The Art Of Feeding & Flushing

To ensure optimal plant growth, it is crucial to determine the right feed frequency and volume based on various factors. The choice of medium, growth stage, temperature, and humidity all play a role in determining the feeding requirements.

NFT Systems (No Media) In NFT systems, covering the entire root mat with the feed is important. During daylight, you can operate the pump continuously or intermittently, with around 10-20 feeds per hour. Adjust the feed frequency accordingly at night. Be cautious of sudden increases in air temperature, as it can lead to root drying if under-watering or pump failure occurs.

Perlite, Vermiculite, Expanded Clay For media such as perlite, vermiculite, and expanded clay, ensure that the entire root mat is sufficiently fed and flushed. Typically, feed once every 1-3 hours during the day and reduce the feed frequency at night.

Soil / Coco Coir / Rockwool When using soil, coco coir, or Rockwool in "run-to-waste" systems, avoiding over-watering to prevent issues like oxygen starvation, pest invasion, and fungal diseases is important. Adding up to 30% perlite or expanded clay can help improve water drainage. The feeding requirements will vary as the plant matures. Here are some guidelines:

• Nutrients or plain water: Using nutrients at each watering for coco and Rockwool. For soils with high nutrient retention capacity, consider using nutrients at alternate waterings to minimize salt build-up and the need for frequent flushing.
• Feed times: Avoid feeding during the lights-off period to prevent water logging. Start feeding at the beginning of the daylight period and stop at least 2 hours before night.
• Feed volume: Aim for nutrient feed volume that produces approximately 10-20% run-off out of the pot. This ensures a proper nutrient balance, flushes out excess salts, and thoroughly waters the root zone and medium.
• Feed frequency: As a general rule, feed once per day or every other day. Lift the pot or slab to check its weight to determine if the plants are ready for feeding. Adjust the frequency based on the soil's dryness or the coco's colour and texture.

Flushing is essential to remove salt deposits, dirt, and algae from the root zone, medium, and other system components. Pay close attention to flushing the root zone and feed circuit. Before replenishing the system with fresh nutrients, inspect filters, inlets, and feed outlets to ensure they are not blocked.

Recirculating Systems In recirculating systems, flushing should be done immediately after discarding the nutrient solution. Start by manually cleaning any visible build-up, then partially fill the reservoir with fresh water and operate the pump to flush the feed circuit, medium, and root zone. Using a garden hose can enhance the flushing process. Repeat this until the wastewater is clear and its electrical conductivity (EC) matches the input water.

Run-to-Waste Systems For coco coir and soil systems, it is generally recommended to flush weekly, while Rockwool should be flushed every two weeks. However, the frequency may vary based on growth stage, salinity, and temperature.

If flushing can be scheduled when the nutrient reservoir is empty, use the existing system hardware. Fill the reservoir with low alkalinity water (pH 5-6) and operate the nutrient pump until the EC of the run-off water is no more than 0.5 mS higher than the water in the reservoir. Additional flushing with a garden hose can be beneficial if the medium surface is easily accessible.

A dedicated reservoir and pump are recommended if the nutrient reservoir cannot be emptied for flushing. Connect it to the existing feed circuit using a 3-way valve that diverts flow to the second reservoir during flushing.

To learn more about feedings & flushing schedules, check out our friends Floramax's blog on this https://www.floramax.com/feeding-and-flushing/