UCG Ratio In New Raised Beds

sfg_newbie(6)July 26, 2014

I'm adding some new raised beds to my vegetable garden this fall and have been collecting and drying hundreds of pounds of used coffee grounds to use in them. I was planning to use a 2:2:1 ratio of coco coir, compost, and dried coffee grounds. Nothing will be planted in the beds until next spring and they'll sit for three or four months under snow.

After scouring the forums I've become concerned that the proportion of coffee grounds may be too high or that I should compost the grounds first.

So, are my ratios okay or would it be better to just add the grounds to my compost and use a 1:1 ratio of compost to coco coir?

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Are these raised beds to be built on the present soil, just raised above that some, or will these be way up and not in contact with any of the present soil?
What you are thinking of is a potting mix for a container. If these beds are to be in contact with the soil you already have then you need a soil mix that is about 92 percent mineral and 8 percent organic matter, your coir, compost, and coffee grounds.
I, personally, would not use coir since I see that as using far too much of our non renewable resources to reach the market place and therefore not fitting in the organic view.

    Bookmark   July 27, 2014 at 6:45AM
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I had a soil test done and my native soil is a very acidic 4.7 so the beds will sit on top of the native soil but with no contact.

Coir is actually a renewable resource as it is made from coconut hulls (and is pH neutral) which is why I chose it over the very acidic and non renewable peat moss.

    Bookmark   July 27, 2014 at 10:59AM
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tropical_thought(San Francisco)

Coir is very expensive, even compared to peat, how did you get the price down. I would compost the grounds first, because I had at one time added straight coffee and some plants shrilled up and died right away. But, I can't say for certain that always happens. I would coffee compost it in bins with browns and then use it to add to the raised bed. Of course, if it sits it will compost itself in the bed in time. I have coir because I used it for my frog, so I have it, to spare but the price of it kills me. 20 dollars for a small bag, which is actually an extra large size bag in the reptile store. I compost it first in bins with all the other junk I compost.

    Bookmark   July 27, 2014 at 12:46PM
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Coir may be a renewable resource in the Phillippines and Indonesia but the amount of non renewable resources needed to get that from there to here makes it close to a non renewable resource here.
Rather then using a container mix for those raised beds make a soil mix of about 92 percent mineral and about 8 percent organic matter.

    Bookmark   July 28, 2014 at 6:24AM
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Okay. I'm wrong. I guess I should just use any old bagged top soil with zero nutrients and have it turn into mud that nothing can grow in in my raised beds.

    Bookmark   July 28, 2014 at 9:38AM
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We're trying to help you avoid an expensive mistake that will become obvious next year when your vegetables don't thrive, and that will take a lot of effort to fix.

Your idea sounds good on paper, but there are factors you haven't considered.

Where do you live? Closest city and state? And was the pH test done by a lab or a home test kit? The home tests are wildly inaccurate.

The usual raised bed is a mix of native soil and local organic materials to improve drainage and correct major imbalances. What you are proposing will be almost 100% non-native organic matter, incredibly light and fast-draining ... which is OK for containers but it's going to be hard to keep it watered for vegetables.

It will also restrict root growth - not a problem for most lettuces and leafy vegetables, but squash, tomatoes and some beans have deep root systems. they will reach the native soil layer and stop ... it's a problem with heavily amended planting holes everywhere.

Having 50-90% native soil (depending on what you have for local dirt) mixed with with the amendments avoids the problem of root restriction because there is no abrupt transition between the raised bed part and the dirt underneath.

To raise the pH in that small area, use powdered limestone as part of the amendment program. The soil test lab would have given you a "X pounds" per 1,000 or 100 square feet recommendation to bring the pH up.

    Bookmark   July 28, 2014 at 11:42AM
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I'm near Hartford, CT. The pH test was done by the UConn soil testing lab. I prepared the sample as they suggested. I did not mess up the test. The pH really is 4.7. I actually amended the soil with their suggested application of lime and it has gone up to 4.8 (yes, another UConn test, one year after the first one) so that is clearly not working.

I was just following the instructions suggested by the SFG book but using coir instead of peat moss because of the acidity problem. The UCG would be in place of vermiculite which is hard to find in my area. So everyone using the SFG method and raised beds is wrong?

I have a horrible, rocky, heavy clay that is like concrete and has a low pH. That is certainly not going to grow anything well. Even mixed with amendments (including lime) the acidity is still a huge issue.

    Bookmark   July 28, 2014 at 12:03PM
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' I actually amended the soil with their suggested application of lime and it has gone up to 4.8 (yes, another UConn test, one year after the first one) so that is clearly not working.'

Yes, it's working, just not as fast as you think it should. Clay soils are very 'buffered' and change slowly. Repeat the application. To be blunt, I think you are overthinking this, looking at like a chemistry lab problem with a formula for solving it. Gardening doesn't work to that level of simplicity.


Look at the vegetables that they list as 'liking' pH 5 ... there's a lot of them. Your pH is 4.8 ... close enough to grow them while you add organic material and more lime.

Don't take pH requirements too literally. If the guidelines say 5.0, the plant will not drop dead at 4.795 ... Plants can't read.

EXAMPLE: I have the opposite problem from you ... silty alkaline desert dirt with caliche, pH about 8.5 (if you pour vinegar on the dirt, it fizzes!) in the unamended places.

Notice that site also says eggplant and chilis need pH 5.0-6.0 , yet they thrive in my garden with some soil sulfur to free up iron and loads of compost and mulch. Basil reportedly needs pH 5.5 - 6.5 but I grow huge basil plants. I can grow everything except blueberries and azaleas and other true acid-lovers.

If I were in your shoes, I would apply more limestone (you are a long ways from overdosing on that) and rake it in. Starting now I would also pile on all the compost and other organic materials I could scrounge locally ... I would not pay for imported coconut fiber, but if a local coffee shop has used coffee grounds, I'd take them. Organic matter improves clay soils quickly.

In the spring, either till lightly and plant or just pull back the piled on organic material ans set out seedlings.

    Bookmark   July 28, 2014 at 4:56PM
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socalgal_gw Zone USDA 10b Sunset 24

I think coir vs peat is almost more of a philosophical question than a gardening one. But UCG and vermiculite are very different. One is organic, one is mineral. They have very different properties.

    Bookmark   July 28, 2014 at 6:16PM
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Thank you for your help.

These are the test results I received after the second test of my original beds which were native soil and peat moss amended with calcitic lime (hence the elevated calcium levels):

pH - 4.8 (up 0.1 in 12 months)
Calcium - 2901 lbs/acre (above optimum)
Magnesium - 354 lbs/acre (above optimum)
Phosphorus - 16 lbs/acre (optimum)
Potassium - 221 lbs/acre (below optimum)
Estimated Total Lead: Low, typical background levels
Soil texture classification: sandy loam
Organic content classification: high

I would still prefer to use raised beds because of the horror of digging in my rocky clay soil. I can put the beds in contact with the ground if you think that would be better.

My concern is really with the UCG and peat/coir. Obviously I need something to loosen up my soil if I use the native soil and I can't produce enough compost yet to add it to all the beds as I make them (I will add it as it becomes available). I gather UCG should not be used "fresh" in the soil because they can steal nitrogen from the plants so I'm hesitant to pile them in in quantity. I'm planning to make compost piles of leaves and UCG in the fall but they won't be ready by spring. I can add that compost around the plants during the summer as it becomes finished though.

So I need to know what would work to fill the new beds. Should I do a native soil/peat moss mix like I did in my original beds and just plan that all the lime will bring up the pH enough?

Here's what I have to work with:

A large pile of native top soil sufficient to fill the new beds (from a completely separate project)
500 pounds of dried UCG
Virtually unlimited maple leaves in the fall
Purchased peat moss and composted cow manure
A local source of low cost fresh cow manure

    Bookmark   July 28, 2014 at 8:00PM
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melfield_wy(5b Wyoming)

You can purchase compost, in bulk from nursery centers, or in bags. It is not too expensive. Many of us have to purchase compost either occasionally or every year - a household just cannot produce enough compost for a large garden. Just the way it is.

In my experience, peat created a whole new set of problems when I tried to use it in my new raised beds years ago (got the idea from the SFG book too). Drainage issues and Ph issues primarily. Compost, compost, compost - it really is the only way to go to amend unfriendly soil.

    Bookmark   July 28, 2014 at 10:05PM
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Thanks melfied!

There are only two kinds of compost in bags around here - mushroom compost and composted cow manure. I've heard that the composted manure is better for some reason.

So you think half compost (either bagged or from my personal supply) and half native soil would be okay and just skip the peat or coir? Would it drain well enough? We get quite a bit of rain in CT.

    Bookmark   July 28, 2014 at 11:18PM
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As many others have found over the years putting a raised bed over compacted poorly draining clay and filling that with what is essentially potting soil can create a whole host of new problems including that of drainage.
A soil pH of 4.7 in Connecticut is not unusual. Correcting that can take some time, depending on how quickly the lime (Calcium) reacts in the soil which can be dependent on how much organic matter is in that soil.
There may be a landscape supplier around Hartford that can supply a good soil mix for you, something with that about 92 percent mineral and 8 percent organic matter mix. Just don't get locked into "topsoil" which means nothing or "garden soil" which means even less. While a 50/50 mix of mineral and organic matter may sound really good it is not since that can present drainage issues as well.

    Bookmark   July 29, 2014 at 6:43AM
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My native soil is fairly similar to yours in pH - blueberries and sheep laurel grow wild, and several damp places on our property grow sphagnum. You want to keep in mind that organic matter breaks down over time creating issues with drainage and air movement in beds if they are only or largely organic matter, so you really do need mineral soil in your beds. (Soilless mixes in containers need to be replaced every year or two for that reason, and you don't want to be replacing your raised bed contents every year or two.) Clay soil when amended can be a real plus in gardening since the soil holds nutrients well so that they are available for plants.

When we created raised beds we dug out the native soil, shoveled it through a soil sieve made of 1" hardware cloth over a wooden frame, and then put the sieved soil back into the bed along with composted cow manure and leaves. (About 1/4 of the original soil volume was rock.) We added 2-4 beds a year (4' x 12' or 16') for 3 years, so it was manageable. We added lime and/or wood ash annually along with more organic material, all of which helps with the low pH over time. We grew wonderful veggies, even the first year, and with a light mulch each year had almost no weeds. Unfortunately, our raised beds were left behind when we moved. Our current property also has native soil with a low pH and gets annual applications of lime or wood ash and organic matter, and grows fine veggies.

If you want to bring in soil to avoid having to dig and sieve, do that and then add composted organic matter and lime. Regardless, having your beds in contact with your native soil will help since soil biota will move more easily into your new beds. I'd also consider turning the unfinished compost into the beds next spring as IME even this far north the compost does quite a bit of breaking down in the fall before it gets too cold, so I am not sure that it will be a nitrogen drain on your beds.

    Bookmark   July 29, 2014 at 8:47AM
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toxcrusadr(Zone 6a - MO)

Second (or third or fourth?) the advice to keep amending, or at least don't try to grow in 100% organic matter.

Coffee grounds are a weak green and will not rob N. I think it would be OK to add some with the composted manure (or mushroom compost - I like to use a mix of types if I buy it), and till in. Keep adding lime. Your soil will improve.

Compost those leaves, coffee grounds, manure etc. and add compost when planting.

If you can, in fall, put down compost or semi-composted stuff and cover with leaves, grass clippings, etc. as a mulch. Worms will work on all this during winter. It's good for heavy clay not to be exposed.

Curious why the lab test said Sandy Loam when you say you have clay?

    Bookmark   July 29, 2014 at 12:46PM
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melfield_wy(5b Wyoming)

I agree w Kissmr... find someone in your area that knows the soil there. What works for me here in cold, windy, Wyoming may not work the same for you in CT. Is there a Master Gardeners group in your area? They might be more likely to steer you in the right direction rather then getting bad advice on "topsoil" from a local nursery. But, really, it comes down to this: ultimately you want soil (not a soil-less potting mixture) that is a well amended, loamy, drainable, worm-loving, mix of native soil and organic manner. This will not happen overnight: it may take years. But that is OK - you can still garden and enjoy the benefits of growing your own food while you make the soil better and better. For now, add a bunch of compost and maybe some lime, work it in really well with the native soil and plant some seeds or seedlings. Over the years, you will learn so much about the soil in your garden and the plants you are working with. It is a joy!

Re: Purchased compost - I've used both mushroom compost and steer manure compost and found them both to be effective. I've usually mixed them together with my homemade compost before application, but this is not necessary.

    Bookmark   July 29, 2014 at 3:22PM
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toxcrusadr(Zone 6a - MO)

With purchased compost you more or less get what you pay for. The lab tests I have run on commercial products in my area showed that the cheapest stuff can have a lot of soil (i.e. low organic matter content). The most expensive ones are not that much better than the mid priced. If I'm looking to raise the bed I don't mind some added soil or sand, especially if the bag is $1.50. But I add some good quality stuff too, home made or purchased. Helps to poke a small hole in the bag and check it out.

    Bookmark   July 30, 2014 at 11:07AM
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Properly made compost should have no soil in it, even if the person making it does so on top of soil.
While back in Sir Albert Howards day it was thought necessary to add soil so the bacteria would be in the mix, they did not seem to know that the materials to be composted already had the bacteria on it to digest it.

    Bookmark   August 1, 2014 at 6:24AM
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Thanks everyone.

I'm going to try to use my pile of native soil and mix it with compost, as suggested, even though it goes against everything I've read about raised bed gardening from SFG and other sources. I don't really understand why the mixture has to be exactly 92 percent native soil and 8 percent organic material but I guess that's just me being stupid.

I would cover the beds with leaves in the fall but they don't actually break down and they'd just have to be removed in the spring anyway, so it seems like double the work. I'm going to use the leaves in compost instead.

toxcrusadr - I believe the soil test said Sandy Loam because this was from my original beds which were a mix of native soil and peat moss which definitely lightened things up.

It seems like the best compost here is the mushroom compost or at least it looks like it. It has a nice, fine texture while the cow manure compost has quite a few small sticks, stones, and other debris.

    Bookmark   August 1, 2014 at 11:24AM
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toxcrusadr(Zone 6a - MO)

Don't get too hung up on the 8% organic matter number. When you send soil to the lab (that has not just been amended with compost) it's kind of a rule of thumb that you want to see 5-10% organic matter content. When amending a new bed with compost, keep in mind compost will continue to decompose and eventually a small portion of it becomes relatively permanent soil organic matter. And about half of the weight of compost is water too. If you added 10% by weight compost to your soil now, it would not result in 10% OM next spring (or even next week). So it's good to start with much more than that percentage when adding compost to poor soil. 1/4 or even 1/3 compost in the mix will do wonders for poor soil. You don't have to start with that much if you don't have it, just keep adding annually. Once you get it where things are growing well, maintenance requires a much smaller amount per year. Most people say 1/2 to 1".

    Bookmark   August 1, 2014 at 4:16PM
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About 92 percent mineral soil and about 8 percent organic matter does not mean exactly, that is a rough ratio to shoot for. Most soil scientists would say that 5 percent OM is adequate, but I have found over the years that plants simply grow better when the OM is in the 8 percent range.
In addition to a soil test from a reputable lab that tells you what the soils pH and major nutrient levels are34 maybe these simple soil tests will be of some help,
1) Soil test for organic matter. 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 drainsâ 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.

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.

    Bookmark   August 2, 2014 at 6:55AM
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nancyjane_gardener(Zone 8ish North of San Francisco in the "real" wine country)

When I started my raised beds (connected to the ground), I loosened the ground (didn't dig) with a fork as much as possible, added free composted horse manure (from freecycle), watered it into the loosened areas, added the raised beds lined with hardware cloth for the gophers, then filled with a garden mix from a yard supply place (NOT bags from the big Box stores, you'll go broke!)I do usually buy a couple of bags for the flower areas to pretty things up!
I do make my own compost and top off as much as I can each year, but with about 8 beds, I have to buy a truckload every couple of years.
I have a little 60s mini tiller that fluffs things up each season that I Love love love! Easy on my back and mixes things up just right! Nancy

    Bookmark   August 3, 2014 at 9:18PM
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Concur that it is always best to buy whatever organic matter is cheapest. for this soil, I would use lime every year (or wood ash, which has pH=10.4, if you wish to be organic), and dig in any organic matter. In fact, hugelkultur is probably a good bet for this situation. pick and throw out rocks as they float to the surface after each winter.

    Bookmark   August 3, 2014 at 10:55PM
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toxcrusadr(Zone 6a - MO)

Lime is not organic? I mean in the 'organic gardening' sense, which seems to be what you're implying. I would think it's as organic as wood ash. It would have more of an environmental impact, since it has to be mined and trucked, but they are both naturally occurring materials.

    Bookmark   August 4, 2014 at 11:54AM
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