Pine wood shavings with Synthetic Urea for clay soil mix

tigershark1976 _

8 years ago

I have heavy claysoil in my backyard and its so bad that I couldnt find a single earthworm after digging a 0.5 meter depth hole.

There are parts of the soil that were improved with compost (raise bed) but its taking me a few years to generate sufficient compost to achieve that. I wanted a faster way to improve the oil so that it could be more suitable for planting.

I'm planning to use 40 kg worth of dry pine wood shavings (around 1 cubic meter) and mix with the claysoil for my new raise bed (about 4m lenght x 1m width x 0.5meter depth x 0.5 meter height). I undestand that mixing the clay directly with pine shavings would worsen the situation in short term (nitrogen used up by pine shavings) so this is my plan.

I will mix the pine shavings with urea progressively, with some matured compost as starter. 1kg of synthetic urea (46% nitrogen) will be mix in water, and pour evenly to the pine shavings pile weekly (to achieve 20:1 C/N ratio) for a month. The pine shavings will be turn every 3 days for areation. After 4 week, where the wood shavings have absorb sufficient nitrogen, i will the use it to mix with clay soil to create the raise bed. I will continue to add 200g of urea/water mix to pour to the soil for another 1 to 2 month for the pine shavings to get stabilized.

Does it sound workable?

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toxcrusadr

8 years ago

The most important question I can think of is, how will you know when the shavings have absorbed sufficient nitrogen??

It might be better to use the wood chips as mulch and let the soil microbes and worms decompose them and work them into the soil. You can use any kind of organic mulch for this - shredded yard waste, leaves, etc. It takes some time but it does work.

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Comments (20)

rayzone7
8 years ago
Heavy mulch + patience = tried and true, easy, way to go over a couple years. Growing taters under that mulch helps me be patient because I love taters and that area is immediately productive.

But, I have been impatient a couple times and have done something similar. I disced leaves/woodchips into my sandy soil and added urea. I planted a season-appropriate cover crop which would tell me if I needed more N. It would also help accumulate any excess N. Then, I would disc in the cover crop and plant another. After 2 or 3 successive cover crops, I was usually happy with the results and resumed my favored lazy way of doing things.
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If you are looking for cheap but durable, go with cinderblocks. If price isn't as big a deal, go with BRICK! Bricks are NATURALLY occuring clay that has had sand added and baked. There are NO chemicals of any kind that can leach out, that wouldn't already be present in your soil! As far as making sure that the blocks don't move, the easiest thing would be to fill the cinderblocks with your growing medium, and yes by all means PLANT in them! Why would you want to give up good growing space?! If you are going with brick you could always mortar them together! They would then hold themselves together in the shape you desire, and you wouldn't have to worry about any shifting! With the cinderblocks, if you bury them about 2 inches deep, they should hold their place pretty well. I wouldn't expect that they would shift very much. As far as your current clay soil goes, I wouldn't remove it! Clay has a wealth of minerals readily available for your plants. The only issue is that it retains water TOO well, and has a tendancy to get very hard, IF/WHEN it finally dries out. In my own case, (I have a very clay soil as well) I have added a large amount of organic material to the soil. I would dig up (not out) the clay to loosen it, then add any organic material you can find (leaves, grass clippings, bags of humus, peat moss, etc.) and mix it in the bottom of the raised beds. Next I would add the clay you mentioned you have on the side of your house with compost that you seem to have access to frequently, and maybe throw a little vermiculite and peat moss as well. This will give your beds pretty nice drainage, while also having water retaining capabilities. Your clay soil has its downside, but it is also a great blessing! Pure clay is not great for growing, but a clay/humus mix is almost ideal! Btw, by adding the organics (pre-broken down) to the bottom layer of your soil, you will be welcoming worms to come up into your raised beds. (You can't get anything better for your soil than worms!) Good luck, and I hope this helps. Remember, clay is not a BAD thing, it just needs to be managed properly!
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After many years of graduate school followed by teaching university environmental science courses I'm pretty comfortable in my understanding of how wood in the forest gets digested, and my ability to interpret observations in the field. What we are talking about here are fresh wood chips coated in wet clay if they are dug directly into the clay soil. This will seal off a good proportion of the surface area of the wood to microbial action and microbial spread. If composted a bit first the situation will be reversed and the clay lumps can get coated in fine particulates and humics, and fungal threads will be able to grow around the clay in a more or less contiguous organic environment rather than be blocked by walls of clay plaster. If you are refering to deep incorporation of organic matter down into the soil... if worms etc could break up clay through the addition of organic matter on the surface you would not see the fromation or persistance of the natural soil horizons we are dealing with (the clay fragipan in the B horizon). I would not have a clay problem because I have had grass growing on my lawn for 42 years since the house was built. This means not only 42 years of root penetration and worm activity on decaying roots, but also 42 years of grass clippings from a mulching mower. Still, there is a claypan nine inches below the surface. The yard is home to a good population of night crawlers. Sure the top nine inches is wonderfully mixed topsoil (due to worms and moles), but that doesn't do my tomatoes any good once that top nine inches dries out at the end of June and the clay blocks deep root penetration to subsurface water. Surrounding the yard is a secondary growth forest that is over thirty years old. Plenty of time for soil life to mix decaying organic material into the clay...it just hasn't happened. And here is what I have observed with brush piles sitting atop clay soil for 20 years (total decay of the brush)... a couple of inches of rich black compost over top of clay (the same with old manure piles). I have cut and developed garden plots out of both the yard and the wilderness areas. This includes deep digging down to 2-3 feet by hand to break up the clay and mix in organic matter so I am intimately aware of the soil structure, root pentration and wildlife penetration. Worms do not live in the clay layer other than for a few permanent vertical burrows, and plants do not put roots down into the clay to a great extent. In a forest, subsurface clay is broken up by penetration and decay of large woody tree roots (over centuries), not from branch and leaf litter. Invertebrate activity will mix surface material into the nooks and crannies left by decaying roots. Most tree roots are on the surface in the nutrient rich layer, with very few deep verticals, which is one reason it takes so long for deep rich soil to form. Darwin's estimates of soil turnover by earthworms as so many tonnes of soil per acre per year (in an English cultivated and/or garden setting) seems impressive until you convert it to inches, which turns out to be something like 1/8 inch of soil brought to the surface each year, so over 8 years you could get an inch of soil covering your wood chips, but even this isn't going to happen in worm depauperate clay.
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Sammy, If you had mixed the mulch into the soil, maybe it would be responsible for the lower N, but that's about it. It would not be the explanation for your high P and high K. Testing for nitrogen in soils is very tricky and, for that reason, some testing labs no longer even test for available nitrogen. The levels of available nitrogen can fluctuate a lot, being greatly influenced by both rainfall and soil temperatures. You could have a soil test in January show low nitrogen and could test the same soil in June and have much higher levels even though you added nothing new to the soil. While it always is good to have a soil test done so you can get a general overall idea of what is going on with your soil, a nitrogen test in January or February is largely irrelevant for warm-season plants that won't be planted for weeks or months yet. The best time to get an accurate reading of available nitrate levels is when the plants are actually growing in the soil because that is the only time the test will tell you how much nitrogen is available right then. There is a difference between how much nitrogen is in the soil too, and how much of it is in an available form the plant roots can access. Or, if you have applied nitrogen to your soil and you want to ensure you have enough nitrogen in that soil, then you apply the nitrogen, water it in and wait a week or two and then send in a soil sample. A soil sample at that time tells you how much nitrogen is available to the plants right then when they need it. While some commercial growers will test their soil after nitrogen applications, it is not practical for home gardeners to do so, especially for those raising plants in pots. You cannot dig up the soil around your plant to send it in and get it tested. Pine bark fines are a major ingredient in many soil-less planting mixes and the controlled-release-fertilizers used in many of those bagged, commercial mixes are formulated to compensate for whatever the pine bark fines will tie up. I haven't found any soil-less mix that works better than Al's 5-1-1 mix and it has a high percentage of pine bark fines. However, most people who use it are either adding in a controlled-release-fertilizer or they are fertilizing weekly (or more often) with a water-soluable fertilizer depending on their specific plants' needs. You cannot use the 5-1-1 mix for much of anything unless you are fertilizing in some shape, form or fashion because the ingredients themselves are not high in available nutrients. I know this whole soil thing must be very frustrating for you, but when you grow in containers, it comes with the territory. Since the roots are "trapped" in the container and must grow only in whatever the container provides them, proper fertilization is key to success and it can be very easy to over- or under-fertilize. That's one reason the Miracle Grow (and other similar brand) fertilizers with a controlled release fertilizer are so widely used--because they take the guesswork out of growing in containers. Once the growing medium in a container is out of balance in terms of nutrients, it can be hard to fix. Once you start trying to fix things, every ingredient you add has the potential to solve your problems but also to create new ones simply because the growing medium is confined to such a relatively small area. Dawn
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rgreen48
8 years ago
I'm curious, what is the ph of the clay? Also, you'll hear different things, but look into gypsum for conditioning the clay. Research it and decide for yourself.

The ph will be buffered by the breakdown of the mulch discussed above, but many pines add a measure of acidity. It would be good for you to know what you are starting with and a general idea of the ph of what you are adding.
tigershark1976 _
Original Author
8 years ago
Thanks guys for your reply.

Toxcrusadr, i wont know when the wood shavings hv absorb sufficient but in most composting guideline, a CN ratio of 30:1 is idea. So i try my best to maintain a lower CN ratio of 20:1 and keep my finger cross. I know woodchip is better but i couldnt get it locally. The pine wood shavings is what i could get from petshop where it is supposing use as beddings for hamster. As for other garden waste such as dry leafs, twigs and branches around my house is more or less depleted by my composting work for the pass few years. Just imqgine, I need at least 10 cubic meter worth of dry leaf just to create around 1 cubic meter worth of compost. Collecting such a huge amount of dry leafs alone could take me a few yrs as im living in a tropical country.

Rgreen, the clay ph is pretty neutral, around 7.2. Thanks for the info, I didnt know that pine shavings could make my soil more acidic. I thought only pine needles is acidic. Anyway, i will monitor the ph and add some lime if necessary.

Rayzone, glad to hear that someone did something similiar and works. I intended to plan some low nitrogen require plant, just as tomato n beetroot. That would give some time for the sawdust to further decompost, before i proceed with high nitrogen demand veg.
kokopellifivea
8 years ago
That's basically what I did. If you need big compost in a hurry, that's the way to go.

Bear in mind that a Trader Joe's coffee sample cup (about 38 grams of Urea ) is roughly equal to two pounds or a shovel full of chicken manure.

Also, the urea is water soluble and will leach down, especially when the pile is new. Put a disproportionate amount of the urea towards the top of the pile. Then water, and keep it wet. If the pile doesn't heat up, water in additional urea until it does.
rgreen48
8 years ago
Looks like you got a good handle on it tigershark. You made me question myself lol, that's a good thing in a case like this...

Here's a link that may help, and keep in mind (as you already seem to be well aware) that organic materials do a very good job at buffering, so there's some room for imperfection. Too much adjustment is often worse than none... http://www.greenhousegrower.com/production/crop-inputs/liming-requirements-and-ph-modification-for-pine-wood-chips-as-an-alternative-to-perlite/

Once the urea and other ingredients are taken into account, you're off and running.
toxcrusadr
8 years ago
koko, being from "a tropical country", tigershark is not going to have a Trader Joe's. :-) Just having a little fun. At least you gave the metric equivalent so that should help.
kimmq
8 years ago
Pine wood chips, Pine needles, etc. will not change the pH of your soil significantly enough to be of any concern. Those pine by products test out at a higher pH (around 5.4 pH) then do leaves from Maple trees (about 3.2 pH).

kimmq is kimmsr
rgreen48
8 years ago
last modified: 8 years ago
The mass of a given volume of maple leaves is less than wood chips or shavings. It's an 'amount' factor. The amount of soil to be amended (and its pH) and the amount of additive (and its pH.) The persistence of those materials also differ.

For example... there have been studies done on woodlands where the pH of pine needles (known to be acidic) doesn't 'significantly' alter the acidity of the soil substrate. Many people understand those examples to mean that you can take any organic substance make it into compost, add it to a medium and you'll be fine. That is not the whole story.

The mass and volume of a woodland 'floor' is nearly immeasurable. The buffering capacity of the minerals present buffer the relatively miniscule amount of organic matter deposited each year through the growth of flora and the activity of fauna.

Further, anything that grew in that woodlands took what it needed and 'preferred' from that very woodlands. It is simply redistributing the mineral strata.

In woodlands themselves there are also 'micro-environments' where fungi, flora, and fauna differ even from stump to stump depending on the permanency, persistence, and make up of the materials. A mushroom hunter knows that well.

Also, considering compost, it is a process where different ingredients are mixed together and the results are an interaction between materials with different characteristics. Again... buffering.

A tsp. of vinegar added to a cup soil does little to alter pH. However, a tsp. of vinegar added to a cup of water does a lot. A tsp. of vinegar added to an ocean is, well...

In this case, pine wood is being used without buffering materials. The pH of the finished product should be taken into account, as should (especially since it will be a raised bed) the relative volume and pH of the soil being amended. If the raised bed will be isolated from the 'ground', that becomes another factor affecting volume, material and environmental interaction, and buffering.

If it were containers, even more so...

Will the pH of the raised bed be affected by the addition of the urea treated pine? Well, the answer is... it might. I really don't mean to cause trouble, and I apologize ahead of time, but I would not, in good conscience, tell this person 'don't worry about it..." You don't have to do in-depth calculations, instead, just a heads up... keep an eye on it and act accordingly.
kokopellifivea
8 years ago
last modified: 8 years ago
Well, may I suggest that pH isn't all that critical for most gardeners? For a few crops, sure, it's important. Also, there are always a few gardens on the borderline----that's the nature of borders, is it not?

I would suggest that for the rest of us, it's good to know which side of neutral you are on so you can default to practices that keep you in the middle, and not, for example, mindlessly lime soil that is already alkaline.

But if you drive your soil from 7 to 6.7 because you loaded up with quite a lot of acidic yard waste, it's not going to make a bit of difference.
kimmq
8 years ago
Garden soil pH is only critical for a gardener if they want the plants they are growing to be able to utilize the nutrients the soil holds. Most nutrients are most readily available when the soil pH is in the 6.0 to 7.0 range.

Acidic materials put into a compost pile will, when finished, be very close to neutral, 7.0 pH. They do the same in the soil. A many years study by Dr. Abigail Maynard at the New Haven Ag Research Station showed that adding Oak Leaves or Pine needles did not make the soils pH acidic. I have observed that adding compost, shredded leaves (many species), and other yard waste usually brought the soil pH here from 5.7 to 7.2 without using lime. Adding only animal manures did the same.

kimmq is kimmsr
toxcrusadr
8 years ago
"I would suggest that for the rest of us, it's good to know which side of neutral you are on..."

I like this! Great precision is not required. Sometimes gardeners (new and old alike, not pointing at anyone in particular, just in general) get the idea they have to be very exact about everything from pH to C:N ratios. I've never owned a pH meter and have tested my soil twice in 25 years. You should see the garden.
gardengal48 (PNW Z8/9)
8 years ago
I agree with tox :-) Been gardening for decades, both personally and professionally, and other than in my soils class in college, never once tested my soil for pH (or for anything else). And the garden thrives!

Having a general idea of what your soil offers in terms of pH and nutrient availability is always a good idea but nature is very forgiving and being overly concerned about these issues can needlessly complicate matters. Precision in gardening is a bit of an oxymoron :-)
tigershark1976 _
Original Author
8 years ago
Just to post an update and at the same time, trying to get some advise from experts here...

After getting advise from the rest, I got myself 1 cubic meter worth of rubber wood sawdust instead of pine wood shavings. After composting for a month using urea (added 1kg/wk), the sawdust does'nt seems to be composting. I intended to added more urea and last Sun, but when I turn the pile, very strong ammonia smell came out from the centre of the pile and I decide to stop wasting resources and seek for advise before I continue doing foolish stuff...

This is the 1st time I try to compost pure sawdust at such a big volume, I usually work on garden waste for my compost and have no issue with it. Can anyone give me some advise what should I do next? My worst plan is leave the sawdust pile aside and let the mother nature take over my work but it would be a nightmare if mother nature needs a decade to finish her work....
toxcrusadr
8 years ago
Rubber wood? Is that from rubber trees? I have never dealt with that kind of wood or sawdust so I don't know how rapidly it can decompose.

The ammonia smell is from too much N as you probably know.The ammonia may also be related to a lack of oxygen, so it helps to turn the pile if it's hot and smelly in the middle.

Possibly the microbes just can't digest the wood very fast even with plenty of N available. Wood tends to decompose fungally first, and that process is slow. After that transformation, bacteria can move in and further break it down.

1 month is not that long for sawdust, or any compost pile for that matter. I would set it aside, start a new pile with other materials you come across, and add the sawdust to the new pile as necessary to balance any new greens. Meanwhile it will keep doing its thing at whatever speed it can muster.
rgreen48
8 years ago
last modified: 8 years ago
Have you been turning the pile? With added urea, oxygen is probably even more important.

Edit... toxcrusadr's post wasn't yet showing... I agree with his assessment.
tigershark1976 _
Original Author
8 years ago
last modified: 8 years ago
Hi toxcrusadr, yup, thats what I suspect when I sense the ammonia... I know sawdust take quite a fair bit of time to get decomposed but I didnt expect no change at all after 1 month of composting. Even the colour of the sawdust remain the same. Now, I wont be suprise if anyone were to tell me that sawdust could take years to be decompost.

rgreen48, yes, I have been turning the compost every 3 days for the 1st 2 weeks but the pile does'nt heat up so I turn the pile once a week instead from 3rd week onwards. On 4th week, that is when I start to smell the ammonia. I guess I need to turn to twice weekly turning of the sawdust pile from now and wait for another 2 month. I will also cut down the Urea mix to 1/2. by then, I should have added 8kg worth of Urea into the sawdust pile.

The sawdust should have absorb sufficient nitrogen and I will start to mix it with my claysoil. From this lesson, I will keep my test raise bed small... perhaps a 1' x 1' raise bed. Just In case if anything went wrong, I can reverse it easily., unlike now, I dont know what to do with the sawdust pile if it really take years to compost..
rayzone7
8 years ago
It depends a lot on the wood: species, branch vs trunk, etc. My earlier post in this thread was referring to ramial wood chips which has a lot of branches and leaves. It compost for me in maybe a year with some chunks still present.

Now, 2 years ago loggers finished some work on my property. I was left with a small mountain of shavings the size of a fingernail from their gizmo thst cuts the trunks to fit on the trailer

I took my box blade and front end loader and made a windrow of this sawdust, essentially, along with branches and also a good bit of soil. I made this a hugelkulture bed for the last 2 seasons.

Last week, I disassembled one end of the bed. Lo and behold, much of the sawdust/woodchips/shavings/whatever was intact with no sign of decay. Granted, I wasn't really trying to speed up this pile. Ramial wood would have been mostly decayed. This was trunk wood, and it hardly decayed at all over 2 years.
User
8 years ago
last modified: 8 years ago
"I got myself 1 cubic meter worth of rubber wood sawdust instead of pine wood shavings"

The density of the sawdust (probably really fine from a fine-grained hardwood) versus the pine shavings (larger and fluffier from a more porous wood) makes a difference. It packs down and goes anaerobic on you

Mixing in some straw, leaves or something else porous will speed up the decomposition by letting more air in.

We compost "kitty litter", which is really locally produced pellet fuel from pine or junipers, after removing the dried poop. The urine-soaked sawdust composts quickly if you have other things in there as layers, such as dried leaves, weeds and tiny twigs. The thicker layers, where cat litter was the bulk of the material for a while, haven't turned as dark and "finished" looking.
toxcrusadr
8 years ago
I have a small sawmill and last summer I sawed a few logs (mostly oak, which is very hard and somewhat rot resistant, plus some other species). The sawdust lay on the ground through the winter. This spring I scooped it up and it was dark brown and partially decomposed. It was not mixed with anything. So it really does depend on species. I used the stuff as mulch, so it can continue to decompose as slowly as it wants to but will not deplete soil N.

Pine wood shavings with Synthetic Urea for clay soil mix

toxcrusadr

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Pine wood shavings with Synthetic Urea for clay soil mix

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