Feb 09

Why Grow Head Lettuce In A Commercial Aquaponics System?

Well, aquaponics works even better than hydroponics, according to research done in Alberta, Canada. So you are going to get a lot more head lettuce a lot faster out of your mature aquaponics system than you would out of soil.

However, the advantages do not stop there. An aquaponics system produces crops on a ‘conveyor belt’ type continuous cropping system. This works well outside in the tropics, or inside a climate-controlled greenhouse elsewhere. It means you can get fancy lettuces all year at twice the amount, twice the speed you would in a soil based system.

Pest control is also safer and easierin an aquaponics system. You are not using soil, so soil pests such as nematodes have been eliminated before you start. If you have a problem with snails, sunfish will live under the rafts and they love to eat any snails that crawl within reach! Using friendly insects such as lacewings and ladybirds (ladybugs in the U.S.) means that the more greenfly etc. there are, the more your friendly insects will feed and breed, provided the conditions and air temperature are right for breeding. So you get more friendly insects for free! Of course, there is always the risk that your friendly bugs will feast themselves out of food, but that’s what you want. No more greenfly etc. To keep a reserve supply of friendly bugs, it may well make sense to have an on-site bug breeding station if you are in large commercial lettuce production. Otherwise, there are plenty of professional friendly bug suppliers out there who will send you bugs by the bushel in the post for spreading about your fancy lettuces with a camel hair brush.

Staffing costs are around 3 qualified and expert staff per 1/16 hectare aquaponics system, plus extra part-time semi-skilled staff for harvesting and tilapia fish processing as necessary. Because you have a 24/7 ‘conveyor belt’  floating raft system, which produces batches of marketable vegetables (fancy lettuces, for instance) once a week, you need temporary harvesting staff on an ad hoc basis. Once the aquaponics system is up and  running efficiently, around 8 weeks from pressing the on button, you will get set amounts of vegetables such as fancy lettuces  ready to harvest out of the system. You will need extra semi skilled labor who are trained in personal hygiene to handle these harvests (once a week, ALL YEAR ROUND). The tilapia fish come on line at table size six to nine months later to be harvested every six to twelve weeks depending on the number of tanks in use. Before that the fish have been growing from babies to adults and fertilizing the water for the plants. No back-breaking work is necessary since the vegetables are grown in fish water on floating rafts. These are lifted out entire onto trestle tables (see picture of lettuce harvest at the commercial aquaponic system University of the Virgin Islands below) and the vegetables harvested at table height.

The tilapia fish only pay your operating costs, since they grow much more slowly than lettuce. Lettuce seedlings take 29 days to grow to marketable size in an aquaponic system. This means you can have at least 12 harvests a year, or more if you seed and harvest smaller quantities of head lettuce or fancy lettuce every week.

Lettuce production compares favourably with other vegetables such as cabbages, which have longer growth periods and lower price points at sale. To recoup the cost of installing your aquaponic system, you need to get the maximum profit per crop and as many crops as possible per year.  Therefore you need to grow crops such as fancy or head lettuce which, with their 29 day grow out period, reliability, marketability, and high market wholesale price for quality organic produce, make commercial sense.

Other crops with short grow out times and marketability such as basil also make sense, as long as you have a high local demand for it. There is no point in growing food you cannot sell immediately at a good price and in sell-out quantities!  Head lettuce fits this bill. So to begin with it is advisable to go in for lettuce production. Don’t forget that after the first six months or so of lettuce production you will also have to market the tilapia from your fish farming.  It is best to get good at marketing two main products before you diversify.  This is not a hobby and you cannot afford to muck about with experimental products at the initial stage.  Stick to a small range of products such as head lettuce which have guaranteed marketability and local demand.

Productivity in a commercial aquaponic system depends to a large extent on professional and trained management who stick to the requirements of a well-thought-out standard operating procedure for this form of agriculture. This should integrate fish farming and hydroponic vegetable production properly. The unreliability due to weather and pest attacks that characterizes soil agriculture has largely been eliminated.   Pest and diseases are usually amenable to properly exercised biological pest control. It is only human error, ignorance and neglect that can ruin your lettuce production, tilapia fish farming, and impact the profitablity of your aquaponic farm overall.  It is here that the need for proper professional training and experience will make itself known very rapidly.  Aquaponic farming is not a just add water agriculture technology.  You need to know how to keep fish, especially tropical fish, and how to grow vegetables both organically and in an aquaponic hydroponic system.  This is NOT the same thing as hydroponics using chemical solutions. Not at all.

If you have a greedy market locally for fancy lettuce, it may well be to your benefit to invest in a reliable commercial aquaponic system and training in this form of agriculture.  You need the right trained  staff and the right equipment to get started with your commercial aquaponic farm. Several tons of fancy lettuces a year can be grown on only one-eighth of an acre (1/16 of a hectare), along with five metric tons of tilapia fish a year from your aquaponics-integrated intensive fish farming efforts. Given the right attention to detail and diligence, of course!

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harvesting aquaponic lettuce from a floating raft

Harvesting aquaponic lettuce from a floating raft, UVI, 2010