Fertometer test in largest gardening magazine in the Netherlands: Groei & Bloei
Fertometer measures plants’ hunger
The roots of plants growing in the ground will grow in every direction, in search of nutrients.
Potted plants however have to find their nutrients in the tiny bit of soil in which they are
planted. Approved retail potting soil contains fertiliser. Over time, this fertiliser runs out, and
these nutrients must be added back into the soil. Until recently, there were no means available
to consumers for measuring the quantity of nutrients in soil.
Professional nurseries have been using the EC meter for years. This meter measures the
conductivity of the soil (Electrical Conductivity, or EC), in order to measure the quantity of
nutrients (ions) present for the plant roots to absorb. Wouldn’t it be great if consumers had an
easy way to determine the situation with the nutrients in their own potted plants at home?
Marius de Rijke is a grower of geraniums (Pelargonium) and other summer-blooming potted
plants in the French Dordogne region. He also happens to be an electrical engineer. Marius de
Rijke developed a simple EC meter for home use: the Fertometer. This measuring instrument
was recently introduced on the market.
The Fertometer is extremely simple to use: you simply drive the metal pin into the soil in the
pot and press the button. There are three light indicators on the meter. One of these will light
up. If the yellow light is illuminated, then the potted plant is suffering from a nutrient
deficiency and fertiliser is necessary. If the green light is illuminated, then there are sufficient
nutrients in the soil. If the red light is illuminated, then adding fertiliser is NOT advisable.
This means that there is more than enough fertiliser in the soil.
Tested and endorsed
The Dutch plant magazine, Groei & Bloei tested the Fertometer.
Test 1
We filled three pots with seeding and cutting soil (which does not contain fertiliser). We
soaked the first pot in pure tap water. When measured with the Fertometer, the yellow light lit
up, indicating undernourishment. For the second pot, we added the recommended quantity of
a composite fertiliser to the tap water. The Fertometer detected the increase in the nutrient
ions, and measured it. The green light lit up. There appeared to be sufficient nutrients in the
soil. We soaked the third pot with a double dosage of the fertiliser. The Fertometer detected
the higher value flawlessly. The red light lit up.
Test 2
The second test demonstrated that the Fertometer is also capable of measuring plants'
consumption of nutrients. We used two pots of equal volume. We put one pepper plant in one
of the pots. We placed three similar pepper plants in the other pot. Both pots received the
same amount of fertiliser. The yellow ‘deficiency’ light lit up much sooner in the pot with the
three plants, as a sign that the three plants had ‘gobbled up’ the available nutrients much
sooner.
Test 3
We conducted the same test with another (larger) pepper variety simultaneously. It was very
easy for us to determine from the consumption that the larger plants, with many leaves, got
‘hungry’ a lot sooner than the smaller pepper varieties. Tests 2 and 3 indicated that rapidly
growing plants with many leaves consume more nutrients and must therefore be more heavily
fertilised.
Test 4
Does it matter which fertiliser you use? Can the Fertometer measure the effects of different
types of fertilisers? Once again, we used pots of equal size, with similar plants. We fertilised
one pot with liquid artificial fertiliser (N7+P5+K7 and trace elements), and the other with
organic fertiliser from the same supplier (N4+P0+K5). Although the organic fertiliser
contains much lower levels of nutritive salts, the manufacturer indicated that you should use
exactly the same amount of the fertiliser (10 milliliters per liter of water). To our surprise, the
plants fed with the stronger artificial fertiliser appeared to become ‘hungry’ again after a few
days (the yellow light lit up again). With the plants fed the organic fertiliser, the green light on
the Fertometer remained lit up for a long time afterwards. This test showed that organic
fertiliser works better, or at any rate, for consumers.