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Improving clay soil for grass

Hi guys,

Last year I started digging over my mum's garden and I will be putting grass down on part of it and will more than likely use grass seed. The problem is she has soil which is quite high in clay and when I come to trample it down to get a flat surface it is going to start to compact.

So how do I go about improving it? Should I dig in top soil or soil improver? Or should I add a layer of top soil over the top of the clay? Or even add lots of sharp sand to the existing clay soil for drainage?



  • FairygirlFairygirl Posts: 53,968
    Grit and manure are the two best options for clay. Sand is difficult unless you make sure you get the right type. The stuff used for building [making mortar] will make it worse, so you need to make sure it's coarse stuff, ie - gritty
    If you can get hold of rotted manure just now, you can lay it on top, and the weather, and any worms around, will help get the manure incorporated, which saves you doing it  :) 
    In a month or two [depending on your conditions/location etc] when it's suitable for sowing seed, you can dig/fork it all over, adding the grit/coarse sand, and proceed from there with the raking and firming to create a seed bed. 
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • BorderlineBorderline Posts: 4,700
    I would not worry too much about the clay-base soil. Many lawns are over clay soil. Do walk over it to even it out so it is reasonably flat. Do this when temperatures rise and no more heavy down-pours. Then pour in topsoil with added grit if you prefer. A minimum of 2 inches. Then again, walk over it to get the air pockets out. Your soil should be ready to lay or sow.
  • CraighBCraighB Posts: 745
    Fantastic I'm glad it doesn't sound like it's going to be a huge job then to improve things. I will wait until the soil drys out a bit because at the minute it is absolutely sodden!

    I can't wait to get started!!
  • Hi newbie here can anyone solve my problem? Like many others i possess a heavy clay back garden.. 230 sqm! Ive added around 6 inches of well rotted horse manure from the 1980s and i went to rotavate it in to the clay and the rotavator didn't even touch the clay! Anyway i realise it's the wrong time of year for machinery in the garden so i flattened out the churned up horse manure and now that's not letting water through either! How am i going to (when dry) get that horse manure into the clay? And will it make a difference?? Many thanks 
  • Didn't reach the clay i mean
  • PosyPosy Posts: 3,601
    Hello, Daniel. As you have discovered, it is better to rotavate before spreading muck, then do it again to get a good mix. I would be inclined to rake the muck back, a section at a time, OR, if you enjoy a workout, take a fork to the job. If you can, adding grit at the same time is really good for clay. Yes, it will make all the difference in the world.
  • Shifted 16 tonne on to the clay cant i compress the manure then rotavate it? The problem is that the rotavator didn't and couldn't dig deep enough.. or is that still not going to be good enough? Appreciate your help btw many thanks
  • Also how long after heavy rainfall will heavy clay be ok to rotavate? Know it needs to be inbetween so wheres the sweet spot? 
  • PosyPosy Posts: 3,601
    It's true that there is a sweet spot between waterlogged and baked, and at the moment my clay soil is actually under water in some areas so working it would be a waste of time. I'm not an expert on rotavators but if the blades don't reach they won't work.
    Are you sure they were not just failing to penetrate because the clay is so solid? When I did some of my clay I had to give the machine a start by breaking up a small area to enable the blades to dig in. After that it was fine.
  • It touched one bit and it chugged up a ball of clay so was defo the wrong time to do it but showed it wasn't going down deep enough. Guess i have no choice but to remove it, rotavate and replace a thinner layer then rotavate again! Fancy earning some money? Lol 
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