A nutrient solution is the mixture of irrigation water (or mineral water) and the nutrients necessary for plants to be healthy and productive.
In particular, a nutrient solution is a key ingredient for hydroponic grow systems and other soilless growing techniques, and will provide the nutrients to the plants at the base of the plant dose.
How do you calculate hydroponics nutrients? There is a formula, which you must take into consideration. The formula for solid nutrient solution is FR = 100 x NA/%. For liquid nutrient solution FR = NA/(%NxDx10).
We shall outline these further below.
However, you may look at those formulas and think that it will be difficult to calculate and balance the nutrient solution.
In this article, we will prepare the necessary steps that will mean you do not make a mistake.
6 Steps for Calculating Hydroponics Nutrient Solution
There are six steps to generate and balance a nutrient solution for your hydroponics system.
Here are the steps along with descriptions.
Step 1 – Test Source Water
Your initial step revolves around testing your source water.
Generally, source water actually possesses some nutrients that you must consider.
After all, you don’t want to end up overdosing your plants with a nutrient.
The results could be given in a variety of units, such as:
- ppm
- mg/l
- meg/l
- mmol/l
To simplify things, you will want everything converted to ppm.
Step 2 – Determine Nutrient Requirements for Your Crop
Now, you will need to determine the nutrient requirement of your crop.
You can conduct your own research to find recommendations, or you can apply what you know if you have written in this area.
If the values are expressed in units other than ppm or mg/L take the time to change all of them to ppm.
Quick tip: Remember, 1 ppm equals 1 mg/L.
Step 3 – Calculate Nutrient Rates to be Added
Once you know what you have and what you need, then you can come up with what needs to be added.
It’s simple enough to take the nutrient requirement values and subtract the values you found in the test results. It will then become evident what needs to be added. You’ll just need to repeat this for every nutrient.
For example, if your plant needs a magnesium level of 60 ppm, and the source water test shows it has 40 ppm of magnesium in it, then you’ll need to add 20 ppm with fertilizers.
That also means that you will need to add 20 mg of magnesium to every 1 liter of solution.
If you test your source water and they receive a negative result, it means that the nutrient concentration is greater in the source water and you should not add any of that nutrient to the solution.
Step 4 – List Available Fertilizers
Once you have the list of nutrients you need to provide based on your calculations from above, find a fertilizer that contains those specific nutrients.
If a nutrient is not needed, DO NOT apply it, because it could harm the plant, and worse yet, ruin the entire system and you will have to start your grow all over again.
Step 5 – Analyze Fertilizer Rates
When selecting a fertilizer, begin with the one that contains a distinctive nutrient that others do not.
For instance, if calcium nitrate is the only calcium source present in fertilizer, start with it.
The formula for solid fertilizer is FR = 100x NA/%N.
- FR refers to the fertilizer rate that needs to be given as ppm or mg/l.
- NA refers to the nutrient concentration that needs to be added from fertilizer in ppm.
- N represents the dilution of nutrient in fertilizer.
The formula for liquid fertilizer is FR = NA/(%N x D x 10).
- D represents the density of fertilizer in kg/l.
- FR refers to ml/l for fertilizer rate.
If the density is in lbs/gallon, then you will use the following formula FR = NA/(%N x D x 11.98).
- FR is the application rate expressed as gal/1000 gal.
Often the nutrients supplied in fertilizer are expressed as a percent which means you will need to divide that percent by the density of the fertilizer.
Step 6 – Repeat Calculation for Each Nutrient
With this formula, one or two iterations will enable you to quickly find the correct fertilizers, balancing the nutrients your plants need.
For certain nutrients, you may need more than one source which is why it may be beneficial to prepare a cheat sheet so you won’t have to do this in several iterations.
It may already be there!
Things to Keep in Mind
When calculating hydroponic nutrients, there are several things that you must keep in mind.
These are as follows:
- Nutrient concentration may be expressed in oxides. Be sure to understand which form you’re using the calculation for, and make conversions as needed.
- There are two forms of nitrogen: nitrate and ammonium. The ratio of these two forms is important, especially in a nutrient solution for hydroponics. Certain fertilizers might have one or the other, and some will have both.
- Many times, the solution will need to be titrated. This can be done by increasing the solution acidity. Three common ways to do this are nitric acid, sulfuric acid, and phosphoric acid.
Nevertheless, remember: Nitric acid provides nitrogen, phosphoric acid provides phosphorus, and sulfuric acid provides sulfur.
When doing your calculations, you will have to factor this in.
Conclusion
To have healthy and productive plants in your hydroponic system, you are going to need to spend some time calculating the right nutrient solution.
You don’t want to feed your plants too much grape juice, or not enough grape juice. Either way, your plants will not be happy!
This process may seem a bit complex initially, but once you get the process down, it’ll flow pretty easily!