Om levels

Discussion in 'Direct Drilling Crops & Agronomy' started by juke, Jan 10, 2017.

  1. juke

    juke Member

    Just looking for opinions as this is something we don't know much about, we have had some soil tests done following two years of cover crop in one field and test done following one season in another

    Field 1 has om levels of 13.8 ℅

    Field 2 7.6 ℅

    pH same in both fields 6.8

    Also from the tests they did they expected the cover crop to put back in 13.8 t/ha of green manure in both fields.

    Is this good bad or indifferent to what any one else is achieving .
     
  2. Brisel

    Brisel Member

    Location:
    Dorset
    What method of measuring was this? Loss on ignition? Be careful of reading too much into this. By all means use the figures as a reference point for future sampling to measure a change. Any kind of fresh OM contamination of the sample will skew the results. In calcareous soils you can have some CaCO3 oxidise in the oven which could artificially boost weight loss = higher OM reading.

    I had SOYL do each field when I had them in for pH/P/K/Mg sampling last year, just on a 1 sample/field basis rather than zonal samples (expensive). Mine varied from 3.9 to 12.1 with most around 5-6%. Unsurprisingly the highest ones were close to an old dairy unit, though this shut down 15 years ago! I've been selling all cereal straw for years until recently with non inversion deep tillage. All in all, it was what I expected.

    The interesting thing will be to go back in 5 years to see what the change has been due to chopping straw & using cover crops with the Claydon system.

    What kind of changes have people seen who have been doing strip till/no till for longer?

    upload_2017-1-10_12-13-17.png
     
    N.Yorks. likes this.
  3. juke

    juke Member

    Not 100 percent sure how it was done, lancrop did the lab tests so however they come to their conclusions.
     
  4. N.Yorks.

    N.Yorks. Member

    What is the management history of these fields? Arable or grassland, what rotations? Regular FYM applications?You've obviously cropped them the last couple of years, but do they have a history of being grass leys?

    Was the 13.8t/ha of green manure an estimate? The volume of vegetation you'll return from the cover crop (CC) depends on the mix of CC species mix and the density with which they have established themselves.

    I would say that after a couple of years of CC's contributing 13.8t/ha back to the soil that wouldn't be enough to significantly boost the soil %OM levels. They will definitely raise them but only gradually. It's something that will need to be done regularly,coupled with additions of FYM, compost, crop residues etc. This is my opinion, so happy to be proven wrong with trial evidence of course.:)

    If you've got these high OM levels, I would wonder what other management has occurred in the past, hence my earlier questions.
     
  5. N.Yorks.

    N.Yorks. Member

    When you say fresh OM contamination of the soil sample, how old is fresh? 2 weeks, or something like 2 months? Thanks.
     
  6. dontknowanything

    Location:
    Cambridge
    Anything that looks like a plant, and not soil.
     
  7. dontknowanything

    Location:
    Cambridge
    13.8t fresh material? That's basically nothing, it's the roots + exudates where the gains come IMO
     
    TelesnaAg likes this.
  8. N.Yorks.

    N.Yorks. Member

    Yes, but my question is what length of time can the OM be classified as fresh? 2 weeks or 2 months or maybe a year?
    At what stage will it not skew the result?
     
  9. dontknowanything

    Location:
    Cambridge
    I don't think anyone could come up with an answer like that unfortunately.
     
  10. Clive

    Clive Staff Member

    Location:
    Lichfield
    You might as well guess SOM than have a test done

    Notoriously unreliable and inconsistent results from labs

    I would use tests like solvita / CO2 burst etc instead that aim to quantify biology - from that you can maybe make some assumptuions re SOM levels and soil health change

    Still maintain the best soil health and nutrition test is yield though !
     
  11. dontknowanything

    Location:
    Cambridge
    I suspect SOM levels are more closely correlated to yield than Solvita, but that's just an instinct.
     
  12. Clive

    Clive Staff Member

    Location:
    Lichfield
    I would agree but there seems to be no really reliable or consistent method to measure SOM really
     
    SilliamWhale likes this.
  13. dontknowanything

    Location:
    Cambridge
    I think the answer is to take enough samples, and average it out.
     
    Clive likes this.
  14. SorenIlsoe

    SorenIlsoe Member

    Solvita measures CO2 releases, and high levels indicates high microbe activity. But funny enough, this also shows CO2 losses!! So the better soil structure and soil life the more Carbon is burned off.
    And in No-til and Conservation Agriculture we want to be climate heroes and also increase SOM (4per1000 etc.).......
     
    Clive likes this.
  15. juke

    juke Member

    Well I'm none the wiser, think this is a little to in depth for me to grasp... All I can say is crops look good there's more worms about in the soil and it's definitely got better structure, water filtration , also getting more friable n a hell of lot better than the machine that must not be named left it.. thanks all for your input
     
  16. dontknowanything

    Location:
    Cambridge
    At least it only took you a few days to come to that conclusion, it took me several years :)
     
    Spud likes this.
  17. Clive

    Clive Staff Member

    Location:
    Lichfield
    The above is all you need to know

    "Most" soil testing is just a way to spend money frankly and of little real use quite often

    Farm like our grandparents did - with your eyes and nose !
     
    juke likes this.
  18. Brisel

    Brisel Member

    Location:
    Dorset
    I am interetsed in measurable outcomes - it helps sell the concept of DD to non farmers (who employ me). When I read stories of "natural capital" I do wonder if future government farm policy is going to pay more attention to this, especially sequestering carbon.

    OM is one measure. What else? I'm running a mob grazing experiment on some arable ground for a few years & will do some comprehensive soil tests (Albrecht) and do some earthworm counts before, during and near the end of the 5-6 year lifespan of the plots.
     
    The Ruminant and martian like this.
  19. shakerator

    shakerator Member

    Location:
    LINCS
    not sure there tbh!

    my crop often fails to establish on "healthiest" bits of soil and seen stonking yields on "abused" areas esp wheat!
     
  20. N.Yorks.

    N.Yorks. Member

    Why don't you just get the micro nutrients analysed in their own right, rather than getting them analysed in the context of the THEORETICAL (non-proven by Albrect) nutrient ratios?

    Every soil is very different and trying to impose a theoretical ratio for nutrients and then attempt to adjust them accordingly is in my view expensive and pointless.

    You've got an account with NRM if I recall from previous posts, they can do it at a fraction of the cost of an Albrecht analysis.
     
    SilliamWhale likes this.

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