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Aquaponic Nitrogen Calculator – The Ratios

Well after all that, we can take a break and have a look at the results from our aquaponic nitrogen calculator.  We have calculated our fish production, worked our our losses of nitrogen and the volume of vegetable production per year.  Now lets take a look at the growing area we need for our farm and some interesting ratios as a result of previous calculations. Bingo, there it is.  We have used the standard number of plants per square meter as most hydroponic farms do and the results very much speak for themselves.  We need at least 6458 m2 of actual growing space for our crops and we are feeding a meager 15 grams per m2. The plant area is the growing area and does not include seedling or other working areas.  Generally most greenhouses will use around 70 to 85% of their space for growing so you will need to make adjustments to the greenhouse size depending on how you set out your growing gear allowing for adequate working space.  There is nothing worse than working in a greenhouse that is cramped and difficult to move crop through.  So be generous, you will thank me later. The growing area is only for the plant side of the farm and does not include the area required for the fish shed.  We will work that out later as we continue with our fish farm design series. Note the plant to fish weight ratio of 9.25kg of veg to 1kg of fish production.  This is very close to some of the published data where they get between 10 and 12kg of growth for every kg of fish.  The final area for every 1 kg of fish is more for your interest than anything of significant use. Let’s switch it up a bit and take a look a a few minor changes and see what happens: Normally we would run a farm at 25 plants per square meter but there are some cultivars that do not need that kind of space which allows us to increase the density of plants.  A word of warning though.  If you have poor air circulation and your plants are too dense, ventilation of the crop will become problematic and you will find mold and fungus are your worst enemy.  Also if plants are too packed in, observing any start of an insect infestation will be difficult to spot as the overlapping leaves provide great protection for the insects you don’t want.  Further to that, if you at high or low latitudes or low solar exposure, you may find keeping your plants with a little more growing space will allow them to spread out and capture more of that solar energy. Anyway moving right along.  The above scenario is the exact design example we used for our project in the UAE.  We had plenty of sun, humidity was low and excellent ventilation in the greenhouse.  The farm still grows at a density of 48 plants per square meter.  We tested some 90 cultivars at that density and switched them back to 24 plants per square meter and the higher density netted higher yields.  However, there were a few plants that did not like it at all.  We even pushed to 96 per square meter.  This extremely high density will only work with some crops and not many.  This is to say, if you are not experienced with the level of designs we do, stick to the 25 plants per square meter.  You can always drill more holes in your raft if you want more later. No I am not doing anything suspect in that water….. That particular cultivar of Radish really enjoyed the higher density however it struggled with nutrient issues due to low oxygen.  Generally, with this plant, once it gets so big (grown for its leaf not the bulb), energy is driven into the bulb and you miss the opportunity for a leaf harvest.  The minor yellowing is one of the results of that. Now we have all worked through that, this is what the overall calculator looks like with the data we have entered.  Very shortly I will release the calculator for you guys and gals to have some fun with.  Until then, enjoy!…

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