How to Maintain Organic Soil in Raised Garden Beds

organic soil in raised garden beds

Soil is where we can make a great harvest, or ruin the entire years crop. Organic growing methods depend on having living soil, and as each season passes, and if we neglect the soil for a season, it can become a little tired and very unproductive.

A novice gardener may think that the soil needs replacing, but the more experienced grower knows that there are a few things that can bring the soil back to life and ready for full production.

This article is all about the methods and techniques we use here in our own yard and we have found them to be satisfactory so far.

But before we jump into the article, the skill of building and maintaining soil is required learning if resilience is needed, and we all know this is a desirable thing, so “23 skills for self-sufficient living” is a good starter for a list.

So now for this post, and how do we maintain our soil? Read on to find out.

How do you refresh the soil in a raised garden bed?

During a growing season, many nutrients are taken from the soil that need time to be available again. Because we are growing food and look to maximize the yield we often drain the soil of available nutrients.

The soil can be recharged naturally or we can fast track it through our actions. The list below details some of the methods to refresh raised garden bed soil in an organic way.

  1. Add Compost.
  2. Sprinkle Rock dust over the soil.
  3. Plant green cover crops like legumes.
  4. Place mulch over the soil to keep biological activity healthy.
  5. Give the bed an organic soil top up.

1. Why add compost to raised garden beds?

Adding compost to raised garden bed soil will replace nutrients, minerals, and trace elements that have either been removed from the soil by plants and vegetables, or have slowly leached into the lower layers of the garden bed through constant watering.

Good quality compost will have all of these elements in a plant available form within it, and the compost can also hold an incredible amount of biological life that is very beneficial to your soil and plants.

What compost is best for a raised garden bed?

There are commercially available composts that are suitable for organic use, however we like to make our own using what is known as the Berkeley method. It is the only method we now use personally, and we find it to be very effective and really fast. Compost for self-sufficient gardening gives the details.

2. Does rock dust improve garden bed soil?

Re-mineralizing your garden bed soil is worth looking at if you are in an area that receives heavy rainfall frequently. We have this challenge where we live as we are in the northeast tropics of Australia and we get tremendous rains at times.

While rock dust can take a little time to become plant available, it definitely improves garden bed soil.

When it is applied with the other items that are on this list, like compost and mulch, the biological activity converts the minerals in the rock dust into plant available forms and this can have a profound effect at times.

Where do you get rock dust from, and are they all the same?

Good garden centers should have stocks of this product. We found two brands locally that started us down a very specific path that now produces all of our fertilizer that we need on site.

This information can be found in this article titled “improve your garden soil with rock dust and chickens“. It explains in detail what we do to achieve great results.

rock dust loaded chicken manure
Taken from the roosting box as described in the linked article.

Whatever brand you find, look for the mineral analysis that should be provided on the product. One that we use has over 70 minerals and trace elements.

3. What do cover crops do to organic soils?

Cover crops are a way to keep biological activity active and with careful crop selection can be a way of replacing nitrogen in the soil.

One method of using cover crops is to grow legumes like cow peas and similar small greens then digging them into the soil a few weeks before you are looking to replant the raised garden bed with vegetables.

The biomass that is now under the soil was home to millions of beneficial bacteria that are now dead and the minerals and nutrients that made up those life forms are now plant available. The cover crops can keep the soil cooler in hot weather as well.

Keeping the soil cool can be a challenge with corrugated steel garden beds, as mentioned in “Organic raised bed gardening, what are the disadvantages?

4. What are the benefits of mulching a raised garden bed?

Mulching a garden bed is a good way of keeping moisture in a garden bed while providing habitat for beneficial biology to interact with the soil interface.

This activity helps to break down soil components into plant available forms that benefit our vegetables.

If you are interested in how much difference a good mulch can make, we have a post dedicated to an event we had in one of our garden beds. The article is titled “growing lots of ginger, is this the best mulch?” and we recommend it.

5. Why does raised garden bed soil keep sinking?

Our raised garden bed soil levels are always sinking, and we suspect that we aren’t the only people who are having this happen to them.

The reason why raised garden bed soil levels sink is because the fill that was put at the bottom of the bed as it was being filled is now rotting down and settling.

sinking soil in raised garden beds
The stump was removed and put into the base of this raised garden bed.

We used a lot of tree trunk sections and large root balls that we came from a few trees that we had removed when placing the raised beds in their final locations.

Because we are in a tropical zone, woody items rot down quickly so we have found the soil level in the beds sinks about 4 inches each growing season. The soil is free draining so the moisture is getting down to these logs and branches to rot them.

It is because of the wood rotting so fast where we live that we use corrugated metal garden beds as described in “Why use corrugated steel raised garden beds?” and why we avoid wood framed raised garden beds.

Even without the woody lumps down at the base of these beds the soil will settle as time rolls on. The organic matter in these beds is required though for long term fertility. This post titled “what is the best soil for organic gardening in raised beds?” explains why.

How do I keep my raised garden bed soil healthy?

Healthy soil grows healthy vegetables, so it is important to keep on top of your soils health. How to tell if your soil is in good condition is the number of worms that are in the soil as you work it. The quality of farm land was once measured by the earthworm count per square foot.

Poor soil has very little biological activity and healthy soil is alive with movement. By mimicking the natural soil building processes that can be found under leaf litter in low lying areas in local parks and nature walks, you can get some idea on what we should be aiming for.

organic vegetables grown in raised garden beds
Light mulch over open spots. No fertilizers used, linked articles explain why.

Observation is the first step in keeping your soil healthy, and then acting on our observations in a methodical intelligent fashion. It is also worth keeping tabs on the soil temperatures near the garden bed edges and why we say this is explained in “Does the soil in metal raised garden beds get hot?”

How do I improve the soil in my raised garden bed?

It is easy to improve garden soil by adding organic matter into the soil as you prepare a bed for the seasons planting.

There are very few situations where adding organic matter is harmful to plants because what we are doing is stepping in and fast tracking what happens in the natural world as woody material slowly breaks down and washes into the soil over time.

Our method of adding this material into the soil is actually a task that our chickens do for us and this article titled “making organic soil for raised garden beds” explains the method in detail.

How do you fertilize raised garden bed soil?

You can fertilize the soil in a raised garden bed in many ways, however if you are looking to grow in an organic fashion then this removes the chemical fertilizers that are stocked in stores.

These chemical fertilizers are good at supplying the plants with just the basic requirements to make your plant look healthy, and while they can look like they are doing a great job, some of them are doing damage to the soil biology beneath the surface.

It is this biology that can allow you to grow organic food in your raised garden beds with simple additions of compost and mulch, without the harmful chemical brews.

Animal manures are a great way of giving nutrients to the soil as well.

What is the difference between raised bed soil and garden bed soil?

The primary difference between the two soils is our ability to define the soil profile of the garden beds as we first fill them up.

We don’t often have the need to dig down a few feet to prepare an in-ground garden bed, but we do have the chance to work with the deeper soil types as we fill a raised garden bed with organic soil.

The raised beds also allow us to have a completely different soil type to allow us to grow different plants that would otherwise not grow in the ground. This is related to soil pH and how we can adapt a bed to be more acidic or alkaline depending on what we choose to do.

How often do you change the soil in raised beds?

If the soil is not harboring disease and the pH is suitable for growing the plants you prefer, there should be no reason to change your soil.

The active organic gardener will be adding things to the soil as each season rolls past, and the soil can actually get more fertile if you are applying sound techniques and practices to your raised beds. Changing the soil is usually a last resort to cure a problem.

When should you change raised garden bed soil?

Changing the soil in a raised garden bed should be done if the soil is found to hold some sort of biological problem and a solution cannot be found to cure it. The task of removing the soil is a hard one and should only be considered as a last resort.

How long does raised garden bed soil last?

Raised garden bed soil is a living substance when you apply good organic growing practices so to rephrase the question, how long does soil fertility last.

This is up to each individual gardener, and the more active growers will be able to increase the soil fertility even as they grow food in the raised garden beds.

To achieve this it does take a bit of observation and knowhow to get into the same behavior that the natural composting processes can teach us about. The first big learning step for us was when we started to make our own compost using the method we mentioned above.

We even went as far as buying a microscope to investigate the life forms that we had grown in the compost piles. It is through this understanding that we now feel confident that we can grow most of our organic vegetables in the soil we have created with the chickens.

We are into our third year of food growing without store bought additives and fertilizers and we have had no problems to speak of so far. If you are looking at making your own raised garden beds and want to be organic, “What is the safest material for organic raised bed gardening?” is worth a look at before you start.


The best advice we can give any beginner gardener is to take a Permaculture Design Certificate course.

It is through a solid understanding of the natural systems and processes that are happening all around us every day that will help guide you towards self-sufficient home life that is sustainable and healthy.

Article by Tim Blanch for He is a qualified Permaculture designer.