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Units of Fertilizer Concentration

February 11, 2018

There are many globally accepted units of fertilizer concentration or fertilizer dose rates. The commonly used units of fertilizer concentration are listed below. We will discuss their merits and consider how you can compare / convert between the various measures.

1. ml/L
2. Ratio
3. % Concentration
4. US teaspoons / USG
5. US tablespoons / USG
6. US FL Oz / 1 USG
7. scoops / L or scoops / USG

The first three units of fertilizer concentration are globally recognised terms / ways to describe fertilizer concentrations, whereas terms 4 – 6 inclusive are US centric. The 7th term is neither metric or imperial but rather describes a method of measuring powder fertilizers. Before discussing these units of fertilizer concentration in further detail we must appreciate that they all describe concentration, fertilizer concentration in this instance.


1. ml/L

The majority of gardeners use metric units due to simplicity and convenience and are comfortable that fertilizer concentration is measured in ml of fertilizer per Litre of water (ml/L). Not only is it easy to describe fertilizer concentration but it is also practical in application terms.

As an example, a fertilizer concentration of 50ml/10L requires you to measure 50ml of fertilizer and mix it with 10L of water prior to applying the mixture to your plants.


2. Ratio

Ratio is a globally recognised term but slightly less definitive than other terms such as mL/L.

Ratios are typically assumed to be on a volumetric basis rather than a mass basis.

A ratio of 1:200 (corresponding to 50mL/L), means that 1 unit of fertilizer is mixed with 200 units of water prior to fertigation.


3. Percentage

Percentage is another globally recognised term describing fertilizer concentration. Essentially it means that 1 unit of fertilizer is mixed with 100 units of water.

By way of an example 0.5% concentration (corresponds to 50ml/L or a ratio of 1:200) requires the user to mix 0.5 units of fertilizer with 100 units of water.


4. US teaspoon / USG

This method of fertilizer concentration requires the user to place a certain number of US teaspoons of fertilizer in 1 US gallon of water.

To allow the user to compare / convert to and from the metric system:

1 US Teaspoon = 5mL

US Gallon = 3.79 L

Therefore 1 US tsp / USG would correspond to a metric measure of 13.0193 ml / 10L of water.


5. US tablespoon / USG

Typically used to describe larger fertilizer concentration, the user places a certain number of US tablespoons of fertilizer in 1 US gallon of water.

To allow the user to compare / convert to and from the metric system:

1 US Tablespoon = 15mL

1US Tablespoon = 3 US teaspoons

To allow a metric user to convert between the two units of measure 1 US Tbsp / USG equates to a metric measure of 39.578 ml / 10L of water.


6. US Fl Oz / USG

Finally, perhaps the least used and measure may be IS Fl oz / USG. Here the user will measure a certain number of US Fl Oz and mix it with 1 USG of water.

Converting to a metric measure this will equate to 78.02ml / 10 of water.


7. scoop / L or scoop / USG

This measurement method typically relates to dry powder fertilizers which you mix with liquid so that you can subsequently “pour” onto the plant roots system.

Please refer to our article describing how to use water soluble powder fertilizer with an automatic fertilizing system.


Each of the above methods of measurement lend themselves to automatically fertilizing with a fertigate automatic fertilizer. Refer to our article on how to choose the most appropriate automatic fertilizing unit for your requirements and then select one of our high quality fertigate units.

Fertilizing your plants will never be easier to achieve on a regular basis and your plants will respond accordingly.

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