Grow Organic Food

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Every so often this story crops up somewhere or other; the latest has cropped up on City Farmer who is reporting work carried out at California State University. The idea is not new but is it good way to feed cities? Is it sustainable? The answers to both questions is no.

Hydroponics has been around for a long time and nothing much has changed about the way it works. The idea is simple; as plants can only take up nutrients dissolved in water then it follows that the easiest way to grow food is to supply all they need in the water they drink. It’s as simple as that. I should add that which ever way you supply nutrients, whether it’s by using manure or any other fertiliser, the nutrients always end up dissolved in water. That is the only way that plants can feed. The photograph shows the roots of hydro watercress.

The problem with hydroponics is that the only to get a stable, reliable and quantifiable dose of nutrients into water is to use artificial fertliser specifically formulated for hydro growing. It’s no use just chucking in a handful of your usual plant food and hoping it will work.

Some will say there is nothing wrong with that but the fact remains that producing hydro nutrients requires the full force of the artificial fertliser industry. That means mining minerals, moving them round the world and then a lot processing to make fertiliser. Not only does that take enormous amounts of energy it also uses up raw material at an alarming rate. The photograph shows tomatoes in a hydro tank.

There is already concern that the world’s supply of phosphate is reaching its end. That will cause a crisis in food production for those relying on artificial fertilisers so using more for the large scale adoption of hydroponic growing will just hasten the crisis. The other big problem with hydro is that it requires a constant supply of energy. The nutrient solution is pumped around by electric pumps and it is usual for there to be heating and lighting in a hydro greenhouse. Some of the energy consumption could be offset by using renewables and simple systems.

Having said all that hydro could be an attractive solution for growing food in cities if it could be achieved in a closed loop system. Some years back there was a trial in Australia of nutrients produced by worm composting. The hydro system was setup on the roof of a restaurant and was to supply salad greens to the chefs. The food waste was to be composted on site and nutrients made to feed the plants. If it had been solar powered it would have been an almost ideal closed loop waste management food production system. I could never find any information on what happened so assumed it failed. If you know different please tell me.

I have also done my own experiments over the years and have tried to produce a closed loop growing system. It is certainly possible for anyone to make liquid fertiliser by pressing comfrey leaves and nettle leaves (separately.) That makes quite a good balanced plant food but because it is made from plants it is not consistent and not stable so is of no use for media less hydro systems. It does work with media based
systems that act as a buffer and iron out any irregularities.

I know there are several brands of ’organic’ hydro nutrients on the market but there is still the problem that they break down over time and need a lot more management. I may be wrong, it could be that some clever person has solved the problems but if they have they have kept it very quiet!

My recommendation would be to use recycled containers of home made growing media and home made fertliser. That does work and IS sustainable.