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Filling raised beds with compost only?

Hi all, 

I have recently moved house and now own a garden. My partner is very understanding and allowed me to build three large raised beds for veg growing - 5m 13cm long, 1m 20cm wide and 22cm high. I now need to fill them! 

Because of the volume, I am trying to keep costs down. I have seen recommendations for filling beds with 50/50 compost and topsoil, however am finding that bulk (peat free) compost is a little cheaper than topsoil. Is there a down side of using compost only to fill the beds? 



  • steephillsteephill Posts: 1,605
    The downside is you will need to fill them again next year! Compost breaks down and reduces in volume over time so will need regular topping up. It is difficult to water if it dries out so you need to be more careful with your watering schedule. In addition it doesn't contain all the useful minerals and the microscopic life and fungi which power soil, they will build up gradually but topsoil has them already.
  • BenCottoBenCotto RutlandPosts: 2,181
    If those are internal dimensions my quick calculation suggests you’ll need about 4000 litres of compost - that’s c. 80 bags. I think it would be much more cost efficient to buy four of the giant bulk bags so look around to see what’s on offer in your neighbourhood. Some suppliers offer a raised bed mix, or you might get two of top soil, one of compost and one of manure.

    Ask on your neighbourhood site or on a local Facebook group for recommended suppliers.
  • FireFire LondonPosts: 7,716
    I agree with the idea of buying bulk bags delivered by lorry to your door. I have filled mine with a mix of manure, topsoil and compost. I don't lose that much each year, but top them up a little with things like home made compost, and manure. They will develop microbial and fungal life over time. They do need watering more than open ground.
  • ehouk1ehouk1 Posts: 2
    Thanks all. Yes definitely looking a bulk bags. Will have a look at options that include topsoil
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