When To Flush Hydroponics

by Lettuce Be | Last Updated: 01/29/2022

A hydroponics system should be flushed for two reasons. You’re either flushing to clean out the system or to remove extra nutrients from your plants. There are significant distinctions between a plant flush that occurs throughout the growth cycle of a crop and a cleaning flush that occurs between crops.

A cleaning flush appears to be rather uncontroversial, but a plant flush is a different situation.

Flushing Between Crops

In order to maintain the plants in a hydroponic system healthy, cleanliness is essential. A hydroponic system’s water reservoir, feed lines, and pump should all be kept wet during the growing cycle. This is enough time for various fungi and bacteria to establish themselves. We know there are beneficial bacteria, but the real problem is pathogenic or hazardous microbes, which tend to proliferate alongside the beneficial ones, especially if the system’s beneficial numbers are low.

In addition to microorganisms, your system accumulates nutrients, nutrient by-products, and salts, which is why flushing is required at the end of each crop cycle. It is possible to verify fertilizer levels in the water, but it is more difficult to determine nutrient levels in the grow media. Because of this, and because you need to know how much and which nutrients are already in the system, a thorough cleansing, flushing, and rinsing is critical to getting the most out of your next crop while avoiding any flavor or health issues.

Another major threat is algae. Although an alga infestation is unlikely to damage your plants, it does feed on the same nutrients that your plants require, reducing crop yield. It’s often the case that the alga isn’t present in large enough quantities to be seen, yet it’s present enough to affect yield and health.

A good flush, along with proper maintenance and a high-quality filter, can help to reduce the presence of algae. Remember that algae compete for oxygen in the water, which is still another reason for starting each new crop cleanly. Plant health is dependent on the state of your grow material, reservoir, pump, feed lines, and drip emitters. Consider each of these factors when undertaking inter-crop cleaning. Old grow media is frequently abandoned since cleaning it fully appears to be too time-consuming. There are various products and methods for flushing your system available.

Look them up! The accumulation of salts or living organisms such as algae is a major problem for drip emitters. To cope with emitter plugging, quality rinse treatments are available, which when used properly, will keep your emitters running for many more crop cycles. The bottom line is to try to get your system and media as clean and disinfected as possible before starting each fresh harvest. Ensure that all disinfectant residue has been eliminated and that the appropriate beneficial microorganisms have been re-established. Maintaining a living soil or water system, as well as disinfected grow media, is a goal. So, after cleaning and disinfecting, make sure to rinse away the cleaning chemicals with plenty of fresh water, let it dry so that air (oxygen) can do its job, and then re-establish beneficial microorganism levels.

Flushing During the Grow Cycle

When researching this element of crop care, you’ll notice that both sides have strong beliefs. Some studies argue that there is no evidence to support the claims and benefits of rinsing or leaching during the crop cycle, but I could not discover any evidence that it is ineffective. Many gardeners believe that depriving the plant of nutrients during its last stages (about 10 days before harvest) reduces the amount of nutrients stored in the leaves, resulting in tastier specimens. However, a similar number of growers do not believe this.

I believe there are facts on both sides of this issue, as with most technical debates. I imagine that when the level of nourishment delivered in the original place is rather high, this rinse or leaching procedure is most beneficial. It’s not uncommon to find salt damage on the leaf of plants that have been overfertilized or where salts have accumulated over time. Almost always, a recommendation to flush or drain the soil is made when this over-fertilized state is corrected. It is common for growers to use more fertilizer than is suggested in order to maximize growth.

This would necessitate some type of flushing. There may be other reasons for flushing before harvest, but the debate and disagreement is intense. I couldn’t discover any research that compared these approaches at this time.

  • How about those slimy roots? – If you can see and feel slimy roots in your system, you should clean them as quickly as possible by rinsing well and flushing the media. The infection can be stopped by applying a diluted dosage of hydrogen peroxide to the diseased roots. Disinfecting your system between crops will help to reduce the chance of this condition developing in the first place.
  • What about old age? – Plants go through a natural aging process. Consider the shifting color of the leaves in the fall. The plant extracts nutrients from some of its leaves and stores the energy in its roots. This isn’t the only aspect of senescence.
  • Some plants are annuals, meaning they only live for one season, while others are perennials, meaning they live for multiple seasons. Perennials must store energy in their roots as part of their aging process. The annuals we plant for food go through the same aging process.

We actively interfere with senescence because we normally desire certain qualities from our vegetables that would be unavailable if they were allowed to fully mature before harvest. The plant’s purpose is to generate seeds and then reproduce. Flushing allows growers to change the taste or other characteristics of their crop before harvest, which is consistent with traditional agriculture.

What about salt accumulation? When growing beautiful plants in the landscape, salts accumulate over time, and leaching or flushing can improve the health and vigor of the plants significantly. Fruit trees that have been exposed to high levels of total dissolved solids (TDS) or inadequate drainage will benefit from flushing. The accumulation of salt on the roots is harmful. Many hydroponic edible crops have a shorter life cycle than soil-grown crops, therefore rhizosphere salts should not be an issue provided there has been no buildup over time. However, if you apply a lot of nutrients, the salt index in the soil or grow media will be higher, and you’ll probably have a lot of salts. Flushing helps with this.

Crop Flushing Timing

Tissue samples taken from the leaves of plants in a controlled study can be used to determine how much phosphate and nitrogen is left after a complete rinsing. This could bring much-needed insight into this area, although research is yet restricted. For the time being, suppose that cutting off the nitrogen regimen and flushing the rhizosphere will aid in the lowering of nutrient levels discovered in the foliage and have an impact on the flavor of said foliage. If you want to do this, flush during the dark cycle so that your plants are less likely to absorb any flushing additives. When the photosynthetic mechanism is not working, plants are much less active in general.

Salt buildup can occur when edible plants are subjected to intensive fertilization, which may be done to increase crop mass or vigor. This buildup can cause nutritional lockup, and signs of malnutrition can emerge as a result. As a result, flushing a plant on a regular or irregular basis can be beneficial rather than simply in the last 10 days of growth. When leaching occurs early in the development cycle, it should be quickly followed by a healthy, well-balanced injection of fertilizer to restore proper nutrient levels. Always remember to flush your helpful microorganisms whenever you flush. During a flush, their numbers will be reduced and should be replenished.The pathogenic bacteria will be lowered as well, and because you won’t be replenishing them, the good-to-bad ratio will improve dramatically.

Cleaning and flushing your systems is an essential aspect of maintaining a healthy crop. Whether you do it before or during the growing cycle, the timing and reason for doing so will be determined by the components that are present in your crop. Take notes while you inspect your plants and then take steps to correct any undesirable symptoms. Growing is enjoyable, and the trials add to the excitement.