Lettuce production thoughts.
I was thinking that lettuce production could be made a "mass production" system relatively easy with 3 systems. I wanted to run my thoughts through here and see what people think.
First system is the seed starting system. It will be a virtical stack of rails each with an NFT/spray system. (similar to the one I have on my first system) The rows will only be about 6 inches apart from eachother (virtical spacing) to let you put a large number of rows on top of eachother. The water will be able to get more airation through the splashing of the spray. And you can have a single Flouresent fixture on a hing to fold down to provide light to young seedlings. and you can get small plastic trays from your local garden shop to serve as humidity domes over each plant.
Second system would be similar. Probably slightly higher spacing virtically. The lights can be mounted just below the rail above, or still be able to hing towards the rear of the unit to allow more functional space when moving plants in and out. This system would be running the light strength nutrients, and would be for the mid ranged plants.
The third system would be the production system. This is where the mature plants will be and could have a few different designs... I would think an angled rail would be more space efficient with the roots being developed by this point. You could have this one with natural or supplimental lighting as needed.
This wouldnt take much room and could probably be downsized to a few 2ft wall spaces (with 2ft flourescent lights) with ease, and would let you produce much more lettuce than a single family could eat in most cases :P
This is just a thought. Let me know what you think and I might make a set for the personal entertainment value :P
How many lettuce heads are you wanting to harvest weekly? Are you wanting to grow more than one variety? If so, what types, and how many do you want to harvest of each weekly? When you say "mass production," are you thinking of a commercial grow operation to sell the lettuce?
I was figuring I could harvest as many lettuce as I can grow with my power/space constraints. More of a test bed for expanding later. The more I can grow in the smallest space with the least energy, the more I can plant for when I get some land. I will probably be wanting to do some commercial growing for the local area later for some side income/to keep me busy.
The reason I asked was basically because the amount of plants, as well as plant needs would dictate the best type of system. But overall for a continued supply of lettuce heads, 3 separate grow stages in rotation is a good plan (seed propagation, seedlings, then maturing plants). However the NFT/spray system will become complicated and more expensive on a large (especially commercial) scale. As well as the spraying will become unnecessary with the 3 growing stages because the roots will grow long enough in the second stage. The two most common methods to grow lettuce commercially are either NFT, or Water Culture systems. Weather the system you use for the maturing lettuce plants (any variety) is an NFT, or Water Culture, I would build the the propagation and seedling setups the same.
Propagation trays you can get at most hydroponic shops and cost only a couple of dollars. They generally hold about 72 sprouts (cells) in each (10x20) tray. Two twin 2 foot florescent lights (T5, or T8), would be sufficient for up to two 72 cell propagation trays for lighting (less light would probably result in elongation). Or two 4 foot twin lights for up to five 72 cell trays. Depending on location and time of year, you may need to use artificial heating or cooling to keep the air temperatures in range.
The seedling setup
Each sprout would now be transferred/transplanted into the basket/cup they will mature in to keep labor to a minimum, as well as allow the roots to grow through the baskets/cups (making it imposable to transplant them again without root damage). Smaller heads like butter lettuce, or grand rapids leaf can probably do fine in 2 inch cups, while large heads like romaine lettuce will probably take 4 inch cups.
The easiest, simplest, cheapest, as well as most space productive seedling setup I can think of is a water culture system. How large depends on how many plants you will be growing. For a commercial setup, a custom built system would be the cheapest as well as most productive. But for a home system, modifying short plastic storage totes with a lid would be the cheapest, as well as simplest (about $8 ea at wal-mart). Using storage totes like the ones I've used in the past. (picture attached). Light proofing the base by painting it black, then white to reflect light. Then cutting holes in the lid spaced closely together (like the attached pictures). They wont be in the system long enough to become crowded.
The main system for maturing plants
The easiest main system could be either a Water Culture, or NFT system. Depending on how many plants will be growing in it either would be very productive. Fallowing the same design setup as the seedling setup, and expanding it to multiple growing chambers as needed is relatively simple. Just spacing out the holes for the lettuce plants farther apart to accommodate the full grown plant. Like to 8 spots per container like I did with my lettuce. However if a large number of plants is planed, or large verity like romaine lettuce are planed. A costume built system would be more cost effective, as well as productive. But again NFT systems are very productive for growing lettuce, although the 4 inch square fence post tubing is very expensive for such a setup. But again large varieties like romaine would benefit from the oversized tubing because of their size. Though small varieties could just as easily use rain gutter downspout tubing instead.
Deciding on how many plants you want to harvest weekly will tell you how large of a system/s you'll want/need to rotate production. As an example if you wanted to harvest 1 lettuce head every day. That would be 7 a week. Generally lettuce plants (most smaller varieties) take about 6 weeks to go from seedling to harvest. So 7x6=42, then add another week for the seeds to germinate (7 more plants)=49. So in that case you would want a minimum of 49 total plants going at any given time to ensure the harvest quota of 1 lettuce head harvested every day. Also each week starting a new batch of at least 7 new sprouts (probably a few extra in case some don't germinate).
So depending on your growing conditions (a large factor in how fast they grow). Sprouts would be ready to put into the 'seedling system" about a week after germination, where they would remain for about 3-4 weeks. From there they would be large enough to go into the main maturing system for another 2 to 3 weeks. So I would expect it to go something like this;
14 to 28 germinating sprouts at any given time (first 2-3 weeks)
21 to 28 plants in the seedling system at any given time (next 3 to 4 weeks)
14 to 21 plants in the main plant maturing system at any given time (last 2 to 3 weeks)
Total growing time "once seeds germinate" between 6 and 9 weeks. Then taking these numbers I would design and build the system/s to accommodate at least that amount of plants. Then I would also know what I could realistically expect in the way of harvest, as well as cost to build, space needed etc.. Even energy consumption once I knew the amount of lights I needed, air pump/s, water pump (if the maturing system was a NFT). By gathering the total wattage for each electrical device, and figuring the amount of hours each will be used. Then imputing that data, as well as what I pay per kilowatt hr (found on your electric bill) into a Electricity Cost Calculator.
Last edited by GpsFrontier; 08-08-2011 at 01:23 AM.
Thank you for the Very impressive and thought out post. It gives me a good bit to think about and work on for my system. You make a lot of very good points, and I will probably use a lot of your ideas.
I will let you know what I come up with. I will be rethinking a few things in my system. and finding some more information about what I am using I will be able to manage my grow medium a lot better, and cheaper.
Excellent thread... a few questions
First, thank you very much for your thoughtful and informative posts in this thread. As suggested, I went to WalMart and bought 4 of their 10 gallon blue Rubbermaid Roughneck totes with lids ($8 each) and drilled six 1-7/8" holes in each lid to accommodate 6 of my 2" netpots with lettuce seedlings that I had already started in rockwool a few weeks ago. Also as suggested, I added an airstone connected to an air pump, added my water and nutes and can't wait to see (and taste) the results. However, this experiment raises a few questions:
1. Do you have any suggestion as to how high the water level should be inside the totes? Up to the top? Just above the bottom of the netpot? Does it matter so much as long as the roots are wet and the water is aerated?
2. Re: the seedling stage. After germination, I read that you suggest a storage tote with more holes spaced more densely together for growth prior to moving into the main system. Other than the closer spacing of the holes, do you do anything different in the "seedling" stage than what you do in the "main" stage? For example, I've also read that the nute solution for seedlings should be 1/2 strength versus growth stage. True? Do you give your seedlings more sun/less sun? Lower waterline of the nute solution to just wick the rockwool versus immersion, etc.?
3. In your pictures, I see you built a shade over your lettuce. I live in Central Florida where our afternoon sun is nearly comparable to the intensity in AZ. Did you find that without shade your lettuce couldn't handle the intensity?
4. What propagation medium would you suggest for lettuce?
5. Finally, for a custom DWC lettuce growing setup, what do you think about using a Firestone PondGard EPDM "Fish Safe" liner inside a wood frame with blue foam polystyrene as a float surface? Any suggestions on how deep a DWC system should be? Is EPDM safe? Any better materials to use?
Thank you for any suggestions or experience you can offer.
I think I can answer a few of those for you.
I germinated and keep my seedlings in a 1/4 strength solution. I tried a 1/2 after the 4th leaves, but they started to curl under. The advantage of the 1/4 strength is that you can germinate them, and the will be able to use the 1/4 strength for a while, not to mention my lettuce were not happy with (and still are not going on their 5th tiny leaves) the 1/2 strength. I get a lot of curl under and have to dilute it back down.
The water should be about the bottom of the netcup maybe just over the bottom. The rockwool will wick the nutrients up and you don't want to drown the poor things :P I would start with just over the plastic on the bottom of the netcup. If the top of the rockwool feels dry sitting at that level raise it a little. If it feels too wet try bringing it down just a hair, but if the rockwool is just touching you should be fine.
I grow in flouresents, and they get a full 18 hour day. But you will definitly want to do some shading from the FL direct sunlight. I am in central florida as well and I am almost certain the humitidy blocking the ability of the plant to breath and the direct sun would cook the little leaves fast.
I really enjoy using polyester batting (baught at any craft store with a sewing section) You cut a little circle the size of the intented net cup. put the seed down in the fibers a little and keep it moist. It will germinate nicely.
(polyester is what STG is made of)
It is PH neutral and non reactive. It is also acid resistant, so low PH levels won't degrade it over time.
I can't comment on the materials you are asking about without more research into them. CPVC gives off fumes over time, and that is increased with higher acid content. So never use CPVC or your plants could taste like plastic or worse could happen. I haven't done much research into what the hazards are, but regular PVC is cheaper. There is also flexible PVC so you might be able to get some PVC based liner. The system your thinking about would work great for lettuce. It would only have to be about 4-6 inches deep, depending on the lettuce you are growing. They don't take a whole lot. If you do use that I would think either a circulation system with an airated res, or good airation in the floting system would be important to prevent root rot. But I have seen people get away without it.
Hello Paul Perkins,
Water level is also the reason the containers/storage tote I used were only about 5-6 inches tall. With the baskets in the lids, the water level in the storage totes only needed to be about 4 inches high. Even so, it still took about 6 gallons of nutrient solution to raise the water level to where I wanted it. With 8 plants in the system, and small plants like lettuce requiring a minimum of 1/2 gallon per plant of nutrient solution. 6 gallons of nutrient solution was plenty of water. If it were deeper, it would have just took more nutrient solution to fill.
But there are a couple of notes here. First, colored plastic cups would be best for protecting the roots from light. But at the same time the system should be light proof anyway, so colored plastic isn't necessary while the cups are in the system. Second, baskets have slats all around them. Allowing it possible for the bubbles bursting on the surface of the water to wet the growing medium. So if using plastic cups and making holes in them, you wont get the same effect of water getting to the growing medium by spritzing. The cups would need be a 1/4 inch or so submerged to wick up through the coco fiber effectively. so it really depends on how many plants are planed, labor, and personal preference.
How deep should a water culture system be? Well first DWC implies "deep water" (Deep Water Culture), and is generally more than 10 inches deep, but that's the only difference. As for how deep should the water be, how big the plant being grown gets is important. Smaller plants have smaller root systems, thus shallower water is workable. For most small varieties of lettuce I would probably go with 4 to 6 inches of water. But for large varieties like romaine lettuce, I would probably want at least 10 to 12 inches. I haven't grown romaine, so I don't know how large the plant gets (only how big the heads they sell at the market are). Either way for a large custom build, I would also use a water pump, and secondary reservoir to circulate the water thorough the system better.
Your post hadn't posted yet when I started my post, so I didn't see it until I was done. Also I think I'll look for some of that polyester batting you speak of. Is it cheap?
Last edited by GpsFrontier; 08-10-2011 at 09:51 PM.
It is fairly inexpensive. I got 2 bags of it from the local micheals for $4.99 each. The stuff I picked up is in a plastic bag that looks like a small pillow. It is a little packed in and is just the loose fibers called poly-fil for stuffing bears and pillows and such.
The loose fiber you can adjust if you want (fluffing it out to hold less water/have more air room) The batting is more like what you would see as a cusion topping in your sofa. you can get either. It is a matter of shopping around to find where you can get it inexpensively. Some places want to charge a lot for a little..... Remember this is the same stuff that is used to make soda bottles, and is not expensive. (the same things used to make those little plastic cups you use most likely as well). The same plastics have a million different names depending on how it is packaged for the consumer.
The bag is about the same size as a bag of perlite only much fluffier. It does act differently than perlite and such so you might want to watch how it reacts in your system at first, but I am really enjoying using it. The two little bags of fluff will probably last me a while. Atleast till I fill up the giant net pots for my tomato plants :P
But it is reusable if you can get it cleaned out. I am going to see what some sulfuric acid does to it (if anything considering the battery boxes are made of similar plastic) It might be a good option for cleaning (dilute Sulf acid). You can get some decently strong acid from an auto store for less than $10 and it will make a lifetime supply of PH down lol... I might as well check it for other uses as well :P though I could always rot out the roots that get caught in after a grow and then sterilize after if I wanted to be a bit more "thrifty" about it. It all depends on how you want to use it. The material is VERY easy to work with once you notice it's tendancies with water holding and such. I leave my pump spraying on my plants 24/7 and they don't complain about too much water. It seems to hold the water just how the plants like it.
PS: I just opened up a bag to see how many 6" net pots (the ones for 5gal buckets) it would fill... I filled up 5 of them and the way the stuff expands when I pulled it out of the bag, I can barely tell I made a dent in the bag after filling all 5 of the 6" pots.. The stuff is very soft and light. VERY comfotable to handle. Imagine your plants resting comfortably in the guts of a fluffy teddy bear :P The kids were all about helping and they were rubbing a piece on their faces after I told them to stop putting it in the pots :P
I think the tomato plants will enjoy it. The roots will have to resistance growing out wherevery they want. And if the wieght to the plant pushes the batting down it will be easy to just add a little more to the top. (the amount needed to fill the 6" pots will squish down to nothing with a little wieght.)
Last edited by jamromhem; 08-10-2011 at 10:43 PM.
I must say that the pictures you posted are VERY impressive. Each leyer would hold 400 seedlings (by what I was able to decifer from the image).
If the bottom layer was the seedling tray, (you can stagger out 200/200 at a couple weeks apart) and the second layer held 200 mid age plants and the top 200 mature you could have a harvest of 200 a week or two (depending on the type you grew) in what looks like a relatively manageable area. I will do some more drawings on your design to see what I can come up with on that regards. I love the idea you have there.
On second thought the mature (heavier) plants should probably be on the bottom lol.. But I didnt want to go back and retype it.
That looks like a wonderful way to get a large amount of lettuce going in no time. It would easily feed a few families and take little investment comparitavly.
Great information, thank you!
Thanks to both of you for saving the lives of 24 lettuce seedlings by telling me not to drown them (which process was already well underway as my nutes were right up to the top of the tubs). I've dropped the nutes level so that the netpots are sitting just barely in the solution and will check and adjust for overwicking periodically. In hindsight, rockwool was not the best choice for DWC because it retains too much water vs. air. Will try the coco chips next.
GPS, thank you for posting your extremely impressive CAD drawings. Yes, indeed, your system (except for the inner recirculating tube) is virtually identical to what I had mind -- down to my plan to "go vertical" with 3 levels with OSB on 2x6 vertical supports with 8" sidewall frames in a 12' x 20' greenhouse!
just a thought. I really like the way the polyester works for my plants. I have the bottom of the netcup being sprayed 24/7 and the plants are loving it.
it wicks just enough while still draining enough to prevent drowning.
I would give it a test if you are concerned about water retention. It will probably be comparable to coco, but I would think it a little cleaner. but I havent used coco so I wouldnt know directly. I just know my lettuce and tomato seedlings are loving the STG cubes and the polyester fluff I have them in. and the $5 i spent on the bag will probably last me years lol.. I underestemeated how far it would go and baught 2 bags, I am not sure I will be getting to the second bag for a while, but I still have a few herb setups to do, and my new lettuce plants to get going.
I will be testing the polyester in the future, price wise it's cheep enough. But I wont be trying to reuse it. Unless all the old roots are completely disposed of, they'll just decay and be food for pathogens. It's too much trouble to try and clean, and too much risk of pathogens for me. The price makes it easily disposable, though it wont be able to go in the compost pile.
The pictures aren't to scale. The greenhouse will be 10x20 (200 square feet), any larger and I would need permits. The 3 layer hydroponic system will be 3 feet wide and run the inside circumference of the greenhouse. I will be growing "live fresh Herbs" and be selling them when they reach about 9-10 inches tall. Ironically my mom just bought one from the only store selling them yesterday (my only competition), so I took pictures of it.
With the plant spacing of 3 inches apart (and 2 1/2 inch pots), I worked out that each level should hold about 900 plants. However that dosen't take into account details like spacing between sections, and around edges. So I expect to get a little under that as an actual number, though I will need to actually need to build it before I can get an exact number. The total amount of plants in all 3 levels will be about 2,700, and I will have a separate propagation area. Most likely underneath the bottom level, but possibly on multi-level rolling carts. I haven't worked out how many plants it would hold if I was growing lettuce, but the spacing would defiantly be farther apart.
The plan is/was to sell 1/4 of them weekly (675 plants) in rotation. However, I have revised my plan (although it wont be in the business plan), and most likely be able to turn out 900 plants a week in rotation. That's 225 more a week than originally planed, and a total of 3600 a month.. It will be more labor intensive, but result in much more money (25% more money) for the extra few hours work (I may even hire a friend to help with that part). I will probably change the spacing for the bottom level closer together to fit 1800 plants. Sell the 900 plants on the top level, rotate the second level up. and transfer 900 plants from the bottom level to the middle level. Of course then transfer 900 seedlings up to the first level from the propagation area, and then I'll need to start some new ones.
Even going with the lower figure of 2,700 total plants, and selling 675 each week my projected profits are quite good to me. Without going into a lot of detail about my plan to sell them through store owners, as well as directly myself at the farmers market etc.. Or breaking down all the operating expenses, here's an example of my projected sales/profits from the one 200 square foot greenhouse.
Projected Monthly Gross Profit
Spring, winter, & fall Estimate
Direct customer sales......(based on average estimate of 250 sold weekly)................$2,000
Vendor sales.......(based on average estimate of 425 sold weekly)...........................$2,040
(assumes no direct sales were made)
Vendor sales.......(based on average estimate of 675 sold weekly).............................$3,240
Projected Monthly Expenses
Spring, winter, & fall Estimate
Direct monthly expenses.......................................... .......................................$650.90
Indirect monthly expenses.......................................... ....................................$265
Direct monthly expenses.......................................... ..........................................$710.90
Indirect monthly expenses.......................................... .......................................$105
Projected Monthly Net Profit
Spring, winter, & fall Estimate
Monthly Gross Profit............................................ ........................................$4,040
Monthly expenses.......................................... ...........................................$915.90
Net Total......................................$3,124. 10
Monthly Gross Profit............................................ .....................................$3,240
Monthly expenses.......................................... .........................................$815.90
Net Total......................................$2,424. 41
Projected Monthly Net Income
Spring, winter, & fall Estimate
Projected Yearly Gross Profit
Spring, winter, & fall Estimate.......................................... .....................$28,280
Summer Estimate.......................................... .......................................$16,200
Total yearly gross estimate.......................$44,480
Projected Yearly Expenses
Spring, winter, & fall Estimate.......................................... ..................$6,411.30
Summer Estimate.......................................... ............................$4,079.50
Total yearly expense estimate.......................$10,490.80
Projected Yearly Net Profit
Total yearly gross estimate.......................................... ....................$44,480
Total yearly expense estimate.......................................... ....................$10,490.80
Total projected yearly net profit..............................$33,989.20
I still need to verify that there's no tax, but I don't think there is on any unprocessed food product. And I'm waiting on a information packet that should arrive any day from the Arizona Department of Agriculture about regulations, and licensing. But I don't expect any surprises. I know there is a $200 a year license fee, but don't think there are any other fees (as long as I only sell in AZ). Also I plan to show the build, as well as share the progress with the forum (once I have the start up funds and can begin construction).
If anyone is interested I do my drawings with Google Sketchup, it's a free 3D drawing program.
Last edited by GpsFrontier; 08-11-2011 at 07:27 AM.
GPS - some thoughts
First, thanks to you, the Rubbermaid tote DWC lettuce is growing like crazy and haven't all died of root rot from a too-high water level!
Second, GPS, I've been thinking a lot about your design, mainly because I'm in the midst of building my own 12' x 20' greenhouse in order to grow hydroponic lettuce, tomatoes, peppers for my family. This thread and both of you, have been a huge inspiration. [Raises a frosty mug of root beer in toast to you]. Thanks!
Anyway, GPS, here are some thoughts I've had about your design...
1. Smart. Your black plastic rolled over elastomeric on a frame idea is REALLY clever. How you came up with this idea, I don't know, but it's very smart. I think I will try this for levels 2 and 3 of my greenhouse.
2. SWC - "Shallow" Water Culture You said that you were thinking of 4" to 6" inch depth of water for your shallow-rooted herbs. I would normally be concerned that a thin water mass may not stay cool enough in summer (or may get too cold in Winter) for the plant roots, but you said that you plan to recirculate the water which overcomes that concern; however, I wonder whether having multiple smaller recirculating systems rather than one large one might make sense (e.g., so that 1/2 strength nutrients of one pH / TDS level could be recirculated to seedlings, heavier concentrations and/or other pH level solutions could go to more mature or different varieties of plants, etc.)?
3. Fish. I'm wondering whether it makes sense to experiment with a couple hundred gallon talapia-stocked "aquarium" (a tank lined with pondgard EPDM)? Feed the fish their fish food and let fish output feed the plants? The bonus is fish to eat and/or sell for $3.00 per pound wholesale. Do you have any thoughts about this? Do you think this might have a chance of working?
4. Greenhouse. I'm planning to cover the inside frame walls of my greenhouse with fiberglass window screen then, on the outside, constructing a hinged frame hung from the top of the frame wall to which I'll attach Lexan corrugated fiberglass panels. These panels will be able to be swung open on hot Summer days for breezes while keeping out most larger bugs; during Winter months, just close it up and it will act like a normal greenhouse. Though the screen may block 15-20% of light from the walls, I'm in Florida so light should still be adequate. Do you have any thoughts or suggestions for improvement to this plan? This same concept could be adopted for a 6 mil plastic cover, incidentally.
Again, thank you both for your excellent comments!
looks like you have a good plan for what your wanting.
Just a small note on the polyester. I went for a walk through walmart and checked out the sewing section and they have the better prices/ selection I have seen around my area.
you have a few options with polyester. the loose fill for the base in larger pottings $3 is a ton of fill, with either "nu-foam" (a tightly bunched polyester used for outdoor seating) as the seedling cubes (almost identical to STG lol) $7-8 for probably close to 100 or more cubes depending on how you cut it. and the batting (1/2" more clothlike layers for quilting) for herbs and top layer cover for oregano and other viny types that will set extra roots.
Those are the ideas I have for the polyester and how I use them. It really is a wonder material lol.. Good for teddy bears and tomatos lol. It is an odd idea I had a while ago, but apparently not as odd as I originally thought it was lol.
Thank you for the suggestions which I'm going to try. Rockwool just stays too wet. Coco looks great, but this poly seems as though it would be perfect for my tomatoes which will be on a drip system. I agree with GPS that I wouldn't reuse the poly for fear of embedded organic pathogens.
Do you surround the poly with anything heavier (e.g. hydroton or river rock, etc.) for physical support of your plants?
I was concerned about it curing correctly under a non-porous surface (the plastic). But he assured me that only one side needed to be porous, and the OSB being porous was all it needed to cure correctly. He suggested rolling on a relatively thick coat, then after laying down the plastic, to use a roller to work out any air bubbles. He also said it would take about 24 hours to cure/dry, so I would give it 48 to be sure. The cool thing is the elastomeric roof covering is waterproof, so if the black plastic ever got a cut in it, the OSB would still be protected. Moral of the story, don't be afraid to talk to or ask your friendly neighborhood hardware store employees (their my best friends).
Funny you should say that, I was at Wal-mart looking at it today as well.
Last edited by GpsFrontier; 08-14-2011 at 05:31 AM.
I don't plan on using any other medium with the poly, though I have thought about perhaps placing a couple plastic rods through the nets pots to give a little solid support for the roots to grow around. The smaller plants won't have a problem with needing support (lettuce, oregano, ect.) For things like tomatoes, and basil I was thinking that a couple or more small plastic rods or stakes set through the net pot would be more than enough to support the plant from the poly compressing as they would take the wieght and not the poly. You could also use a couple zip ties and loop them through the holes in you pot or something along those lines to make a hammock to hold the plant wiehgt up, and to serve as a more solid means for your plant to root around.
If you use the nu-foam it is fairly rigid compaired to other forms of poly, but costs a little more. Though I have only given those options consideration if a problemm would arrise. The people who run STG use only the poly without additional medium or support.
I would only think you would have problems in a strong wind... In that case I would probably put a cover of the medium (which is good practice most of the time anyway) and perhaps you could use a plastic clip to place around the base and then have it tied off to the net pot on the sides.. Once the root mass takes over the pot the need for support will decline.
Hi! I am a Botany student and am too interested in DWC Hydroponics. I really like your design. I will really appreciate, if could solve few of my queries.:
What should be the time frame for changing the water in the reservoir for DWC?
How should be the specific design for the reuse of the water (considering your above design)?
What would be best option as per you, I mean to keep the water flowing or to keep it still & changing it later. and in both cases what would be time frame to change the water.
Are there any chances of getting the water contaminated with the Mosquitoes in DWC, if yes, How could we prevent it?
I planning to cultivate 1000 lettuce a week using DWC, so it will be helpful if you could provide me a rough idea about the space that will require and a rough diagram/design about showing how the flow of water will work to preserve as much as water.
I have a few thoughts on your questions. The mosquitos could be controled in a few ways.. if using a constant water flow it would reduce the likelyhood that they would even consider it as a place to procreate. Also with regular water changes (every couple weeks in most hydroponic systems) They will be less likely to take hold.
Another option is if you use bleach to get the chlorine levels similar to that of a pool. (I have been germinating my seeds in a 10ppm+ bleach solution and they don't mind). I use a higher concentration for germinating because it tends to be stagnant water and more likely to become infested with various things than moving water.
If using bleach do not use H2O2 you will make salt water and nagate the purpose of adding either because they react with eachother.
Water conservation is a tricky question, because the amount of water in the res and if you use it as dump water or if you refine the water after use decides the conservation of it. Typically hydroponics is more water efficient than normal growing. The water is held away from the open air so it condences back into the system rather than floating off into the flow of air. Also the water change cycles will depend on your ability to maintain the quality of the nutrients, as well as the size of the res. I think it was mentioned before lettuce typically uses 1/2 gal of nutrients a week (might be wrong on that one it is somewhere in the forums) So if you have a larger res and can maintain it's quality you can go longer before changes. If you use a smaller res you have to change more often because the plants use up the nutrients and you would be starving them of what they need.
On a side note about the polyester medium. I have been playing with a few varieties of it to see about the quilities as a medium.. The quilt batting is my favorite so far. The poly-fil for stuffed animals and pillows tends to be a thicker fiber and seems to wick very little. If using the poly-fil I would suggest a top drop from what I have seen so far... The quilt batting wicks nicely in comparison. I have some oregano and cilantro on a piece of batting and the oregano is starting to germinate with just the moisture that is wicking up from the edges of the batting that I have in the humidity dome. Not to mention the large surface area provided from the poly (the small pockets of air in the batting) lets the dew form all through it. I will make a thread with my findings on what I have tested so far and try to keep it updated as I find things.
Last edited by jamromhem; 08-18-2011 at 09:30 PM.