Om levels

[mikep]

To follow on from the Rev.d Silliam's sermon, it is astonishing when you think about it, but plants exude up to 70% of the sugar that they've made, via photosynthesis, out of atmosheric CO2 and water, into the soil. If you have healthy and undisturbed soil there should be a good network of mycorrhizal fungi in it, which burrow into the plants roots and take sugar in exchange for vital nutrients and water. This sugar they use to make glomalin which sticks particles of soil together and help form its structure as well as being the base of humus, the best and most stable form of SOM.

Thus manures and incorporated residues are all very fine, but will be eaten by soil creatures from bacteria and fungi through to all the tiny crustaceans, nematodes and worms. This feeds the system, but won't build stable SOM nearly as well as permanently covered undisturbed soil (ideally covered with a permanently growing crop, hence why cover crops or herbal leys are so beneficial).

But it's a fiendishly complicated ecosystem and, as Bactosoil points out, a lot can go wrong. Once you've built it up though, things get better and better...

As now it has been shown that you can forget the plants and just add sugar (which comes from plants) to the soil to increase som, perhaps you should choose high sugar catch crops if you are growing them to maximise bound som.
Sometimes too much micro management or over thinking and you loose sight of the actualitè.

 

[SilliamWhale]

To follow on from the Rev.d Silliam's sermon, it is astonishing when you think about it, but plants exude up to 70% of the sugar that they've made, via photosynthesis, out of atmosheric CO2 and water, into the soil. If you have healthy and undisturbed soil there should be a good network of mycorrhizal fungi in it, which burrow into the plants roots and take sugar in exchange for vital nutrients and water. This sugar they use to make glomalin which sticks particles of soil together and help form its structure as well as being the base of humus, the best and most stable form of SOM.

Thus manures and incorporated residues are all very fine, but will be eaten by soil creatures from bacteria and fungi through to all the tiny crustaceans, nematodes and worms. This feeds the system, but won't build stable SOM nearly as well as permanently covered undisturbed soil (ideally covered with a permanently growing crop, hence why cover crops or herbal leys are so beneficial).

But it's a fiendishly complicated ecosystem and, as Bactosoil points out, a lot can go wrong. Once you've built it up though, things get better and better...

Bless you

 

[N.Yorks.]

To follow on from the Rev.d Silliam's sermon, it is astonishing when you think about it, but plants exude up to 70% of the sugar that they've made, via photosynthesis, out of atmosheric CO2 and water, into the soil. If you have healthy and undisturbed soil there should be a good network of mycorrhizal fungi in it, which burrow into the plants roots and take sugar in exchange for vital nutrients and water. This sugar they use to make glomalin which sticks particles of soil together and help form its structure as well as being the base of humus, the best and most stable form of SOM.

Thus manures and incorporated residues are all very fine, but will be eaten by soil creatures from bacteria and fungi through to all the tiny crustaceans, nematodes and worms. This feeds the system, but won't build stable SOM nearly as well as permanently covered undisturbed soil (ideally covered with a permanently growing crop, hence why cover crops or herbal leys are so beneficial).

But it's a fiendishly complicated ecosystem and, as Bactosoil points out, a lot can go wrong. Once you've built it up though, things get better and better...

You seem to differentiate between OM returned from manures and cover crops. Surely all 'previously living matter' that ends up in the soil ends up being broken down by the soil organisms. Permanently covered undisturbed soil with vegetation growing is only going to find an equilibrium between death of roots and leaves, cycling of nutrients and regrowth of fresh vegetation which then maintains a cycle. How does this lead to stable OM in the soil more than if manures and crop residues are returned.

I suppose if in your scenario the vegetation that grows changes to woody species like trees then you'll end up with more lignin being cycled back into the soil, which will be broken down more slowly than green leafy material, but that isn't going to happen in a conventional arable field. Perhaps in an agroforestry system maybe.

Don't forget the value of manure and other residue breakdown in the soil to cycle nutrients back to plant available forms, that is carried out by the host of microbes in the soil.

Are you just getting focused on the one thing that is 'more % OM' in the soil and forgetting the importance of natural nutrient cycles etc? OM in soil has a number of functions.

 

[Richard III]

You seem to differentiate between OM returned from manures and cover crops. Surely all 'previously living matter' that ends up in the soil ends up being broken down by the soil organisms. Permanently covered undisturbed soil with vegetation growing is only going to find an equilibrium between death of roots and leaves, cycling of nutrients and regrowth of fresh vegetation which then maintains a cycle. How does this lead to stable OM in the soil more than if manures and crop residues are returned.

I suppose if in your scenario the vegetation that grows changes to woody species like trees then you'll end up with more lignin being cycled back into the soil, which will be broken down more slowly than green leafy material, but that isn't going to happen in a conventional arable field. Perhaps in an agroforestry system maybe.

Don't forget the value of manure and other residue breakdown in the soil to cycle nutrients back to plant available forms, that is carried out by the host of microbes in the soil.

Are you just getting focused on the one thing that is 'more % OM' in the soil and forgetting the importance of natural nutrient cycles etc? OM in soil has a number of functions.

Manure is certainly a very valuable soil amendment, a good food source for soil life and broad spread of bioavailable nutrients, but it is very poor at being turned into stable long term O.M. Even applied compost pretty well disappears after about 10 years.

The easiest way to boost soil O.M. is to put a field down to grass. Even if all the grass is removed as silage and no muck applied, the soil O.M. will go up. Why? Lots of mycorrhizal roots producing glomalin and no disturbance.

I consider residue on the surface more as food for anecic worms than as an amendment to increase soil O.M.

 

[Hartwig]

The easiest way to boost soil O.M. is to put a field down to grass. Even if all the grass is removed as silage and no muck applied, the soil O.M. will go up. Why? Lots of mycorrhizal roots producing glomalin and no disturbance.

+ no fungicides applied at all !! And hardly any other -cides ....

 

[N.Yorks.]

Manure is certainly a very valuable soil amendment, a good food source for soil life and broad spread of bioavailable nutrients, but it is very poor at being turned into stable long term O.M. Even applied compost pretty well disappears after about 10 years.

The easiest way to boost soil O.M. is to put a field down to grass. Even if all the grass is removed as silage and no muck applied, the soil O.M. will go up. Why? Lots of mycorrhizal roots producing glomalin and no disturbance.

I consider residue on the surface more as food for anecic worms than as an amendment to increase soil O.M.

What figures have you got for glomalin build up in different management systems?

Also, what proportion of soil OM is actually glomalin in say a grassland situation?

You say that compost will disappear in ten years, the fact is that it hasn't just disappeared it has been transformed/broken down into other compounds which have been consumed by living organisms in the soil which are also releasing plant available nutrients and other compounds. Anyone using compost or FYM and returning crop residues should be doing so regularly on an annual basis to keep on replenishing this OM. In other words you supply OM back to the soil regularly, which mimics what would happen naturally in grassland and scrub/woodland. You are keeping the whole soil ecosystem alive as you are cycling carbon and other compounds back to the soil.

I take your point that if the soil is undisturbed then you can get this AM fungi association with the roots, but that is tricky in an arable situation, especially if there are already high Phosphorous levels in the soil as might be found in this type of management. I understand the benefits of grassland and other natural land uses regarding OM build up, but this doesn't allow a wider range of food to be produced?

 

[Richard III]

What figures have you got for glomalin build up in different management systems?

None sorry, I would love to see some if there are any out there.

You say that compost will disappear in ten years, the fact is that it hasn't just disappeared it has been transformed/broken down into other compounds which have been consumed by living organisms in the soil which are also releasing plant available nutrients and other compounds. Anyone using compost or FYM and returning crop residues should be doing so regularly on an annual basis to keep on replenishing this OM. In other words you supply OM back to the soil regularly, which mimics what would happen naturally in grassland and scrub/woodland. You are keeping the whole soil ecosystem alive as you are cycling carbon and other compounds back to the soil.

I agree that FYM ect. is good for the soil, but unfortunately not a complete substitute for the sticky breakdown resistant products of mycorrhizal fungi. One of the problems we seem to have created with modern agriculture is that we have completely ignored this point. Modern varieties have smaller root systems that need to be spoon fed and don't bother with mycorrhizal associations. Fungicides and cultivations kill them, and as you say high phosphate levels cause problems.

I understand the benefits of grassland and other natural land uses regarding OM build up, but this doesn't allow a wider range of food to be produced?

I certainly don't have the answers to this, I do like ley/arable farming systems though, especially ones like @martian 's that push the boundaries. I realise we can't all farm like this though, there just isn't the market for meat.

 

[N.Yorks.]

I agree that FYM ect. is good for the soil, but unfortunately not a complete substitute for the sticky breakdown resistant products of mycorrhizal fungi. One of the problems we seem to have created with modern agriculture is that we have completely ignored this point. Modern varieties have smaller root systems that need to be spoon fed and don't bother with mycorrhizal associations. Fungicides and cultivations kill them, and as you say high phosphate levels cause problems.

I don't think FYM etc is a substitute, its surely complimentary. Part of the bigger functioning system. Lets not just get hung up on one thing.

 

[mikep]

As @Richard III says
"One of the problems we seem to have created with modern agriculture is that we have completely ignored this point. Modern varieties have smaller root systems that need to be spoon fed and don't bother with mycorrhizal associations."

This is absolutely right and why you will find it very difficult to square the circle. To make full use of the soil and it's fauna you have to take a large step back, you won't get four tonne without fertiliser or sprays which by default will damage the ecosystem. You may be able to compromise and reduce inputs but in the end you never get something for nothing and will have to accept compromised soil or lower yields.
Wheats of the past before modern breeding could probably give two tonne with minor inputs and modern machinery. Do the maths and see if it would work for you, I would be happy with this yield, especially if I can make some premium, as my land is poor, wet, has BG and in a good year will only do three tonne so I cannot afford to spend the money now required to reduce this on wheat and late or spring planting are out here.

 

[Philip Hedeng]

As @Richard III says
"One of the problems we seem to have created with modern agriculture is that we have completely ignored this point. Modern varieties have smaller root systems that need to be spoon fed and don't bother with mycorrhizal associations."

This is absolutely right and why you will find it very difficult to square the circle. To make full use of the soil and it's fauna you have to take a large step back, you won't get four tonne without fertiliser or sprays which by default will damage the ecosystem. You may be able to compromise and reduce inputs but in the end you never get something for nothing and will have to accept compromised soil or lower yields.
Wheats of the past before modern breeding could probably give two tonne with minor inputs and modern machinery. Do the maths and see if it would work for you, I would be happy with this yield, especially if I can make some premium, as my land is poor, wet, has BG and in a good year will only do three tonne so I cannot afford to spend the money now required to reduce this on wheat and late or spring planting are out here.

I heard from SW Seed (Sweden) that they're looking for better mycorrhizal association among other things in future varieties. There's probably a long way to go, but they're looking at old material more now than before to find desired traits.


There seem to be some kind of consensus here that grass leys produce more stable SOM than annual rotations. Is there a difference to other perennials like clovers, lucerne, plantain, chicory etc?

 

[N.Yorks.]

Have a look at this. I know its coming at the problem from a slightly different angle, but.........

http://rodaleinstitute.org/a-complete-how-to-on-farm-am-fungus-inoculum-production/

 

[Philip Hedeng]

Just some frustration that it takes so very long time to build up SOM levels. The more organic matter we apply and the better the soil health is, the higher microbial activity we get, and these microbes burns off a lot of the applied C to CO2.
But it is a fact that plowed farmland loses C fast. Here in Denmark measurements since 1985 shows that some soils loses 1,2 t C/ha/year (app. 4 t CO2).
No-till and cover crops can stop or reduce this, but it is difficult to change the trend.
http://csanr.wsu.edu/no-till-soc/

Many who plant trees for timber never get to see the outcome of it, but they do it regardless because they know the cycle would be broken otherwise. I'm thinking about this often, our perception of time. I attended a meeting where one of the more noteworthy agronomists said that 60 years to get a positive effect from better farming practices was a lot of time (pointing to a long term trail of SOM content in different systems). Of course it is, you think at first, but then.... is it really? Not when you're getting into the 70th year, or 150th year with bad practice, which is happening all around the globe apparently, and the effects are starting to show. But is carbon farming exclusive to perennials you think, even during a long period of time?

 

[mikep]

I heard from SW Seed (Sweden) that they're looking for better mycorrhizal association among other things in future varieties. There's probably a long way to go, but they're looking at old material more now than before to find desired traits.


There seem to be some kind of consensus here that grass leys produce more stable SOM than annual rotations. Is there a difference to other perennials like clovers, lucerne, plantain, chicory etc?

Bit I repeat the fact you cannot get something for nothing, if your crop takes 100kg of pottasium then you either lose that from the soil or replace it end of. If you want high yield you need to use artificial fertility and so you mess around with the soil ecology. The break in the system is what we take out we don't return as manure (human) or compost from food remains as would previous generations in a low input cycle.

 

[Philip Hedeng]

Bit I repeat the fact you cannot get something for nothing, if your crop takes 100kg of pottasium then you either lose that from the soil or replace it end of. If you want high yield you need to use artificial fertility and so you mess around with the soil ecology. The break in the system is what we take out we don't return as manure (human) or compost from food remains as would previous generations in a low input cycle.

Oh, I couldn't agree more. I don't believe in a system with output that doesn't need input. But maybe we can utilize our resources better than previous generations so we can target higher yields easier than they did?

 

[mikep]

Oh, I couldn't agree more. I don't believe in a system with output that doesn't need input. But maybe we can utilize our resources better than previous generations so we can target higher yields easier than they did?

That is the best outlook but my fear is that the green lunatics will get the keys to the asylum and reduce the options available. The threat is very real as any idiot can have a say and most are not just ignorant but actually being told lies and indoctrinated by the likes of Greenpeace, SoilAssociation. The joke is that any shortfall in European production would be made up by imports over which there is no control on inputs used.