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| Greetings everyone! I'm a long time reader of the forum, I've decided to stop just reading and start posting as well!
I have a question for anyone that may have had this issue before or is currently gardening in the way I'm thinking I need to as well. I have a raised garden bed in our backyard, its about 8'x20'. When I did a really quick soil test (put some soil in a jar of water, shake it up and see how it settles) I have found that it mostly consists of sand. My main concern is the depth of the soil. I heard from some neighbors that the garden used to be a sandbox (would probably explain the mainly sandy composition of the soil). When constructed, it was placed on top of the clay soil with a weed barrier, then some slightly larger than pea sized gravel (~3-4" deep), and then the soil. Right now above the gravel if the soil is placed evenly thick over the entire garden I maybe get about 5" of soil. I'm finding that when turning the soil I'm constantly hitting and digging up the gravel. So the easy answer would be go get some more soil and put it on top since the soil is still 6-10" away from the top of the raised bed, but that would also be quite costly as I would either have to buy many many bags or have a bulk truck load delivered. What I was thinking, was as the season comes to a close, I would move the soil to one area of the garden at a time, then sift and remove the gravel. I would also remove the weed barrier so that the plants can grow further into the soil below. This would increase my soil depth without having to buy more. Would taking the gravel and weed barrier out be the best option, or should I just bite the bullet and procure more soil (compost, peat moss, top soil, etc) to increase my soil depth? Right now to solve the depth issue, I have moved the soil into mounded rows so they are at least 8" deep but this has also restricted a lot of space in the garden for plants and root growth. I'm also finding it hard to keep the soil moist (I mulch with black plastic and/or grass clippings) since CO is very dry, windy, and the soil drains REALLY well. Thanks everyone! |
Follow-Up Postings:
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| g'day, you have room on top just add organic material, first if it were me, i'd add a good layer (8") of spent mushroom compost or source some humusy type compost most local tips recycle the stuff, then plant the plants and mulch (6"-8") with spoilt hay type mulch in short order what was there will be no issue. len |
Here is a link that might be useful: lens straw bale garden
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- Posted by lisanti07028 z6NJ (My Page) on Sun, Jul 22, 12 at 18:06
| I don't have raised beds, but I did have lots of gravel and rocks in various parts of my gardens, and nothing did particularly well until I got it out, and it was a job and a half. If you have time and room, your idea of moving the dirt a bit at a time would be the easiest way, I think.Maybe you can round up some friends with shovels and wheelbarrows to help you out. Good luck, and keep the Ben-Gay handy. And the Advil. |
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- Posted by tropical_thought San Francisco (My Page) on Sun, Jul 22, 12 at 19:11
| I wonder why the gravel would harmful? It would seem like it could just sort of blend in the with soil unless it was limestone in which case it would ruin the ph. Do you know what kind of mineral? I know landscape fabric is bad for the soil layers. There are soil layers with names like O A B and landscape fabric messes them up. |
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- Posted by tishtoshnm 6/NM (My Page) on Sun, Jul 22, 12 at 20:04
| I would sieve it out. Areas where we have had lots of gravel was compacted and difficult to dig into and a general pain in the backside. Granted, I also try to sieve out pebbles/gravel in my vegetable garden, hoping that every bed will one day be acceptable for growing carrots. DH has this annoying habit of shoveling the snow from our gravel driveway and piling it around the trees. The snow is good but he forgets when he gets deep to try and not scrape up the gravel and so we are now picking gravel out from these areas. |
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| Definitely get rid of the weed barrier, they serve zero purpose. Slightly larger than pea gravel should be no problem but it is over the weed barrier so your only good alternative would be to lift the soil and then remove the gravel and then get rid of the weed barrier. I landscaped for quite a few years and the only good thing that weed barriers, as long as they were not plastic, were good for was if some one wanted the old mulch or rocks removed we could use the fabric to move the rocks into a pile or just pull the fabric and mulch out in one big lump. |
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| The soil I have is Lake Michigan beach sand and in some places I found gravel, or a lot of stone, under the sand. All that I have done is add lots of organic matter to that sand which helped slow the movement of water through that soil, helped hold nutrients in that soil, generally made that sand into something that plants would grow strong and healthy in. All you need do is add organic matter, compost, shredded leaves, straw, yard waste, to that soil to make it better. You do want to get that OM up to about 6 to 8 percent in that soil. |
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| Thanks everyone for the input. I did add organic matter this year (2nd year since we bought the house and garden) which I will also do every year. The problem with just adding organic matter is if I want to get up to the total depth of soil I want/need would require about 5 cu yards of material. Calculating out the price, I'm probably gonna be looking at close to $250 no matter what way I do it (many bags or dump truck delivery). It will be a lot of work to remove the gravel, especially since I'll have to wait for the rhubarb to go dormant before I can remove it, so it'll start getting to be cold outside as well. I'm thinking the easiest way to sieve the gravel will be to make a frame out of 2x4's with some small opening wire fencing to hold the gravel but let the soil fall through? Then there is what to do with the gravel... I don't really grow root crops, would it hurt to just move the soil and gravel enough to remove the weed barrier and then till up the clay underneath with all of the soil and gravel to get a good mix? This would make the density of the gravel in the whole mix fairly low. |
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| Your last sentences are the best solution. |
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| If you buy all of the organic matter your garden might need you will be spending a lot of money every year, but if you use the yard waste generated, and most often simply thrown away by others and which is available for free, you can get more than adequate amounts of organic matter into your soil at very low cost. There is no good reason to remove that gravel. |
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- Posted by lisanti07028 z6NJ (My Page) on Tue, Jul 24, 12 at 10:14
| The 2x4 frame and hardware cloth are the way to go; I made mine about 3 feet by 2 feet and put it on sawhorses. You could also make it just bigger than your wheelbarrow and sieve as you shovel. What you do with the gravel depends on the size of the gravel and how much there is of it, Do you need a nice little path somewhere? Perhaps something under your garbage cans? |
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| I agree, there's no reason to go through al that work to remove the gravel. the weed barrier is under it you say? Well if it were me, I'd just get to the end of gardening season, (oh my I wouldn't want to disturb rhubarb!), and pile leaves, brush, dead plants, anything dead on top, and wait out the winter. If you have any compost, put it on the beds before the mulch/brush/leaves, and leave it be. Come Spring, you'll have deeper soil to plant in. Like Kim said, free is the way to go, at least for me. I garden in pure rock and rubble, and the only way I can afford to do it is with raised beds of soil I've created for myself, with my own compost and time. If you want to dig in the Spring and meet the weed barrier, try to rip it and pull out bits at a time. The gravel won't harm your garden, might even help it drain over that clay layer. Mulching with black plastic is not my way to go, as plant mulches are, yes, free, and eventually turn into nutrients for the garden. Since you still have room above the current soil level to the top of the raised bed, mulching over the winter is good. Do you have any containers? Every time a plant dies not from disease, I dump the plant part into the compost, and the dirt in a corner,and cover it with brush. About once a year, that pile gets mixed with compost and dumped on the raised beds. Plants which need deeper roots go there, and the rest kind of grows higher as the seasons pass. Slow, cheap, hey it works! Good luck. |
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- Posted by coach_grumpy 6a ID (My Page) on Fri, Jul 27, 12 at 23:06
| "I don't really grow root crops, would it hurt to just move the soil and gravel enough to remove the weed barrier and then till up the clay underneath with all of the soil and gravel to get a good mix? This would make the density of the gravel in the whole mix fairly low." I would have to agree with RpR. If I have understood the OP's postings, the layer above the gravel is mostly sand and the layer under the sand, gravel and weed barrier is clay. The problem with the sand is that the organic materials added to the sand annually will decompose and leave the sand. Thus the neccessity to continue to add copious amounts of organic material every year to raise the level of the bed. By removing the weed barrier and incorporating the underlying clay and soil into the sand, you will have a much improved base to work with. Then you would not need to add as much organic material each year to maintain bed depth. |
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| Enough organic matter needs to be added to any soil each and every year to replenish what the Soil Food Web has digested to feed the plants growing in that soil. Mixing clay into sand, or sand into clay, or expanded shale, or what ever, will not replace the need to add organic matter. Without organic matter the Soil Food Web cannot live and function and what ever mineral material might be added to any soil will not get converted into plant useable nutrients if the Soil Food Web is not busy working on doing that. |
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