Thanks. I hope it wasn't a mistake building raised beds instead of using our native soil. I wonder if amending clay would have been better in the long run. :(

Silt is compositionally similar to clay. Particle sizes of inorganics <70 microns. As people who try to loosen up their clay soil with sand quickly learn, clay + sand = concrete.

Lead + Alchemy = Gold!

Do you guys think it would be worth it to pay more for better balanced soil? This stuff is $15/ cu. yd. Elseware topsoil goes for about $30. I'd have to check the composition, of course.

I have several raised beds with soil like you described. I don't know what other sources of OM you have, I just want to share what I did with mine. On the bottom of the bed I put a layer of semi -decomposed logs, stumps, twigs , lots of them, from the forest on my property. Then a layer of leaves. Then a mix of silt, loooots of UCG, leaf molds, shredded paper, and milorganite. That mix was really fluffy after stirring. Then a layer of pine straw as a mulch. Never had a brick or concrete crust there. Next year after building those beds, they had marvelous soil, soft, blackish, full of worms.

Stay away from "topsoil". That word doesn't have a definition, so you don't know what you're buying. I've seen bagged "topsoil" that is total crap. As I like to say, you don't know what soil that stuff was scraped off of the top of. If you're going to buy something, buy good compost, and dig it in. As to "balanced soil", you don't have a clue how balanced or unbalanced it is until you get a chemical assessment. Without that, compost is your best bet. That will fix at least some of your problems.

"Topsoil" is defined as the top 4 to 12 inches of soil. So "topsoil" can be anything from a good mixture to all sand to all clay. Perhaps this article might be of some help.

http://msue.anr.msu.edu/news/the_shocking_truth_about_topsoil

A good soil mix to look for is about 45 percent sand, 25 percent clay, 25 percent silt, and 5 percent organic matter. Some people will tell you that you would not be able to find that mix but there are places that do have it and more would if people purchasing soil would demand it.

Any soil that crusts as water evaporates from it is a problem, although that does indicate the soil is trying o stay moist.

Well, I mixed it when wet, so maybe it would have behaved differently if I had just poured water on it undisturbed.

Reading around Gardenweb for the past couple months, it seems that the most common recommendation is to fill raised beds with a combination of soil and compost, rath than just compost.

Maybe I will look for a better source for soil.

Most bulk soil providers (or landscape supply yards) will have soil mixes available that would be a great fill for a raised bed. They are often referred to as "garden soil mixes" or 3-way (sometimes 5-way) mixes and typically include a screened mineral soil base (i.e. garden or topsoil), compost or composted manures and some drainage enhancers like perlite, coarse sand or bark. More expensive than topsoil but far less expensive than any bagged mix.

And they are ready to plant in from the get-go!!

I agree that some nursery or landscape-related outfit will have sources of garden-mix soil that you could probably trust. If their business depends on their plants growing, and they plant in this stuff, it's probably good. Go there first. Don't hesitate to amend even that stuff with compost.

In fact, get a sample of the stuff and do the same tests on it that you're doing now.

Looks like I'm going to be running around this week asking for dirt samples.....

The biggest problem with using leaves as organic material is you are going to need a lot to raise the om by a couple percent. Depending on where you live you can usually find free or cheap local resources. I would start by making a compost pile. Look for straw, aged manure, spent brewery grains, spent coffee grounds and wood chips. These make excellent composting material. Craigs list can help find some of these and a little research can help with the rest.

But the advantage of leaves is that one can have a huge amount of them for free. True that a large pile of leaves doesn't contain a lot of material. I do 90% of my composting with leaves, and shredding them reduces the volume by a factor of at least 5. Several piles of leaves, for me, turns into one (smaller) pile of compost.

We are starting to compost this year too, but won't have any in time to start the beds.

hafamily, you say you're starting to compost, so presumably have some stuff. Think of trench composting (search here and on webs). Get a bunch of organic material (food, leaves, wood bits, whatever) and cover them with the soil that you're getting. It may not be perfect for planting the first year - depending on what you're planting - but be fine pretty quick.

No, we haven't collected anything yet except manure (which is mixed with tons of wood shavings and needs to be composted).

I look on composting not so much as starting 'collecting' but rather as stopping 'throwing away'. Stuff accumulates just through daily living. All you need to do is keep it and put it in a dedicated place. Could be a bin, could just be a heap. Today DH has planed a piece of timber (wood shavings) and we have produced a cafetiere of coffee grounds, 3 orange peels, 4 teabags and a paper bag the bread came in. And we haven't even done any cooking yet. The junk inserts from the Sunday paper go in the recycling bin. But they could just as easily go into the compost.

hafamily, you'll hear different opinions on the web, but some say it's possible to plant directly into manure. Personally I'd say if it smells 'earthy' and not much like ammonia (that 'manure' smell) and can be mixed/covered with what you bought, it'd save you a lot of work. Depends what kind of manure, too, horse manure seems good to go pretty quick. What you plant first year may be a bit of an experiment, and obligatory warnings about some edibles in fresh manure. If you can put it down and wait before planting, the longer the better. Oh, if you have compost worms (red worms) teeming through that manure, all the better, they'll break it down quick.

Thanks for the ideas!

re the horse manure, my concern is mostly with the wood shavings. There's a lot in there! I figure they willmcompost pretty quickly with our hot summers though.

I wouldn't worry much about the wood shavings in terms of using the manure directly, the worst they'll do is tie up some nitrogen for the first little while, and perhaps not at all since they're mixed with manure already and partway along their path. If you're really worried, some fertilizer (smallish amounts). The wood shavings will break down well in time. They might even help in terms of evening out any 'excess' nitrogen in the manure, which is sometimes a concern for fresh stuff.

I will consider it. Thanks.

Re planting in manure, I would not do so in fresh manure. That is richly endowed with urea, which will decompose into ammonia, which is highly corrosive, and which will kill plants. That process of urea decomposition takes place naturally on a time scale of weeks. Yep, that's the ammonia you're smelling. So unless the manure has completely dried out, after a few weeks it should be OK to plant in, and apply directly to plants. Manure that dries out before the urea decomposition has completed will restart that decomposition once moistened. But that's likely to happen only in exceptionally hot, dry weather.

If your manure has worms in it, the urea is long gone.

Now, aged manure can still be loaded with human pathogens.

I won't tell you whether to buy or amend what you have, as I dealt with clay for years and occasionally wish I had bought some soil sooner. What I ended up with after adding compost (and a little soil) for many years was low raised beds anyway, due partly to importation but also the 'fluff' factor of aerating the clay.

I don't know how much soil you are buying, but $15 difference in cost is not that much when you consider that you'll be living with and working that soil indefinitely. The first 10 lb of tomatoes will pay for that.

Whatever you decide to buy, the moment you are filling those beds is your best opportunity to blend in compost. If you don't have any, and the soil you are buying is not already loaded up pretty well, consider buying some compost to blend in.

Finally, the soil you mentioned in the original post was sandy silt which seems to be an excellent candidate to blend with clay. You might consider tilling up the ground where the beds will go, add some of your new soil, till it together, then add the rest on top and till it once more. This will create a smooth transition from one type to the other and is actually a good idea anytime you are adding one type on top of a different type.

Thanks toxcrusader. With all the building of raised beds, compost bins, irrigation systems and running around for soil and compost etc, dh will probably not be open to renting a tiller this year, lol. I do have friends that have been successful gardening in the clay though, and at some point in the future will likely do as you suggest for a melon and corn bed.

And you can start that the slow easy way by building a compost pile on top of the spot for a couple of years. But that's a different topic. :-]

Good luck and keep us posted on your progress. We expect vegetables too (heehee).

I tend to avoid topsoil for basic raised beds, especially if there is clay on the bottom. You are going to have to amend with compost anyway and if you just add topsoil on top of clay you are setting yourself up for drainage issues.

Here is an alternative. Use a spade to break up the clay about six or seven inches down. Add about four inches of compost. Use a rototiller (you will need a fairly powerful one) to turn and mix the clay and compost. Or, you can use a shovel and turn it by hand if you choose. You will have to go over the bed several times. You will also be adding air, and those together will bring the soil level up about 8 inches. (Later with rain, it will later settle down about two inches.)

Since I usually do 10 inch beds, that gives me a good soil level and still leave room for four inches of winter mulch, plus the fact that each year mulch will break down and add a new layer of compost on top.

The clay you have in your yard is valuable. It has essential minerals and local biology that you want in your raised beds. Combing it with the one thing it lacks, organic compost, gives you a great soil.

Richard Brennan, I agree with the concept to mix things into the existing top 7 inches of soil. I added in medium/ coarse sand and local peat moss. I also till in other organic material....the result? I have wonderful soil to work with.

I've done this both ways - digging down and amending the clay, and building up. I dug down into the clay when I bought my house in '90 and began amending. Eventually through addition of compost and some soil here and there (bagged 'topsoil', leftover sandbags from the flood, some river bottom silt that a boat ramp owner had to move), the beds got to be 4-6" above grade by themselves. I didn't really set out to have raised beds and didn't put borders till I needed them. That took years. The soil got really nice though.

Recently I moved some garden beds due to shade and simply moved all soil down to the original grade and put it into a new box. Right on top of the grass with a few layers of newspaper. I didn't till first or dig anything in. These beds are in their 3d year and doing fine. Drainage - and this the point of the story - is fine. In fact these beds get pretty dry in the hot summer (that may be partially due to shallow tree roots underneath sucking water). But even when I didn't have big trees yet, my slightly raised beds over clay did not have drainage problems. Your soil (and your mileage) may vary.

Often one of the primary reasons one opts to use a raised bed rather than an inground planting is because the soil is not ideal or too hard to work. And this includes clay. Drainage in a raised bed is typically always superior to that of an inground bed simply due to the elevated nature of the bed and that fact that the soil used to fill is not compacted and is of a different textural consistency.

You do not need to till or loosen any underlying clay soil. Unless the raised bed is a fully sealed container, drainage will not be an issue regardless of underlying soil type. People even build raised beds on a concrete pad!! And concrete poses even more drainage issues than clay!

I finally have had a chance to call around looking for a bulk garden mix, and I found only one. What do you all think about these ingredients:

one part aged leaf compost

one part mushroom compost (which also includes poultry litter, horse manure, coco shells)

one part compost (mostly from food waste)

one part pine fines

one part peat moss

one part topsoil

one part river sand

$47/cubic yard.

Is that too much organic matter?

Are these 'parts' by volume or weight? That's 5:2 which sounds like a lot, but compost is going to be a lot lighter than soil, so it may be closer to even by weight. It might be a bit high which may result in some shrinkage over the next year or two as organic matter decomposes further and shrinks. But it's probably better to overshoot on the organics than to skimp, because it's harder to add it later. If you get shrinkage you can add a little more topsoil/compost blend as time goes on. If your beds are not huge, you can tweak things later with a few bagged products if necessary.

I would go look at this stuff and feel it before buying. If you like it, buy it.

It's by volume. The fellow on the phone said they take a bucket of each item and mix it together.