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with 25yrs of mulching why is my clay soil no improving

Last Friday Carol Klein said that adding compost for a few years would improve heavy clay, but that not working that well  for me.

I have been mulching with various materials, compost mushroom compost and horse manure for the last 25 yrs. Its improving , but its still sticky with a pH of 8+.

During winter the ground can become waterlogged, a problem may be caused by a broken land drain, which has recently been repaired,

I can get some shrubs to grow, but annual perennials are still problematical.

What else could I try. Would treating the soil with ammonium sulphate to lower the pH help? 



  • FairygirlFairygirl Posts: 52,070

    If there's a clay pan underlying the soil, it won't make much difference what you do.The fact that you have land drains is very telling I'm afraid. The easysolution is raised beds.

    Mushroom compost is alkaline, so if you've been adding a lot over 25 years, that could be why your ph is high too. 

    It's a place where beautiful isn't enough of a word....

    I live in west central Scotland - not where that photo is...
  • PosyPosy Posts: 3,601

    You have two problems, I'm afraid. Heavy clay improves best when you add grit and coarse sand as well as compost. Personally, I am not convinced by the "Just spread it on the soil" approach. It is worth digging right down, breaking up the pan and mixing the grit and compost in as much as you can. Stable and farmyard manure is better than mushroom compost and in huge amounts.

    The waterlogging may be caused by water draining onto the land, or by natural springs as well as by rainfall. It's possible to spend a fortune on drains but raising the beds can help. I build up the soil so that it rises above the high water table in winter but fruit and veg need proper raised beds.

    The pH should settle down if you add manure and lots of plants flourish in a high pH so don't despair! Choose plants that like what you have rather than trying to change nature.

  • BorderlineBorderline Posts: 4,699

    Mulching does not neccessarily change clay soil structure. But certainly holds moisture and stops the soil's surface from drying out too quickly.The more you plant in shrubs etc, the more you will disturb soil and add lots of compost and manure.

    Dividing plants and re-planting, planting densely so that most of the time, the soil is covered. It's this action that changes the structure over time. Growing large shrubs and plants that create a big shadow normally helps in general. Shrubs will suck up some excess moisture whilst in the summer months, the soil tends to not dry out as much when not exposed to the sun.

    Also, choose quite a few evergreen shrubs to keep a nice canopy in places. Helps to control rain compacting the soil's surface in the winter time. 

  • ObelixxObelixx Posts: 29,130

    I have friends who bought a one hectare plot of heavy clay covered in tatty old pines, tatty old birch trees and riddled with bracken and brambles and other unspeakable nasties.   They had help clearing old trees and started digging out beds less than 10 years ago while builders did the house.   They now have the most amazing garden full of beautiful trees, shrubs, perennials, climbers, water features and bulbs.

    This is it 18 months ago - view as a slideshow if you don't have adblock installed. 

    Every year she buys 100s of bulbs for autumn planting and pots for him to plant and he orders a lorry load of council compost which he has dumped in the drive and then barrows it out to the ornamental borders after the bulbs and any new trees and shrubs have gone in.  He lays it on several inches thick on the ornamental garden but uses his own compost on the veg plot as it is regularly hoes to deal with weeds from seeds.

    He only digs when creating another bed or planting a new tree or shrub but has found that the consistency and fertility of the soil has improved immeasurably over the years.

    This garden is now open under the Belgian Open Gardens scheme and regularly features on their equivalent of GW and in magazines.

    Vendée - 20kms from Atlantic coast.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
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