Testing Your Media
When you run a test to compare two (or more) kinds of growing media, you need to make sure all growing conditions are the same.
For example; if you are looking to test the bigger block sizes, you need to use seedlings that were grown the exact same way for transplanting into the blocks. Start your seeds or cuttings at the same time, in the same starters. From these young plants you choose similar size plants to transplant into the blocks you want to test.
All plants should be exposed to the same conditions: light, temperature, humidity, nutrient, etc.
The only thing you need to do different is the amount of water. Different media have different water holding capacities. (see Growing Media) Therefore the amount of water and the frequency of watering need to be adjusted to the individual medium. An example would be comparing clay pellets in a 4” pot with a 4” Grodan block. Clay would need continuous watering (or at least very frequent), whereas Grodan needs intermittent watering.
If you choose a media with buffer such as peat to test it versus a non-buffering media you need to choose what your goal is. If your goal is to see how much growth you can get for equal amount of nutrient—then you feed the plants according to the un-buffered media. (see picture) Or you choose to feed /water according to the individual media’s requirement—so you can see the best possible plant/growth from each media.
Media with no buffer requires less nutrient, as the media does not hold back any nutrient from the plant.
Other experiments to evaluate media.
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Rooting Test
How well are the roots able to utilize the entire volume of the medium? Meaning do the roots grow throughout the whole medium.
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Blue dye test
When you fertigate (water with nutrient solution) will the solution spread throughout the medium, so the food reaches all the root tips? This uniformity test can be tested by doing a blue dye test. The blue dye test is great if you are looking for a fast media evaluation.
You can use the same methods to test any medium against another. If you use loose media, put each of them in a long plant container.
