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Green manure crops on heavy clay soil

Our garden is fairly large about 10 m by 10m.
Its a lovely space but the soil is heavy clay which with the heavy rainfall in Scotland is mostly waterlogged and squelchy.
I have tried putting in 3 french drains but they don't seem to have done much to help.
I spiked it last year and have added agriculture gypsum and some sharp sand but again to no great avail.
I have been reading up on green manure crops which could open up the soil.
I am sure I read somewhere potato crops were great at doing so, does anybody have any experience of this and can advise which potatoes or other crops are best at working on clay soil.
Thanks in advance.


  • Further to advice above, if it is a veg bed you want then I find the best green manure crop is Hungarian Grazing rye. It has very deep roots and unlike mustard does not affect your crop rotation. You would have to wait till spring to sow any as it's too cold now.
    AB Still learning

  • ObelixxObelixx Posts: 29,636
    The trick is patience and annual applications of well-rotted manure and garden or municipal compost by the barrowload.  Apply annually in autumn in thick layers and leave for the worms to work in over winter.   If the soil is really claggy, add layers of grit.

    Clay soil is very fertile and full of lovely minerals.  You just need to get it opened up so that plant roots can get in there and access the nutrients.   

    Lots of plants love clay soils.  You need to ascertain whether yours is acid, neutral or alkaline and then go with the flow for choice of plants.  Raised beds are also a good solution to improving drainage.

    Just to be clear, potatoes don't improve soil.   That all happens when the gardener digs the trench to plant them and then earths them up and then digs again to harvest.   Green manures add organic matter but don't improve drainage.
    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • PosyPosy Posts: 3,601
    It's worth investigating whether you have a high water table - that is, if there is nowhere for water to drain. In my garden, a stream runs across the top of the slope so we get very wet ground. Underground springs emerge in it, too, so we have standing water after heavy rain. You can garden in these conditions but you need to do exactly what Del suggests and also try to raise planting areas a little to help your plants. Building up borders and raised beds make all the difference and there are ways of planting trees to support their roots, too. In conditions like this you need to choose tolerant plants that will put up with wet conditions.
  • Iain41Iain41 Posts: 13
    Thanks for all of your great advice.
    I have added manure to one of the beds over the last couple of years, it's now quite full of plants so it will be a little more difficult.
    Not sure What I can do about the grass, it just doesn't drain and if I put compost on top it will kill it, any suggestions how best to deal with it?
  • FairygirlFairygirl Posts: 53,933
    edited December 2018
    How big an area of grass are you talking about Iain?
    I understand the problem only too well, but if you can tackle it yourself, and it's not a big area, you can add loads of shingle, compost and manure to create a free draining soil for grass. I did that here when creating a garden from slabs and gravel. My grass is only about 15 square metres in total. I made a raised edge, as there was some gravel paths to make round it later , and then dug all of the aforementioned in to the existing soil, before seeding. Of course, it suffered this year because of the drought, but in normal years the grass is fine, and excess rain can get away.
    I also have raised beds, mainly because of the ground being so compacted and lifeless under the gravel/slabs. Other areas which had been compacted grass had the turf lifted, and manure left on over winter. I was then able to work the soil quite easily, using lots of compost when planting anything. I plant according to my conditions/climate, and that's also key to getting a good result  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • FairygirlFairygirl Posts: 53,933
    I should have said - lift the turf you have, then dig in loads of stuff and let it settle over winter. You can then adjust in spring, level and re turf or seed depending on your budget and time.
    The turf you lift can be stored upside down, and left to turn into topsoil to utilise in beds etc.  :)
    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • Iain41Iain41 Posts: 13
    Thanks fairygirl, you come from my neck of the woods so know the joy of West coast rain. So really there is no easy option, the reality is it has to be lifted and relaid and or more drainage fitted. I'll continue to spike it as much as possible until next year and maybe try and rectify it in sections. 
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