How to Recycle Potting Soil
Planting containers add beauty to indoor and outdoor spaces, but yearly potting soil replacement expenses add up quickly, depending on the number of outdoor planters. One way to keep your gardening budget low is to recycle last year’s potting soil. Gardening experts sometimes warn against recycling potting soil because there is a risk of transmitting diseases through the soil and because the soil is often depleted of nutrients. You can put these worries aside if you sterilize the soil and replenish nutrients to bring new life into the soil for growing healthy, beautiful plants.
Allow the plants in the outdoor planters to completely die off to remove the live root system and foliage.
Pull the dead plant from the outdoor planter and shake the dead plant over an empty 5-gallon bucket to remove potting soil clinging to the dead root system.
Discard the dead plants in a compost pile or over a garden area to decompose. Another option for recycling the dead plants is to spread the dead plants on a lawn and mulch them with a lawnmower. There’s no need to throw dead plants out with the garbage when they can decompose to contribute to healthy soil.
Scoop the remaining potting soil in the outdoor planter into a wheelbarrow by hand or with a garden trowel. If the planter is small, simply pour the soil into the bucket.
Pick any remaining roots, rocks and debris out of the potting soil by hand. You can also sift the soil through a screen.
Add approximately 2 gallons of peat moss and 1 gallon each of perlite and prepared compost for every 5 gallons of potting soil in the wheelbarrow. The peat and perlite aid in moisture retention and the compost restores nutrients to the potting soil. You may also choose to amend the soil with a slow-release, granular fertilizer or add fertilizer to potted plants according to individual plant needs.
Turn the potting soil in the wheelbarrow with a shovel or trowel to mix the potting soil and amendments.
Transfer the potting soil from the 5-gallon bucket to a large, disposable aluminum baking tray and cover with aluminum foil. Fill the pans within 1 inch of the top of the baking pan so the pan is still easy to handle. Use multiple trays or work in small batches if you have a lot of potting soil to recycle.
Place the aluminum baking tray in an oven preheated to 180 to 200 degrees Fahrenheit. Bake the soil for about 30 minutes to kill any harmful bacteria in the soil. Place a meat thermometer in the pan to ensure the soil doesn’t reach temperatures above 200 degrees F because this could cause plant toxins.
Remove the trays from the oven at the end of the baking cycle and dump the potting soil from the aluminum baking pan into the wheelbarrow; allow it to cool. Repeat the previous steps until all of the soil is baked and cooled.
Test the potting soil pH level with a soil pH self-testing kit. The soil should have an ideal pH level of around 6.8. Add lime to the soil to increase pH levels or iron sulfate to lower pH in soil. Mix in a small amount at a time and retest the potting soil until you get the ideal pH level. You may wish to wait to adjust pH levels for individual plants, because pH needs vary among different plant species.
Scoop the potting soil from the wheelbarrow into large, plastic storage containers with a shovel, then cover with the lid. Store the potting soil in a cool, dry place until you are ready to use it.
How to Recycle Potting Soil. Planting containers add beauty to indoor and outdoor spaces, but yearly potting soil replacement expenses add up quickly, depending on the number of outdoor planters. One way to keep your gardening budget low is to recycle last year’s potting soil. Gardening experts sometimes warn …
Recycling potting soil
Recycling potting soil
What do you do with your old potting soil? The current heatwave is a good opportunity to turn dry dusty old soil into a useful mineral rich medium for use in next month’s winter planting. Ideally is to mix this new medium with matured home made compost but if that is not available then the following procedure at least provides a good base for successful container gardening.
Soil used in pots, trays and containers looses its vitality very quickly. With some basic tools, particularly a good sieve and matching bucket, the first step is to sort this material. It is worth separating it into stony gritty compost and fibre filled compost, as much as possible. The aim is to create rough material for use in the bottom of containers and a finer, grittier material for use in the top half of containers.
To restore this material involves gently working water through the sifted soil, adding nutrients at the same time. For the bottom soil, animal manure pellets are dissolved in water (1 teaspoon to 2 litres water) in a bottle over 2 days. It must be well dissolved. For the top soil a seaweed extract (1 teaspoon to 1.25 litres water). The seaweed extract can be used immediately.
It should take about 10 minutes to work the liquid through the dry soil. This should be done slowly to aerate the soil and help the water bind. It is like a gentle baking procedure, turning and turning the soil, spraying as you go. Once damp (not wet) place the material in direct sun for a day or two, returning to spray again from time to time. The end material should be like very well cooked rice.
Happy container gardening
There is no reason to discard old potting soil. It can quite simply be made into a mineral rich slow-release growing medium. Baking the soil in the sun aids the slow release aspect. The material does lack the active biological content of mature compost but this can be added later (get some from a friend’s compost bin) or even consider starting a mini kitchen compost system. Being self sufficient in potting soil is possible.
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Recycling soil. The current heatwave is a good opportunity to turn old soil into a useful mineral rich medium for use in next month's winter planting.