Fertilizers

Jump to Subsections:
Units of Measure
Fertilizer Recipes
Fertilizer Calculator

All organisms need an variety of elements to grow and thrive.  The primary element used by most life forms on earth is carbon, and plants get theirs by pulling it out of the air in the form of carbon dioxide (CO2).  Plants grown in the ground get other necessary elements directly from the soil, but in the Bucket Hydroponics system, these elements are mixed into the hydroponic fluid in the form of inorganic salts.

Macro-nutrients

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)

The ratios of the macronutrients are the most important part of any fertilizer blend, as they determine the overall growth characteristics of the plant.  Whenever you see 3 numbers on the front of a bag of fertilizer, these refer to the amounts of N-P-K.  Note that many fertilizer blends will supply nitrogen in up to 3 forms:  nitrate, ammonium, and urea.  In hydroponics, plants should be getting the majority of their nitrogen in the nitrate form, while the ammonium and urea forms should be kept to a minimum.

Secondary nutrients

  • Calcium (Ca)
  • Magnesium (Mg)
  • Sulfur (S)

Micro-nutrients

  • Chlorine (Cl)
  • Iron (Fe)
  • Boron (B)
  • Manganese (Mn)
  • Zinc (Zn)
  • Copper (Cu)
  • Molybdenum (Mo)
  • Nickel (Ni)
  • Cobalt (Co)
  • Silicon (Si)

How much of each nutrient should we provide in the hydroponic solution?  I have relied upon 4 main sources of information in determining how much of each nutrient to provide for general growing:

  • Dr. Bernard Kratky, pioneer of bucket hydroponics
  • Dr. Howard Resh, hydroponics guru
  • the widely-known “Lucas Formula”
  • Bobby Smith, also known as MHPgardener on YouTube

Here are the recommended concentrations for each nutrient (in parts-per-million or ppm):

N P K Ca Mg S Cl Fe B Mn Zn Cu Mo Ni Co Si
Kratky 112 31 142 90 28 2.0 1.0 1.0 0.2 0.2  0.1
Resh 180 50 210 180 40 3.0 0.5 0.5 0.1 0.1 0.1
Lucas 106 211 190 106 63 42 2.1 0.2 1.1 0.4 0.2 0.02
MHP 103 95 202 100 29 34 11 2.1 1.1 1.1 0.3 0.3 0.05  4.1

The MHP recipe is the same recipe that I outlined in the Step-By-Step Guide.  As you can see, the MHP recipe is pretty close to the average of the recommendations by Kratky, Resh, and the Lucas Formula.  I have found that it has worked pretty well for me so far.  If you would like more information about the MHP recipe, check out Bobby’s 10-minute instructional video on YouTube.

You should also be aware that the type of water you are using can influence the final concentration of certain nutrients.  As discussed on the Water Quality page, groundwater can contain significant ppm levels of calcium and magnesium, so you may want to compensate by decreasing the amount of added fertilizer.

Units of Measure

Fertilizers come in either a dry powdered form, or a liquid form in which the inorganic salts are already dissolved.  It can be a bit confusing when comparing the amounts of nutrients in different types of fertilizers.  To make it simpler, I normalize everything by considering each nutrient in terms of parts-per-million (ppm) in the final hydroponic solution.  Since there are several different units of measure commonly used, the following relationships are helpful in calculating the final ppm of each nutrient:

  • 1 ppm  = 1 mg/L = 1 milligram / liter = 0.001 g/L
  • 1 % = 10 g/L = 10 grams / liter
  • 1 % = 10,000 ppm
  • 1 gallon (gal) = 3.78541 L (liters)

As an example, let’s say you want to make up 5 gallons of the MHP recipe.  Masterblend 4-18-38 dry fertilizer contains 18% phosphorus (P), so if you weigh out 10 grams of the fertilizer, it will contain:

10 grams x 18% = 1.8 grams of P

If you then dissolve the 10 grams of the Masterblend into 5 gallons of water, the final concentration of P will be:

1.8 g / 5 gal = 1.8 g / 18.93 L = 0.095 g/L = 0.0095% = 95 ppm P

With liquid fertilizers, it is a bit less complicated, since you are simply making a dilution of the concentrated fertilizer with water.  For example, let’s look at Dyna-Gro Pro-TeKt, which contains 7.8% Si.  Using the relationship 1% = 10,000 ppm, Pro-TeKt contains 78,000 ppm Si.  If we take 1 mL of Pro-TeKt and dilute it into 5 gallons of water, this will result in a 18,927-fold dilution, which results in the following final concentration:

78,000 ppm / 18927 = 4.1 ppm Si

Fertilizer Recipes

Seedling Blend, using Liquid Grow:
1 gallon water (3.785 L)
1.2 mL Liquid Grow (Dyna-Gro)
1.2 mL pH Down (General Hydroponics)
pH = 6.0
Nutrient concentrations (in ppm):

N P K Ca Mg S Cl Fe B Mn Zn Cu Mo Ni Co Si
22 29 16  6 1.6  0.2 0.3 0.3 0.1 0.2 0.2 0.2 .003  .0003  .005

Regular-Strength Blend, using Masterblend:
5 gallons water (18.93 L)
10 g Masterblend 4-18-38
10 g calcium nitrate
5 g magnesium sulfate (epsom salt)
1 mL Pro-TeKt (Dyna-Gro)
5 mL pH Down (General Hydroponics)
pH = 6.0
Nutrient concentrations (in ppm):

N P K Ca Mg S Cl Fe B Mn Zn Cu Mo Ni Co Si
103 95 202  100 29 34 11 2.1 1.1 1.1 0.3 0.3 0.05 4.1

Extra-Strength Blend, using Masterblend:
5 gallons water (18.93 L)
12 g Masterblend 4-18-38
12 g calcium nitrate
6 g magnesium sulfate (epsom salt)
1 mL Pro-TeKt (Dyna-Gro)
5 mL pH Down (General Hydroponics)
pH = 6.0
Nutrient concentrations (in ppm):

N P K Ca Mg S Cl Fe B Mn Zn Cu Mo Ni Co Si
124 114 243 120 34 41 13 2.5 1.3 1.3 0.3 0.3 0.06 4.1

Bloom Blend, using Masterblend:
5 gallons water (18.93 L)
12 g Masterblend 4-18-38
6 g calcium nitrate
6 g magnesium sulfate (epsom salt)
1 mL Pro-TeKt (Dyna-Gro)
5 mL pH Down (General Hydroponics)
pH = 6.0
Nutrient concentrations (in ppm):

N P K Ca Mg S Cl Fe B Mn Zn Cu Mo Ni Co Si
74 114 243 60 34 41 13 2.5 1.3 1.3 0.3 0.3 0.06 4.1

Jungle Juice Blend:
5 gallons water (18.93 L)
25 mL Jungle Juice Grow (Advanced Nutrients)
25 mL Jungle Juice Bloom (Advanced Nutrients)
25 mL Jungle Juice Micro (Advanced Nutrients)
2.5 g calcium nitrate
1 mL Pro-TeKt (Dyna-Gro)
5 mL pH Down (General Hydroponics)
pH = 6.0
Nutrient concentrations (in ppm):

N P K Ca Mg S Cl Fe B Mn Zn Cu Mo Ni Co Si
113 79 147 91 26 13 1.3 0.1 0.7 0.3 0.1 0.01  .007 4.1

Fertilizer Calculator

I have created a Fertilizer Calculator to help you determine the precise nutrient concentrations in your fertilizer solutions.  It is available for free as a Google Spreadsheet, which can be viewed at this link.  This version cannot be edited, so feel free to download a copy to your personal account to make changes.  Once you have your own copy, you can alter the volumes, amounts of fertilizers, and even add new fertilizers.

If you already have a Google Drive account, click this link and then go to “File” –> “Make a copy…”.  Save the copy to your Google Drive.  Alternatively, if you would prefer to download it as an Excel spreadsheet, you can go to “File” –> “Download as” –> “Microsoft Excel (.xlsx)”.

Once you have a downloaded version that you can edit, open the file.  The first tab is called “Calculator”, shown here:

calculator_tab

You can enter the amounts of the defined fertilizers in the list, and the total volume of your fertilizer solution, either in gallons or liters.  The nutrient concentrations (in ppm) are then updated.  If you are using a fertilizer type that is not shown here, you can enter your own.  Just go to the “Fertilizers” tab, shown here:

fertilizer_tab

Enter the new fertilizer name and the concentration of each nutrient, as a percentage.  Then go back to the Calculator tab and enter the amounts for all the fertilizers you used, as well as the total volume.  The final nutrient concentrations are then updated.

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One thought on “Fertilizers

  1. My thanks to writer of this useful article.I am having difficulty in growing plants and trees. I am using many type of fertilizer without knowledge of about amount needed and the time to use. This article comes in time. I want to set a simple hydroponic system in my place and I am reading abou this interesting subject .

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