Hydroponic Feeding

Rule of Thumb

A heaped handful of GROMOR fertilizer weighs approximately 50g. Pacing up and down an area in lines one pace apart and throwing a handful of fertilizer in a wide arc into the air for every pace taken, will apply 60g/m2 (600kg/ha). Throwing a handful of fertilizer every second pace will apply 30g/m2 (300kg/ha).
1 Litre GROMOR Accelerator = 600g
1 Cup GROMOR Accelerator = 140g
1 Handful GROMOR Accelerator = 30g

1.Water pH

Before making up a nutrient solution, it is essential that the water pH be checked. If the pH exceeds 6,4, acid should be added to the water BEFORE any fertilizer is added.

How much acid to add, depends on the pH and the buffering capacity of the water. Initially add 125ml Nitric Acid per 1000 litres water, gradually adding more until the pH drops below 6,4. Once a rate per 1000 litres is established, a weekly pH check will usually suffice.


  • The pH of water from the same source, does NOT always remain constant.
  • If the nutrient solution goes cloudy when adding fertilizer, it is precipitating and the elements will not be available to plants. Seek advice!
  • Acid is dangerous. Avoid contact and make sure NO metal touches the acid in its concentrated form.

Concentrate Solutions

Keep the calcium and phosphate sources separate, when making a concentrate solution.

  • Don’t make concentrate fertilizer solutions more concentrated than 1kg fertilizer in 10 litres water - preferably not stronger than 1kg in 20 litres.
  • Make certain that the water used to make the concentrate solution, has a pH less than 6,4
  • Use concentrate solutions as quickly as possible - preferably within three days
  • Dissolving fertilizers in a bucket of water, is effectively making a concentrate solution, making the above rules applicable!

Chemical Drought

Chemical drought occurs in crops grown in bags, where there is insufficient run off. The EC around the root ball increases to unacceptably high levels. It can be identified, by taking weekly leachate EC readings, which should not exceed those of the nutrient solution by more than 10%.

To rectify the problem:

  • Place the “drippers” as close to the plant stem as is practically possible, but NOT directly onto it.
  • Allow for 20% runoff at each watering.
  • Apply a watering regime that will not allow the media to dry out.

Give a light watering at sunrise

Because plant growth begins slowing down about 5 hours before sunset, maximum use must be made of the time from sunrise to +/-2pm

  • Open tunnels to get a change of air and give a light irrigation at sunrise.

Institute a 10px feed in the hot months

This will lessen the chances of cracking fruit. (If practical, this feed should constitute 1kg Calcium Nitrate or Calmag N in 1000L water rather than a complete nutrient solution).

Recirculating Nutrient Solutions (eg. gravelbeds)

Recirculating nutrient solutions should be dumped and replaced with a freshly made up solution, every 2 weeks, to avoid a nutrient imbalance from developing.

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