In nearly every soil recipe for cannabis, the recipe calls for an additive to aid in soil aeration. The point of these additives are to ensure that the soil drains water and retains enough air for the roots to thrive. It is important for the soil to remain moist because nutrients like nitrogen are only mobile when water is present. However, it is also very important that the soil not be overly saturated with water as it will suffocate the roots and promote detrimental bacteria growth. With that in mind, let’s take a look at the options for soil aeration.
Earth Worms are my favorite aerators of all time! While going about their work of decomposing solids in the soil, earth worms create tunnels and other voids in the soil that can both trap air and allow for increased drainage. A strong colony of earth worms can create a situation where you don’t need additives for aeration at all. Red Wigglers are a type of worm that are ideal for this given that it is very unlikely that they will overpopulate. Rice hulls are a good choice for an aeration starter in this case.
Rice Hulls, an agricultural by-product, are inexpensive and can be used at exactly the same rates as other aeration additives. Rice hulls will degrade over time – but it will take a year or so. When they degrade, the silica contained in the rice hulls are released and can be used by your cannabis plants. I recommend using rice hulls if you plan to use earth worms. By the time the hulls break down you should have a good colony of worms doing the aeration work. As an added bonus, rice hulls are a great sustainable addition to your soil.
Perlite is one of the most common additions for aeration and is created by heating volcanic glass until it expands. It is very light weight, retains water well, allows for drainage, and retains air as well. It is widely used in commercially available potting mixes. Perlite is extremely light and has the habit of ‘floating’ to the top of soil mixes. Perlite will last much longer than rice hulls, but eventually will break down into a gooey substance that isn’t helpful in soil. However, this can take years.
Pumice is a volcanic rock with good aeration properties. It retains air and allows for drainage well. It’s great for aeration, but is very heavy. If lifting heavy objects is a concern, you may wish to avoid pumice. It can also be costly but it will last almost indefinitely in your soils. “Lava rock” is commonly found for landscaping and makes a good aerator as well. If you can find a supply of small lava rock it can perform just as well as the most costly pumice. Be aware that lava rocks can be a bit jagged, so it can be hard on hands and roots.
Shale is commonly found in landscaping centers and can be acquired relatively cheaply. Shale can also be very heavy but does well as an aerator. The downside of using shale is that it tends to be solid and smooth so, although it will aide in drainage, it will not retain much water or trap air.
Expanded clay can make a solid, durable aeration amendment. It will hold some water and is very easy on the hands. While heavier than rice hulls and perlite, it isn’t as heavy as lava rock and shale.
Finally, while you can use gravel and other commonly available materials for aeration, it is very important that your aeration material is non-reactive and neutral in PHa measure of the acidity or alkalinity of a solution More. Using crushed limestone can modify the PHa measure of the acidity or alkalinity of a solution More of your soil. This can be nearly impossible to control in some situations and create major issues in your soil. It is best to use tried and tested materials for aeration when possible.
Happy Harvests!
— The Lit Farmer —