How to rejuvenate old garden soil – While repotting, Old potting mix and more

Rejuvenating potting mix – How to rejuvenate old garden soil

A potting mix will be depleted of nutrients over time, this is a reality that most gardeners don’t realize until their plants stop growing or show poor signs of growth.

But why does potting mix get depleted of nutrients over time?

  • Leeching of nutrients through drainage and continuous rains.
  • Slow release of organic matter through drainage.
  • Plant’s growth, age, and root system.
  • Heavy feeder plants

To understand how plants deplete the potting mix, let’s understand that plants are:

  • Light feeders
  • Medium feeders
  • Heavy feeders

Consumer in place of feeder for easy of understanding that plants that are are heavy consumers deplete the potting mix of nutrients faster than light consumers.

There are 3 ways you can keep your potting mix fertile.

Top up method – How to add nutrients to old potting soil

Just like a prepaid mobile recharge to keep the phone services running, the top-up is probably one of the best methods to keep your potting mix full of nutrients and fertile. How to do that:

  • Prepare a uniform mix of the following items in the given proportions:
    • 500 grams vermicompost
    • 500 grams of cow manure powder
    • 100 grams neem cake powder
    • 100 grams of mustard cake powder
    • 100 grams bone meal powder (only for acidic potting mix)
    • OPTIONAL: 100 grams of wood ash
    • OPTIONAL: Handful of perlite, it won’t hurt to add a bit of drainage and aeration but it is not necessary.
    • OPTIONAL: Handful of cocopeat if your plant needs to retain more water.
  • When you are plant is due for watering, spread a 1-2 inch layer of this mix on the surface of potting mix in your container.
  • Water slowly first only so that the top mix is wet. After you finish watering all containers with this addition. Then water again from the first container but this time do deep watering till the water starts draining out. This is not necessary to do but in my experience, I have noticed that the first round of water settles the mix well on the surface so that when you water again, it gets distributed uniformly.
  • This method works great for perennials and fruit trees.
  • It takes anywhere between a fortnight or month for organic fertilizers to break down and start providing nutrients to plants therefore this is a great slow-release feeding method.
  • This method also helps in mimicking the natural ecosystem in forests where layers of organic matter on the surface are formed over years, proving home to helpful fungi, bacteria, and food for the plant.

Rejuvenate while repotting

When your plant outgrows your container or if the container is broken or when your plant is struggling for space to grow then it is time to repot your plant.

Repotting is a great opportunity to make up for the loss of nutrients in the soil.

There are two ways to re-pot:

  • Repotting with the entire pot ball of the plant: In this method, you extract the plant with the entire mix that has formed the shape of the container over time. This is usually done when you did not expect the plant to outgrow the pot so fast.
    • Make sure the plant is not watered for a day or two.
    • Extract the plant gently by tapping the sides and loosening the mix.
    • Fill the new container with the fresh potting mix, press it to clear air pockets
    • Put the full ball so that the surface of the plant matches the surface of the new container.
    • Fill potting mix across all sides pressing firmly.
    • Water thoroughly.
    • Keep in partial shade for a day or two.
  • Repotting with root pruning and trimming: In this method as the name suggests, you prune the excess roots (mostly the thin fiber-like from the sides) from the plant.
    • The steps are similar to the aforementioned but once the plant is extracted, gently dust off the potting mix from all sides to expose thin fibrous roots.
    • Then using a sharp sterilized scissor trim the roots. To reduce the size of the ball.
    • Don’t do it excessively unless you plan to make a bonsai out of the existing plant.
      If roots are outgrowing the old container from the bottom, you may chop them off too.
    • Get rid of the clay soil as much as possible.
    • Now prepare a liquid mix of 5ml liquid Humic acid + 1 ml of liquid seaweed extract in 1 to 1.5 liter of water and drench the plant after you finish adding the potting mix. This will help the plant recover from the shock, promote faster root growth, and also promotes microbial activity in the mix.

Rejuvenate old potting mix – Rejuvenating old potting soil

Potting mix is a precious commodity in your Terrace garden. When you have a lot of plants this may certainly add to your expenses unless you are making your compost, getting cow manure for free. But whether or not you have a zero-budget garden, it is a good idea to reuse old potting mix after rejuvenating it. But let me tell you that this is a tedious process although the result is rewarding.

How to rejuvenate old potting mix

Before we talk about rejuvenating potting mix, let’s understand how to choose a potting mix for reuse:

  • If your plant suffered through bacterial or fungi infection or was affected by insects in some way, then I would not recommend it for reuse. However you still want to use it, you may have to use it by worm composting[7] according to research at Cornell University (NY USA)
  • Don’t reuse potting mix if you have grown heavy feeders last year. Such potting mix has a higher level of nutrition depletion.
  • Check for Ph levels
  • This works great for vegetables and kitchen gardens.

How to rejuvenate old potting mix: Here is the step-by-step way to rejuvenate your old potting mix:

  • You would need a large plastic sheet, a large container with drainage holes, a trowel, and a rake if possible. Large plastic bags.
  • Spread your mix on the plastic sheet, a rake comes in handy here. Remove pieces of roots any unwanted stones etc. Loosen any clumps that may have formed.
  • Wash your mix: Take a large barrel with drainage holes, covered with a plastic net. Fill it with soil and saturate it with water.
  • Once the water stops draining, pour the potting mix back onto a plastic sheet, spread it, and leave it in the sun till fully dry and fluffy
  • 50/50: Once the mix is dried, take an equal quantity of the fresh potting mix and mix them both.
  • OPTIONAL: To adjust Ph add Neem cake or bone meal powder or lime.
    Put this mix in bags and leave them in dark & dry storage for about 2 weeks to cure and brew.
  • That’s it your rejuvenated potting mix is ready.
  • When you use it to plant, don’t forget to add the Humic + Seaweed mix mentioned while repotting.
  • You may do this process 2 times for your old mix and in some cases maybe 3. After that, your mix loses its ability to recharge itself.

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