The nutrient solution in the nutrient reservoir needs to be renewed with fresh solution on a regular basis, ideally once a week, to ensure that all of the nutrients are available to your plants.

Between these changeovers the reservoir and pH levels need to be checked. The quality of the water and the size of your plants will determine how often this needs doing

TOPPING UP

As the plant takes up the nutrient solution, the amount of liquid in the reservoir will obviously decrease.
When the level gets low, the nutrient solution can become too ‘thick’ and the pH can rise sharply.
Therefore the reservoir should be kept topped up frequently.

Topping up involves a certain amount of guesswork, as without measuring the conductivity you cannot tell exactly the nutrient strength of the remaining solution in the reservoir. However, there are some general rules to follow.

Summer (hot conditions)

In hot conditions, the plant will have a high rate of transpiration, and will therefore draw up more solution (water) to replace that lost through the leaves. This will result in the nutrient solution becoming ‘thicker’, as the ratio between nutrients and water decreases in the solution.
You should therefore simply top up with plain water to dilute the solution.

Winter (cold conditions)

In cooler conditions, the transpiration rate will be at a minimum so a full strength nutrient solution can be used.

Spring/autumn (average conditions)

The nutrient solution will only slowly become diluted in average conditions as the plant uses the nutrients as well as water. If this is the case, top-up with a half strength nutrient solution.

ADDING NUTRIENT ADDITIVES

Once the nutrient solution has been topped up, any nutrient additives can be added.

CORRECTING THE PH LEVEL

If you leave a nutrient solution in a container, the pH level will remain stable. However, once it is put into the system, and the plant starts taking it up, the pH of the solution may alter. It will therefore need checking and correcting regularly, to ensure that the pH remains within the ideal range of pH 5 — pH 7. In some hard water areas the pH level can go outside of this range within 24 hours and the solution will therefore need adjusting daily. To correct the pH level, add drops of pH solution (up/down) and test until the desired level of pH 6 is reached.

RENEWAL

After about 7 — 14 days, one or more of the nutrient elements may be either in short supply or totally used up, which means that the plant is not getting everything it needs for optimum growth. In addition, the type and quantity of nutrients needed by a plant will change as it goes through the different stages of growth. Therefore renewal of the nutrients solution is essential, to ensure that there is sufficient availability of all the nutrients needed for healthy plant development.

Regular renewal of the nutrient solution will also ensure that unwanted salts are removed from the system. This will avoid any problems caused by salinity.