Chopped straw incorporation as a catalyst to kick start soil biology

Goldilocks

Member
BASE UK Member
Location
Oxfordshire
( Not sure this thread is in the right place , I tend to see the Direct drilling section as the sustainable /conservation ag section rather than pure direct drilling )
Just wanted to share my thoughts on shallow straw incorporation to see what people think.
I think it is fair to say that common thinking is that best way to put carbon into soil is with a material that is as close as possible to the soils natural C:N ratio of around 10: 1 ( i.e. compost or similar )
Just think about it from the point of view of a soil organism. it might think " Oh, Mr farmer has just put some nicely balanced material on the field that doesn't need any breaking down to assimilate it into the soil , I can just roll over and go back to sleep! "
Another scenario might be a farmer incorporating a mass of chopped straw with a C:N ratio of around 80:1. The farmer might also have been very clever and applied a bit of Nitrogen fertiliser. The soil organism might now wake up with a start and think " Crikey Mr Farmer has just applied loads of material that needs breaking down to get it nearer to a C:N ratio of 10:1. He has also given us a nice N source so I better get S...ing and create a population explosion to deal with this stuff ! "
The resulting population explosion converts the applied mineral N into organic N in the bodies of the soil micro organisms and is therefore prevented from leaching over winter. Once the straw is assimilated the soil bugs will die off and slowly release the organic N in their bodies to the growing crop.
Point being is that we want a functioning soil with organic matter turning over rather than just sequestering carbon in highly stable forms. My scenario is obviously only sustainable if lots of carbon is going into the system to keep giving the bugs fresh material to work on..........
To summarise Hypothesis :In a high yielding ,high N input, commercial arable system incorporating high C:N ratio material + N fert better than compost ??
 

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
Oxygen required as well, influenced by cultivation? Soil temperature, time of year? Time it takes for the process to work? Trace element particularly manganese lock up by the soil bacteria followed by release. CO2 release?

The OP hypothesis is pretty much right IMO, but we are only scratching the surface.

Big volumes of chopped straw lying on the surface, wet, without addition of something to aid the decomposition process might be good for carbon sequestration but they aren't good for crop nutrition short term.

I have seen subsequent cereal crops nearly starve to death over winter due to N and Mn lockup as the soil bacteria tries to break the straw down, particularly if you add a big dose of oxygen by ploughing it in.

Autumn N is banned of course, as DEFRA are still living in 1980.
 

Goldilocks

Member
BASE UK Member
Location
Oxfordshire
I view straw as needing to go through a worm first generally
Yes , worms and other large soil dwellers are the first stage in the breakdown process , but same argument applies that you are making the worms etc work for their carbon and creating activity in the soil??? ...
Some Farmers this harvest have justified selling straw for mega bucks and say they intend to use the money to buy compost , just wondering whether they would be better buying distressed straw and applying it to fields with a tractor drawn chopping/bedding machine ( + some N ) and doing the composting in the field ?
 

Goldilocks

Member
BASE UK Member
Location
Oxfordshire
Oxygen required as well, influenced by cultivation? Soil temperature, time of year? Time it takes for the process to work? Trace element particularly manganese lock up by the soil bacteria followed by release. CO2 release?

The OP hypothesis is pretty much right IMO, but we are only scratching the surface.

Big volumes of chopped straw lying on the surface, wet, without addition of something to aid the decomposition process might be good for carbon sequestration but they aren't good for crop nutrition short term.

I have seen subsequent cereal crops nearly starve to death over winter due to N and Mn lockup as the soil bacteria tries to break the straw down, particularly if you add a big dose of oxygen by ploughing it in.

Autumn N is banned of course, as DEFRA are still living in 1980.
As I understand it you can get a derogation to use Autumn N if you can justify it via FACTS qualified advisor .
 

Brisel

Member
Arable Farmer
Location
Midlands
As I understand it you can get a derogation to use Autumn N if you can justify it via FACTS qualified advisor .

Has this actually happened? I'm not asking if it has been done quietly by applying manures with available N to a crop with no autumn N permission from RB209 or something to kick start a cover crop but a written recommendation designed to satisfy a RPA inspector.

You're asking a good question with this thread. IMO leaving as much straw standing would provide a slower release source of soil organism food. As I look toward spring oats as a break crop with less grass weed pressure & an alternative to or alternating with oilseed rape I'd like to bale less if I can get the residues through a tine drill. The thought of a big fibrous mat of decaying straw for late Sept sown wheat is not a pleasant one but there must be others doing this away from livestock areas?

@juke - you grow lots of oats & run a Claydon. Do you bale the straw or chop it? Can you get it through the leading tines or are you increasingly swapping the tine for a disc as your soils improve & need loosening less?
 

juke

Member
Location
DURHAM
@juke - you grow lots of oats & run a Claydon. Do you bale the straw or chop it? Can you get it through the leading tines or are you increasingly swapping the tine for a disc as your soils improve & need loosening less?

we shave of winter oats n bale normally , spring oats really long stubble and chop the last couple of years... its a very rare occurrence for us to plant any cereals with the leading leg on now just beans cover crops and osr . we use the apm longer legs for rape and beans that you suggested, got a worn set of proper claydon legs that we still do use on the odd occasion on some really abrasive land that we contract drill. after that its leading disc for the cereals...

ive re read the postings more now, I should add we have a newholland tx combine that wont be chopping as fine as you guys with newer combines. ours leaves a more coarse longer chop, which to be fair is probably better in the case of a rain event not as much material on the bottom for the drill to cope with. I know I keep preaching about the disc but this is the absolute ideal time to use it, please make sure you use new a shares to act as a sweep to give a clean as possible row for wheat to come away without any hinderance from the oat straw especially if it does turn a bit damp in these situation where we are dealing with chopped material have the batterboards more or less just skimming along doing just enough just to try and alleviate any trash issues. the other thing we do which im sure all you southern guys do is drill the inside of the headland first so any trash that is attached to the drill is dumped on already drilled ground doesn't cause any issues in the new crop within reason...
 
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JD6920s

Member
Mixed Farmer
Location
Shropshire
we shave of winter oats n bale normally , spring oats really long stubble and chop the last couple of years... its a very rare occurrence for us to plant any cereals with the leading leg on now just beans cover crops and osr . we use the apm longer legs for rape and beans that you suggested, got a worn set of proper claydon legs that we still do use on the odd occasion on some really abrasive land that we contract drill. after that its leading disc for the cereals...

Longer legs!!
Can you please elaborate?
 

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