Can you have too much Organic Matter?

Chae1

Member
Location
Aberdeenshire
I'd say you can, have seen us put a serious tonnage of muck on a field and you would expect the following crop to be fantastic. Its not, sometimes get a poor crop.

Same when you plough down a long term ley, you always get best crop in second year.

It must be something to do with volume of stuff for bugs to break down?

I go for little and often around 18t/ha.

Perhaps its because i plough it down.
 

Chae1

Member
Location
Aberdeenshire
On a soil I'm sure you could because it could act as a smother and prevent ideal growth. But in a soil? Highly doubt you could have too much. OM is what makes up and feeds the soil, how can you have too much soil in soil?

If its not being broken down to produce N?

Surely it requires a certain amount of energy to break it down also.

When chopping straw arable farmers need to account for a certain amount of extra N to break it down?
 

Blaithin

Member
Livestock Farmer
Location
Alberta
If its not being broken down to produce N?

Surely it requires a certain amount of energy to break it down also.

When chopping straw arable farmers need to account for a certain amount of extra N to break it down?
Ah, but straw isn't the only kind of OM ;)

If the OP is just tilling in a whole turds load of straw into the soil then yes, I can see you quickly running into a case of too much. It would upset the balance of decomposition and soil make up as well as probably lead to poor growth due to root exposure since loose straw isn't the greatest growing medium.

However if it's just a generalized "Can you have too much organic matter, in varying stages of decomposition, feeding and making up a portion of your soil." then I would be really surprised if the answer was yes. It would probably have to be an incredibly high number.
 
What's the OM content of peat? Soils like the Fens in England and the Liverpool plains in NSW must have had a very high content when first farmed and still high now.

I've tested some fields this year and have results varying between 3.8 and 4.7% That's after in the teens of years in set aside and 12 years of me farming it Organically with cattle and very occasional spring cereals. It's had lime, slag and plenty of muck. Goodness knows what it was when the barley baron put it into set aside!

I'm not going to worry about too much.
 

Kiwi Pete

Member
Livestock Farmer
How accurate are OM tests?

Never had one done.
Not really accurate, but useful nonetheless.
Perhaps the "deader" or less biologically active the soils are, the better the test shows what's there? Same could be said for most soil tests.

Google 'liquid carbon pathway' if you want to fill in a happy hour, plants themselves possibly are the biggest providers of SOM, which is why I doubt you can have too much "as a percentage" as per the OPs question - but you can easily put too much muck on, as per your statement
 
Not really accurate, but useful nonetheless.
Perhaps the "deader" or less biologically active the soils are, the better the test shows what's there? Same could be said for most soil tests.

Google 'liquid carbon pathway' if you want to fill in a happy hour, plants themselves possibly are the biggest providers of SOM, which is why I doubt you can have too much "as a percentage" as per the OPs question - but you can easily put too much muck on, as per your statement

Accurate in that you 'cook' off everything that isn't mineral to get the figure.
 

Kiwi Pete

Member
Livestock Farmer
Accurate in that you 'cook' off everything that isn't mineral to get the figure.
Yes, out of a teaspoonful of soil!
:ROFLMAO:

That's farmers, and science :LOL:

Based on this, your carbon stocktake is basically little better than a good guess - if you take a photo of some sheep running through a gateway, can you tell how big your flock is? ;)
 

Dry Rot

Member
Livestock Farmer
Surely organic matter only "works" if it contains micro fauna and flora? Make a bonfire and see how long it takes for plants to grow back on the site of the fire. Lift a dung heap and see what grows back, and how well, where the dung was stored. One is dead and the other is living.

Sterilise muck from a muck heap and nothing will grow on it. What is that process customs use to kill off bugs and render imported seeds etc. harmless? Gamma radiation? Sterile organic matter is of no use to plants even if it contains 100% "organic matter".
 

Agrispeed

Member
Location
Cornwall
We've been increasing OM for about 10 years and have grassland fields at 18% now.

I have been told the figure will plateau at some point (although no one can tell me when) The soil will still build carbon, but not as a %, but you will continue to build soil if that makes sense. We have entered into a load of extra testing as the results as measured (30m grids across a field and at 3 depths, sent to 2 labs and through 3 organisations) got results that are apparently impossible to achieve according to some, and has caused a lot of arguing between 2 factions of soil scientists.

Soil biology is quite good at metabolising chemicals, so I think some of the chemical guys recommend keeping OM low to improve the effectiveness of chemical control. o_O:facepalm:
 

Poorbuthappy

Member
Livestock Farmer
Location
Devon
We've been increasing OM for about 10 years and have grassland fields at 18% now.

I have been told the figure will plateau at some point (although no one can tell me when) The soil will still build carbon, but not as a %, but you will continue to build soil if that makes sense. We have entered into a load of extra testing as the results as measured (30m grids across a field and at 3 depths, sent to 2 labs and through 3 organisations) got results that are apparently impossible to achieve according to some, and has caused a lot of arguing between 2 factions of soil scientists.

Soil biology is quite good at metabolising chemicals, so I think some of the chemical guys recommend keeping OM low to improve the effectiveness of chemical control. o_O:facepalm:
I keep thinking of your measured increase in carbon and organic matter when I read all these holistic grazing detractors. There's been a few links posted on here lately and others elsewhere. People claiming the Savory's and Salatin's of this world aren't actually doing as much good as they claim.
So very interested to hear the results of both your testing, and the subsequent scientists' debates!
 

holwellcourtfarm

Member
Livestock Farmer
I keep thinking of your measured increase in carbon and organic matter when I read all these holistic grazing detractors. There's been a few links posted on here lately and others elsewhere. People claiming the Savory's and Salatin's of this world aren't actually doing as much good as they claim.
So very interested to hear the results of both your testing, and the subsequent scientists' debates!
There is huge scientific disagreement about effective ways to measure soil health. There are many accepted specific soil tests but it seems none are robust enough to resist challenge. When it comes to soil those claiming scientific certainty are arrogant or lying.
 

Agrispeed

Member
Location
Cornwall
There is huge scientific disagreement about effective ways to measure soil health. There are many accepted specific soil tests but it seems none are robust enough to resist challenge. When it comes to soil those claiming scientific certainty are arrogant or lying.

There is a soil scientist at a certain southwest university who refuses to accept that grassland will sequestrate carbon, apparently only temporary cover crops can do that?! :scratchhead:
 

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