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How long should nutrient last


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Old 04-19-2009, 11:37 PM
GpsFrontier GpsFrontier is offline
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Question How long should nutrient last

I read somewhere that strawberry plants require a minimum of .5 liters per plant of nutrient solution. Assuming this is true, I have 32 strawberry plants and they would require 16 liters or about 4 gallons of nutrient solution. I think that was for one week and should be changed every week. I have a 50 gallon nutrient tank feeding these 32 strawberry plants and assuming that they require 4 gallons of nutrient's per week to feed on, then the 50 gallon's of nutrient should last 12.5 weeks before needing to be changed (provided that nothing is growing in it or contaminated it) and topping off the reservoir with fresh water so that is always at 50 gallons. My question is, is my thinking about how long the nutrients should last before being used up correct or am I not even close? I am using the Flora series nutrients and try to keep the ph at (6.0). I don't have a ppm meter though I want to get one in the future when the funds are available for it.

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Old 06-23-2009, 10:43 AM
JD4x4 JD4x4 is offline
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Default Inexpensive TDS checker

GPSFrontier- Thanks for all your posts, they are very helpful. I'm a newb to both gardening as well as hydroponics and am just about to plant my first crop in my freshly-built 11 bottle setup (probably peppers & maybe lettuce), but isn't TDS one way of checking the nutrient solution?

If so (I'm still reading & learning) I found out that Harbor Freight tools is now selling a very inexpensive TDS meter and have bought one but not used it yet. I'm sure it's not up to the standards of more expensive ones, but as a newb I figured $17 was a gamble I'd be willing to take in case I can't grow anything! Their item number is 94759 and the specs are 0-999 ppm and 5% accuracy, for what it's worth. Now I just need to learn how to use it! :-)
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Old 06-23-2009, 11:02 AM
n1zjd n1zjd is offline
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I would have to disagree with your assumption. As you already know the plant uses different nutrients in different amounts. I would not recommend running your nutrient solution for ANY more than 1 month. Now you can continue to use the same nutrient solution for a LONG time provided you know what the plants are using in the proper ratios and can add them back as needed. Just topping off the rez with plain water will cause several problems. First of all your TDS will continue to drop as you as add plain water. Now your using GH nutes which is great because they have pH buffers built in that do great provided your mixing your nutes in the proper ratios, there lies your second problem. As the plants deplete the nutrient solution of a specific nute it will throw off the ratio of nutes in the solution and therefore throw the pH off. If your serious about growing and plan to keep the strawberries going for a long time then with the proper research on the nutrient uptake of the strawberries combined with an TDS meter, I recommend a Hanna meter, then you can create a formula specific to strawberries that would allow you to add back the nutrients that the plants are using in the right amounts and maintain proper TDS and pH. There is alot to it and thats why most people change out the res every 2 weeks however its not a requirement. I'm no expert but have been growing hydro for 4 years and would be glad to help you as best I can. I understand the reason for wanting to use the same solution for a greater length of time because a 50 gal res is a pain to change out every 2 weeks. Good luck
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Old 06-23-2009, 08:21 PM
GpsFrontier GpsFrontier is offline
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Quote:
Originally Posted by n1zjd View Post
I would have to disagree with your assumption. As you already know the plant uses different nutrients in different amounts. I would not recommend running your nutrient solution for ANY more than 1 month. Now you can continue to use the same nutrient solution for a LONG time provided you know what the plants are using in the proper ratios and can add them back as needed. Just topping off the rez with plain water will cause several problems. First of all your TDS will continue to drop as you as add plain water. Now your using GH nutes which is great because they have pH buffers built in that do great provided your mixing your nutes in the proper ratios, there lies your second problem. As the plants deplete the nutrient solution of a specific nute it will throw off the ratio of nutes in the solution and therefore throw the pH off. If your serious about growing and plan to keep the strawberries going for a long time then with the proper research on the nutrient uptake of the strawberries combined with an TDS meter, I recommend a Hanna meter, then you can create a formula specific to strawberries that would allow you to add back the nutrients that the plants are using in the right amounts and maintain proper TDS and pH. There is alot to it and thats why most people change out the res every 2 weeks however its not a requirement. I'm no expert but have been growing hydro for 4 years and would be glad to help you as best I can. I understand the reason for wanting to use the same solution for a greater length of time because a 50 gal res is a pain to change out every 2 weeks. Good luck
Yes, I have learned a lot more since I first posted this thread a few months ago. I diddn't really mean that I wanted to use the same nutrients for 3 months but I was just using the math as an example. I understand that just about everyone recommends changing the nutrients every 1-2 weeks. I am sure this is because the plants drink up the nutrients and throwing off the balance of the individual elements in the solution. I mostly mean that with such a large amount of nutrient solution in relation to the number of plants that the balance is not thrown off as fast as it would be with less solution. I am mostly going by the look of the nutrient solution (clear verses cloudy), how the plants look (nice green color and still growing verses the growing slowing down and/or color loss). Also by how often I need to adjust the pH level to decide when to change the solution. I still don't have the funds for a TDS/PPM meter. I am basically changing the nutrients about 3-4 weeks.

I have taken care of some problems with the design of the system and now it functions using 32 gallons of nutrient solution instead the 55 gallons it took before. For me it is not really about the hassle in changing them but the amount of nutrient concentration used to make that many gallons of solution. At $25 a bottle and all 3 needed in combination to create the proper solution it is quite expensive to change them. At 10mil pre gallon, that is just over 2 cups each of all 3 (Gro, Micro and Bloom) to make the 55 gallons. That comes out to amount $10 every time I change the nutrients. By making the changes to the design of the system and cutting the amount of solution required to 32 gallons I have cut this cost just about in half. But because there is less solution it should go out of balance faster. How much faster I don't know because I don't have a TDS/PPM meter so I can't compare the readings.

It is my understanding that topping off with water is important because If I didn't the solution would become concentrated as the water evaporates. As the plants use up the nutrients, adding a diluted solution back instead of just water might be desirable. A TDS/PPM meter would help with telling how much. Although they cant tell me witch elements of the solution are being depleted faster and I am not a chemist and don't have access to those elements. So changing the nutrients as a whole is needed to insure they are back in the proper proportions. The basic idea in my original question simply is, by using a larger nutrient reservoir wouldn't that mean that the solution would go out of balance slower because of the extra volume of nutrient solution for the same amount of plants? I have been interested in Hydroponics for over 10 years but only growing hydroponics for a few months.
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Old 06-24-2009, 09:57 AM
JD4x4 JD4x4 is offline
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Default Same Thoughts

I had the same thoughts regarding your solution/balance theory as well as the cost, but like I mentioned I'm also a newb & haven't started growing quite yet so I don't have a clue. I was thinking that a little more solution per plant would give you a bit of 'fudge' room if you were trying to maximize the change interval without depriving the plants, and without a TDS meter. I'm interested to see what the more experienced (and poor, like me) forum members think about that.

I also didn't have the $ for a meter, but then I found the Harbor Freight meter which I'm going to use. It's only $17 + shipping and from what I've been reading about EC & TDS I figure as long as the meter is temp compensated (it is), gives consistent readings (it does), and you 'calibrate' it to your water & nutrients it should work reasonably well. This link and this one are two of the reasons I'm going to try it, even though it's not 'lab' quality by any stretch.
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Old 06-24-2009, 07:47 PM
GpsFrontier GpsFrontier is offline
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Originally Posted by JD4x4 View Post
I had the same thoughts regarding your solution/balance theory as well as the cost, but like I mentioned I'm also a newb & haven't started growing quite yet so I don't have a clue. I was thinking that a little more solution per plant would give you a bit of 'fudge' room if you were trying to maximize the change interval without depriving the plants, and without a TDS meter. I'm interested to see what the more experienced (and poor, like me) forum members think about that.

I also didn't have the $ for a meter, but then I found the Harbor Freight meter which I'm going to use. It's only $17 + shipping and from what I've been reading about EC & TDS I figure as long as the meter is temp compensated (it is), gives consistent readings (it does), and you 'calibrate' it to your water & nutrients it should work reasonably well. This link and this one are two of the reasons I'm going to try it, even though it's not 'lab' quality by any stretch.
I just thought I would mention as a reminder that there are any number of things that can go wrong with nutrient solution. For this reason I personally wouldn't want to use a larger tank just to try to get more time between changes. When I first designed my system I hadn't taken into account the cost of of the nutrients. I would rather use 10 gallons of nutrients and change them once a week, but it takes all of the 32 gallons to flood the system without running the pump dry (a flaw in my system). I have made some changes and save about 23 gallons (from the original 55) of nutrients per change now, but I know that I can do better after these plants are done. I also hadn't done any research to find out how much nutrient solution was required per plant to give me an Idea of how fast the nutrients would be depleted from the solution (live and learn). I would want to use at least twice as much as required as a buffer zone. Maybe a little more if the plants are heavy feeders (something that I didn't know about before eather). My 32 strawberry require 4 gallons of solution if what I have read is correct, and 10 gallons would be more than twice that giving me that buffer zone I want.

I can easily convert the system into a Aeroponic system, all I need is a pump that doesn't cost an arm and leg. Because the pump needs to be a high pressure pump or the emitters wont spray, but would rather just dribble out. With a Aeroponic system I would be able to support the same 32 plants on as little as 3-4 gallons of solution if I wanted to. I would love to hear from anyone who knows about Aeroponics and about pumps for it.

Sorry I haven't really looked into testers in detail, I just know the basics on how they work so I don't feel I can give any recommendations on which brand to get. But Thanks for the links I will be having a closer look, $17 certainly sounds cheep enough and probably would be better than the nothing I have right now. Let us know how it works for you...
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Old 06-25-2009, 10:36 AM
n1zjd n1zjd is offline
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Take a look at ebay for TDS meters. Do a search and take a look at the Hanna meters. They are tried and true testers and they dont cost that much. I have several of them.
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Old 07-03-2009, 11:13 AM
JD4x4 JD4x4 is offline
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Default Info on the Harbor Freight TDS meter

Just an update about the Harbor Freight TDS meter now that I've got it and used it. It seems to be a reasonably nice pen type meter with temp compensation but non-replaceable probes. It also seems to give me repeatable readings but I've only used it a few times in different tap/distilled/spring waters.

The big negative - it only goes to 999 ppm so it's not usable with the G.H. Maxi nutrients I'm using since they start off at 1300+ ppm. :-(

Since they call it a "Water Purity" tester I suppose I should have guessed there would be a catch, eh? :-)
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Old 12-03-2012, 12:06 PM
jollygreenmidget jollygreenmidget is offline
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Quote:
Originally Posted by JD4x4 View Post
Just an update about the Harbor Freight TDS meter now that I've got it and used it. It seems to be a reasonably nice pen type meter with temp compensation but non-replaceable probes. It also seems to give me repeatable readings but I've only used it a few times in different tap/distilled/spring waters.

The big negative - it only goes to 999 ppm so it's not usable with the G.H. Maxi nutrients I'm using since they start off at 1300+ ppm.
Why couldn't you dilute your test sample with the same amount of distilled water and interpolate?

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