what soil to use for raised bed?

18 years ago

I have extremely rocky soil in the only area of my yard I can garden in. I planned on just making an 18-24" tall raised bed but am wondering what to fill it with. I want an organic garden but am having problems finding a source for organic soil. What would I want anyway? topsoil? planting mix + compost? I live in Campbell, CA so if anyone knows where to get organic soil in the SF Bay Area please let me know.

Thanks,

Jason

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Comments (10)

dereckbc
18 years ago
Organic Soil? Did you mean to say organic Gardner? Organic soil is an oxymoron per se. In other words it is man made by taking native soil that you already have and adding organic matter to it.

Improve your native soil by adding organic matter ("om") to gain two important benefits: more water retention and better drainage. Use animal manures for their combination of om and nutrients, along with at least one other om, such as compost, ground bark, leaf mold or peat moss.

Read your fertilizer labels and apply the recommended amount to your garden area. Use a rule of thumb for adding organic matter: 3 inches of native soil can usually incorporate 4 to 6 inches of combined manure, compost and so on.

Add an inch of sharp sand to the mix and lime if needed, then till the elements in together. Be sure no distinct layers remain after tilling.

Cannot help you in finding the ingredients you need in your area. Been to Campbell before, could be a long and expensive haul to find the ingredients.
Kimmsr
18 years ago
All soil is organic. What you want to do is add lots of organic matter, compost, manures, shredded leaves, etc. to the soil you have to improve it. The definition of "topsoil" is the top 4 inches of soil, so whome ever sells "topsoil" can call anything they scrape off the top 4 inches of the property they own as just that. More often than not when you buy something called "topsoil" you also get "weed" seeds mixed in that you do not want. Just add organic matter to what you already have to make good soil.
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Let's consider two issues in turn: what kind of soil, and then how much. The quality of your produce is directly related to the quality of the dirt they grow out of. This makes sense, because plants consist of energy from the sun, oxygen and carbon from the atmosphere, and matter from the soil in which they live. Therefore, it is worth your while to make sure that your beds are full of good dirt. You want to pay attention to a few factors in garden soil, mainly nutrient content and drainage. Once you know what you want, you can buy cheap ingredients and mix them to get what you desire. Base: good ol' dirt A good base for a garden soil mix is the cheap topsoil that you can get at your garden center. Lots of stores sell topsoil for cheap in the spring, like maybe $2 or less for a 40-pound bag. That seems like a lot of dirt, but it's really a negligible amount once you start filling in your bed. Nutrients: compost & peat moss You also want to have a lot of nutrients, so it is a good idea to add in some compost. It's great if you're making it, if not they sell it at garden stores. It's incredibly rich, so it's okay to mix in only a bag or two per raised bed. Peat moss is also a good idea, as it is full of organic matter. It comes in big bags, and is really concentrated so you don't need all that much to have an effect, maybe half a bag for a medium-sized bed. Drainage: sand/vermiculite & peat moss You also need drainage, which refers to the ability of water to seep out of the topsoil. (This is what distinguishes a swamp or marsh from "good" land where you can grow things like tomatoes or corn.) This is aided by little holes in the soil. Since water seeks the lowest level, raised beds inherently have good drainage, but you can make the situation even better. It's a good idea to break up your substrate (the area under your bed) pretty well with a fork or spade before building your bed. You also want to make sure to mix in your added soil with some of your substrate, because an abrupt border can lead to problems with compaction: sometimes roots will never penetrate the substrate if it's not mixed, and drainage will be reduced. It's a good idea to mix some sand into your bed's soil to increase drainage; vermiculite (the white chunks in potting soil) also works, but then it looks too much like potting soil and not enough like a garden for my tastes. The light texture of peat moss can also aid quite a bit in creating better drainage, in addition to the nutrient benefits. That said, it will take a LOT of dirt to fill your raised beds. I built some beds that are 5' wide, 10' long, and 1' high. Each one required a bag of peat moss and 1,600 pounds of topsoil! That's 40 bags of that cheap topsoil, which even at a low price came out to hundreds of dollars for a few beds. I highly recommend against using potting soil or your bill will easily stretch into the thousands of dollars. The way to do it on a budget is to: 1) buy cheap materials 2) mix it yourself 3) use topsoil that is on sale, or maybe even free from a local landfill 4) you can even fill the bottom with straw: a straw bale is pretty cheap and gets you a lot of organic matter. It will biodegrade in a year or two if it's buried at the bottom of your bed, it will increase drainage, it will not hurt your plants, and it's a lot easier to move than dirt. In Scandinavia, they traditionally grow potatoes in straw without even any dirt, and they do fine (plus then they come out totally clean!) 5) don't use potting soil! unless it's old potting soil that you have tossed in your compost pile or something I hope all that helps -- good luck building! Also, it might be a good idea to line the bottom with chicken wire or hardware cloth if you have problems with varmints in your area (so they can't dig up into your bed), or to line the bottom with landscape fabric (to prevent grass etc. from growing up into your bed)
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What kind of soil do you have? Most of what I saw on my short visit to Cape Cod was sand and raised beds on sand tend to drain too quickly. Start with a good reliable soil test (a basic soil test from UMASS is $15.00) for soil pH and major nutrient levels. These simple soil tests may also be of some help. 1) Soil test for organic material. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top. 2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains’ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up. 3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart. 4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell, to a point. Too much organic matter can be bad as well. 5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy. Once you know more about the soil you have then you can make a more intelligent decision about whether raised beds might be needed. kimmq is kimmsr
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paquebot
18 years ago
Depending upon where you live in the Bay Area, there's a place in Fremont that may have what you want.

Martin

Here is a link that might be useful: Tri City Rock
paquebot
18 years ago
If you're north or east, maybe a place in "Valley Joe" would have what you want.

Martin

Here is a link that might be useful: Bay Shore Materials
timelessrogue
18 years ago
If your soil conditions are as bad as you say they are, raised beds are an excellent solution and an easy fix ... I've been in that situation and basicly did the same thing. I would check out a couple of home improvement or gardening centers or even Home Depot and ask about getting a load of good topsoil ... they do this sort of thing all the time and should be able to arrange to have it delivered to you. Just be sure to take a look at what is being offered to make sure it's suitable before you buy it or arrange for delivery.
pnbrown
18 years ago
IME, stuff sold as 'topsoil' is not much good for vegetable production without considerable amendments and improvements itself. If there is no other option, get a load, but expect to have to add lime and manure - which you will have to buy bagged, probably. It will take some time to get the ph and fertility up, just as if it were ordinary ground. Bear in mind that such stuff marketed as topsoil can really be most anything, from a mixture of sand and composted landscaper's chippings to actual soil stripped off building sites or etc(if the latter, the ph may not be an issue, I don't know what the natural ph tends to be in the SF area). Or most likely a mixture of all sorts of sources. It's a catch-all term that doesn't mean much.

If you can find a place that makes balanced compost and sells in bulk that is best. Another possibility is get stable cleanings delivered, but that will need to sit and compost itself for a good while - a year or so.
carolb_w_fl_coastal_9b
18 years ago
Hi - did I miss the part where you said what you intend to plant in those raised beds?

If it's veggies, then compost would be my 1st choice - mixed w/ some soil & other organic amendments.I add alfalfa pellets, cornmeal or cracked corn, bone meal when I build a bed & mine are for veggies.

If it's ornamentals/herbs/flowers, then you needn't go so 'rich', IMO.

HTH
timelessrogue
18 years ago
I must disagree to a certain degree about the 'stuff sold as topsoil is not much good' thing, which is why I said 'make sure it's suitable before you buy'. You're right though that it is the top six to eight inches of top soil (hence it's label) scraped off building sites. I have bought such 'topsoil' several times in the past with much success ... after inspecting it first. You can ever ask where your supplier is getting it from and go look at the site to ascertain just what kind of dirt they're selling you. If it doesn't look right, just don't buy it!

The stable cleanings is an excellent suggestion ... another idea I have used in the past. However, don't get 'fresh' stuff if you can avoid it. You will have to compost it though. You could buy bagged manure ... again, at a garden or landscaping center ... that is already composted but it will be more expensive.

Again, good luck ...
kathyp
18 years ago
Hi Jason -
I'm in San Jose, with similar soil. I have had very good results with a lasagna bed, at least for the first few years. I bought hay (there's a place on Senter Rd in SJ that delivers), and got it wet. Layer it in the bed with compost, graass slippings, basically anything that you have. Let it sit for a while, or plant into it - either one works. This method has worked for me for the past 5 years. Now the soil in the beds is wonderfully rich and crumbly. This is how I did all the beds on my property, raised and berms.

Good luck!
Kathy
wintrrwolf_yahoo_com
13 years ago
I am trying raised beds this year. And am using mostly goat and rabbit manure since this type of manure doesn't have to age it can be put directly in the bed. Started out with the thick wet straw/manure/urine mix on the bottom to create a weed and grass blocker tested it out in one spot and within 3 days it started killing the grass and such underneath, I made it about 4 inches thick. I may plant directly into this mix in a few days or add some soil. I did not like the topsoil I bought from walmart it came out of the bags in mud form and then dried into hard clumps.
I would not use cornmeal if you are growing from seeds since it has a germination blocker in it which makes it great for weed control. I think for dirt I may try some potting soil from local DG or FD to mix in with my manure...

what soil to use for raised bed?

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