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improving heavy clay soil


is it recommended to mix in some grit/sharp sand along with some well rotted manure (i have a bag of unopened B&Q farmyard manure from autumn) to improve heavy clay without changing the acidity? how deep do i need to dig it in?

if it helps, the area will be used for herbs at one end and fruits at the other - the herbs will be dry ones (oregano, lavender, thyme, rosemary, sage) so i need it free draining as possible.



  • BobTheGardenerBobTheGardener Leicestershire, UKPosts: 9,265

    Yes, grit, sharp sand and any kind of organic matter will help improve heavy clay.  However, herbs don't need much in the way of fertilizer and they have a more concentrated flavour when grown in poorer soil so put most of the farmyard manure in the end where you'll be growing the fruit which will really benefit from it.  Clay is naturally very fertile anyway so will provide everything the herbs need as long as you really improve the drainage - many are Mediterranean plants which naturally grow on poor stony soils on slopes etc. so good drainage is essential. 

    A trowel in the hand is worth a thousand lost under a bush.
  • djjjukdjjjuk Posts: 211

    hi Bob,

    yes re: the herbs. that's why id wanted to improve the drainage, have you any recommendations on depth of digging the grit and manure in?

  • BobTheGardenerBobTheGardener Leicestershire, UKPosts: 9,265

    For drainage you want to dig the grit in as deep as you can really to at least a foot and the more the better - even up to 50% in really heavy clay - a mere sprinkling will have no effect.  For the manure it depends on what fruit you'll be growing but many fruit plants have relatively shallow 'surface feeding' roots, so the manure doesn't need to be dug in so far and can even just be spread on the surface after improving the drainage - the worms will take it down into the soil over time.  Google "no dig gardening" for more on that technique.

    A trowel in the hand is worth a thousand lost under a bush.
  • Hostafan1Hostafan1 Posts: 25,151

    I'm on heavy clay too. We only have between 4-6inches of decent soil in places before we hit clay and rock. I'd go along with the advice re digging in manure for the trees, but I'd suggest you built raised beds,,even 6" high and add lots of grit for the herbs. The problem can be , that if you make the ground nice and open in one place, ( by digging in grit etc ) it can form a sump where water finds it easy to collect. 

    You've not been there long, and , like all gardeners , you need to learn , not only from the helpful advice from others, but from trial and error. We all make mistakes along the way but enjoy your garden.

  • DovefromaboveDovefromabove Central Norfolk UKPosts: 61,238

    Did anyone hear the fascinating Farming Today programme on The Soil?  So very interesting and relevant for gardeners as well as farmers - you can listen again here image

    “I am not lost, for I know where I am. But however, where I am may be lost.” Winnie the Pooh

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