say I could add a little wormfarm tea. Pete and I have been talking about setting up a second system and running them side-by-side. One would be fed with bought nutrient solution and the other one we would feed with nutrients sources only from our property. This would of course be a competition. I’m really keen to test this: can we grow hydroponics in a self-sufficient system? And if the production is lower, but we save money on nutrients, does the cost-benefit balance out?

What do you think?  Have you tried hydroponics?  Any tips?  Any questions?

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