clay soil for tomatoes- raised bed?

13 years ago

hi,

i live in southern california and i just moved into a new house. i had palm trees and a lot of other shrubs in the yard removed, and am deciding whether its worth the expense to build a raised bed or not. the top soil is good, but after 1 foot i see gray clay. i'm interested in planting tomatoes, zuchinni, eggplant, fig trees, and a persimmon tree.

should i be concerned about the clay underneath? if i build a raised bed, i will only be giving it one extra foot of dirt, so does it matter?

thanks!

jenny

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Comments (7)

sumith2008
13 years ago
If you could afford it i would. I also recently moved to cali. We are going on our 6th month. Our backyard was nothing but rocks and sandy clay like soil. It was pretty ugly but i could'nt really afford to build raised beds and fill it with fresh compost.

http://www.youtube.com/watch?v=HoaceSK1Qi4

http://www.youtube.com/watch?v=-W8ucc4dXuU&feature=channel_video_title

Our backyard is slowly coming to life :)
readheads
13 years ago
Definitely work it.

You don't have to go too crazy; here is what I did for 20 tomato plants in a 10 ft x 20 ft area which yield about 800 heirloom tomatoes. For each plant:

1. Get a 6+ cubic foot wheel barrel, put a homemade "sifter" on top (basically 4 pieces of 2x6 each 3 foot long with 1/4" welded wire screen stapled heavily to it)

2. Get a couple of bales of peat moss and humus (buy the best you can)

3. Dig out ~20 inch diameter hole down to the clay. As you are digging, put each shovel thru the sifter into the wheelbarrel. After each shovel or two clean the "bad" out of the sifter and put in a shovel of peat and humus.

4. Continue digging until you have nice deep cylindrical hole. When you are done you will have a wheelbarrel full of nicely screened and improved soil (probably overfilling which you can deal with in various ways).

5. When the hole is done, just empty the wheelbarrel into the hole (it will now overfill the hole). Just mound it up the best you can. The hole will be nice and fluffy. Strive to keep it that way for the whole season.

6. Move to the next hole. It takes about an hour a hole once you get going.

7. Each year I try to dig the hole out again and add some more peat and humus. I put the tomatoe plants into the same hole each year.
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I got your email, Louise - Sorry, I've been away at a bonsai show & visiting friends/family. This is a tough one. As I understand it, you have a concrete block planter constructed atop a concrete slab, with no way for the water to make its way into the sand below the slab. Drilling holes in the block walls won't improve drainage. The only 2 ways to effectively improve drainage would be to make sure there is a 'bridge' between the soil in the planter and the sand below the concrete so the water can percolate through the soil, or to make sure the soil you use is porous enough that it holds little or no perched water. This would mean that your soil particles would have to be large & stable, insofar as their structure is concerned. Even the soil you see me holding above would be inappropriate for your application because that soil depends on the wicking action of the earth (in RBs) to ensure it doesn't remain saturated after rain/watering. It looks great, but if you have high standards it would be a disaster in a container or in your app. I'm thinking that about an 80% fraction of a mix of all purpose sand and all purpose gravel and 10% each of pine bark fines and Michigan (reed/sedge) peat or good compost would probably be the direction I would head. In subsequent years, I think all you'll need to do is mulch with pine bark to keep the soil healthy. If expense isn't a major consideration, you could use Turface MVP as the base ingredient for your soil. Topsoil and fine sand just isn't going to drain w/o help. The alternative would be to remove the old soil and cut a hole in the slab so water can drain from the soil in the planter, but it would have to be a hole of considerable size - preferably at the lowest point on the planter's bottom. If you have pictures, it's possible that something else might be devised that will allow the water to move out of the soil via some sort of passive wicking mechanism that we/you could devise, but I'd have to see the application in order to envision the possibilities. There might be a way to employ a false bottom by placing FRP panel on top of cement blocks that are resting on the bottom & building it like a self-watering container in reverse - where you employ a wicking column of soil to REMOVE water instead of supplying it, but I don't know how far you want to chase the issue? ;-) AL
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Your best bet would be to double dig it and work some nutrients into that clay now and then mix some in with the top soil.....It's not an easy task but honestly I started off 5 years ago with the worst soil imaginable and Just yesterday I was marveling at the look of the soil in my beds....my raised beds.....but I made the beds long before the sides were put on them....and the dirt is really nice now. Lots of grass clippings and leaves go on top as mulch and and then later they are worked into the soil. Oh did I mention that I have a bunny I got from freecycle and he makes me plenty of poop for my beds.......I feed him good and let him romp around on my deck and he makes me fertilizer to help break down the grass clippings and leaves.
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I'm not sure what you read that made you so pesimistic. I will tell you that I certainly felt that way to start with. I live in the NC piedmont which stands for a deep vein of red heavy clay soil. White clay is even worse as it indicates that air can't get into the small particles and rust the iron to red. However it is plenty hard and slimy clay like when wet. We have the largest hand thrown pottery community here. Thirty miles south, the soil turns to sand and the interface is the brick capital of the country! I doesn't appear that anything except grass will grow in this soil. However, if ammended heavily with bulk, it does wonderfully as it holds water and nutrients extremely well. We are in the country. I found a cattleman who has cow manure/bedding piled up and mixed after being mucked out of the barns. I bought a dump truck load (I actually bought two and moved it multiple places later) and had a third to a half of it dumped in my ~25' x 35' garden and tilled it in. That could have been between 6 to 10 cu yds of black composted manure. That changed the texture of the soil and it is still there after 6+ years. Gas was much cheaper then and it cost me $60 for delivery and $50 for the manure. Would be much more now for delivery.
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Many kinds of maples are adapted to heavy soils and are planted in them by the thousands, as along streets for instance. It is the Japanese maple that is unusually touchy about drainage. If this planting site is big enough your best bet would be to excavate the clay soil and replace with lighter soil. If it is a narrow strip and the area becomes quite wet even that may not work, water coming in from the sides. Planting a tree or shrub over loosened soil is not a good idea because as the soils settles after planting the new specimen may sink to a level below the desired depth. Digging organic matter into a heavy soil will not have a lasting effect on the texture of the soil as the organic matter will gradually decompose and disappear. Even when non-decomposing amendments such as sand are used to alter the texture of backfill if the planting area is a small one there will still be the problem of how water moves into and out of the planting area being affected. Small areas of one soil texture surrounded by a much larger area of another are often a setup for problems. A large bed of soil amended with sand or similar material will also pose the problem of what to do when the dug over area rises up like a loaf of bread after the amendments are dug in - unless a soil already has a fairly high sand content a huge amount must be used to alter the texture of the finished bed significantly. If you can't excavate and replace a wide area of soil there or put a layer of more suitable soil over the top then it many just be that you can't safely plant Japanese maples in that particular spot. However, since you are in a fairly mild climate zone possibly it would be acceptable to plant them in suitably large tubs and place these on top of crushed rock or other covering in the same location.
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jolj
13 years ago
You can mix the clay with sand, but that will be a 50% sand to clay in order for it to work. So the best thing is to improve the soil with organic matter.
readheads has the right ideal, but I would not put tomatoes in the same bed for 3 years, with out changing to bean or corn.
I know people who do & have great tomatoes every year, but you may not be that lucky.
If you could get plastic 55 gallon drums & cut rings 12" tall as raised beds over the hole to hold the nice humus in place.
You can use a sawzaw to cut the rings.
Just for the fun of it, post this question on the soil forum. To see what those guys think.
luv_figs
Original Author
13 years ago
nice tips! am researching compost sites now. thanks!
bluemater
13 years ago
You can make an attractive raised bed inexpensively. I made a 3'X5' raised bed next to my small townhouse and I grow 6 tomato plants every year.

And, yes, dig down at least a foot or so to get rid of rocks and clay. I had to as there was nothing but rocks and clay after 4" of measly topsoil near the building.

I chose composite lumber for its durability but you can use cedar or redwood if you want wood. Make it at least 12" high, 18" is better (3 1X6 boards).

>
sunsi
13 years ago
Beautiful outdoor living area, bluemater, lots of homey touches.

luv_figs, I agree with all that has been written here--believe me it will be quite a project the first time but thereafter maintenance will not be so bad, just incorporate compost yearly. If you don't have a lot of worms it would even pay to purchase some online and have them shipped to you to add to the beds--worms loosen the soil including the clay and your plants will love the castings. Good luck and let us see pictures of your garden when it's done. :)
todathome
13 years ago
We live in Valencia and our soil was all clay and rocks. We built raised beds out of 2X6 lumber and dug out the clay soil at the bottom, about 1.5 feet below the soil level. Mixed the clay with gypsum and sand and a large amount of amendment. Raised portion is about 1.5 feet above the surrounding level. We also have a short seating area around the top with additional 2X6 and the result is easy weeding. The tomatoes have been fantastic each year! We have a drip system connected to the sprinklers and it does a great job. We are able to set plants in mid-March and continue to harvest until about mid-December, depending on weather. Each year we supplement the raised beds with new amendment.

clay soil for tomatoes- raised bed?

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sumith2008

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clay soil for tomatoes- raised bed?

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sumith2008

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