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New Garden soil preparation

I have a new build and the garden has been left with the top layer of good soil removed. Its basically heavy clay and rocks. I want to make sure I get the soil right before planting but as a newly learning gardener Im so confused. Should we:
1) Just add top soil. If so how much? And should there be a different amount for the borders and for the lawn. Like 10cm for lawn and 30 in the borders?
2) Work with the soil already there. Like till it with compost. If so how much compost - 1 cm?
3) A combination of both? Improve the soil then add top soil.

I have spoken to a number of gardeners and have gotten different replies. Some say top soil. Some say not. Some say 10cm, others 5. 

Added to the complexity Im thinking -
1) Even if I add top soil some plants will have longer roots? Like trees etc? Should I just add soil for each plant?
2) If I choose plants that are listed as can grow in clay then does that mean I can just plant them in? Its confusing because a lot are listed as clay but also well draining. How can it be both?
3) I saw somewere that you can add cardboard to stop weeds. Should I add this, then add topsoil.

Basically whats the best way to prepare the soil before adding structures and plants. Any tips, tricks, ideas to get the best start to a garden?

Posts

  • BobTheGardenerBobTheGardener Leicestershire, UKPosts: 11,391
    This is going to be tricky to answer without photos of the area.  I can generalize by saying that if all the topsoil has been removed so that you have been left with a clay subsoil, then you are going to either need to add a LOT of organic matter, such as well-rotted farmyard manure, mushroom compost etc.  I mean at least a 15cm thick layer dug in to a couple of spades depth, then about half that amount spread on top and left to nature for a few months to be taken down by the worms.  That would give you a really good start, but it will take several years of similar treatment each autumn before it becomes really 'good' soil, as it needs to develop the necessary soil ecosystem to be properly fertile.  Alternatively or in addition you can dig the subsoil over to break it up as much as possible then add at least 20cm depth of bought-in topsoil, mix in about 25% of well-rotted manure and could then plant immediately once the soil has settled (a few weeks.)
    However, if there are drainage issues already, those won't go away by burying them under a layer of topsoil, so best addressed first.
    Lots of folk (including me) on heavy clay soils build raised beds to help with the drainage issue for certain plants and I add about 10cm of well-rotted manure to all of my (non-raised) beds and borders every year.
    A trowel in the hand is worth a thousand lost under a bush.
  • JennyJJennyJ DoncasterPosts: 7,723
    Bob's covered it all, but I will add this - I think builders are supposed to replace the topsoil. They often use only a thin layer and use it to bury subsoil that's got all kinds of rubbish in it and has been badly compacted by the machinery, but if they haven't left any at all, it might be worth asking. The worst they can do is say no, and you might be able to get them to provide some topsoil to add after you've improved the clay subsoil and got rid of any rubbish.
  • newprojectgardennewprojectgarden Posts: 104
    edited February 2021
    Hi,

    I have recently moved into a new build. I have been improving the soil over the past 10 months. I wouldn't worry to much about over thinking things, it's quite simple really.
    All you want to do, is break up the current soil (it will be very compacted) and add organic matter (I have added organic compost, grit and some sand,different types of multi purpose compost). Adding these materials to your current soil will make it a nicer textured soil for plants to grow in. Their roots will be happier as the soil is less compacted, drainage should improve as well which most plants will prefer.  It will help break down the clay over time. You can plant into this soil mix that you create.

    It's hard work but I have double digg..ed all of my beds 2 times now (there are lots of youtube videos showing how to double dig if you're not sure). Its basically digging a trench and forking organic material into the bottom of the trench then filling the trench back up with the soil from the next trench you dig..

    Last spring I also mulched the top layer of the beds (a layer of organic compost in my case).

    Also adding plants helps improve the structure of the soil as they grow.

    The soil has already drastically improved. And will continue to improve each year.

    Think of it like you just need to feed your soil some goodness and break it up so it can breathe and break down, creating a nicer environment for your plants roots.




  • Hi,

    I have recently moved into a new build. I have been improving the soil over the past 10 months. I wouldn't worry to much about over thinking things, it's quite simple really.
    All you want to do, is break up the current soil (it will be very compacted) and add organic matter (I have added organic compost, grit and some sand,different types of multi purpose compost). Adding these materials to your current soil will make it a nicer textured soil for plants to grow in. Their roots will be happier as the soil is less compacted, drainage should improve as well which most plants will prefer.  It will help break down the clay over time. You can plant into this soil mix that you create.

    It's hard work but I have double digg..ed all of my beds 2 times now (there are lots of youtube videos showing how to double dig if you're not sure). Its basically digging a trench and forking organic material into the bottom of the trench then filling the trench back up with the soil from the next trench you dig..

    Last spring I also mulched the top layer of the beds (a layer of organic compost in my case).

    Also adding plants helps improve the structure of the soil as they grow.

    The soil has already drastically improved. And will continue to improve each year.

    Think of it like you just need to feed your soil some goodness and break it up so it can breathe and break down, creating a nicer environment for your plants roots.




    Thanks. What I am concerned about is the stones. Does it matter. Sure I could remove some. But its like counting grains of sand on a beach. It will be impossible to remove them all. If I remove as many big stones does it matter to the plants there are loads f small stones around?
  • JennyJJennyJ DoncasterPosts: 7,723
    Small stones/pebbles are no problem, they'll help with drainage. My (sandy) soil is naturally full of them, all sizes, and I only bother pulling out the biggest ones (talking the size of my fist, or bigger) when I come across them. They get thrown under the hedge or at the base of the fence.
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