NFT - nutrient film technique is a system of shallow gutters each with a emitter tube and draining into a water capture manifold. From there it returns to a reservoir where the submersible pump runs twenty four seven. Lots of words but really it is very simple. Nearly everything under the "Kratky" section and the "Germination" section remains the same. I will expand on a couple of topics here and drill down on several others. Needless to say this method is highly efficient and one of the standards used by hydroponic growers worldwide for the production of leafy greens. If this system were in a greenhouse in warm weather climate the natural sunlight and reservoir management are all you need to produce a never ending supply.
This however is where we leave a process of nearly hands off and enter a much more hands on activity. You will begin to learn the importance of reservoir management. This doesn't mean a burden but you learn how pH and EC- electro conductivity interact. This interaction is a picture of what portion of the nutrient mix your plants are using.
At first this might seem intimidating but once you see the graphical picture the light bulbs go off and the wow factor sets in. At least it did for me anyhow.
Simple but important for the NFT. Well I suppose you could ignore this but it was only after I figured out the needed details and began to keep accurate growing records did I really see a quantum leap in the quality of the product we produced..
So here are the key categories to pay attention too.
EC - the electrical conductivity of the nutrient.
Electroconductivity meter. For now let's suffice to say if you want to understand this issue and the full meaning….there are pages and pages to describe it and way beyond the need or scope of this project. Suffice to say it boils down to how much the soup is charged. Generally for leafy greens we want the number under 2.0
Let's face it most people have a computer and it doesn't matter what kind. We all have access on our computers to a spreadsheet application. Enter the data and the spreadsheet can generate a graphical picture of numbers. While the numbers themselves at the start of this will be strange in a short period of time it is like taking your temperature. It takes on meaning and tells the story of your plants botanical health.
move the pH up - Potassium carbonate
move the pH down - Sulfuric acid.
What! Yep both are food grade and when correctly used pose no risks to your health. Be careful as both of these are considered powerful chemicals and can cause burns. When used in the quantities we use they pose minimal risk, mainly a splash risk for your eyes, Wear safety glasses when in use. For the Potassium carbonate it usually takes a tad or tad and dash on the crash day and one additional day. For the Sulfuric acid, 3.2 milliliters is the most I use and normally the climb starts at 1.5ml and goes up a small amount each day. On really big systems this is handled with a dosimeter pump that constantly monitors the pH, injecting tiny amounts constantly as the sensor picks up the increases. So what is a Tad. Well here are the measurements Tad: 1/4 tsp. · Dash: 1/8 tsp. · Pinch: 1/16 tsp. · Smidgen 1/32 tsp. They actually make these measuring spoons
This plot covers nearly a two month period starting and ending with a water exchange event. It was not till I started a rigorous record keeping plan did I begin to see what was actually taking place with the nutrient. Unlike a raft system where there is more water present that the plants will use to complete their growth cycle (at least on these very small systems) this is not the case with NFT. As you look at the graph you can see a number of downward spikes followed by an upward drift, until it repeats again.
With each fresh charge of water and nutrients the Calcium, Magnesium and Potassium all positively charged are rapidly picked up by the plants. The pH goes down with the plants removing these positive ions. The pH is brought back in range with a buffer, in my case I use Potassium carbonate. Within a couple more days the plants are using more of the Nitrate which has a negative charge. With the removal of the negatively charged nitrate ions the pH continues upwards. Through trial and error I got to where I am today doing a boost on or about day nine in the cycle. The pH is the the indicator. The pH levels will bounce back up around 6.5 each day and finally pop to 6.8 or so. Time for the boost. The same is true at the end of the boost cycle where two things call for full exchange. One is the pH levels but at this point nearly 25 gallons of nutrient has been consumed. I pull down the remainder till I can't suck out anymore. Add 30 gallons of water and new nutrient for that amount of water and off we go again. Remember whenever you add nutrient you want to add it in a balanced form. The boost is highlighted as orange circles. Each spike is a water change out. Do you need to get this involved? Hmm, I will say absolutely with the NFT. I don't see the need with the simple Kratky system unless you are growing lettuce. Basil, Arugula and Mustard are really forgiving. Basil is happy at pH levels near neutral or 7.0. Arugula and Mustard like their nitrogen. Lettuce though is more particular. Get the soup over charged and you end up with tip burn. To little calcium and you end up with weak plants that suffer from all sorts of ailments.
Is my information vetted by a higher source? No I have not submitted my thoughts through a peer review process. One of my favorite expressions comes from Hawaii and the words in Hawaiian are "I Ka Nana No A 'Ike". Meaning = By Observing One Learns. I have taken this to heart since first learning the expression. It is serving me well. The size and quality of the product tells its' own story.
There are lots of nutrient regimes on the market. Under my discussion of the "Kratky" approach I stuck with the "Materblend" formula. It works and if you are happy stick with it. I have not run the "Masterblend" in the NFT reservoir. I use "Hydro-Gro Leafy" and Calcium Nitrate. A two part mix. "Hydro-Gro" is sold by Cropking out of Ohio. They are a large hydroponic equipment supplier as well as large commercial High Tunnel Green house supplier. Same as before mix your nutrients in separate containers. "Hydro-Gro" has a base table of how much of each component for the amount of water. I calculate the boost amounts simply by determining the EC of the tank as a percentage of the target EC. Using that number I calculate the amount of the macro/mini portion and calcium portion needed to return the reservoir towards the target range. In the big league water samples would be sent off and a more accurate assessment of each portion would be achieved.
This was a crucial step in my learning curve. Early on I went from the "Nicu" stage onto the main table. I was always two steps behind maintaining the harvest sequence. I started to play around with just holding them in the tray. Nope. It works for the raft but the plants were inconsistent. First off putting a bigger plant with lots of roots into a net cup is far different than putting a 1" cube in a 1" hole and not damaging a very fragile root. Bought four more gutters and four lights and set up what I call "Kindergarten" All this is - an extension of the main table. I hold them here two additional weeks so they are approaching a special growth point. The exponential growth phase. When they hit the big table they are in full go mode. Roots are well developed in the gutter and undisturbed. During the course of the next several days the newly moved plants will almost double in volume. This maximizes the opportunity of the big table. Mine is two layers of 6 gutters on each layer. Six cells to each gutter. Every pair of gutters turn over every five weeks. It would be nice to turn 3 gutters per week but I would need two more Kindergarten gutters and space is already a premium.
Simply, my term for the Kindergarten merely relates to the start of school. The nursery gutter is often the term used in the literature. But look at the close up picture. Think about trying to plant a tiny fragile root into the gutter cover hole. On some gutters the hole is quite large. The gutters from American Hydroponics for instance are a two in hole. Their nursery gutters also have a large diameter hole but are spaced close together. When the seedlings are ready to plant, an extra transplant step is required. With the Cropking gutters, the seedlings go directly into the main gutter. No additional steps. My problem was mainly limited space just 200 square feet. I soon realized that if I wanted to harvest two gutters a week I needed another 18 inches in width to the table and it just isn't there. Furthermore the added expense of four additional high end LED lights to cover the added width didn't pencil. (To recap I have two layers stacked) The baby seedlings also don't need 16 hours of light. The solution was to separate the seedlings on a different rack with their own pump and timer. This also facilitates running an intermediate nutrient concentration so as not to burn there tender roots. On transplant day the seedlings now at a bit past three weeks old go onto the main table. An empty set of gutters goes to the nursery rack and planted with starts from the "NICU." By the way if you don't understand the term, it stands for neonatal intensive care unit. I find it apropos.
Empty four foot gutter ready for transplants. Each week we clean with bleach and wipe out with peroxide to kill any lingering chance of disease issues. This is the lower of two racks on the kindergarten rack. Alternating back and forth guarantees a steady supply for the main table
At the three week point ready to move onto the main grow table
This is a closeup: This is a very delicate stage and these are ready for their first week in Kindergarten
With reservoir management all wrapped up the rest is now up to the pump and light timers along with the plants in the system. Not much more interaction needed. Observe and watch for pest and disease issues. The previous graphical example is what I have found to work for my grow room. This is not to mean it won't work for someone else but should only be used as a guideline until you develop your own picture. I wish I had had the graphical representation when I started. Lots of ink has been spent within the literature and I have possibly oversimplified the process. Just seeing the crash after two days on fresh soup and pulling it back up and then seeing the steady hill climb was very revealing. Now it is a routine. There are still times when Pythium will develop in the roots and yield will be compromised or poor air flow due to high humidities result in sweaty bottoms and result in grey mold or Botrytis. But by paying particular attention to the EC and pH, the interaction of the two which may seem like small things I am at a point of fewer overall negative issues. Seasonally the curve will change. In the spring I bring the EC lower. Warmer days in the grow room mean the plants suck in more water. The EC needs to be reduced. Likewise in the fall the EC raised as the plants don't drink as fast. Wait, I'm growing is a temperature controlled system. Yep I know what you are thinking. I did too. I do not have that answer but I know that now at the waning days of winter it is time to cut the mix back for Spring and Summer.
Root zone health is essential to successful growing. The above shows the roots from a completed line of lettuce. This is actually flipped. You are looking at the bottom of the root zone against the gutter. This tan color is typical. What you don't want is to see black root streaks. Indicative of "Pythium." Any sign of it when cleaning, Drain the system, wash the reservoir with a mild Hydrogen Peroxide solution and refill with fresh water and nutrient. You will know since the size of the plants in the gutter are falling behind those that are up and coming.
I have one last section to add. The Bato Bucket system. I will probably work on that during the course of the spring so it will be a while. However there is one last area here to explore. I need to review a lot of the early literature I read during my startup as a refresher. But here is the thing. Numerous volumes all talk about you need to plant what you harvest every week. Yes absolutely true. They talk about having a nursery of seedlings to plant "When Ready," okay but either I completely missed what I am about to share or they didn't cover it. They don't talk about how long it takes to get to that ready stage and having healthy seedlings at all three steps. For me the timeline is 3 weeks. Be prepared to allocate space to carry the additional plant load. If you are cutting 12 plants per week, you have another 48 plants in the main pattern plus 24 in Kindergarten, 12 each for week one and two there, 12 in the NiCu with their cotyledons out and then the final set of 12 under the curtain germinating which equals the current week cut. That translates to a factor of 8. Just imagine if you were cutting 1000 per week.. This last part may just be the keys to driving the Lamborghini. It took quite a while to fully understand the intricacy of this one issue. It also took a great deal of trial and error. Once I got all of this completely in sync…. Well the supply side is the smallest issue.
3181 Mill Bay Rd. #1 Kodiak Alaska 99615