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.
Keep the calcium and phosphate sources separate, when making a concentrate solution.
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:
Because plant growth begins slowing down about 5 hours before sunset, maximum use must be made of the time from sunrise to +/-2pm
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 should be dumped and replaced with a freshly made up solution, every 2 weeks, to avoid a nutrient imbalance from developing.