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A question of manure

Last post 22-01-2009 11:43 AM by bogweevil. 10 replies.

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  • 14/01/2009 05:10 PM
    • siskin
    • Berkshire
    • 14 Jan 2009
    • 4
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     I've just been offered a load of manure for my allotment. I guess I should be grateful as manure is like gold dust in our community but the horses have been bedded on something which I've not heard of before - a hemp based material. It's biodegradable and apparently rots down quickly. However Terry Walton in 'My Life on a Hillside Allotment' cautions against the use of stable manure where wood shavings have been used as bedding, as the soil becomes depleted of nitrogen in the slow process of rotting down. Does anyone know, please, if the hemp based bedding might cause the same problem? Thanks.

  • 14/01/2009 05:21 PM
    • Alix
    • Bristol
    • 19 Dec 2008
    • 47
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    The thing with the woodchips is that they are fresh. They produce ammonia as they rot down just like all fresh manure. I've used manure like that when faced with totally solid clay and it was ok. Hemp is a great plant for many reasons, I'd hope it wouldnt contain anything harmful if used as horse bedding. I'd use it as long as it is properly rotted, just like with all manure, compost or mulch. Make sure it hasn't all been sprayed with something to make it decompose more quickly as I've heard has been a problem for some people.I suppose the issue of what the hemp may have been sprayed with whilst growing may arise, but would there be much of it left by now? I would be interested if anyone could answer that question. At this time of year I assume you wont be putting any plants in for a while? In which case I would't worry, but if you are, test it on a small patch this year, and keep the kind donor's phone number!

  • 14/01/2009 05:38 PM
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    Woodchips do not produce ammonia as they rot, although fresh manure does produce ammonia. They contain very little nitrogen and therefore don't produce ammonia, but it is their lack of nitrogen that causes the trouble. The woodchips are slowly broken down by soil organisms that temporarily deplete the soil reserves of nitrogen to make the proteins they need to grow and breakdown the timber.  Hence if you dig in woodchips, plants may go yellow thruogh lack of nitrogen - easily remedied by use of the fertiliser sack, but it is best to avoid this and let the woodchip/manure rot down naturally for a year or two.

    Hemp is perfectly safe, is not treated with hormone weedkillers, and not being woody less likely to cause extremes of nitrogen 'lock-up' but still best to let rot down before using.  This should be quite quick - a matter of a few months at most.

    You can dig in fresh manure if it is free of woody stuff, unrotted straw and indeed any other carbon-rich unrotted material.  The nutrients will be mostly captured by the soil, and by the time planting season comes around the ground will be safe to use.

     

    Boggy

     

     

     

     

     

     

    Beware the bat-eared bogweevil
  • 15/01/2009 12:05 PM
    • Alix
    • Bristol
    • 19 Dec 2008
    • 47
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    thanks for clearing that up. I'm still insure about fresh manure unless you've got quite a while before planting, as I've had it cause high soil acidity before, ruining a massive pumpkin crop. However, this was combined with poor drainage which never helps either acidity or decomposition. Personally I'd avoid anything fresh (not disagreeing here, probably just a matter of different soil), but I'm sure the hemp will be fine.

  • 15/01/2009 02:06 PM
    • siskin
    • Berkshire
    • 14 Jan 2009
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     Thanks so much for all the info. My manure heap is already growing! By the way, the hemp bedding looks rather like woodshavings, so do ask first if you are about to refuse any.

  • 15/01/2009 02:34 PM
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    Manure is actually alkaline and does not cause acidity.

    Fresh manure - very simple - if more than two months to planting add at no more than a bucketful per square metre, less than two months to planting add to compost bin (5cm layer every 15cm of other gubbins) or stack for use in autumn.

     

    Boggy

    Beware the bat-eared bogweevil
  • 16/01/2009 07:08 PM
    • Alix
    • Bristol
    • 19 Dec 2008
    • 47
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     I dont wish to argue, we put in the manure, the ground went acid, I tested it.It might have been the lack of drainage or something but it was alkali before, I know because I worked that patch for 4 years and we had clay with lime beneath, and we'd had it tested all over.

  • 21/01/2009 04:36 PM
    • siskin
    • Berkshire
    • 14 Jan 2009
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     Some of the manure we have delivered is so soaked with urine that my eyes and skin smart as I'm collecting barrowloads of the stuff! Maybe it's that which causes the acidity? Incidentally some fellow allotmenters collect urine and pour it over their compost heaps. One chap swears it's why he grows such enormous onions!

  • 21/01/2009 05:05 PM
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    Your eyes probably smart because of the ammonia which is rich in nitrogen, and this represents an annoying loss of nutrients and a little pollution.  Burying or, better, stacking it in a compact covered mass until you need it will limit nutrient loss.

    In theory ammonia will result in acidificiation as soil bacteria convert the ammonia to nitrate, which being soluble is washed out of the soil by rain taking bases with it.  In practice because manure typically contains abundant bases the manure raises the pH and also its level of ammonia is usually quite low.  With concentrated fertiliser such as sulphate of ammonia the loss of bases is more significant.

    Soil seldom changes pH quickly, so a sudden change after adding manure suggests some other cause, perhaps due to faulty testing methodology.  Clay soils in particular have a very strong buffering capacity and their pH is especially hard to change in the short term. Remember that testing soon after application might give a more acid reading than you might expect as the carbon dioxide released from rotting manure will acidify the soil water.  This is only temporary.  But the carbon dioxide can suffocate roots which is one reason to delay planting after adding fresh manure.

    As lime is cheap, any soil acidity can be easily rectified.  In the unlikely event of manure lowering the pH further the lime will counter the acidity and if as is likely there is a slight raising of the pH by manure, well it just means you won't have to add more lime quite so soon.

     

    Boggy 

     

    Beware the bat-eared bogweevil
  • 21/01/2009 05:57 PM
    • siskin
    • Berkshire
    • 14 Jan 2009
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     Thanks Boggy. It's good to understand the reason behind things. May I ask just one more question as you mention lime? Is the use of lime compatible with organic growing? I assume it is, as I imagine it to be a natural ingredient of some soils? Thanks for all the info.

  • 22/01/2009 11:43 AM
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    Lime and liming is apparently compatible with the tortuous logic of organic gardening!

     Boggy

    Beware the bat-eared bogweevil