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Clay Soil

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I have an allotment. Unfortunatly, the soil is very clay and heavy. I have fork in some green waste as a soil conditioner. I feel this is not eneough. I have been told that adding some sand would improve the soil. Would you advise me of what kind of sand I could add to the soil and where I can get some.



We do this in the "adobe" clay areas in the desert, but it is a lot of work!
It should be a fairly coarse sand (40-16 grit) which may be hard to find, and you will need massive quantities. Dig out the bed to about 30-50 cm deep, and take the soil off to one side. Mix the soil with the sand, about 1 part sand to 2-3 parts native soil, plus one part organic matter--compost is ideal. This is also a good time to put in some of the slower nutrients, such as bone meal, and pH adjusters, such as lime or sulfur.
Mix it thoroughly: there shouldn't be any lumps or layers. I usually mix it on a plastic tarp, and move it from one end of the tarp to the other until it is well blended.
Put 2 cm of the mix into the bottom of the bed, and scratch it in to make a transition layer--any sudden change in soil texture will stop the drainage. Fill the rest of the bed with the mixture, and water deeply to settle it. in a week or so, when it's no longer mud, you can plant.

As a simpler method, you could do the same, but use just compost, about 1 part compost to 1-2 parts native soil. The compost will "flocculate" the clay, causing the tiny particles to stick together in sand-sized clumps, with air and water spaces in between.

Even simpler, but much slower in clay, is to simply put compost, or thoroughly composted cow or horse manure, on the soil surface twice a year. After several years of this treatment, the soil will be black and soft, and full of earthworms This is actually the ideal treatment, since it winds up mimicking a natural soil profile, with high organic matter at the top, and gradually lower amounts to 50-70 cm down.

The sand treatment may be necessary for some things that need perfect drainage, such as squash, melons, and their kin, and some herbs. The other treatments work just fine for most veggies and ornamentals, though. Hope this helps!

11 Feb, 2011


blimey, I didn't read all of the last answer - have a slightly different suggestion, but if I'm repeating anything, apologies. What you need is some sharp horticultural grit rather than sand, which any good garden centre should sell in largish bags, plus as much composted material as you can get hold of, so from the garden centre, you will find soil conditioning compost, and from your local recycling centre, they may sell compost for this purpose. If you have an allotment association, they may have composted material for sale too.
I'm also wondering what you mean by 'green waste' - if you mean compost produced from green waste, that's fine.

11 Feb, 2011


Thank you Tugbrethil as I am so glad that you said "simply put compost, or thoroughly composted...manure, on the soil surface twice a year. After several years of this treatment, the soil will be black and soft, and full of earthworms This is actually the ideal treatment, since it winds up mimicking a natural soil profile, with high organic matter at the top, and gradually lower amounts to 50-70 cm down."

I was worried that I would have to sand and compost my whole garden. I am far happier adding surface compost and manure over time. Parts of my garden are fine but others are purple-gray with thick, sticky clay that sticks to my fork when I try to air it.

11 Feb, 2011


id plan the days and hire a mixer etc as you sound like you have a long heavy job on Mmah

11 Feb, 2011


From what I have been able to find out, Bamboo, horticultural grit runs around 32 to 16 grit--I'm not sure what the metric measure would be! I have found out that larger sizes, like pea gravel, tend to make a really hard "concrete", when mixed into clay. In fact, if you used only sand, with no organic matter, you could wind up with "puddled clay"--the original waterproof lining of many an English canal!

12 Feb, 2011


Hi and welcome to GOY. Do you have a farm which has cows on it, a stables or a mushroom grower. From the farmer with cows, you should be able to get well rotted cow manure. From the stables, well rotted horse manure and from the mushroom grower, spent mushroom compost. Look in your yellow pages under the headings I have given and phone around for prices. Mushroom compost will usually be less expensive than the others although our local stables piles up the manure and local gardeners are free to come and take away as much as they can carry. Be warned though it may well contain thistle seeds which will have to be dealt with when they start growing. We bought a house with a vegetable garden that had been given over to lawn. It was very compacted and the soil was very thin over clay. I decided to double dig it. We started in the autumn and double dug the whole area. We used cow dung from the local farmer. As we planted potatoes in the spring we added extra dung in the bottom of the potato trench. It was hard work but it paid off. I double dug it for seven years in a row adding dung every year and we ended up with 2 foot of the best soil ever. My son was at Uni and had to take in a soil sample from the garden to do tests on it. The American lecturer wanted to know where we bought it because he reckoned it was fantastic stuff. I know double digging is frowned on nowadays but I wonder if it is not a good old fashioned idea that should be revived. I am not fanatically organic but I do worry about adding chemicals. In the area where you have puddling it may pay you to put in some form of drainage. Do start a compost heap before all else.

12 Feb, 2011


tugbrethil - if you can find it, horticultural grit in large bags at garden centres over here only comes in one size - I've used tons of it over the years on solid clay gardens (along with lots of humus rich materials, obviously) and it's done a good job - but it's the very devil trying to find the large bags now anyway, my local centres just aren't stocking it any more.

12 Feb, 2011


if you know wear theres a quarry and you can get a van or something they often sell you half a ton for a drink normaly .

12 Feb, 2011


Well, maybe where you live, Nosey - don't forget, I live in the smoke...

12 Feb, 2011


well i guess sorry lol none the less there are a lot of quarries about . more than youd imagine .

12 Feb, 2011


I noticed that Mmahmood lives in Fife so he should have no trouble accessing a quarry. There is one just south of Kirkcaldy and just north of Kirkcaldy there is a mushroom grower. Fife was once the heart of mining in Scotland but the rural area is full of farms. As he is in an allotment it is possible that others have the same problems as him and they could have a load delivered between them. I would be surprised if this is an established allotment that it has lain in this state for years.

13 Feb, 2011


sounds like a cunning plan to me scotsgran . come to think of it while asking who wants grit etc on the allotment the other people on the there must have sucsess excuse my spelling growing veg etc . always worth seeing or asking how your neighbers have grown there plants .

18 Feb, 2011

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