The Two Simon's Theory

Discussion in 'Direct Drilling Crops & Agronomy' started by Simon Chiles, May 2, 2014.

  1. Simon Chiles

    Simon Chiles DD Moderator

    This Winter, because of too much rain and time on our hands, @Simon C and I came up with a theory that we think explains all sorts of things. When we talked about it we found that he had one half of the jigsaw and I the other. Since then I have discussed it with other members of this forum and we are now conviced we might have a theory and also more importantly some solutions. I must also stress that this doesn't just apply to direct drilling.
    This is it:-
    Any residue of decaying graminaceous material ( sprayed off grass, volunteers or chopped straw from wheat, barley and oats etc. ) are, in anaerobic conditions ( normally wet ), producing considerable amounts of Phytotoxins. These mainly consist of acetic acid but some of the others are butyric and proprionic acids as well. These Phytotoxins are damaging seedling roots and making the plants more succeptible to pathogenic attack ( Fusarium and Phoma ) and, depending on the amount of material and lack of oxygen, can even totally wipe out a crop. Even if the crop survives we think it is affecting plant health and growth and the acidic conditioins are favouring weeds such as blackgrass allowing them to become competition for the crop.
    We think these phytotoxins are fairly immobile in the soil; acetic acid concentrations are more than halved 15mm away from the decomposing material. We also think this effect lasts for up to 8 weeks ( depending on temp.) starting from when the material comes in contact with the soil.
    Decomposing material from anything leguminous, rape and linseed etc. does not have this effect.

    We think this explains several things, one of which is declining yields, especially in rape. We also think that it explains why autocasting can be so hit and miss. If the chopped straw lies in a dry inert layer then your rape will probably be OK, but if the straw turns into a wet soggy matt then production of these phytotoxins will destroy your crop. We also think that often slugs, leatherjackets, wireworms etc are getting the blame for some of these crop failures.
    It isn't just small seeds and direct drilling, if you had a lot of grass weeds and you spread beans on the surface and ploughed them in you wouldn't have much of a crop either.
    We also think that Strip till is benefitting from having a super row cleaner that sweeps aside the straw to help the situation. However, in severe conditions even this isn't enough.
    So going back to our schoolboy chemistry we think the solution to neutralising these acids is lime, and so far we seem to have had excellent results.
    Of course you could just wait until all the straw had decomposed, then you wouldn't have the problem anyway.
    We also think that the reason that this hasn't become so apparent before is due to the effect only happening in wet conditions and therfore sometimes in drier conditions you can get away with it.
    We also think that for cover crops to become successful in the UK we need to think carefully about what to grow and how to destroy them for best effect. For example it would be OK to have barley in your cover if you are going to graze it hard with sheep, but you certainly don't want it in if you are going to dessicate it just before drilling.

    It will be interesting to see if the press want to publish our theory or whether they ignore it for fear of upsetting too many advertiserers of machinery and chemical supplies.
    Last edited: May 3, 2014
    Sharpy, Acke, SimonD and 15 others like this.
  2. Steevo

    Steevo Member

    Interesting stuff. Would you say this applies to all crops grown after cereals? Is it less of a problem if your previous plant residue is standing rather than lying in contact with the soil?
  3. marco

    marco Member

    tipperary, ireland
    Would you think that high calcium soils suffer less from this problem?
    TWF likes this.
  4. Badshot

    Badshot Member

    So instead of applying starter fert, apply some lime granules with the seed.
  5. Simon Chiles

    Simon Chiles DD Moderator

    Yes it applies to all crops as far as I'm aware although possibly Lupins may be more resistant as they can tolerate acidic conditions.
    It would be less of a problem if you could keep the straw standing but in reality when you drill you would flatten the straw and start the 8 week clock.
  6. Simon Chiles

    Simon Chiles DD Moderator

    Yes but not completely immune. @Cab-over Pete has some customers that insist on applying lime to high pH soils with good effect.
    Last edited: May 3, 2014
  7. Simon Chiles

    Simon Chiles DD Moderator

    You're getting the idea. Obviously the more residue you have the more lime you'll need.
    I've applied prilled lime before drilling and when I opened the slots to see the results there was a lot of lime actually in the slot.
  8. tr250

    tr250 Member

    Think you speaking a lot of sense. We bale all our straw for our own use but last year I chopped two strips and the rape in these two strips is rubbish it's behind trio I don't think it would of affected it if it had been done without discs to mix straw in
  9. Barleycorn

    Barleycorn Member

    If you look back the government used to subsidise lime, it never subsidised nitrogen.
  10. Say you were growing spring barley and you had recently sprayed off a whole load of weed growth. Would you expect these deleterious effects to become apparent immediately, or might the crop start growing normally, and then succumb slightly later on. Our spring barley was planted into a lot of decaying black-grass this year which was only sprayed off shortly before drilling and has looked pretty good up to now. But ... it has been very dry. Now we've had a bit of rain I wonder if we'll see any problems emerging.
  11. RushesToo

    RushesToo Member

    Have you got pictures you can show?
  12. Simon Chiles

    Simon Chiles DD Moderator

    The dry weather will help your situation and if the barley has grown enough it won't be affected. A bit of rain isn't going to hurt, it's when your soil start to become waterlogged that the problem will arise. Phytotoxins , obviously, will gradually increase slowly to start with, peaking to a max at the 4 week mark then gradually decline. As with all chemical reactions the time of the reaction is temperature dependant. In extreme cases I seen the newly emerged seedling start to turn brown, wither and die. The level of effect will depend on the amount of decaying material present, sometimes it just slows up growth for a bit and the plants recover, although I suspect a hard knock at this stage must affect final yield.
    Feldspar likes this.
  13. Steevo

    Steevo Member

    It might also explain why despite not liming our fields for 20+ years, we've tested them and only found odd spots that need lime, mainly the wet spots. Furthermore, we've never chopped any wheat straw in the same period.
  14. marco

    marco Member

    tipperary, ireland
    This could very well lead to a simple change in rotation. Winter barley cut the start of August would leave an 8 week gap before a following winter crop.
  15. The Ruminant

    The Ruminant Member

    You say it's graminaceous material decaying in anaerobic conditions. Might this explain why rakes appear to work? They 'turn' the decomposing straw etc, allowing air in and encouraging the aerobic, rather than anaerobic, breakdown of material.

    Also, do you think it's the 'acidic' conditions created by the decaying material that encourages blackgrass, or the anaerobic conditions that encourage both the production of the various acids and the growth of blackgrass? A moot point because the end result (and the obvious solution) remain the same whichever way round it is.

    Very interesting theory, thanks for sharing.
    balbirniefarm and martian like this.
  16. The Ruminant

    The Ruminant Member

    One more thought! As your soils become more biologically active, (and are under a no-tlll system), the top layer of the soil becomes much better structured with more air pockets. Would this, coupled with an increased speed of breakdown of the material (due to enhanced biological activity) mean the problem will lessen the further into the system we go?
  17. Simon Chiles

    Simon Chiles DD Moderator

    I think it might be the acidic conditions that are favouring the blackgrass, at the same time as your crop , it's competition, is being weakened.
    Initially I thought you might be right about the more rapid breakdown occurring in more biologically active soils but for my part the biggest problems I've encountered have been after long term grass which sadly knocks that theory.
    The Ruminant likes this.
  18. Clive

    Clive Staff Member

    After a few discussions with Simon over the winter the more I think about this the more I think they are spot on with this theory, it fits and explains so many situations and problems that I think the circumstantial evidence is overwhelming

    Not just relevant to zero-til either, all arable systems would benifit from respect to this theory it explains why tines on strip till drills or sub cast osr seems to work well, why lime seems to be best used after a cereal and ahead of osr, why since zero-til i have found wheat after oats the biggest challenge etc

    in countries without a martine climate this would be much less of an issue as its often much dryer after drilling
    Last edited: May 3, 2014
  19. lexion610

    lexion610 Member

    Interesting idea, it certainly explains some of the phenomena i've noticed.
    This is OSR following wheat back in autumn 2012. The right has been raked, the left untouched until drilling. It is relatively free draining but it was definitely moist, so anaerobic conditions were certainly possible in the wheat stubble. The straw was baled, do you think phytotoxin levels would be significant enough if only the stubble was left?
    The field has been in DD 14 years so I would say that soil biology doesn't have much to do with it and it was limed 2 years before this picture was taken. As you can see, the difference is definitely not slugs, spraying or soil type.
    Steakeater likes this.
  20. franklin

    franklin New Member

    After chopping winter barley straw in the "year of constant rain" I can say that I will never do so ever again. The stuff poisoned the land. Nasty.

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