![]() ![]() In addition to being filled with plant roots, the air pores in perlite can capture solids like algae, debris, and biofilm, with a similar result: blocked percolation. Roots can fill up small pore spaces (like those in vermiculite), causing clogging, debris build-up, and pooling water. This means that when plants with an aggressive root system (either very mature plants or plants like mint and chives with lots of roots) extend into perlite, the pore spaces can get mucked up and blocked. Perlite, on the other hand, is composed of smaller particles. ![]() After all, there’s pore space to spare between the fairly large particles. With large aggregates like hydroton, plant roots growing down into the pore space isn’t going to affect the percolation much. 2) Aggressive root systems can cause blockage. You’ll have to weigh the pros and cons of that to decide whether you think this is sustainable or not. That said, we don’t use that much of it relative to all that is there (in 60 years we’ve used less than 1% of the world’s perlite ore) and it’s inexpensive. Although it will eventually renew, it’s not renewable in human time. Cons of perlite 1) Perlite ore is not a renewable resource. Those types of media can be mildly basic, which influences system pH and complicated pH dosing. A neutral media can be much more convenient and better for long-term system health. Perlite is also pH neutral, unlike some media like expanded shale and rock wool. Since perlite is not sourced from an organic source (similar to coir and peat) and has been sterilized in the creation process (being superheated), it has had almost no chance for bacterial, fungal, or insect pests to get into it. Some soilless media must be sterilized before being used to avoid the introduction of pests and diseases into the system. Since most applications (in soilless mixes or in systems like Bato buckets) use a relatively small amount of the medium, perlite is fairly cost-effective. You can get 4 cubic feet of perlite for $14 dollars at a hydroponic or greenhouse store (or online), while other sterile pH-neutral media, like hydroton, can cost nearly twice that. Perlite is a huge help in this area, as the large particle size not only provides air pockets and has no compaction problems, but actually has some oxygen-holding capacity and exchange. ![]() Growers can avoid anaerobic zones by keeping the water oxygenated (use correct flow rates, turbulence, and air stones) and avoiding build-up and compaction in the growing medium. The point is: avoiding anaerobic zones is crucial! Since their thing is decomposing, this is very bad news for plant roots. This allows for anaerobic bacteria (decomposers) to come in and start doing their thing. A lack of oxygen in water, soil, or anywhere that there are roots growing (the root zone) causes anaerobic conditions. 2) Perlite helps deal with anaerobic conditions.īecause perlite holds air so well and because it’s a coarse texture, it can do wonders for systems dealing with oxygen issues. You can sterilize the media with heat (using a rented soil sterilizer) or chemically with a hydrogen peroxide solution or bleach solution (remember to rinse it extremely well if using bleach). If you have a bad infection of something like pythium, then you’ll definitely want to wipe out any inoculum (the infecting part of a disease, for example, the spores) before using that media with new crops. The only time you might throw perlite away is if you have a very bad disease problem and no good way to sterilize it. Pros of perlite 1) Perlite is usually reusable. Read on to get details on the pros and cons of perlite. Growers should choose a medium based on how much it weighs, how easy it is to handle, how it impacts system pH and diseases, the size or texture, etc. That said, there are both pros and cons to using perlite in hydroponics. Many hydroponic growers use perlite as their primary medium (especially if they’re growing in Bato or Dutch buckets). Perlite has been used for decades in insulation, cement, and building materials, but recently has been used more and more for things like filtering and as a growing substrate. ![]() This makes it very lightweight and gives it air holding capacity-a real benefit for growers trying to keep root zones aerated. Perlite is ore that has been superheated in a kiln until it expands like popcorn. ![]()
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