Production Advice – of Interest to Growers

Companies that use drip irrigation are advised to thoroughly clean their system prior to the next irrigation season. In practice many systems, headers, lines and drippers are often dirty and sometimes plugged.

For many years now we have known about the importance of irrigating and fertilizing no more than the plant or tree requires. With the increase in the production of nursery crops in large containers, bags and other above ground containers, the usage of drip  and micro irrigation has grown tremendously. Not every user appreciates the need for regular maintenance of both inline and spaghetti style drip irrigation. This has been noted in the European nursery industry where it was not unusual find irrigation systems clogged with iron, calcium and/or fine sand deposits.

This contamination can have several causes. The use of irrigation water that is too high in iron, calcium and/or bicarbonate can cause problems, as will water that is too high in pH. By-products of fertilizers can also cause problems. Calcium creates deposits when mixed with phosphorous and sulphuric acid. As a result Calcium Nitrate needs to be kept separate from phosphorous and sulphuric acid as all these deposits can also cause problems with irrigation filters.

Regular cleaning

Contamination influences the delivery of drippers and micro sprays. It is therefore important to clean the entire system on a regular basis. This should happen prior to the start of the irrigation season, and a dripper that is mostly or entirely clogged is best replaced.

The system has to be designed for easy flushing. Many systems in shade tree production are closed off with caps, where a small tap would make the flushing much easier and faster. Growers are advised to flush all the lines every two weeks throughout the growing season. A good rule of thumb is that the longer and harder the flushing, the better the cleaning. From several suppliers chemicals are available to clean and maintain drip irrigation systems.

Cleaning materials

The best known and most applied chemical for keeping fertilizers in suspension is nitric acid. Discuss with your supplier the concentration of nitric acid to be used and incorporate the material into the liquid feed formula.

Another important product is hydrogen peroxide — a highly oxidizing form of hydrogen and oxygen. Organic contamination is broken down through the oxidizing action of the peroxide.

Bleach can also be used. But it has one serious drawback. If it comes in contact with organic materials (eg. the crop), chlorinated hydrocarbons can be generated. These are damaging to both crops and the environment.

The above-mentioned cleaning materials can also be combined. For example a combination of nitric acid (3%) and hydrogen peroxide (3%) deals with all sorts of contamination. To be most effective this mixture needs to remain in the irrigation lines for 24 hours. This combination can be pre-mixed and will save time as a result.

Another possibility is bleach followed by nitric acid (both at 3%). These cannot be mixed. As the mixture will generated Chlorine gas, a highly toxic chemical. The technique for use of these materials together is first filling the lines with bleach followed by a clear water rinse, followed by the nitric acid, in turn followed by clear water.

Hydrogen Peroxide

In addition there is a product made up of hydrogen peroxide and an organic acid. According to the supplier a constant concentration of 25-30ppm is sufficient to keep the drip system clean, but caked-on dirt will take up to 5 weeks to disappear.

Another product in existence is a disinfectant based on hydrogen peroxide (47%) which has vinegar added. As a result of the addition of vinegar works better than hydrogen peroxide alone, is not nearly as aggressive and is almost odorless.

For horticultural production, environmentally-friendly water treatment equipment is also available. This machine is mounted in the irrigation header where it creates a magnetic field in the line. This results in more complete dissolving of nutrients and reduces the amount clinging to the inside of the irrigation lines, which, in turn, reduces  the surface area that slime and algae can attach to.

When using acids for cleaning, it is recommended that acid resistant gloves and safety goggles be worn. It is also advisable to hang the drippers outside of the pots.

Finally after every round of cleaning, it is important to properly flush all the lines to prevent the loosened dirt from clogging the drip emitters.

source: This e-mail address is being protected from spambots. You need JavaScript enabled to view it