So, you want to make your own nutrient solution? Not sure where to start? You’re in luck! Today, that’s precisely what we’re going to talk about. Let’s dig in!
The first thing to understand as we work through it is this: There is no perfect solution for every crop. You’ll have a few bumps in the road as you experiment, and that’s okay! With that in mind, there are a few things to consider in the solution, especially when dealing with multiple species and crop cycles.
Things such as weather conditions, irrigation water quality, physicochemical substrate conditions, crops system management, irrigation dosage, and frequency of irrigation all play a role in how you come up with your solution. Thus, it’s best to choose a nutrient solution appropriate to all of the above, not to mention providing fertilizers that take into account the composition of the irrigation water.
You’ll also need to be evaluating your plant, and modify the composition of the solution as needed. There are some great resources out there regarding studies of solutions and what might be best for your plant. At the end of the article we’ll give you the best tools we found.
Phew, with us so far? Terrific! Okay, so what if you’re looking to cultivate multiple different species together? Well, it’s best to choose something that covers all your bases. What’s cool about plants is that they adapt well to growing at a wide range of nutrient concentrations. Makes sense, right? In nature there are no perfect conditions everywhere. They’d have to adapt in order to survive! This means that many different solutions can be used successfully to grow a hydroponic crop. It does not mean that they will yield the same, though!
A basic piece of feeding your plants is to ensure adequate concentrations of all nutrients throughout the life cycle of the crop, but never go over. As we’ve discussed previously, excessive amounts can damage the crops, waste money and resources, and pollute the environment! But if we get the solution right, that means that plants grow healthier, faster and cheaper too!
My first stock solution!
So you’re probably wondering “okay, so we’ve talked about how important is, what would something like this look like?” Good question, let’s do an example and see how these play out.
We’re going to make the formulation for NFT (Nutrient Film Technique), prepared by Dr. Allan Cooper at the Glasshouse Crops Research Institute in the U.K.
To simplify, let’s suppose we have a reverse osmosis system and will be using high quality water (low EC, less than 0.05 dS/m) so we can overlook the salts dissolved in the irrigation water as they are scarce.
If you’re concerned about your irrigation water, it might be a good idea to get a water analysis from your local government website, a water distributor, a nearby college or university, or you could even pay around $45 for an independent one. The salts provided by irrigation water must be subtracted from the total to get the right total amounts.
Normally in the water analysis, concentrations are not expressed in weight units but in parts per million, moles, milliequivalents, weight percent, etc. In this case, you must convert units. There is a handy calculator here. If you’re not familiar with inorganic chemistry (valence, molecular weight, etc), not to worry! Many programs such as this open source one have their own unit converter.
When you’re preparing your concentrated stock solution, always keep your calcium salts and other “incompatible” salts separate. Otherwise they will precipitate. This is the reason you need to have separate A and B solutions and you only mix them in the low concentrations required for irrigating. Here’s two good resources on how to use fertilizing salts:
In our sample case, these are the concentration of salts that we need, in grams per liter for each solution.
Getting the idea? Awesome!
Mixing the solution
Alright, let’s keep rolling. To make your own solution, besides of the salts, you’ll need a couple items in your toolkit:
- A scale with a precision of at least 0.01g
- Distilled water
- Two appropriate containers big enough for storing your concentrated (A and B) solutions. In our example we will use a couple 2 liter opaque plastic bottles.
We are preparing 2 + 2 liters (A + B) of stock solution concentrated 100 times. Dissolving them in water we will be able to prepare 2 x 100 = 200 liters of nutrient solution (approximately; it depends on the desired final conductivity). Do not concentrate stock solution more than 300x.
Go ahead and toss in 1 liter of distilled water in each of the two bottles (A and B). Then, add the weights of the salts in the amounts calculated for this concentration (table 2), and this volume, and finally add the rest of the distilled water to make up to two liters.
Note that the math is actually quite simple: if we need 1.003 grams per liter in the final solution, and will make 2 liters of concentrated at 100x, then the needed quantity will be 1.003 g/l x 100 x 2 l = 200.6 grams
Store the concentrated solutions in a cool, dry place, safe from solar rays. Make sure that there are no precipitated sales (you can tell by the small crystals inside) when we need to prepare the solution. Then use like you use any concentrated solution, add the same volume of each bottle in the tank with the irrigation water to raise until the optimal EC for our crops. Then, you can acidify the solution with a little bit of nitric or phosphoric acid to pH 5.8 (the optimal for NFT)
Wow! That’s a lot. Does all of that make sense? Here’s another chart with an example of final concentration of essential mineral elements in 4 different recipes:
Hopefully, now you know a little more about building out a nutrient solution and can start testing in your lab! Let us know if you have any questions. Happy growing🌱