Dr Christine Jones

Watched a webinar hosted gratefully by Oakbank Seeds with Dr Chistine Jones on Biological pathways to Carbon soil enrichent.

she indicated that crop residues (stubble, straw and above ground debris) contributed only a tiny amount to soil Carbon, with most lost to the atmosphere as CO2. Root exuded Carbon was, in her opinion, far more important.

If I remove cereal straw and sell off farm for animal feed, then plant a 8 way cover crop, am I gaining or losing soil Carbon??

The carbon from the straw has been fixed on my farm but for all eternity will be stored in FYM incorporated on someone elses farm.
 

Cutlerstom

Member
Arable Farmer
Watched a webinar hosted gratefully by Oakbank Seeds with Dr Chistine Jones on Biological pathways to Carbon soil enrichent.

she indicated that crop residues (stubble, straw and above ground debris) contributed only a tiny amount to soil Carbon, with most lost to the atmosphere as CO2. Root exuded Carbon was, in her opinion, far more important.

If I remove cereal straw and sell off farm for animal feed, then plant a 8 way cover crop, am I gaining or losing soil Carbon??

The carbon from the straw has been fixed on my farm but for all eternity will be stored in FYM incorporated on someone elses farm.
She said root exudates build soil carbon faster than above ground biomass by a factor of between 5 and 30times. So if you keep the straw AND plant a cover crop you are going to be best off! We all know its more complicated a decision that just looking at value of straw in the swath, vs value of nutrient exported and even carbon content. Balers and associated logistics running all over the place, in sometimes less than ideal conditions could mean you need remedial work which could undo any previous SFW building! If you can bale and stack yourself, in the dry however....
 
The above ground dry matter from straw and stubble on a descent wheat crop
is about 5 tonnes per ha which contains carbon
is she saying the below ground roots are 25 to 150 tonnes per ha
not sure her figures stack up
the total biomass of a cereal crop including roots less grain is not 30 tonnes or more
I would like to think it is as the amount of carbon a notill farmer could sequestrate will make a lot of money at 150 tonnes
need to look at the Ahdb wheat bench mark growers guide

edit looked it up 1tonne per ha of root dry matter by gs81 above ground 19 tonnes per ha straw and grain
 
Last edited:

EddieB

Member
Arable Farmer
Location
Staffs
I don’t think she is saying that the root mass is >5 times higher, just that the roots will build soil carbon far faster in a no till situation because that carbon stays in the soil, whereas leaf biomass is lost. That’s how I understood it but could have got the wrong end of the stick completely.
 

martian

DD Moderator
BASE UK Member
Location
N Herts
My understanding is that plants exude up to 70% of the sugars etc that they make via photosynthesis directly and deliberately into the soil. Most of this food is taken up by bacteria and fungi (mostly AMF, or mycorrhizae) who go on to feed the plant with phosphates and other nutrients, as well as water, in a happy symbiotic exchange. This is the liquid carbon pathway that Christine talks about, it supercharges the soil food web, by feeding the creatures at the bottom of the pile and the glomalin that AMF create is the stable base material of humus.

This is why we want living roots in our soil for as much of the time as possible. It's been really noticeable here this year where we've had a couple of fields we sprayed off in the autumn ready for drilling which never took place as the rain beat us to it. The soil is sad and flat compared to where we have a decent cover crop, even where there's a coat of chopped straw.
 

moretimeforgolf

Member
Arable Farmer
Location
North Kent, UK
Problem with straw is that the microbes breaking it down are all breathing out CO2 hence net gain of OM to soil system is less than might be expected compared with root exudates which are converted into soil OM much more efficiently.
I used to be obsessed about chopping and retaining all straw, now I’m more relaxed about it. I’m selling more straw in the swath or swapping for fym. For me cover and catch crops are more likely to build organic matter faster.
 

Two Tone

Member
Mixed Farmer
I’d be very interested hearing @Warnesworth ’s opinion on this. I was fortunate enough to share a zoom meeting with him last week and everything he said makes a great deal of sense.

The trouble with a lot of these things, such as Dr Jones describes, we can only hope that the research behind it is reasonable rather than trying to prove a point and not swayed by personal or political opinion.

On the other side of the equation is the fact that if any system is already working for us, we can be reluctant to want to change it, or even want to listen to anybody suggesting we change it. This can often be described as a case of an “Inconvenient Truth”.

I have my feet in both camps (Conventional -v- Zero-til) at the moment. I know which side I want to end up on, but any business has to make sure that it works for them.

When we talk about CO2 and Net Zero targets, it is very easy to apportion blame when not all of the facts are taken into consideration. A couple of years ago, I looked at trying to find out how much more CO2 was extracted from the atmosphere by our crops, when Nitrate fertilisers are used to enhance photosynthesis within a crop.
I’m not a research scientist and trying to find the information wasn’t easy. Trying desperately not to “over-prove” the point, what I found was that on this 320 ha mixed farm using about 35 tonnes of Urea and another 35 tonnes of Doubletop, increased the amount of CO2 this farm captures above what it would capture without the addition of Nitrate by almost 5,000 tonnes a year!
Remember this is on top of what the crops and grass would achieve, without the fertiliser.
On wheat in particular, the extra CO2 it captures is almost 30 times more CO2 than it took to manufacture that fertiliser!

So, it comes over as rather annoying that when our politicians refer to farmer’s Carbon footprints, that they “Conveniently forget” the photosynthesis side of the equation, let alone the extra increases that fertiliser cause in CO2 capture.


However, it is heartening when something is said that one has had some experience of in real research.
A few years ago, CNH experimented with a special Combine header called the Dual Stream Header. I am not going to bore everybody with it. There is a good thread about it on TFF if anybody wants to look at it. DS wasn’t a new concept insofar as it had been tried before in the 60’s, but didn’t work then because the “double-cut straw” was not pushed to the ground by cage-type rollers, which cause it to contact the soil to make it rot.

I also looked a couple of years ago into what happens to straw after harvest. If it is left on the surface, once Zero-til farmers have got through the 2nd - 4th year pain barrier, hopefully enough worms will have built up to pull it below the soil surface.
Here in lays another dilemma: Left on the surface in contact with the soil, it will rot, releasing CO2 and Methane as it does so. Burying it, might prevent such losses to the atmosphere and help build up Organic Matter as well as feed the following crop. Either the plough or the worms will do this. But can the worms do it fast enough, compared to the plough, to prevent further excessive CO2 and methane release back to the atmosphere?

I’m so new into the Zero-til story that I have an awful lot to learn. Especially when it come to cover crops.
Yes, I can see the advantages and it all make sense on paper.
However in practical terms, maybe not so:
Wanting to plant my Zero-til (winter) crops 2 weeks sooner than I would do conventionally, will mean this happens in no more than 4 weeks since the previous crop was harvested! This means planting a cover crop in a time when it might be difficult to get anything to want to grow anyway.........This is my dilemma at the moment.

It is all very interesting listening to the scientists, but “gut feeling” is often a practical Science and/or Art which needs listening to, too!
 
Last edited:

Goldilocks

Member
BASE UK Member
Location
Oxfordshire
I used to be obsessed about chopping and retaining all straw, now I’m more relaxed about it. I’m selling more straw in the swath or swapping for fym. For me cover and catch crops are more likely to build organic matter faster.
IMO, residue on the surface helps build the worm population more than increase OM.
Both good points . I often shoot myself in the foot by retaining straw and then ending up with sub optimal establishment of following crop which is lower yielding and adding less root exudates than a high yielding crop established after straw removal .........on the other hand as Richard 111 says the straw is great worm food and also encourages fungi rather than bacteria in the soil system . ........Like all things in Regen Ag. it is all a case of finding the best compromise.
 

Arable Scotland: Alternative markets and new cash crops

  • 127
  • 0
1623313380628.png


Arable Conversations: Alternative markets and new cash crops 11.30 – 12.30 on 29th June 2021

Join us at Arable Scotland on 29 June at 11.30 am for an interactive ‘Arable Conversation’ that will discuss ‘Alternative markets and new cash crops’. The session will cover the seasons market potential and the current rollercoaster grain prices. New crops being trialled in Scotland, opening new doors and opportunities for the cereals sector will also feature. Chris Leslie from AHDB, will lead the discussion and be joined by the following panellists.

To register for the webinar visit www.hopin.com/events/arable-scotland and for more information about the event visit...
Top