Fertiliser programmes

Mixing hydroponic fertiliser yourself ?

The commercially available fertilisers consist of a complete fertiliser supplemented with macronutrients. They are offered by some hydroponics and/or fertiliser companies and vary depending on the hydroponic plant. An example of a fertiliser programme is the hydroponic tomato programme offered by Hydro-Gardens.

In this programme, growers purchase Hydro-Gardens Chem-Gro tomato formula. It has a composition of 4-18-38 and also contains magnesium and micronutrients. To make a nutrient solution, it is supplemented with calcium nitrate and magnesium sulphate, depending on the variety and/or growth stage of the plant.

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Advantages of fertiliser programmes

Disadvantages of fertiliser programmes

Modified Sonneveld recipe / herbs

It is at the discretion of the breeder which fertilizers he uses to produce a nutrient solution according to a recipe. The fertilizers commonly used include:

Advantages of nutrient solution recipes

Nutritional solutions allow fertilizers to be adjusted based on the nutrients contained in water sources. An example: A gardener uses a water source with 30 ppm potassium and produces the modified Sonneveld solution for herbs that requires 210 ppm potassium. It would have to add 180 ppm potassium ( 210 ppm - 30 ppm = 180 ppm ) to the water in order to obtain the amount of potassium required in this recipe.
With recipes, nutrients can be easily adjusted. When a leaf analysis report indicates that a plant has iron deficiency. It is easy to add more iron to the nutrient solution.
Since recipes make it easy to adapt, fertilizers can be used more efficiently than in fertilizer programs. Using recipes can be less expensive than using fertilizer programs.

Disadvantages of nutrient solution recipes

It has to be calculated how much fertilizer has to be added to the nutrient solution. (Link to performing calculations). Some people may feel intimidated by the calculations involved. However, the calculations only require uncomplicated mathematical skills based on multiplication and division.
A high-precision scale is also required for the measurement of micronutrients, since the required quantities are very small. Such a scale can be found on Amazon from 30.- €: e.g .: KUBEI 100g / 0.001g.

This is about the calculation of nutrient solutions for your own needs

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Calculation of the concentrations of nutrient solutions using the following two equations

The calculation of the amount of fertilizer that has to be added to the nutrient solutions is part of a successful hydroponic production. Only multiplication, division and subtraction are used for the calculations; no advanced mathematical knowledge is required.

If you want to know more about the compositions and concentration information, the article series can be too Stoichiometry and a look at the conversion of Mol and grams When specifying the concentration of the individual elements and connections, it is helpful to better understand the complexity of the topic.

If you master the general process, producing nutrient solutions and adjusting the amount of nutrients is child's play.

Fertilizer recipes for hydroponics are almost always given in ppm (in the long form: parts per million). This may differ from the fertilizer recommendations for growing vegetables and fruits outdoors, which are generally given in lb / acre (pounds per acre).

First you have to convert ppm to mg / l (milligrams per liter) using this conversion factor: 1 ppm = 1 mg / l (1 part per million corresponds to 1 milligram per liter). For example, if 150 ppm nitrogen is required in a recipe, 150 mg / l or 150 milligrams of nitrogen in 1 liter of irrigation water are actually required.

Ppm P (phosphorus) and ppm K (potassium) are also used in recipes for nutrient solutions. This also differs from the fertilizer recommendations for growing vegetables and fruits in the field, which use P2O5 (phosphate) and K2O (potash). The fertilizers are also given as phosphate and potash. Phosphate and potash contain oxygen, which must be taken into account in hydroponic calculations. P2O5 contains 43% P and K2O contains 83% K.

Let us check the previous circumstances:

1 ppm = 1 mg / l
P2O5 = 43% P
K2O = 83% K

Nutrient solution tanks are usually measured in gal ( gallons ) in the United States. When we convert ppm to mg / l, we work with liters. To convert liters into gallons, use the conversion factor of 3.78 l = 1 gal ( 3.78 liters corresponds to 1 gallon ). The invoice is also given below for continental interested parties.

Depending on the scale you use to weigh fertilizers, it may be useful to convert milligrams into grams: 1,000 mg = 1 g ( 1,000 milligrams correspond to 1 gram ). If your scale measures in pounds, you should use this conversion: 1 lb = 454 g ( 1 pound = 454 grams ).

Let us summarize these circumstances:

3.78 l = 1 gallon
1000 mg = 1 g
454 g = 1 lb

Now we have all the necessary circumstances. Let's look at an example.

How do you determine how much 20-10-20 fertilizer is needed to deliver 150 ppm N with a 5 gallon tank and a fertilizer injector that is at a concentration of 100:1 is set?

First, write down the concentration you know you want to reach. In this case it is 150 ppm N or 150 mg N / l.

Note that we multiply by 1. This allows you to cancel the units that are the same in the numerator and denominator. Now we can paint "mg N" and get the unit g N / l water.

Continue this process by converting liters into gallons. Most containers are still traded in gallons ( 3.78 liters ). Entertaining here: the metric system was invented by the Britten. If you want a metric result, omit this calculation step.

Now there are only grams of nitrogen left per gallon of water.
We'll get closer to it. Now we want to convert grams of nitrogen into grams of fertilizer. Remember that our fertilizer is a 20-10-20, which means that it contains 20% nitrogen. It can be imagined that 100 grams of fertilizer contain 20 grams of nitrogen. 

So where do we stand now? We calculated how many grams of fertilizer are needed in each gallon of irrigation water. At the moment we have a normally strong solution. Our example prompts us to calculate a concentrated solution of 100: 1. This means that for every 100 gallons of water that are applied, 1 gallon of stock solution is also applied via a fertilizer injector. We also know that our storage tank holds 5 gallons. Below see calculation for metric system (liters).

In gallons

In the calculator: 150 x 1: 1000 x 3.78 x 100: 20 x 100 x 5 is 1417.5 grams on 5 gallons of water (in the storage tank)

After we have deducted everything, we have a gram of fertilizer left. This is the amount of fertilizer we need to put in our storage tank to apply 150 ppm N at a concentration of 100: 1. Multiply and divide and you get the answer 1417.5 grams of fertilizer.

In liters

In the calculator: 150 x 1: 1000 x 100: 20 x 100 x 10 is 1500 grams per 10 liters of water ( in the storage tank )

After we have deducted everything, we have a gram of fertilizer left. This is the amount of fertilizer we need to put in our storage tank to apply 150 ppm N at a concentration of 100: 1. Multiply and divide and you get the answer 750.0 grams of fertilizer.

This means that for every 100 liters of water that is applied, 1 liter of stock solution is also applied via a fertilizer injector. We also know that our storage tank holds 10 liters. 

If we measure in pounds, we have to put 0.75 kg / 1.15 lb fertilizer in our storage tank to apply 150 ppm N with a concentration of 100: 1.

You have just completed one of the two equations. Now let's look at the other one.

We just found that we need to add 750 grams of fertilizer to deliver 150 ppm nitrogen at a concentration of 100: 1. The fertilizer we used was a 20:10:20. In addition to nitrogen, we also add phosphorus and potassium. With the next equation we determine how much phosphorus we supply. This is basically the reversal of the first calculation.

We start with the amount of fertilizer that we put in our tank. The final units are ppm or mg / l. As with the previous calculation, we use our specifications until we receive these units.

Multiply with the concentration of the nutrient solution.

Multiply to convert to liters.

Next, convert milligrams of fertilizer into milligrams of phosphate.

Next we will convert grams of phosphate into grams of phosphorus, assuming that phosphate contains 43% phosphorus.

Finally, we convert grams of phosphorus into milligrams of phosphorus.

When we calculate this, we find that we have added 32.25 mg / l P or 32.25 ppm P. This is the second equation. We can also use them to determine how much potassium we have added. 

We added 124.5 mg / l K or 124.5 ppm K.

With these two basic calculations, you can use any nutrient solution recipe program. How they are used to calculate a recipe can be seen in this article:

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Fertilizer Calculator for Hydroponic Systems & Soil * Version 0.25.7-en * 2025-07 * Basics of nutrient solutions  * Manual/HowTo. More at https://borgmann-aquaponik-hydroponik.ch -  * Download Fertilizer Calculator (³³ *

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The script ( download here ) allows you to create your own fertilizer mix for hydroponics or soil from over 50 different fertilizer salts and over 200 NPK fertilizers can also be used.

Procedure

1) Select the example nutrient solution or specification and display it

Tried and tested nutrient solutions from the literature, see  in the drop down menu Predefined nutrient solutions 

Don't let the years fool you: practically nothing has changed since 1966, only the temperament of the discussions about it. What you should keep in mind is that for several years there have been breeds that require an extremely high dosage (EC value >= 4.0) to thrive. Select a nutrient solution here and click    

In the graphic shown below, the required elements are displayed as bars. Each red bar represents 100% of an element. This graphic facilitates the following mixture of added fertilizer salts.

2) Add fertilizer salts and/or ready-made fertilizer

Select from the Drop-Down  

the first additive.

Indicate the quantity in grams per litre (g/L) or milligrams per litre (ppm). Then click on

In the graphic (above) the quantities are now displayed in relation to the specifications (if you have selected one). This way you can see how exactly the quantity information corresponds to the specifications in percent.

The table also shows what amounts this corresponds to in grams, milligrams (ppm), moles and milli-moles. A column shows you the text Target And Actual value the fertilizer mixture - but only if you have chosen a specification. In the graphic at the bottom of the screen you can see the display as a long shot. Here you can better see the relationships between the individual elements. 

3) Add more substances (fertilizer salts)

To add more substances click on  

After each selection of another substance and quantity, click on   

4) NPK fertilizer add to

The program can also take standard fertilizers into account. These usually only contain the macro-nutrients N (nitrogen) P (phosphorus) and K (potassium). With the button  

<ou can  add another variety of NPK fertilizer that has a different mixing ratio. This means you can combine fertilizer with 10-20-30 and 8-16-24 and see immediately whether the amount of the individual elements is too large or too small. To see the result, after entering the quantity and magnitude (gram or PPM), click on  

5) Search for items in the fertilizer salts/finished fertilizer list

In the input field Search for element in fertilizer additives/prefabricated fertilizers  

(e.g. Fe)

   you can search for an element independently of the rest of the program. All fertilizer salts and finished fertilizers are searched for this element and displayed in a list sorted by content. Please only enter one element and click on 

 The element names are also under the graphic bars at the top and bottom of the page. In the table, the element name is in the left column, its common name is in the column on the right. 

Intention:

This fertilizer calculator was originally only intended to add up various NPK fertilizers and calculate their total NPK at the elementary level. Since this makes little sense without comparative values, a few standard hydroponic fertilizer recipes were added to give the value a certain significance. Further refinements (Ec value, pH value) were added over time, as it is helpful to have prior knowledge of the expected conductivity (EC) and the pH value. The scope requires a different programming language, but since our customers use a wide variety of operating systems, only HTML and JavaScript remained as common denominators. Unfortunately, I'm not a fan of these "languages".

This means you can always have this "calculator" with you, even without internet. A browser (built from 2000? for very old browsers, an untested alternative is commented out) and this HTML page will suffice.

All data is stored on this page and allows you to easily expand the scope as you wish according to your own needs. If you also want the graphical representation without internet access, download the file Chart.js to your local machine and adjust the path in the script: https://borgmann-aquaponik-hydroponik.ch/chart.js... It is version 2.9.4. You can find them on the Internet here: https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.js - at least that's how it was this morning. Good luck!

PS: If there are errors or useful extensions (including fertilizer), you are worth a message write to me.

The fine print

²) When fertilizer mixtures (NPK + X) are used, it is not possible to calculate the EC and pH because the composition is unknown. The values used are then estimated - and can therefore be viewed as "fantasy". When it comes to empirical values, they are marked with (real).

⁴) The pH and EC values should be viewed with scepticism. Not always are the information provided by the manufacturers correct! - Always check with pH and EC meter -!

 ⚠️ Please note that some of the chemicals used can be toxic, harmful or explosive. The author assumes no responsibility for errors in the program.

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