Horse Manure on Very Clay Soil - How long before soil becomes "workable"?

pinkskyinthecity

1. Friend's clay soil will be topped up with lots of horse manure soon. What's the best way of getting this decomposed into the soil? Would they need to cover it with cardboard and wait for a long time before they can grow on it? Upon inspection, the soil is very compacted (they still double-dig each year and walk on the soil) and there are very few worms in it. I know it'll take many, many years to become nice, friable aerated soil. 

Uff

I don't think this question is easily answered and you've partly answered it yourself by saying  'I know it'll take many, many years to become nice, friable aerated soil'  but it becomes more workable as soon as you start to introduce the horse manure if the manure is well composted and the worms get to work and gets better as time goes on. 

A cardboard mulch would help but a manure one would be better, more worms. Walking on it won't help as it will become compacted again. 

We can help nature but it's a how long is a piece of string situation that depends on different things as I'm sure you know. 

Posy

It depends how hard they want to work. I garden on soil that was compacted clay with waterlogging all winter. If they want to improve it fast they need lots of composted manure - horse or farmyard - mixed up with straw. Avoid the wood chippings now used in many stables. Coarse grit is also very useful.
They should dig over the soil to about 12 -18 inches, pile on the muck and dig again to mix it all up, then grit, dig again, then more muck. They need to avoid creating a pan by breaking up the lower level of soil so that there isn't a solid surface underneath.
They can mulch regularly to continue improvement.
If they do this they can then plant into it, no waiting, no cardboard, and the soil will improve year by year. However, when clay is really solid, sticking a bit of muck on and waiting is a waste of time. You need to create an environment in which worms can live and thrive and do their work first.

Fairygirl

When I restructured this garden, it involved putting a fence in. The area that was fenced had been grass - clearly being walked across on a regular basis by various people who didn't realise it wasn't a public space. I stripped the turf off in late summer and put a layer [a couple of inches] of fresh manure down [I worked in a riding stable ] and by spring it was fine to plant into the new border. In wet, cold areas like this, that can make a difference to the length of time because ground doesn't dry out, but it was still only about 6 months. Winter frost can help too. 
The only other addition was compost, and that was bog standard cheap stuff, and was generally added with the plants. Nothing but clay soil here. 

Double digging won't make any difference to the structure of clay unless you're adding organic matter, and it certainly won't help if you constantly walk on it. 

Chris-P-Bacon

No quick fix I'm afraid. My garden was (still is) grey silty clay. Floods in winter, then slightly less damp in summer. I raised the beds by about 6", got rid of the lawn (completely pointless) and initially dug in compost and manure - a bit of grit but that doesn't do a lot of good in clay - it just turns clay into gravelly clay and helps with compaction (sand is even worse). 
It's taken 6 years to get it just about workable. Every winter I mulch with compost. It's getting better ..slowly. I now practice 'no dig' ...it's early days to say it's better than digging...saves my back though.
If anything I've learnt to live with it and plant accordingly...having said that, I've had plenty of failures and planted completely the wrong on many occasions. 

Redwing

Very good advice from @Posy and @Fairygirl above.  I've gardened on clay for over 40 years and the more organic matter the better, both dug in and top dressed (which is easier as the worms do all the work).  The best way to avoid compaction is stay off the soil when it's wet.

Fairygirl

It's the reason I made raised beds for the vast majority of this garden.
We have serious annual rainfall here, so it's by far the easiest method in the long run.
Mine vary from around 6 inches in height in the sunniest bits against the house, to around 2 feet in height. 
That way, you can tailor the soil drainage capabilities, regardless of what comes out the sky, and regardless of the main soil in the plot   

fidgetbones

Next doors garden is clay. When I took it over I gave it six inches deep of well rotted manure. (an entire lorry load on the veg plot). By spring it was forkable and I planted potatoes in to it and got a lovely crop.  I only fork  to plant. I dig holes only if something needs a big hole.  Add more compost or fym each year and only fork it through the top layer when planting.  Double digging just brings more clay to the surface and you don't need topsoil two feet thick.

pinkskyinthecity

Thanks for your advice, guys. I guess years of constant deep top dressing with manure is the way forward. I'll show him this thread for him to consider his plans.

nick615

Definitely Question not Suggestion but, as with so many topics, there are unanswered factors of availability, cost, transport etc. involved.  A common theme is to add vegetable matter of some description to the soil so, whilst possibly of little nutritional value, grass mowings can usually be sourced cheaply and free in most areas.  Watchful walks in a local park, or chats to neighbours, could increase the options? 

Posy

Cost is always a matter for consideration but muck is usually inexpensive,  fortunately,  and many gc's deliver. My council has a big bag delivery scheme, too. If you really do have heavy clay there is no point at all in buying plants until it's improved so it comes down to whether you can make a garden at all. You can, of course, chuck on a bit of vegetable matter but it would take a lifetime to make any difference.