Carbon audits.

[farmerm]

As has already been said, soils just keep building and the organic matter finds its way deeper into the soil profile. I saw a plateau in soil carbon after 10 -15 years but was only looking at the top 6 inches.

Soil carbon in the top 6 inches is the easiest to build and the easiest to loose.. What is the point in paying farmers to capture carbon in the soil for 10 years and then the farmer have a change in policy, stop taking the payment (or gov stop paying it) and he reverts to plough and powerharrow and let it all go again... I just can't see how such a scheme can offer value for money unless it somehow ties the land use indefinitely. What is the benefit in increasing the average organic matter (in a fragile state) in UK soils by 0.1% per year if that quantity of carbon being released by global deforestation and fossil fuels is on a vastly different order of magnitude?

 

[Muddyroads]

Carbon is stored in organic matter, regardless of it being in wood above ground or roots and other organic matter underground. In a carbon mature woodland as old trees falls and decomposes new one are growing to replace them. Microbes decompose organic matter and release carbon dioxide back into the atmosphere regardless if the material is wood above ground or organic matter in the soil. If you revert low organic matter land to permeant pasture or woodland I believe both can be carbon sinks but both will reach a carbon maturity. As the organic matter content of a soil increases the faster the rate of oxidisation becomes. A 10 year old grass lay on a dairy farm may still be sequestering some carbon but I will bet at a much lower rate than carbon is being lost though oxidisation from a cultivated field of fenland peat. If we are going to take the route of reducing atmospheric CO2 and using soil as a carbon store and increasing grassland OM by 0.01% per year then it seems pretty dumb to continue growing salads and vegetables on high organic matter land that is being oxidised as a result.

My thoughts entirely. We’re primarily organic beef and sheep but intend to start growing some field scale veg next year. From a business perspective I see this as an opportunity to diversify the farm and get away from purely producing red meat, but my gut instinct is that this is likely to be a backward step for the farms soil.

 

[farmerm]

My thoughts entirely. We’re primarily organic beef and sheep but intend to start growing some field scale veg next year. From a business perspective I see this as an opportunity to diversify the farm and get away from purely producing red meat, but my gut instinct is that this is likely to be a backward step for the farms soil.

I would think having a 1 year veg within a 10 year grass rotation should be fairly soil carbon neutral...

 

[Brisel]

What is a the best way to measure soil carbon? I'm on chalk soils which have tested at 4.5 - 13% organic matter based on Loss On Ignition tests. There has been a long held belief that calcareous soils show an artificially high LOI carbon value due to reduction of calcium carbonate and trapped water not removed by the drying process first. All vehemently denied by the likes of NRM Cawood Laboratories of course.

I'm sure I could test a low baseline SOC by leaving the samples on my Rayburn all weekend then posting them to a lab on a Monday so I'd have no problem showing a big net increase in a few years time if I did it properly the second time. I also have little doubt that I could generate SOC maps of my fields like I already have for conductivity and P, K etc.

Seriously, I would like to know more about how to measure soil carbon properly as I'm in year 3 of direct drilling & will start no tilling next year. I already have cover and fodder crops in the rotation.

 

[DaveGrohl]

What is the benefit in increasing the average organic matter (in a fragile state) in UK soils by 0.1% per year if that quantity of carbon being released by global deforestation and fossil fuels is on a vastly different order of magnitude?

Totally. When you run a business that's losing money hand over fist you don't start fannying around with the small inefficiencies, you start with the major problems and concentrate on those. All of this carbon footprinting malarky is basically tinkering around the edges by people who think just a bit more paperwork will solve everything. Paperwork never solved a damn thing.

 

[Still Farming]

Number crunching app is it?

 

[DaveGrohl]

Soil carbon sequestration varies greatly, not least with grazing practice as I understand it.
Set stocking can be of zero benefit, rotational grazing of some benefit, and mob grazing the most beneficial.
Many other factors have an effect too, some of which will be relatively constant in a given environment (like climate), others can be variable.
An accurate figure is going to be difficult to achieve, but I completely agree with the op sentiments that it is going to become a useful tool in terms of rebutting the vegan argument and quite possibly for future payment schemes.

Mob grazing? I take it that's in a region of low rainfall? I shudder to think about the state of my soils if we mob grazed with cattle during a normal moist summer.

 

[Treg]

The key phrase in your sentence is "was once" What sense is there in having payments that reward soil carbon capture if the carbon is not sequestered indefinitely? Do you then have to impose fines at some point in the future for land owners that allow previously captured carbon to escape again?

I agree on the second point, livestock farming doesn't need to be demonised for its environmental impact any more than other food production methods, but demonising it though any means suits the Vegan agenda!

I think I see where your coming from, as a Organic farmer on the surface Carbon credits sound great but if my soils are already high in carbon & the payments are for capturing more , I would gain less than a Arable farm that changed to a no till or livestock system .
I also am thinking along the lines of @Muddyroads & grow a bit of Veg , would that mean we'd have to pay back some credits because we would release CO2 back into the atmosphere or will they pay us not to grow Veg

 

[Poorbuthappy]

Sources please to why you think set stocking as having zero net carbon gain/loss. I totally disagree with that assumption based on my thesis on soil micro arthropod abundance and diversity against grass ley age. There were huge gains in soil carbon up to 10 years in temporary grass leys set stocked.
(No I’m not taking the pee).

But you weren't looking at pp?

This guy quotes lots of research that backs up the assumption, though admits there are plenty of unanswered questions.

 

[CornishTone]

What is a the best way to measure soil carbon? I'm on chalk soils which have tested at 4.5 - 13% organic matter based on Loss On Ignition tests. There has been a long held belief that calcareous soils show an artificially high LOI carbon value due to reduction of calcium carbonate and trapped water not removed by the drying process first. All vehemently denied by the likes of NRM Cawood Laboratories of course.

I'm sure I could test a low baseline SOC by leaving the samples on my Rayburn all weekend then posting them to a lab on a Monday so I'd have no problem showing a big net increase in a few years time if I did it properly the second time. I also have little doubt that I could generate SOC maps of my fields like I already have for conductivity and P, K etc.

Seriously, I would like to know more about how to measure soil carbon properly as I'm in year 3 of direct drilling & will start no tilling next year. I already have cover and fodder crops in the rotation.

I’m working on a soil carbon project at the moment. The process of accurately assessing soil carbon is quite lengthy and onerous, especially if you want to assess it at depth. Taking soil samples and bulk density samples at specific depths down to e.g. 50cm across different fields, soil types or management regimes. It becomes costly in terms of man hours more than anything.

We obviously have no chalk down here so I’d be interested to know how it is dealt with on your soil given the “problems” of LOI?

 

[Poorbuthappy]

As has already been said, soils just keep building and the organic matter finds its way deeper into the soil profile. I saw a plateau in soil carbon after 10 -15 years but was only looking at the top 6 inches.

It seems all the studies that say it plateaus fail to look beyond this.

 

[Poorbuthappy]

Mob grazing? I take it that's in a region of low rainfall? I shudder to think about the state of my soils if we mob grazed with cattle during a normal moist summer.

Plenty doing it in high rainfall areas.

 

[farmerm]

I think I see where your coming from, as a Organic farmer on the surface Carbon credits sound great but if my soils are already high in carbon & the payments are for capturing more , I would gain less than a Arable farm that changed to a no till or livestock system .
I also am thinking along the lines of @Muddyroads & grow a bit of Veg , would that mean we'd have to pay back some credits because we would release CO2 back into the atmosphere or will they pay us not to grow Veg

Those that have produced the most efficiently but least environmentally are now the ones that have the greatest opportunity to be rewarded for undoing the damage they/we have done.

 

[Poorbuthappy]

Can you tell us more about the good farming techniques that can rebuild soil OM whilst giving the producer a sustainable profit and don't rely on the import of feed or fertiliser from outside the holding? It is far easier for the Dairy farmer buying in straw, forage and concentrates to increase the soil organic matter on their holding than the arable farmer that enables them to do so. Should the dairy farmer be paid for his increasing soil organic matter if the effect of the wider production system produces a net loss?

Anyone considered why Brazil is slashing and burning as much rain forest as it possibly can right now?

Because they know short term they can get productive crops from that land and long term the rest of the world will end up paying Brazil massive amounts via carbon credits in order for them to replace the rain forest that they have destroyed.

Look at the work of the likes of Gabe Brown or Joel Salatin and others. Building soil whilst running profitable and more productive systems than similar neighbouring farms.

Others doing it in this country too, just that they are a couple of examples of long term effectiveness.

 

[Still Farming]

So how does it tie in with say farmers receiving green payments for grass greening and envoirnmental and then do 3-4 cuts of grass and burn gallons of diesel ???
Nuts the lot of it?

 

[Poorbuthappy]

Those that have produced the most efficiently but least environmentally are now the ones that have the greatest opportunity to be rewarded for undoing the damage they/we have done.

That is the annoying thing about environmental schemes. They should reward those already doing the good stuff as well as those seeking to change.

 

[Kiwi Pete]

It seems all the studies that say it plateaus fail to look beyond this.

They aren't looking at growth of soil as a possibility, let alone something easily done; a symptom of too much intellect and not enough common sense.

Even with cheap&cheerful LOI testing it's amazingly apparent just how easily results can be adapted to suit an agenda, the top cm of soil here is hugely rich in OM.... because it is brand new soil, made from OM.... hence it stands up to mobs of cattle in a rain event.
It doesn't even really get muddy like it used to (unless you push the limits)

 

[Kiwi Pete]

That is the annoying thing about environmental schemes. They should reward those already doing the good stuff as well as those seeking to change.

And that's a fair part of the reason it shouldn't be a simple SOM test.
Measure a real outcome: infiltration, aggregate stability - these are what you're actually doing for the public.
You can't offset their holidays and purchases, but you can sell them clean water

 

[Brisel]

I’m working on a soil carbon project at the moment. The process of accurately assessing soil carbon is quite lengthy and onerous, especially if you want to assess it at depth. Taking soil samples and bulk density samples at specific depths down to e.g. 50cm across different fields, soil types or management regimes. It becomes costly in terms of man hours more than anything.

We obviously have no chalk down here so I’d be interested to know how it is dealt with on your soil given the “problems” of LOI?

We just knock 1% off to compare it with an average soil, whatever one of those is. I think texture is important to help calibrate the level - 5% on a blowing sand is extremely good. 5% on a black fen soil would be worryingly low.

There's a trade off between the cost of each sample and that dictates the number of samples people are prepared to pay for. 1 sample per 100 acre field isn't really going to tell you much but for thousands of fields at £15/sample for just LOI in the top 6"+ sampling costs you can build a good picture at landscape level. For over £100/sample you'll have great detail but fewer samples. I don't know what the right answer is.

Doing a carbon audit is one of my winter projects & I had every field tested by LOI 4 years ago.

If you can't measure it, you can't manage it.