Help with soil composition in raised garden beds

I am looking for some help with preparing the soil for my raised garden bed. The garden bed directly sits on my yard and is not boxed in from the bottom.

The dimension of the raised garden bed is as follows:

Length: 2.5 meters
Width: 80 cm
Height: 60 cm

This is 1.2 cubic meters which according to soil calculators is 1.8 tonnes of soil.

I believe I need to fill the garden bed with the following:

1. Organic soil
2. Organic garden mix
3. Compost
4. Green mulch
5. Zeolite
6. Perlite
7. Vermiculite
8. Seamungus


I need to get the products in 25-30 litre bags.

By my calculation and talking to some landscaping supplies, I need around 40-50 (25 liters each bag) bags to fill the bed.

The issue I am having is figuring out the ratio of the above 8 products I need to use.

Can anyone help me out?

Thanks.

you're overthinking it. If youre bringing in soil, you may not need to do improvements to it with all that stuff. What are you trying to plant? That will probably dictate how you structure your beds.

If you are improving the soil below the bed as part of this process, fair enough, but again may not be necessary depending on what you want to grow. Ie we have heavy clay and I've planted natives everywhere. Also the kafir lime loves it, the rosemary has taken over an entire corner of teh yard, daphanes love it, various acacia and succulents are thriving. Everything is going going gangbusters 5 years in despite some requiring well drained soil. I've had a handful of plants fail only. After establishing them in basic dug out holes with good soil, they've taken to the clay exceptionally. No huge job.

seamungs is magic though. you probably can do away with the compost if you use seamungus.

@noname

Thank you for your reply.

Here is a picture of the bed: https://i.imgur.com/jrYQw6G.jpg

you're overthinking it. If youre bringing in soil, you may not need to do improvements to it with all that stuff. What are you trying to plant? That will probably dictate how you structure your beds.

You are right, I am overthinking it a bit. After reading through Fu Manchu's post I have info overload. But I also want to get the garden bed fill correct to save me from issues down the lane. I want to get it right the first time because the amount of time/money I have spend filling the garden bed.


I am trying to plant veges and flowering plants, one lemon and orange tree.


If you are improving the soil below the bed as part of this process, fair enough, but again may not be necessary depending on what you want to grow. Ie we have heavy clay and I've planted natives everywhere.

Given the garden bed depth is around 60cm and I will put around 60cm of the good stuff, do I need to improve the soil the garden bed is sitting on? Wouldn't 60cm of fill be sufficient for what I want to plant?

Are you saying, I can just put in some good quality garden soil with seamugus and that's it?

Also, is garden soil and garden mix the same thing?

Thanks.

Fu manchus post is lawn specific. You could do it for garden beds I suppose but it's not necessary. A lawn is rooted across 100%of the surface area, a garden bed won't be.

60 cm sounds like enough for what you want to plant. Even if you have clay under that, it should give the plant enough time to establish an be fine.

And yeah, good quality soil, some seamungus will be more than enough for most garden beds. Some mulch over over top qould be good too.

Soil underneath doesn't look like clay either. You're good to go with just some good quality soil and some seamungus and mulch the top . The rest is just not necessary. Fertilise your plants as necessary with more seamungus/seasol. Keep in mind you can overdo it. The breaking down of mulch and seamungus re applications will be good enough to keep the soil ecosystem going IMO.

If I were to dig a bit further down, I would hit red clay:

https://i.imgur.com/LQH7Imn.jpg

https://i.imgur.com/sO5b0ef.jpg

When you say quality soil, will these do?

https://www.bunnings.com.au/scotts-osmo ... x_p3010198

https://www.bunnings.com.au/garden-basi ... x_p0274300

Hmm clay is annoying. Whack some gypsum over the top of it before you fill the garden up. The gypsum isn't a permanent solution but should give your soil eco system and plant roots time enough to work on it. It should improve somewhat by virtue of the good stuff on top of it (over time of course).

And when I say good quality soil, it doesn't need to be in bags. Buy it by the cubic meter from a landscaping supplies store. It should come out cheaper than bags by a mile.

Just google bulk soil and have a look what the local place has on offer. They will label what it is.

I agree with the above, get a landscape yard to tip a load on the driveway and load it with buckets or wheelbarrow. You can go and inspect it first to see what you like. They sell by volume. Fluffed up garden soil won’t be that heavy.

Yes it does some out cheaper. But is not an option for me due to access issues. I have to get it in the 25L bags.

you dont have a door going from you garage to the backyard? or a path around the side? seems odd

if you do, the intent is to have it dumped on your nature strip or driveway then just transport with a wheel barrow to the location. Not dumped in your back yard directly.

Backyard access is not the issue. I can access my backyard via side access.

Issue is the front of the property. Front of the property is on sloping land. That amount of soil put in the front yard or driveway, would roll down to the footpath. My nature strip is very small, so putting it there is not an option.

you can also get it in a bulk bag