Two-part fertiliser for growing in coco fibre

The fertiliser does, however, have its place in a decoupled system, where the pond water feeds a separate crop without ever returning to the fish. Coco blocks irrigated by drip irrigation with run-to-waste are the simplest example: the fish water serves as the base, and a fraction of the dose of Coco A+B tops up what it already provides. In this case, you adjust the feed to the measured conductivity rather than to the full dose, starting from the pond water and adding the fertiliser until you reach the target range. For seedlings destined for the coupled circuit, rockwool cubes rinsed in clean water remain preferable to a coco plug fed with fertiliser.

Water until it begins to drain from the bottom of the pot, once a day for the first few weeks, then up to twice a day on mature plants, at a rate of 4 to 6 litres per square metre per day. If you are growing in small pots, the root volume dries out faster and needs more frequent watering, whereas a large coco block holds moisture for longer. Letting the grow medium dry out slightly between feeds improves root aeration and limits the risk of rot. The fertiliser is suitable for hand watering, run-to-waste drip irrigation and ebb-and-flow tables. During intensive growth, adjust your feeds so that 10 to 20% of the solution drains out of the bottom, which prevents salt build-up. If you add PK 13/14 with very hard water, correct the pH with a pH down for growth rather than a pH down for flowering, to avoid a deposit that would block the drippers.

After three to four weeks, a check of the grow medium tells you whether the nutrition is still balanced. Squeeze a handful of coco into a little water and measure the liquid you collect: a conductivity of 1.1 to 1.3 mS/cm and a pH of 5.5 to 6.2 indicate a grow medium in good condition. When the conductivity is well above this range, salts have built up around the roots, and flushing with slightly acidified water at pH 5.8 clears them before you resume feeding at the usual dose.

Each kit contains one bottle of A and one bottle of B of the same volume. The 2 x 1 litre kit makes up 250 litres of solution, enough to feed a few large pots of tomatoes or strawberries for several weeks. The 2 x 5 and 2 x 10 litre kits are intended for a whole greenhouse or for drip irrigation over several rows, and make up 1,250 and 2,500 litres of solution respectively. Choose the size according to the volume you water each week, then store the bottles closed, away from light, which degrades the iron chelates, away from frost and out of the reach of children.