Topic: Clay soil improvement

[AndersonC]

My allotment is a clay soil, not to heavy at the top but it gets denser as you dig down.

When it's nicely tilled up the topsoil is good, but following some rain and sun it compacts and nearly sets!

Options I am considering are:-

1. Liming it
2. Adding peat and manure
3. Adding sharp sand

Could I do all three or is there one wonder cure from the above? Obviously liming won't be ideal for everything due to pH issues, but for slightly alkaline soil (pH 6.5-7.0) it would be OK for most things.

Many thanks 

[Tee Gee]

What ever you decide do not do these two together;

1. Liming it
2. Adding peat and manure

Lime should not be applied at the same time as organic matter or fertilisers, it may cause the release of ammonia, which wastes nitrogen and may damage tender growth.

This article might help you decide;

http://www.thegardenersalmanac.co.uk/Data/Soil-Clay/Soil%20-%20Clay.htm

[Ian Pearson]

1. Liming has some benefits for clay structure; it facilitates flocculation, the process of soil particle aggregation. In other words it helps to make soil crumbs.
2. Any organic matter will improve the soil structure and general fertility. Add all you can get your hands on for maximum effect. Digging in will have the fastest effect, but just adding to the surface is going to help.
3.Sharp sand is fine in theory, but you will need huge quantities to make much difference.

And 4, the one you didn't mention…. green manures will put organic matter into soil without all the hassle of digging it in. The roots will grow down, then rot in situ when you hoe off the tops.

[AndersonC]

Morning and thank you both for the information and advice.

[BarriedaleNick]

I am on London clay and it is amazing how much organic matter it will "eat".  I add bags and bags of manure, leaves, coir, compost, hops and anything I can get my hands on and still it wants to be clay.  These days I just pile it on top and it get worked in naturally - it is so much better than when I got it - in those days I had to chip a hole in the clay fill it with compost and plant it that!

[Ian Pearson]

Yup, my old plot in West London was the same. After ten years of scrounging up every bit of organic matter I could find, the soil was getting pretty good, and very fertile.

[ACE]

Go up the tip and get some council soil improver (they cannot call it compost). Free from some councils but cheap anyway. I get it for about £12 a ton if I pick it up myself. Just go on a dry day otherwise you are paying for water. Stables are desperate to get rid of their manure. Double dig and fill up the hole, then it can rot in situ, two years down the line and you will have lovely workable soil.

[Nora42]

We have the same in North London and we have had our plot for 1 year the previous tenant had added grit to two of the beds to improve the soil. when it's fairly dry and you are digging there is an audible crunch we get clay boulders with grit in them when it rains. it makes me giggle.

Last year I added bags of manure and barrows of garden compost you wouldn't really know where that went. But we grew over wintering onions in one bed this winter Spring they are big and fat and obviously happy.
clay soil is very fertile and having it makes you obsessed with compost, manure autumn leaves rotting straw and anything else you can lay your hands on for free that might improve your soil.
Nora.

[Bill Door]

I am with Ian Pearson.  You can do as much of 1 to 3 as you like (take heed of Tee Gees warning).  However, green manures help in two ways.  The roots start the process and the cut down plants continue it.  If you want improvement then sow Hungarian Grazing Rye in August.  Cut it down and dig it in in the spring.  One word of warning is that digging it in will be hard work, the soil improvement is a blessing.

Bill

[digmore]

Hi guys,

Instead of going down into the clay, come up with scaffolding planks as raised beds. Take any soil out and then back fill with compost/manure then top off with the top soil you just removed. One plank high should give you the depth required to grow most things.

Just keep adding to the bed each year with fresh manure.

Just an idea...

Digmore. 

[AndersonC]

Wow a treasure trove of advice - thanks all.

OK just to clarify I have been putting up raised beds and then digging out, removing weed roots, then laying a bit of manure in the hole - 4" or so of rotted stuff, then sorting the soil and filling back in. I didn't mix any manure into the "top" soil.

I have a mate who farms beef cattle - bulls to be precise. I'll ask him for a load of b....s....!!!

Like the idea of green manures too. Will keep checking the pH to determine any liming/gypsum requirements.

Thanks all again for the advice. 

[Tee Gee]

I didn't mix any manure into the "top" soil.

Will keep checking the pH to determine any liming/gypsum requirements.

Well in this case if you find you need to raise the pH you can add lime as it is not in direct contact with the manure!

But spread it on the surface and let the weather take it in.

Something like this;

[ancellsfarmer]

"Enjoyed" 27 years on Wealden clay, makes some of the best and prettiest bricks in the country!. I endorse all the advice above but would stress the timing of your cultivation. If possible, if you wish to dig, try and get it done in autumn, by mid October. leave it in brick  form,ie cut a spadefull and turn it up , dropping any grass and litter into the trench. Leave it to weather in the frost and keep off it!. Add your well rotted FYM or compost and  rake it over, in Feb/March when not too wet. One year got a "load" of spent mushroom compost (8 cubic metres ! ) on 200 sq metres. By Sept it had disappeared completely.

[craggle58]

I've got really heavy clay in Yorkshire. I get about a ton and a half of manure delivered by a farmer every year. I find its very important to dig and fork this in well to about 18 inches. Leaving a mulch on top is a waste of good manure and all the goodness just washes away. The main drawback is all the weeds that the cow manure brings with it. I also find slug problems much worse after heavy manuring.

Also in planting areas that need really free draining soil (mediterranean herbs etc) I add leaf mould and incorporate sandy soil from elsewhere (buiding and sharp sand is expensive and lacks nutrients). It's hard work but regular digging is essential (not in wet conditions). I also don't overly use a tiller/rotivator as making it too fine just causes it to solidify when soaked.

In an ideal world I would definitely have chosen a site with sandier soil as it makes life so much easier.

[juju]

I agree with TEEGEE If you go on line and ask for USES OF GARDEN LIME one of the uses is lime it helps the break the clay soil down. Don't put it where your planting spuds and tomatoes as both these don't like LIME.

[Gordonmull]

Patience. Just keep adding organic matter. Every weed you chuck on the bed, every load of grass clippings, manure, spent compost, etc, anything that was previously vegetable, will get you there. Look underneath my name to see where I am with my clay - I have sympathy.

[Silverleaf]

Horrible heavy clay here too. It's quite fertile if the number of weeds it can support is any indication, but it floods in winter and cracks and goes rock hard in summer. Digging's next to impossible most of the time!

I'm using raised beds which I originally filled with some very sandy topsoil then compost, and I keep adding manure, grass clippings, compost, etc. Hopefully it's helping.

[Russell]

Might I just mention the beneficial effects of spent hops from a nearby micro-brewery?
I find its best to lightly fork it in to already-broken but cloddy land, and then just a few weeks (in summer) is enough to make the soil really friable.
I know the spent hops pong a bit but there are no weed seeds and the worms love it.

[Deb P]

Highly recommend mushroom compost if you can get hold of it. It contains a mix if peat, manure, straw and some lime and benefits clay soil as  well as adding some bulky organic matter. I put mine on in the autumn and fork over lightly in the spring.

[aj]

We use anything and everything to mulch with, plus green manures etc.

Last year we had some horse manure from a local, which made a huge difference to this year's spud bed. You can see the difference between that area and the adjoining spud area.

This year I am leaving a patch fallow and have put a one foot deep mulch on it [weeds, straw, coffe grounds, all foliage, shredded paper etc], and ALL the weeds are put on there to mulch down. I looked the other day and it is already mulching well under the surface.

Unfortunately we had several tonnes of cow manure delivered several years back, which was contaminated by Aminopyralid so are very wary about manure as we had to get it all removed [we had mulched and dug it in all over the plot and it all had to be hand dug back out again] and it still affected our plot for a good two years. So just be careful about what you are adding and know your sources.