Those of you who grow cannabis on COGr slabs will perhaps encounter a few small problems. Slabs should be soaked in water first. How can this be done? We used wood and some carpet to build a two-level rack for aqua trays. Our solution consists of a simple wooden frame placed on a bathtub. To make the wood surface slip-resistant we wrapped the upper part of the frame with some carpet. This allowed us to simultaneously work on six slabs. The water to be used for soaking slabs was mixed with a buffer agent in a tank and poured with a measuring jug into a funnel, which was left in place in the opening. To prevent water coming out of the top openings on the right, we placed the right frame a bit higher and well-sealed, in order to leave the slabs a little slanted on the bathtub. by Robert B.
But there is also something important that should not be overlooked. Slabs should be soaked for three days, in any case, on the left lower part of the slabs you will see a couple of drain holes to allow water to flow out. Water comes out of the aqua tray in a dark brown colour. If you collect the water and measure its EC value, it will measure around 3.0, or occasionally above 4.0 EC. (If you can no longer measure the value, then mix the collected water in a 1 to 1 proportion with tap water and measure the value, multiply it by two, then deduct the EC value of tap water, this will give you the EC level of the slabs.) The COGr in the slab is mixed with a couple of chemical products to make the COGr suitable for the root system. After soaking, the chemical products and COGr produce a brew with an extremely high EC level. For seedlings to develop a good root system and grow, the EC level in the slab should not exceed 2.0. Therefore if you supply pH-adjusted water through the slabs until the EC level dumped in the drain reaches a level below 2.0, then mix a nutrient solution with buffer agent and then further supply a couple of litres to the slab. This way your seedlings will receive the required quantity from the start.
In the blooming phase, you will add fertiliser for plants that are particularly in need of nutrients, so that the EC level measured at the drain exceeds 4.0 EC. If later you wish to reuse the COGr slabs, you should reduce this level to below 2.0 EC. You could do this three days before the harvest; the plant will no longer be fed with fertiliser and will ripen properly, your marijuana will have a better taste and its effect will be optimal.
If you do not plant your seedlings directly on COGr slabs, you could still plant them in loose, soaked and rinsed COGr placed in pots. The plants will be planted in a pot without soil, and in a pot with soil. When you later transfer the plant grown in a pot without soil onto the slab, the plant will root. With COGr slabs there will no longer be much work to do. Plants are first allowed to grow and, later, when transferred to the slab, they will complete their blooming cycle with no waste whatsoever.
PS: With an excessively high EC level in the first harvest, our yield was halved. Try it out, and form your own opinion based on the results you get.
COGr is an alternative medium to mineral wool, which is indeed less labour-intensive, as you do not need to soak it first for it to become impregnated with buffer agent for at least three days (for the agent to take effect). COGr should be pre-treated before using it with plants. In addition, COGr, like mineral wool, if used in combination with an enzyme product, can be used several times. Old roots should be removed, in order to retain the positive properties of the growing medium for the plants. Both experience and manufacturers say that these slabs can be used about nine months. At the end of this period, the COGr surface will change into a surface infested by fungi. This means that, after nine months, the fungi growing in the COGr slab will decompose the grainy and fibrous COGr and change it into a mealy mass. (Fungi only grow in an intact habitat, which is a good thing for you as it means that you have used the slabs to the best of your skills!). We did not attempt to grow plants on these decomposed slabs any further, we simply replaced them. However, we would suggest doing this. Those who wish, can obviously use one of the old slabs to see how plants react on the decomposed surface.
Waterlogged COGr could however be problematic. Before placing plants on top of these slabs, they should be pierced with a screwdriver on both top and bottom. One or two watering cycles per day during the bright phase will not do any harm, especially for young plants, for roots not to get mouldy on the waterlogged medium. If the plant tips are getting pale green or even white during growth, this means that roots growing in the COGr slab are rotting as a result of the excessive humidity. A solution, in this case, is reducing the watering frequency.