Allotment Gardening Advice Help Chat

Growing => Grow Your Own => Topic started by: Dai on April 07, 2014, 15:09

Title: Treating heavy clay subsoil
Post by: Dai on April 07, 2014, 15:09
Hi all.
yesterday i dug my bean trench at the top of my sloping plot (about a spit and a half to two spits deep and about eleven foot long) the problem is that after going down a spit i found heavy, stoney clay so i had to use a mattock to dig the rest of the depth. (it was quite hard work)

i will obviously be filling the trench with cardboard, organic matter and manure but is there anything else i can put in the bottom to try and break up the clay? or make it growable?

Thanks.
Title: Re: Treating heavy clay subsoil
Post by: moose on April 07, 2014, 15:42
You can buy stuff called Clay Breaker. Not sure exactly what it is but it is supposed to do what it says on the packet.
If you are able to fill a trench 2 spits deep with manure,paper, compost etc. I'm not sure you really need to add anything else.
Title: Re: Treating heavy clay subsoil
Post by: RichardA on April 07, 2014, 17:15
I double dig one of my plots every year (I work on a 5 plot rotation system) . I dig out to one spade deep which is about where my subsoil starts anyway and then break up lower sub soil to fork depth and then add a lot of garden compost over that and cover with top soil from next spit. Nothing unconventional in that but I make very sure I never bring the subsoil up into the top soil layer. Getting to the point though -- I do find that crops love this extra effort especially those with roots that go well down such as potato, parsnips etc. and after a year or two the top soil does seem to be much richer and much deeper as the compost is carried down into the subsoil by worms and movement of moisture etc. Hence I think (and this is just my opinion) you will be OK with heavy composting of your bean trench without treating the subsoil at all (unless it is very acid/alkaline in which case some rectification of ph might be useful). Bean roots will find the compost and go through it into the subsoil if they want to and the broken up subsoil will be good for drainage and penetration of roots and good worm action. Come next year that spot with good compost, good drainage and the benefit of the leguminous action of the beans will be a prime growing spot.
Best of luck
R
Title: Re: Treating heavy clay subsoil
Post by: Christine on April 07, 2014, 18:07
Dai you are doing the right thing going down that far and breaking up the soil - it may be hard sweat now but you are breaking the back of a problem that has probably been developing on your plot for years (previous tenants not digging decently). RichardA's advice is good too.

The more manure and compost you can gain and produce over the summer will be most productive for next year. At least beans produce a goodly crop of greenery that can be composted in the future.

There is no easy way to bring a clay plot into tiptop condition - it's taken me seven years to get mine into a decent state. I've dug deeply, taken an area out of production till the end of May one year and grown buckwheat which was dug in as green manure, scavenged chicken and pigeon manure for the compost heap to rot down along with the other things like vegetable peelings, pea and bean remainders. I've spent quite some time over some autumns sweeping leaves and creating leaf mould to be dug in - in fact, it's been a standing joke about me being a better leaf sweeping operative than the local council. 

The only cheering thing is that clay is a fertile soil once you get it dug over properly and bulked up with manure, compost, leaf mould. It's not a bad soil at all - but you have just found the problem with yours. Stay with it, keep your mattock sharpened and over the years things will be a lot easier.
Title: Re: Treating heavy clay subsoil
Post by: Dai on April 07, 2014, 20:51
Thanks for your replies people, think ill leave the clay breaker until the end of the year and keep hacking away at it with my mattock. Cheers!
Title: Re: Treating heavy clay subsoil
Post by: barley on April 07, 2014, 22:54
try adding sharp sand it helps a bit
Title: Re: Treating heavy clay subsoil
Post by: surbie100 on April 08, 2014, 08:36
I'm doing something similar to RichardA, but with stable manure instead of garden compost. It's back-breaking to begin with, but it does make a big difference, in terms of drainage as well as increasing the number of worms.
Title: Re: Treating heavy clay subsoil
Post by: Kleftiwallah on April 08, 2014, 11:33

But. . .on the positive side, clay does have more water retentative? qualities than a sandy sub-soil.

Cheers,   Tony.
Title: Re: Treating heavy clay subsoil
Post by: Dai on April 08, 2014, 20:46
thats true, my only major worry with it though is that its jam packed with stones as big as my head!  :(
Title: Re: Treating heavy clay subsoil
Post by: Goosegirl on April 09, 2014, 11:13
Try and get hold of some gypsum (calcium sulphate dihydrate) because that works by combining the tiny clay particles together to make a better soil structure, and is probably what Clay Breaker is, but I guess will be cheaper. Also, seaweed meal will have the same effect but maybe not as quickly or as much.
Title: Re: Treating heavy clay subsoil
Post by: Snoop on April 09, 2014, 16:46
Keep the faith - you'll get decent soil quite quickly.

My winter veg patch was rock hard when I got here - clay baked to terracotta by the sun. It was really hard work at first. So much so I nearly gave up, but I'm glad I didn't. Each year I add lots of muck and compost. The first year I also covered the soil with a few inches of loose hay so old it was deemed unfit for animal use. Even by the second year, there was a tremendous difference in soil texture. Far easier to work and even a decent tilth, though it still sets pretty hard in summer. Even so, I can grow onions and garlic in it quite successfully. And its brilliant for brassicas and sweetcorn.
Title: Re: Treating heavy clay subsoil
Post by: ptarmigan on April 09, 2014, 16:51
Agree with poster above.  Keep adding the organic material - anything you can get hold of.  I've been doing that for 3 years now and the difference is really noticeable - for the better.  Seaweed, compost, mulching with cardboard and grass cuttings on top, manure, spent mushroom compost - it all helps. 
Title: Re: Treating heavy clay subsoil
Post by: Jackypam on April 09, 2014, 17:13
Will it ever get to the point that it doesn't dry out and get cracks an inch wide if it doesn't get watered for a fortnight?
Title: Re: Treating heavy clay subsoil
Post by: surbie100 on April 09, 2014, 17:28
Will it ever get to the point that it doesn't dry out and get cracks an inch wide if it doesn't get watered for a fortnight?

Yes, if you keep the top hoed it should cope. I'm going to mulch a lot this year to keep the top friable.