The BEST Compost For Raised Beds & How To Use It Properly

Gardening in raised beds grants the home gardener a substantial level of control over the growing environment for their plants. One of the biggest things we have control over — soil and soil health. And there is no single better way to improve the soil than by using compost. But what is the best compost for raised beds? And how do we apply it — and WHEN do we apply it — for maximum benefits for our vegetable beds?

A wooden compost bin full of mixed organic materials and apples that can be used as mulch once it breaks down.

The inclusion of compost is vital for the success of raised beds (or any garden beds), serving as a crucial ingredient that can replace commercial fertilizer entirely if done properly.

Its presence ensures that plants receive the necessary quantity of nutrients to support robust growth and abundant fruiting. Optimal results in gardening are best achieved by using a high-quality compost.

See my articles on the best compost for strawberries and how to shred leaves for mulch or compost for more information.

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What Is The Best Compost For Raised Beds?

When it comes to raised beds opting for organic compost is paramount. Raised beds commonly cater to annual vegetables and other food crops, which have higher nutrient requirements compared to other plants. The best choice is MIXED organic compost that you create yourself from a variety of sources and allow sufficient time to properly mature.

On our homestead we have three primary sources of compost that we make ourselves.

The first is from our chicken, duck, and geese coops and houses.

We utilize a method of coop management known as the deep litter system (that link takes you to my article which explains how to do it step-by-step) and the result is a ton of high-nitrogen compost.

The second is from our Icelandic sheep sheds.

Each spring the sheep are released back onto pasture and their house is completely cleared out of a winter’s worth of sheep manure and urine mixed with straw and alfalfa hay.

The next is one that everyone (regardless of having room for any animals) can make — kitchen scraps and things like newspaper and cardboard scraps.

Finally there are shredded leaves and leaf mold, weeds (minus seed heads!) and grass clippings and trimmings from bushes and trees.

We also live close to a mushroom farm which gives away free compost and we collect that too.

The result is a super rich mix of organic matter that is full of beneficial nutrients to feed the soil and thus the hungry vegetables in my raised beds.

Another thing we may add at some point in the future is a vermicomposting (worm farm) compost station for worm casings.

The compost must be well rotted and mature. Do not, for example, add fresh chicken litter into your garden — it must be allowed to decompose for a year or more.

The exception to this would be something like rabbit manure which can be applied directly and immediately.

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Can You Fill A Raised Bed With Just Compost?

Can you fill a raised bed with just compost?

Yes!

It’s a myth (one of many gardening myths) that you cannot or should not use compost as your sole growing medium.

In reality, using only compost (or as much as possible) is one of the BEST growing mediums.

And we have decades of experiments from the no-dig no-till gardeners (such as Charles Dowding) proving that vegetables and fruits thrive in this environment of compost as a sole growing medium.

Again, a mixture of composts is really best and the compost should be well-rotted and matured.

How To Add Compost To Raised Beds

The process of filling raised beds with compost for the first time and how to add compost to established beds.

To Fill Raised Beds The First Time

If you’re filling your new raised beds for the first time, you may be wondering how much compost is optimal to use. You have several options and I’ll go over some of the most successful and popular.

  1. Fill your raised bed 100% with compost: as mentioned this is entirely a legitimate and fantastic choice. The downsides are that buying compost can be expensive and/or you may not be able to produce enough on your own if you don’t have a lot of land or any animals. Technically speaking, you only need 6-inches of compost to start planting, so you can fill the bottom raised beds with lesser quality soil, leaves, logs and branches (hugelkultur), etc.
  2. Triple mix: a term used in the gardening industry for a mixture of compost, topsoil, and usually peat moss that might be an equal mixture of the three materials. However, sometimes this is not the case so ask for the ingredients and ratios before committing. A more sustainable alternative to peat moss such as leaf mold or coconut coir is also gaining in popularity.
  3. The 6:3:1 ratio: 60% topsoil, 30% compost, and 10% peat moss (or leaf mold or coconut coir).
  4. 50/50: Half compost and half potting soil or top soil works too.
  5. Square Foot Gardening Mel’s Mix: an equal mixture of 1/3 compost from mixed sources, 1/3 vermiculite, and 1/3 peat moss (or again — leaf mold or coconut coir).

In summary — the amount of compost you can add to your raise beds, according to experts, starts at about 30% compost for optimal growing conditions but it can go as high as 100%.

Mixed sources of compost are best!

If your raised beds are already established and full, you should be reapplying compost regularly and we will go over that next.

Here’s a step-by-step guide on how to add compost to raised beds after they are filled according to your preferences or what you have available:

  1. Gather your materials: Prepare the compost you intend to use. If you haven’t already, ensure that the compost has undergone proper decomposition and curing to maximize its nutrient content, prevent weed growth in your beds, and eliminate any potential harmful pathogens a may be present in animal manure.
  2. Assess your raised beds: Take a look at your raised bed to determine if any existing plants or debris need to be cleared away. Make sure the bed is ready for the addition of compost.
  3. Calculate the amount needed: Estimate the quantity of compost required based on the size of your raised bed. Aim for a layer of compost that is around 1 inch thick. But even a 1/2 inch of compost in a healthy raised bed can suffice.
  4. Spread the compost: Evenly distribute the compost over the surface of the raised bed. Use a shovel, garden fork, pitch fork, or a garden trowel to spread the compost layer evenly.
  5. Incorporate the compost: In a no-dig bed, there is NO digging or tilling. Your work is done with the spreading of a layer of compost. However in a raised bed where you are actively improving poor quality soil, you may need to mix or till in the compost, if so — use a garden rake or a hand tool to gently work the compost into the top few inches of the existing soil.
  6. Level the surface: Smooth out the surface of the raised bed to ensure an even layer of compost. Do this gently to disturb the soil underneath as least as possible. This also helps prevent water from pooling in certain areas.
  7. Water the bed: After adding the compost, water the raised bed thoroughly. This helps the compost settle and aids in the integration of nutrients into the soil.
  8. Consider mulching: Yes — compost itself can be considered a mulch on its own! Optionally, you can apply a layer of additional mulch on top of the compost to help retain moisture, suppress weeds, and further enrich the soil. We add chopped straw (garden straw), grass clippings, shredded leaves, even wood chips! (See my article on the best mulch for an organic vegetable garden.)
  9. Monitor and maintain: Keep an eye on the moisture level of the raised bed and regularly check the progress of your plants. As the compost breaks down, it will continue to nourish your plants, but periodic additions will be necessary.
  10. Reapply compost: as the compost breaks down to feed your soil, it must be reapplied and we do this twice annually. Some people only do it once in the spring with great success. We add compost first in the spring right before we plant, and again in the fall as we close the garden down for the season. Compost can also be added to planting holes and this especially useful for succession planting of hungry crops.

By following these steps, you can effectively add compost to your raised beds, providing your plants with the nutrients they need for healthy growth.

For poor soil conditions, you should be adding compost into each planting hole along with adding a layer to the top of the bed.

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Do I Need Fertilizer If Using Compost?

Maybe.

Our new raised bed garden was just filled this spring with new compost, top soil, and (unfortunately) peat moss. We have 60% compost in our beds as that was the best we could do on a budget and with what we had available.

Since the soil is disturbed we will be adding a soil conditioner of humic acids and an organic fertilizer this first year.

Next season the goal is to add compost and fertilize only if the plants are clearly showing signs of hunger and need.

As the years go on, as we continue to practice the no-dig principles of leaving the soil as undisturbed as possible, the compost should be more than enough.

These are the three products we’re using in our raised bed garden this year on top of the compost:

The two fertilizers are used in conjunction for best results with vegetables at different stages of growth. The soil conditioner I’ll apply once.

How Often To Reapply Compost In Garden Beds

When constructing a raised bed, it is recommended to incorporate compost into the filling mix. This ensures that the bed is initially enriched with compost for optimal plant growth. Additionally, it is advisable to add compost to the top layer of the raised bed at the start of each growing season as an annual practice.

But again, this depends on you and your conditions.

We applied a top dressing of compost to our filled raised beds (remember, our raised beds are 60% compost) this spring.

We will be doing the same in the fall before mulching the raised beds and putting them to rest for the season.

Some people choose to apply compost only once — in the fall or the spring.

In a few years when our undisturbed soil is teeming with beneficial bacteria and life, we may switch to only applying it once too.

We also apply a cup of compost to the planting holes of heavy feeders like tomatoes, peppers, and squash plants.

Some people do not.

How Much Compost Do I Need For A Raised Bed?

In order to determine the amount of compost required for a raised bed, it is necessary to ascertain the volume of the bed in cubic feet.

Volume = L x W x H

V stands for soil volume
L stands for your bed length
W stands for your bed width
H stands for the height of your bed

My raised beds are 17-inches high and 5×5 feet.

Converting the 17-inches of height into feet, gives me 1.4 feet in height.

So the calculation is 5 x 5 x 1.4 giving me a total volume of 35 cubic feet.

This means that to fill my raised bed entirely with compost I will need 35 cubic feet or 1.3 yards of compost per raised bed.

To top-dress the raised with compost with a 1-inch application, I will need to calculate the area (5×5 feet in my raised beds) plus the inch of volume.

That calculation for my raised beds is expressed as So 5x5x0.08.

That 0.08 is an inch converted to a foot.

I will need 2 cubic feet of compost to top-dress.

Make sure you convert all numbers to the same unit of measurement (feet or inches are best in my opinion).

To figure the calculation for a top-dressing of compost, you’ll need to know the size of the area you want to cover, and the depth of compost you need to apply. The amount of compost required is the product of three things multiplied together: the width, the length and the depth.

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Do I Need To Mulch On Top Of Compost?

Now, it’s important to note that compost itself serves as an excellent mulch.

And as it breaks down, compost releases nutrients into the soil, enriching it and promoting healthy plant growth. Therefore, applying a layer of compost can serve a dual purpose of providing both the benefits of mulch and the nourishment of compost.

However, it is beneficial to apply mulch on top of compost in a raised bed and we choose to do so. Here’s why:

  • Moisture retention: Mulch helps to retain moisture in the soil by reducing evaporation. It forms a protective layer that slows down water loss, ensuring that the soil remains consistently moist for plant roots to access.
  • Weed suppression: Mulch acts as a natural weed barrier by blocking sunlight from reaching weed seeds, preventing their germination and growth. This reduces the competition for nutrients and resources, allowing your plants to thrive without the interference of weeds.
  • Temperature regulation: Mulch provides insulation for the soil, moderating temperature fluctuations. It helps keep the soil cooler during hot summer months and warmer during colder periods, providing a more stable environment for plant roots.
  • Soil protection: Mulch acts as a protective shield, preventing soil erosion caused by heavy rain or wind. It helps maintain the structure of the soil, minimizing compaction and preserving its fertility.

As noted, we use chopped straw, grass clippings, wood chips — all sorts of things.

Mulching, next to generating compost, is likely the most important thing you can start doing in your garden and I have several articles to help you get started.

Recommended Reading

Metal raised beds last for 20+ years, are cheaper, safe, rust-proof, pest-proof, and just look better to me.

After lots of research, we have made a decision — these are the raised beds we will be installing in Spring of 2023. Follow me along on Instagram or right here on the blog for all the designing and planning and planting.

9 in 1 Metal Raised Garden Bed Large From Vegega

Final Thoughts

We’ve covered the best compost for raised beds and the correct way to apply it. The best compost will almost always be from a variety of sources like animal bedding, manure, kitchen scraps, grass clippings, mushroom compost etc. But if you don’t have a mixture or cannot make enough, just do your best with what you have. Leave a comment or question below if you have anything to ask or add!

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