How to reuse and recharge old potting soil (4 Easy Methods)

reuse and recharge old potting soil

Reuse your old potting and container soil to save money! Container gardening is fun, easy, and has numerous advantages. One disadvantage, however, can be costly. Potting soils are not cheap and even just a modest amount of container veggies can send expenses through the roof.

In this article, let’s look at two ways that we can repurpose old, spent potting mix to save money in our garden. And on top of that, let’s discover even two more ways to revitalize and recharge the soil from our old containers from last year into a brand new potting mix, just as good as any on the market!

Part 1: Repurposing and recycling old potting soils

Literally, every crop I grow outside of lettuce, carrots, and maybe beans are done through a progressive series of plugs to pots and then moved on to either larger pots or the garden itself.

Multiple times throughout the year I’ll have excess soil and potting mix that normally for most people would be simply discarded or destined for the compost.

Rather than throw away that spent soil let’s look at two ways that we can reuse it to save both time and money.

Reuse old potting soil method #1 Fill or top-up raised bed

The first way that we can reuse spent soil is to simply use it as a fill for our raised beds.

Either to fill up and use as a base in new beds that take an extraordinary amount of fill as you well know or by topping off existing beds that have sunken down and can use an extra layer of clean organic matter.

When simply using the old soil as fill you can empty the pots, weeds, and all into a wheelbarrow for ease of transport.

However, when using as a topping mix I do like to take out the larger debris in the particulate matter as well as eliminate any weeds that might be there. This is because we’ll be applying this stuff right at the bed surface.

Looking closer at the above image, you can clearly see that there’s nothing wrong with this potting mixture and it’s almost silly not to repurpose it.

Reuse old potting soil method #2 back into containers

The second way that we can repurpose old spent soil is to place it in the bottom of new pots that we’re about to put new plants in. Much like we did with our raised beds only on a smaller scale we can take that old mix and place it directly in new pots that we’re about to make.

We can fill the bottom of the new pots that are about to be planted anywhere from 25 to 30 with that old soil.

After just a few large pots this can save you a massive amount of new potting mix that we won’t have to buy or make.

Simply fill the bottom of the new pot with a quarter or even up to a third of the old soil mix and then plant like you normally would with your new fresh mixture and you’re good to go.

The plants won’t know the difference and you’ve just saved yourself 30 percent of your input cost. But the real action is in recharging or revitalizing this mix so that it can be used as it was intended to pot up new plants.

Also, read How does soil affect plant growth? [Importance of Soil].

Part 2: Recharging or Revitalizing soil

Recharge soil Method 1: Mix it Up!

The most widely used method to recharging spent soils is to mix them at a specific ratio with a new potting mix. Commonly one-quarter to one-third of the old soil is used with three-quarters to two-thirds of the new soil.

We mix the two to bulk up the new mix as well as extend the life of the old. Because the old soil is mostly inert this is a great way to recharge it with some new life as well as a proven method to bulk up and make your new potting soil go further.

The ratio in which you choose to mix will depend on the condition of your old soil. When soil is used to grow plants it changes in both composition and structure Plants themselves will use up the nutrients and soluble elements in the soil as they grow and produce.

Furthermore watering your soil washes out even more nutrients as well as particular organic matter. This leaves us with a relatively inert sometimes sandy mixture.

So if your spent soil is particularly old, crusty, or even hydrophobic don’t be shy about increasing that ratio to even 50-50.

Recharge soil Method 2: Add Amendments!

The second way to revitalizing old soil mixes is to simply add back to them the amendments that make potting and container mix so great in the first place.

In order of preference, I add amendments like alfalfa meal for natural nitrogen and plant hormones, rock dust for soil remineralization, oyster flakes for extra calcium, canola meal for more natural nitrogen, rock phosphate for the only organic phosphorus available, Epsom salts for magnesium, and sulfur and both dolomite lime and elemental sulfur for ph control.

Pre-mix your preferred amendments together to allow for a more even application. Two more amendments worth mentioning are worm castings if you can get them and good old compost.

On top of the amendments that we just added because the overall structure of the soil has likely changed due to all the watering, We’re gonna have to add back in a light organic base as well, usually in the form of coconut fiber or peat moss.

Because of the unsustainable nature of the way peat moss is harvested I do try to use coconut fiber wherever possible.

Keep track as you go along trying to make the ratio of the old soil to the amendments plus organic base to hit that ratio you’re after.

another benefit of that coconut fiber and peat moss

Also, another benefit of that coconut fiber and peat moss is if your old soil is really really dry and possibly hydrophobic this is a great way to add moisture back into the mix.

Whichever method you choose whether to reuse or revitalize your spent container soil just know that there’s always an avenue out there to recycle that lovely dirt.

With a little bit of time and less effort than you think you just might save yourself money and also make your farm a little more self-sufficient along the way.

Hey, thanks for reading guys if you’re getting value in this please share with your friends and family. Happy Gardening!

Also, read How to prepare the best soil mix for raised beds [Perfect Guide].

I am Fenil Kalal. Professionally I have done Engineering in Information and Technology. Gardening is my passion/love/favorite hobby and I have 5+ years of experience in Gardening.

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