Most cost effective way to build soil carbon

mikep · Nov 13, 2016

N.Yorks. said:
Add material that once lived to the soil, it then starts to be broken down by living organisms such as fungi, bacteria, actinomycetes, algae, protozoa and larger organisms like earthworms down to nematodes. In a cubic meter of topsoil it is estimated there are around 7 trillion individual organisms. I mention just this one figure to put into context the enormity of the living mass within the soil, and I am sure that the actual figure in any given area of soil will be highly variable. Put this another way, in a grassland soil the approx. weight of bacteria is in the range of 1-2 t/ha and fungi 2-5 t/ha.

In your minds visualise two groups of soil matter: the first used to be alive, the second is still alive.

The matter that used to be alive (crop residues, FYM, compost, destroyed cover crops, dead microbes etc) will not just remain they will be 'dismantled' from their whole into smaller fractions i.e. they are broken down by the living matter within the soil. Basically it's a massive food chain
.
Plant matter/ crop residues can be split into:

rapidly decomposed: sugars, starches, proteins

less rapidly decomposed: cellulose, hemicellulose

slowly decomposed: waxes, resins, lignin

Some of these crop residues can be broken down quickly by a relatively few number of organisms and others will be broken down gradually by a diverse range of organisms. I'll avoid attempting a detailed description of which organisms do what, as we'd probably be here all night and I'd probably not get it totally correct either.

Basically it's a massive food chain.

The value of all this to farmers are huge.
The breakdown by-products will partly be plant nutrients that can be used by growing crops to satisfy their nutritional requirements. This is why FYM use provides N, P, K, Mg, Ca. The type of matter that is being broken down will determine how quickly these plant nutrients can be re-cycled.
There are also a number of compounds excreted by the organisms that are responsible for maintaining soil structure which in turn is critical to maintaining pores within the soil through which water can drain and air can diffuse.

If you take away the organic matter from the soil these beneficial characteristics start to reduce.

By now hopefully you envisage the soil as having a number of inter related mechanisms, a bit like an engine and gear box. If you stop the supply of fuel into an engine you know what happens. If you stop/restrict the feeding of once living matter (OM) then that restricts the ability of the complex array of living organisms to exist and that in turn restricts the benefits that we need in order to maintain soil fertility and crop production.

Another dimension to appreciate is that the array of organisms present in the soil will be larger when more diverse types of organic matter are available. So a soil that just gets a stubble ploughed back every year will have a narrower range of living organisms than a soil that gets stubble, FYM/compost, cover crops etc. The current thinking is that a soil that has a greater diversity of organisms will be more likely to recover from a system shock such as prolonged water logging or a drought or perhaps even a change in cultivation policy.

Basically, there isn't one cost effective way that should be favoured, you'll get more resilient soils that are able to maintain long term function if you 'treat them' to as wide a range of once living material.

And finally the humus is a "chemical junkyard" as it is the accumulation of resistant plant material and microbial waste products. Humus is stable and very slowly broken down.

It's all about re-cycling.......... be it FYM, dead roots already in the soil or compost!

I've tried to condense what could easily be written down on hundreds of pages into a few paragraphs, I hope you get the gist.

All true but you dont mention the controlling factor which by and large is oxygen supply. All the soil living elements require a supply of oxygen in some form mostly free form but regulated supply. This is the driving force and where the analogy to fire comes from, increase the supply and the rate of breakdown increases as the aerobic elements are in control, reduce the supply and it slows down.
A compost heap may steam but turn it at the wrong time and it can burn.
The slower the reaction the more thorough and more efficient and this is where no till has an advantage by keeping a steadier level of oxygen going into the soil.
I always was amazed that in the ploughing days you would plough up last years straw discoloured and brittle but more or less intact and it would disappear within weeks when it hit the air.

clbarclay · Nov 13, 2016

There is a interesting thought about oxygen and the rate of organic material decomposition relating to compost.

I will have a lot of tree prunings this winter. The easy solution to 'dealing' with them is to push up and burn, but it seems a waste of raw material that could be composted. The conventional method seems to be chip the wood fine, keep mixing with high N material and aerating till it's ready. A rather cost and energy intensive, short term option.

Leaving branches just piled up is a very long term option. Has anyone found an effective middle way to compost all the wood that is too small for wood burners?
For example, any idea how long it would take to compost chunks of wood up to 2" diameter mixed with FYM?

N.Yorks. · Nov 13, 2016

clbarclay said:
There is a interesting thought about oxygen and the rate of organic material decomposition relating to compost.

I will have a lot of tree prunings this winter. The easy solution to 'dealing' with them is to push up and burn, but it seems a waste of raw material that could be composted. The conventional method seems to be chip the wood fine, keep mixing with high N material and aerating till it's ready. A rather cost and energy intensive, short term option.

Leaving branches just piled up is a very long term option. Has anyone found an effective middle way to compost all the wood that is too small for wood burners?
For example, any idea how long it would take to compost chunks of wood up to 2" diameter mixed with FYM?

You've got nothing to lose by trying it and then telling us what happened.

I suspect what you'll get is breakdown of the smaller twigs and leaves and the large stuff will remain recognisable in the heap, and would eventually breakdown, but that would take more than a couple of years. The bigger material would probably hold the structure of the heap in a more open way to create air pockets and aid the aerobic bacteria. Maybe because of the larger branches you may not need to turn as often.

clbarclay · Nov 13, 2016

I did a bit of googling after posting, no mention of feild scale composting, but some small holding sites talking about composting prunings by piling high N materials on top and several talking about Hugelkultur, a method which can be used to compost whole tree trunks and grow crops on as raised beds, although I can't see that working with no till combinable crops.

I might try some test heaps, if the smallest branches don't need to go through a chipper then that would help.

N.Yorks. · Nov 13, 2016

clbarclay said:
I did a bit of googling after posting, no mention of feild scale composting, but some small holding sites talking about composting prunings by piling high N materials on top and several talking about Hugelkultur, a method which can be used to compost whole tree trunks and grow crops on as raised beds, although I can't see that working with no till combinable crops.

I might try some test heaps, if the smallest branches don't need to go through a chipper then that would help.

I guess if you can reduce your chipping activity to the very big stuff and leave the rest that will cut the processing costs.

Once you have a batch ready send some off for analysis, to get P, K, Mg & S concentrations, the pH and the C:N ratio. If you get C:N ratio to less than say 17:1 you will not notice any short term N lock-up. Do your research on C:N ratios, because what you don't want to do is produce a compost with excessive ratios that will lock N. I'm not saying this is going to be a real issue, just be aware of it that's all.

Edit: The analysis will tell you the total N too, which won't contribute any (<3%) plant available N, however it will help you remain compliant with NVZ total N loading from manure rules.

Old McDonald · Nov 13, 2016

clbarclay said:
Has anyone found an effective middle way to compost all the wood that is too small for wood burners?

No.

A few weeks ago I created another compost bin from concrete blocks, about 3 x 2m. I started the first one in 2003. I have yet to use anything from it. The position of the bins are in the vegetable garden area, surrounded on two sides by grape vines. The grape prunings go into the compost along with anything salvageable out of the veg garden and all household vegetable compost and paper. It receives lime and N fertiliser as and when it crosses my mind to add some.

As you say, the easiest way is to burn tree prunings, but, like yourself, I do not like doing this. I have very close to 500 olive trees. Two years ago I chipped everything and used it as a mulch on my wife's shrub garden. Last year I chipped some and used it as a mulch back on to some olives that had shown stress from lack of water that summer. I covered this mulch whith comfrey leaves this summer. It also received some prilled N and liquid Urea as part of my fertiliser programme for the olives. Again no visual signs of breakdown.

I also put some out as a windrow on a piece of ground that is low in OM. Apart from the leaves falling off their is no visual change in the twigs.

We finished the olive harvest today, and subject to planting 800 almond trees, my main future task is to prune the olives. This year will require a heavier pruning than last, and my wife and I were discussing this over dinner. I am inclined to go for the labour intensive system of taking as much as I can for firewood and chipping the rest. It will eventually break down, and if it takes several years that is not a problem.

I find that part of the enjoyment of life is facing these new challenges. After more than 60 years of gardening and farming, I would be sorely disappointed if there was nothing new to discuss or problems to solve.

New Puritan · Nov 14, 2016

This is a really interesting thread, with some well made points.

@Old McDonald - your quote:

Old McDonald said:
I am sure Turner would approve of you importing nutrients, after all he did say "every time you sent a vehicle into town it should return with sewage sludge, sawdust (these two were the main components of his compost heaps) wood shavings, vegetable waste from greengrocers, or even old hessian sacks," - another quote from my own writing. Sir Albert Howard's Indore compost also relied on importing nutrients from other people's land.

I really like that sentiment, but how practical is it to do that? Just thinking that to do this by the book would require various permits from the EA; and how much would you really get in terms of tonnes per hectare? I'm not knocking it - to some extent I have always done this when my land area consisted of back garden and allotment(s); but now I run a farm it isn't going to be easy to get enough to feel worthwhile. Having said that, I do still do it.

What's the best source of bulky organic matter? There's been a few threads on here about this sort of thing, and I know it does really depend on where one is located and what's available nearby. I've built a compost heap in the yard using a load of old conventional hay bales that have been at the back of a barn for 14 years. I collect spent coffee grains from a couple of cafes, as well as some unsold vegetables from a shop and it all goes on the heap. But it will probably give me only a couple of tonnes at best.

The best way I can see of increasing OM in the soil is to make it in situ, rather than carting it in from somewhere else, hence I have 2 years in 6 of grass / clover ley; and all straw is chopped and ploughed in. And before anyone seizes on the "p" word, my land is certified organic and, at present, there really doesn't seem to be a way to be min or no-til and organic, but that's a subject for another thread perhaps...

NP.

Old McDonald · Nov 15, 2016

NP, Regarding practicality, you answered your own question. You can produce some, but never enough. Turner failed to produce enough too despite his undoubted extreme efforts. Offhand, I think
he did not specify his shortfall. He was self-sufficient feed using grass and growing his own cereals, together with beans and comfrey as his protein sources, so he managed that part of his requirements - but not the OM needs.

I think cost of collection or transport to the farm is the biggest problem. At this time of year there are absolute mountains of leaves and fine twigs available at every oil mill in southern Eorope. Most people collect this up with their olives as they are harvesting and the mills separate it out prior to weighing. We keep ours on the place. It is a cost to the mills to dispose of this waste, but it is very lightweight and although my eyes lit up when I first saw such a "free" source of OM, I decided the transport of the material would not warrant the end quantity.

As I posted at #36 on this thread I too think the best solution is grass leys and arable rotation, but I favour Elliott's 4 years of each.

Old John · Nov 15, 2016

clbarclay said:
There is a interesting thought about oxygen and the rate of organic material decomposition relating to compost.

I will have a lot of tree prunings this winter. The easy solution to 'dealing' with them is to push up and burn, but it seems a waste of raw material that could be composted. The conventional method seems to be chip the wood fine, keep mixing with high N material and aerating till it's ready. A rather cost and energy intensive, short term option.

Leaving branches just piled up is a very long term option. Has anyone found an effective middle way to compost all the wood that is too small for wood burners?
For example, any idea how long it would take to compost chunks of wood up to 2" diameter mixed with FYM?

One of my old college tutors had a firm that basically had the idea of piling up green waste,or any not too big woody stuff, into heaps. From memory, about 10m2 and 3m high. Add on top pig slurry and turn using a teleporter, I can't remember how often, then add more slurry until it's all nicely composted. Never got round to it myself, but it looked feasible. The idea was to get local councils to pay you to take their green waste. Managed to do that one year but it was carted about 50 miles by lorry the next year, very green!

Old McDonald · Nov 20, 2016

clbarclay said:
Has anyone found an effective middle way to compost all the wood that is too small for wood burners?

@clbarclay, Further to my previous post using the same quote (#86) I was pruning olives yesterday and remembered something I previously did.

There were several areas of unused land when I purchased here, including one depression, ex quarry I think, of over 2000sq m and shoulder depth; plus some smaller areas. The biggest area now forms part of an olive grove, and there are some 55 to 60 trees on the area concerned. It was filled mainly by grading and adding any organic material I could find including prunings. On a smaller area I tipped prunings and ran over the heap a few times with the tractor, then scattered yellow lupin and cereal rye seed over. No fertiliser, just let it take its chance. I had a good take and growth and then graded soil over the top. It was only about 300 sq m but is planted up with maybe a dozen almond trees at 6x4m spacings. Not a lot of extra trees, but better than nothing. Planting the whole 800+ trees was interrupted by the olive harvest and dry weather - too dry to plant trees without watering in, and I am not too keen on that job. Like most of W. Europe today is wet so hopefully planting restarts tomorrow and the olive pruning can wait. As long as it is finished by late winter that is fine.

Anyway, I decided to again dump the prunings in a windrow as last year, but there is a lot more than then. In case you do not know, olives are evergreen so the leaves come with the pruned wood. The reclaimed almond area is separated from this windrow by an underground drain topped to the surface with stone and a fence beyond the drain. Where I placed the windrow is lower than the ground surface on the other side of the fence and is wet all winter, so I have decided to try and raise the ground level sufficient so that there is a shallow ditch of sorts over the top of the drain. The area where I am dumping the prunings is about half an acre of solid clay with up to loaf of bread sized stones despite me having scarified and carted off many, many link box loads. It grows very little and has been used as a close run out area for goats. If I can eventually grow some decent grazing I will be well pleased.

Whenever convenient through the summer I ran the tractor over last year's windrow in the hope it would break up the twigs, but they did not dry sufficiently. They are pretty well flattened though, with a good mulch of leaves interspersed. I have some lupin left over from sowing the proposed almond grove last year and have decided to scatter this over the now flattened windrow from last year to see what effect it has. Germination will be above the existing soil level and hopefully the roots will work their way amongst and through the now shallow mix of leaves and twigs and begin the breakdown. A summer legume crop of Cowpeas to follow is also a possibility.

I would like to chip/shred all the prunings, which will increase in volume over the years, but lack the time unless I build a big pto driven one that prunings can be thrown in. It is on the "to do" list for the future, but might never happen.

I might also scatter seed on the new windrows and see what happens. I will keep you informed.

Old McDonald · Dec 16, 2016

@clbarclay, Further to my last post, I have had a good take of yellow lupins and rye (I decided to throw this in since I had some left over too) on last year's windrow.

I have decided not to do the same with the current prunings, but wait until spring and then decide about sowing cowpeas. I can easily irrigate it through the summer. I will allow the crops to seed so that they might self-sow in future.

Intermittent showers have seriously disrupted pruning and planting so I am not going to attempt to chip anything this year. It saves an enormous amount of time. All I am really interested in for this small area is to be able to give the stock a close-by run out from their housing, so hopefully I will never need to cultivate.

I will keep you informed of progress or the lack of it.

IEM · May 27, 2017

Here's a thought: lots of people saying PAS 100 green waste compost no good - it's dead, gets too hot etc etc.
If I windrowed it once on the farm in heaps about 2m high and left it for 6months + would this improve it and make it more biologically active? Would be cheaper than making my own from wood chip/fym etc.

Old McDonald · May 27, 2017

It cannot really be "dead" can it? I would also have thought that if it heated it was a good thing. It is obviously goingto be very inconsistent as to quality, nutrient content, and probably also OM. I know there is a standard, but some is possibly well above this standard.

If it it not tested before you buy, it would be worth the small additional cost to have your own analysis carried out. Probably worthwhile anyway if you are buying any quantity. I am sure your extra 6 months stockpiling will do no harm if the windrow is not open to the weather, in which case leaching might occur. In that case do an analysis before windrowing, and again after the 6 months. You then have all the info you need.

At worst you are importing OM to your land, and allowing for the actual cost, that is almost invariably beneficial.

N.Yorks. · May 27, 2017

IEM said:
Here's a thought: lots of people saying PAS 100 green waste compost no good - it's dead, gets too hot etc etc.
If I windrowed it once on the farm in heaps about 2m high and left it for 6months + would this improve it and make it more biologically active? Would be cheaper than making my own from wood chip/fym etc.

Compost process:
First phase of "Thermophyllic microbes", these start the breakdown of the compost feed stocks, their activity leads to high temperatures which they are able to tolerate and continue their breakdown of the organic matter.
Second phase of "Mesophyllic microbes" which start to take over from the thermophyllic ones as the compost temperature reduces. The breakdown of OM still continues just at a lower temp with a different range of microbial species.

Once the C:N ratio of the compost has levelled out around 18:1 (I think it's around that level, need to check) then the compost is said to be stable and isn't likely to change a whole lot more.

If you were supplied compost that had a high C:N ratio then this is an indication that it hasn't finished composting and wouldn't be stable. So once you introduced moisture and air to the heap it would kick start the ongoing breakdown of the OM until it eventually stabilised.

Don't forget that you use compost to add to the soil and it's really the soil biology that wants the OM so that it can get on with breaking it down. Any OM added to the soil is really "food" ,for want of a better description, for the soil microbes etc.

IEM · May 30, 2017

Yes I agree that it is food for the soil life and biology moves into it once it has been spread on the field as demonstrated by all the black worm casts which appear - by the time it has passed through an earthworm I guess it is pretty active.
However much has been written about the art of compost making and letting it heat but not get too hot etc etc. Should I just ignore this and spread it as it is on arrival at the farm. It is pretty consistent for organic material and gets shredded/turned as many times as is necessary at the composting site. We then cart it to the farm and heap it up as high as we can where it sits for 6-10 months before spreading.
We have nutrient analysis of it from the site and tbh it barely changes year to year.

N.Yorks. · May 31, 2017

IEM said:
Yes I agree that it is food for the soil life and biology moves into it once it has been spread on the field as demonstrated by all the black worm casts which appear - by the time it has passed through an earthworm I guess it is pretty active.
However much has been written about the art of compost making and letting it heat but not get too hot etc etc. Should I just ignore this and spread it as it is on arrival at the farm. It is pretty consistent for organic material and gets shredded/turned as many times as is necessary at the composting site. We then cart it to the farm and heap it up as high as we can where it sits for 6-10 months before spreading.
We have nutrient analysis of it from the site and tbh it barely changes year to year.

Your not looking for the compost to be particularly active, you are looking for it to be stable, as per the C:N ratio comment earlier. It needs to be applied so the soil biology can use it. They use it to live and increase their own populations, which is what you want as its the by-products of their existence that you want which improve soil structure etc. Earthworms are a bit different as you also want them to burrow and redistribute the OM.

With compost you aren't getting it to import microbes to the soil, although this will happen, instead you are using it to add 'food' to the soil for existing soil biology .

If the compost is stable with C:N ratio around the 20:1 region get it spread so it can be useful. I am assuming here the compost hits the PAS100 requirements and is suitable for agriculture etc.

Old John · May 31, 2017

clbarclay said:
There is a interesting thought about oxygen and the rate of organic material decomposition relating to compost.

I will have a lot of tree prunings this winter. The easy solution to 'dealing' with them is to push up and burn, but it seems a waste of raw material that could be composted. The conventional method seems to be chip the wood fine, keep mixing with high N material and aerating till it's ready. A rather cost and energy intensive, short term option.

Leaving branches just piled up is a very long term option. Has anyone found an effective middle way to compost all the wood that is too small for wood burners?
For example, any idea how long it would take to compost chunks of wood up to 2" diameter mixed with FYM?

One of my old lecturers from college came up with a system of composting quite big branches and trimmings.
Basically pile branches in a heap about 10m by 10m and 3m high. Add , preferably pig slurry, to the top until it soaks to the bottom, but not too much to make the site wet.
Leave for a week or two and then "turn" the heap with a loader of some sort. I.e. Move it a few yards and reheap. Add more slurry and repeat until it's composted.
I think you could put stuff up yo two or three inches on heap, but a good mixture probably works best. The thicker the branches the longer it will take.

Kiwi Pete · Jul 21, 2017

clbarclay said:
There is a interesting thought about oxygen and the rate of organic material decomposition relating to compost.

I will have a lot of tree prunings this winter. The easy solution to 'dealing' with them is to push up and burn, but it seems a waste of raw material that could be composted. The conventional method seems to be chip the wood fine, keep mixing with high N material and aerating till it's ready. A rather cost and energy intensive, short term option.

Leaving branches just piled up is a very long term option. Has anyone found an effective middle way to compost all the wood that is too small for wood burners?
For example, any idea how long it would take to compost chunks of wood up to 2" diameter mixed with FYM?

I run large woodchip as bedding in my barn, will let you know how long it takes to break down but according to the previous owner, a couple of years in the heap..
Have you considered using a retort and making charcoal from the bigger diameter wood? I realise this is an old post, but that's how I'm aiming to speed up the process with all the branches from hedges etc., small can go straight to the heap, but anything worth sawing up will be going in my oil drum "pyrolyzer" (apparently that's what I made) not burnt to ash, but char

Inky · Jul 21, 2017

Kiwi Pete said:
I run large woodchip as bedding in my barn, will let you know how long it takes to break down but according to the previous owner, a couple of years in the heap..

2-3 years, we had to leave it 3 before it broke down enough that we were happy to spread it on our grasslands.

Old McDonald · Aug 8, 2017

Kiwi Pete said:
I run large woodchip as bedding in my barn, will let you know how long it takes to break down but according to the previous owner, a couple of years in the heap..
Have you considered using a retort and making charcoal from the bigger diameter wood? I realise this is an old post, but that's how I'm aiming to speed up the process with all the branches from hedges etc., small can go straight to the heap, but anything worth sawing up will be going in my oil drum "pyrolyzer" (apparently that's what I made) not burnt to ash, but char

I have been putting my tree prunings in a windrow for a couple of years, chipped some in 2015, and begun to autumn sow lupins in them. I want to raise the gorund level a few inches where I am doing this - there is a piped former ditch immediately the other side of a fence where I am doing this and the ground on the other side is higher, so run-off leaves the area wet. The idea is to recreate a ditch over the drain.

I am interested in the design of your "pyrolyzer" and any info you care to add. I came on this thread a few minutes ago to ask whether anyone was making their own charcoal (biochar as some like to call it) and remembered your post.

As a general question is anybody else making it? I am thinking small scale - an aquaponics system of raising my own crayfish to replace bought prawns, and to supply a few summer vegetables without the need to apply copious quantities of water.

Most cost effective way to build soil carbon

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