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Basic Nutrient Strength Question


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  #1  
Old 12-12-2014, 02:52 PM
JHazzardB JHazzardB is offline
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Default Basic Nutrient Strength Question

Hey guys! First post and super excited to finally join the forums.

I have a basic nutrient strength question. I use tap water for my reservoirs (not the best) with a PPM of 285 and EC of .58 or so. It can vary daily or weekly by a smidgen.

If I'm aiming for a nutrient strength of say 900ppm (around 1.8-1.9EC) to feed some tomatoes, I should be looking for a final reservoir PPM of 900+285=1185 correct?

I use the Advanced Hydroponic nutrients with the 3 part Micro, Grow, and Bloom (pH perfect) stuff.

Also, I haven't learned the way to make my own nutes yet or follow any custom recipes. However, if I know what is in the Micro, Grow, and Bloom nutrient bottles, can I tell how many PPM of N-P-K and Ca I'm adding? I also have a bottle of General Hydroponics CalMag (1-0-0 5%Ca and .1%Fe)

For instance:
Micro bottle is labeled as 2-0-0 with 2.4%Ca and .05% Fe
Grow bottle is labeled as 1-0-4
Bloom bottle is labeled as 1-3-4
Mixing in equal parts is 4-3-8 with 2.4% Ca and .05% Fe

From knowing this, can I tell how many PPM of each nutrient I add when I raise my reservoir by the desired 900ppm?

I'm not good with numbers and have started rambling with excitement. I don't have any strong feelings any way to try to hit the 900ppm or 1.8EC target, I'm just trying to get a good understanding. Thanks in advance everyone!

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  #2  
Old 12-12-2014, 11:14 PM
GpsFrontier GpsFrontier is offline
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Hello JHazzardB,
First just like to say welcome to the forum.

I think you already know that the tap water can be problematic, and not really a good choice for your water source. In some places their tap water is fairly good quality, but that's very few places. You should consider using a better water source or you may wind up with problems you can never get rid of. An example I like to use is if you start with the wrong ingredient's to bake a cake, don't be surprised if it doesn't come out right.

I know a lot of people like to use PPM/EC meters and feel it's imposable to grow good plants withough't them. But realistically their not necessary. In Over 7 years of growing hydroponically, I don't even have one and never did. They can't do the only thing I want them to. All you need to do is fallow the manufactures nutrient mixing recommendations. In your case the advanced nutrient calculator recommendation calls for 16ml per gallon (4 liters) of water for full strength nutrient solution. 1 Tbsp is 15ml, one tsp is 5 ml.

Now for seedlings I typically use about 1/4 strength nutrient solution. Then once they get bigger I step it up to 1/2 strength. Once they start to really get going bump it up to 3/4 to full strength. You can easily tell if the nutrients are depleted or not strong enough by the yellowing of the newer leaves. How often you need to change the nutrient solution will depend on on factors like the water volume compared to size of the plants, as well as how much water the plants are drinking daily. Here is an article about Nutrient solution reservoir size.

Quote:
From knowing this, can I tell how many PPM of each nutrient I add when I raise my reservoir by the desired 900ppm?
No it doesn't work that way. NPK is just a BASIC estimate. There are 16 essential macro and micro mineral salts needed for healthy plant growth.

Nitrogen (N)
Potassium (K)
Phosphorus (P)
Calcium (Ca)
Magnesium (Mg)
Sulphur (S)
Iron (Fe)
Manganese (Mn)
Copper (Cu)
Zinc (Zn)
Molybdate (Mo)
Boron (B)
Chlorine (Cl)

And Carbon, hydrogen and oxygen are absorbed from the air and water. The rest of the elements, called mineral salts/nutrients, are dissolved in the nutrient solution. NPK values wont tell you what any of essential mineral salt values are. Not to mention that you have no idea what the original PPM of your water supply consists of to begin with either. This is the bigest reason I don't use PPM/EC meters because that is what I want them to tell me. All the meters can tell you is the total concentration of everything, it cant break it down and tell you how much of each there is. PPM/EC meters can only tell you relative strength, that is the total of everything combined. If you want to know the totals of each element you need to have a sample sent out for lab testing. Another problem with PPM/EC meters are they are notorious for giving false increasing, even when cared for, calibrated, and stored properly. A decent meter will run $100 or more, and for $120 I can make 5,000 gallons of nutrient solution. I'd rather spend my money on nutrients, and by the toys when I get rich.

As for making your own nutrients, you can if you want to. I used to want to as well, but I don't bother even trying for one very good reason. Over the years I have compiled a list of Cost Effective Hydroponic Nutrients that makes it not worth the effort to bother trying to make my own. The most cost effective ones cost less than 2 cents per gallon of full strength nutrient solution. I don't think I can even make them for that. And making your own isn't as simple as just fallowing a recipe. You really need some understanding of chemistry, and a really good scale.

Here is a recipe for tomato's from the University of Arizona

Table 1. Fertilizer salts (adapted from Jensen and Malter, 1995)
Fertilizer Salts element supplied grams of fertilizer needed per 1000 liters of water to provide 1 mg/l (ppm) of the nutrient specified
Boric Acid [H3BO3] B 5.64
Calcium nitrate [Ca(NO3)24H2O] (15.5-0-0) N 6.45
Ca 4.70
Cupric chloride [CuCl22H2O] Cu 2.68
Copper sulfate [Cu(SO4)5H2O] Cu 3.91
Chelated iron (9%) Fe 11.10
Ferrous sulfate [FeSO4] Fe 5.54
Magnesium sulfate [MgSO47H2O] (Epsom salts) Mg 10.75
Manganese chloride [MnCl24H2O] Mn 3.60
Manganese sulfate [MnSO44H2O] Mn 4.05
Molybdenum trioxide [MoO3] Mo 1.50
Monopotassium phosphate [KH2PO4] (0-22.5-28) K 3.53
P 4.45
Potassium chloride [KCl] (0-0-49.8) K 2.05
Potassium nitrate [KNO3] (13.75-0-36.9) N 7.30
K 2.70
Potassium sulfate [K2SO4] (0-0-43.3) K 2.50
Zinc sulfate [ZnSO47H2O] Zn 4.42

Also you need to know which chemical salts can be mixed with each other and which can't. For the same reason most liquid nutrients come in two or three parts. If they were mixed together in one concentrate some of the mineral salts would bond with others and wont dissolve in water so they wouldn't be useful to the plants. Here is a blog written by a chemist and hydroponics enthusiast, he has also created a free nutrient calculator called the hydro buddy to help make your own nutrients if you are still interested in trying.

Science in Hydroponics
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Old 12-13-2014, 06:04 PM
JHazzardB JHazzardB is offline
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Thanks for the quick response GPS!

A little background: My reservoirs are are the 10 gallon Rubbermaid Roughneck containers from Home Depot. They have some autofill valves so they maintain a constant (tap) water level, about 6 gallons. They get changed roughly every 10 days. Sometimes I add nutes to them. I use my little PPM meter (I know, I know...) because it helps me see the concentration. I know it will never tell me what exactly is in the water but it helps me maintain where they were when I mixed them if that makes any sense.

I went ahead and did a little test using my nutes. I poured a liter of water and added 1ml of each, then bumped to 2ml and then 4ml. I was able to use my little meter to give me readings of .93EC, 1.29EC and 1.91EC. When I checked my reservoir, I was sitting at 1.93EC. Which is a little "hotter" than recommended on the bottle but I'm not gonna sweat it just yet.

I don't have TOO great of an interest in making my own. I like to trust the manufacturers and am going to read up on your link of Cost Effective Nutes.

Hopefully I'm going to post some pictures of my set up and get some feedback on how to improve things!
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Old 12-13-2014, 07:04 PM
GpsFrontier GpsFrontier is offline
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Hello JHazzardB,
Quote:
They get changed roughly every 10 days. Sometimes I add nutes to them.
I'm not sure you understand what I mean by changing the nutrient solution. I mean dumping out all of the old nutrient solution and mixing up a whole new fresh batch. That is the only way to ensure a balanced nutrient solution. Plants don't take up the different mineral salts/elements evenly, they take up what they need and leave the rest. Again the problem with PPM/EC meters is they cant tell you what is in the water. If you just rely on what numbers you see on the meters, then you will eventually wind up with some elements being at toxic levels.

Like I said plants don't take up the mineral salts evenly, and only absorb what they need and leave the rest. That means when you add more nutrients, you not only add what the plants used, but you are adding what the plants didn't use as well. That means that for those nutrients the plants don't use as much of, the adding of more nutrients will lead to a build up of them in the water, and eventually they will reach toxic levels if all you do is just add nutrients tell you get a number on your meter. Because PPM/EC meters cant tell you the levels of each element in the water (the only thing I want them to do), they wont be able to tell you when a particular mineral element is depleted, or at a dangerous or toxic level, so they just don't help.

Not to mention whatever mystery elements are in your source water to begin with will build up as well. As an example: often times there is a lot of calcium in the water supply, and a buildup of calcium can bond with the iron causing nutrient lockout of both calcium and iron. Our source water here in the desert has a lot of excess iron, calcium, and Manganese, not to mention many other minerals. So I use RO or filtered water only.

To ensure a balanced nutrient solution, you need to completely change it regularly (and should use a good source water). How often depends on the size of the plants compared to the amount of water volume, even temperature and humidity. But for me, I generally change it anywhere from 1 to 4 weeks.
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Last edited by GpsFrontier; 12-13-2014 at 07:26 PM.
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  #5  
Old 12-13-2014, 08:23 PM
JHazzardB JHazzardB is offline
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No worries! We're on the same page! Reservoirs get completely drained and washed out every 10 days or so for the reasons you mentioned. I was just trying to state that I add a few mL of nutes to try to keep it around the starting EC (not sure why...prolly peace of mind). But then every 10 days, it gets empty and washed out.
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Old 03-14-2016, 12:00 AM
mitchnc mitchnc is offline
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Default New here

Hello everyone,

I'm brand new here and wanted to say thanks for this info.
I only started hydro two months ago. I started with a 27-gallon res and have been growing DWC lettuce and kale. It's going well.

I just set up 12 5-gallon buckets to expand. I want to grow tomatoes, peppers, cukes, Bush beans, bok choy.

I've been very confused and anal about nutrients because I don't totally understand them.
I'm using GH micro/grow/bloom and just following the label, even though my ppm meter shows way lower readings than I think I should be shooting for.
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Old 05-30-2016, 09:50 AM
Rye Rye is offline
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I started with seed for kale around the first week of April. I sprout them under a 52w light and then moved up to a 400 watt light. Thats when they really took off.
However, in concerns to the nutrients. I followed GPS's advice for 1/4, 1/2, and full strength with out using a pen. At the point were I got to full strength, with a 400watt light, the Kale exploded. Now, it's beginning to fad a bit. What I noticed, by the pen, when it was at it's best growing I was showing readings of 180 x10 PPM. Way over strength. However, now it's starting to slow ( need to change water, and it's only showing 135 x10 PPM.

The pen doesn't show me what is depeleted, and I am not sure of the accuracy as I should be torchingmy plants with a level that high. But, they are responding well. I have been cutting 4-6 cups of fresh baby kale leaves every two days off of 15 plants. More than enough to supply the house. When I moved to my NFT with 100 plant slots, I plan on running 20 kale, 50 spinach, and the rest lettuce or chard.

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