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9073Re: Wood chips as mulch: Re forest soils and more soil science

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  • Jeff
    Mar 1, 2009
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      HMM YES, on further consideration I was the one confused...
      mulch wouldn't pull nutrients for the soil more than 1mm or so (less
      than 1/8 inch).. UNLESS incorporated.. and by the time it is shredded
      enough for frost or earthworms to do this... it would already be well
      on its way to decay...




      --- In fukuoka_farming@yahoogroups.com, La Clarine Farm
      <laclarinefarm@...> wrote:
      >
      > Linda, I am sure the increase in water retention provides a better
      > microclimate for the soil microbes and that's why they are seeing
      > increases in growth on the mulched plots. Happy microbes = happy
      > plants, right? I agree with you that the mulch layer impacts the
      > nutrient levels very little directly.
      > My experience is that this layer eventually gets pulled into the
      soil by
      > earthworm and frost actions, where it slowly gets broken down and
      > releases various nutrients. But its greatest use is for soil moisture
      > retention.
      >
      > -Hank
      >
      > Linda Shewan wrote:
      > >
      > > I could argue with this but I am not as scientifically based as
      Jeff so I
      > > would certainly say things wrong BUT my understanding is that the
      wood
      > > chips
      > > lock up nitrogen ONLY if they are dug into the soil. Left on top they
      > > do not
      > > 'pull' nitrogen out of the soil. I believe there are studies
      > > supporting and
      > > dissenting this view but a couple of supporting sites are below:
      > >
      > > A 2004-2006 Washington study showed that applying a 5-foot wide,
      6-inch
      > > thick layer of wood chips provided the best weed control in all three
      > > years,
      > > although it needed reapplication in year three. This treatment also
      > > produced
      > > the greatest tree growth and fruit size.
      > > In a related trial, a Gala apple block was used to compare a
      4-inch wood
      > > chip mulch in the tree row with a herbicide strip. In the first year,
      > > mulched plots consistently had 15 percent to 20 percent higher soil
      > > moisture
      > > at the end of each irrigation cycle than the bare ground plots. In the
      > > second year, the two treatments were watered independently
      according to
      > > need, and mulching reduced cumulative irrigation application by 20
      percent
      > > to 30 percent.
      > > -----
      > >
      > > Concern: Wood chip mulches will tie up nitrogen and cause
      deficiencies in
      > > plants.
      > > Evidence: Actually, many studies have demonstrated that woody mulch
      > > materials increase nutrient levels in soils and/or associated plant
      > > foliage.
      > > My hypothesis is that a zone of nitrogen deficiency exists at the
      > > mulch/soil
      > > interface, inhibiting weed seed germination while having no
      influence upon
      > > established plant roots below the soil surface. For this reason, it is
      > > inadvisable to use high C:N mulches in annual beds or vegetable
      gardens
      > > where the plants of interest do not have deep, extensive root systems.
      > > From: http://www.sustainable-gardening.com/WoodChips.php
      > > <http://www.sustainable-gardening.com/WoodChips.php> and an
      interesting
      > > discussion on
      > > http://www.gardenrant.com/my_weblog/2008/09/the-hort-guru-a.html
      > > <http://www.gardenrant.com/my_weblog/2008/09/the-hort-guru-a.html>
      > >
      > >
      > > Cheers, Linda
      > >
      > >
      > > From: fukuoka_farming@yahoogroups.com
      > > <mailto:fukuoka_farming%40yahoogroups.com>
      > > [mailto:fukuoka_farming@yahoogroups.com
      > > <mailto:fukuoka_farming%40yahoogroups.com>] On Behalf Of Jeff
      > > Sent: Sunday, 1 March 2009 1:17 PM
      > > To: fukuoka_farming@yahoogroups.com
      > > <mailto:fukuoka_farming%40yahoogroups.com>
      > > Subject: [fukuoka_farming] Re: Wood chips as mulch: Re forest soils
      > > and more
      > > soil science
      > >
      > > This email is an attempt to clear up the misunderstanding that have
      > > arrisen as of late about wood mulch
      > > -and of course how this relates to forest soils and
      > > how separately it relates to natural farming
      > >
      > > I will start with the sciency part,., then get more common speak as
      > > the post goes on
      > >
      > > > It would seem to me that the fact that many forests have super
      > > fertile top soils that are many feet deep could possibly be that
      > > multitudes of > leaves, sticks, branches, trunks, etc., have fallen
      > > undisturbed over > millenia.
      > >
      > > when you say fertile soil you must have a basis of comparison..
      > > ok so old prairie soils have deep dark A horizons.. the rotting roots
      > > of the grasses are responsible for this .. this is the theory behind
      > > 'rhizodeposition' that Bob Monie toughts..
      > > this works because of several factors..
      > > a) grass roots go deep instead of spread out like forests
      > > b) grass roots are upto 75% of the primary production as opposed to
      > > around 18% for trees (mostly goes into 'wood')
      > > c) roots actually are somewhat resistant to decomposition due to
      > > content of anti-microbles and higher percentages of lignin
      > > so the result is somewhat decayed organic matter with high nutrient
      > > value mixed deeply in the soils lll this is for prairie soils
      > >
      > > in forest soils the majority of the organic matter is above the
      soil...
      > > the leaf and stick litter is called the o-horizon...
      > > in frigid climates like boreal forests this can over eons become
      > > several feet thick, also in bog/peat situations this can likewise
      > > become thick- this is due to slow decomposition because of cold or
      water..
      > >
      > > in temperate climates it is at most inches thick...
      > > in tropical climates it is even less (usually less than 1")
      > >
      > > immediately below the O-horizon is an E horizon... this is where all
      > > the acids from the leaf litter remove the nutrients and send them
      > > packing.. ending up in the stream or deeper in the soil profile...
      > >
      > > the nutrients then are bound mostly in the living matter and the
      > > O-horizons..... (recently dead stuff)
      > >
      > > but the soils are often 'deep' because the acids do break down bedrock
      > > and roots crack it to increase weathering of the soil...
      > > so the actual soil profile might be deep but the nutrients are still
      > > mostly shallow...
      > >
      > > I fail to see how adding wood chips to soils could possibly
      > > > decrease the fertility of soils, unless one has been adding chemical
      > > > fertilizers for quite some time, resulting in dead soils. Perhaps
      > > I'm mistaken?
      > > >
      > > It doesn't decrease the fertility... it temporarily sequesters
      > > them.... this has to do with the natural balance of the carbon to
      > > nitrogen ratio.... this topic has been covered several times in the
      > > archievs....
      > > basically bacteria have a low carbon to nitrogen ration relative to
      > > the wood chips this means the bacteria suck up all the nitrogen so
      > > they can break down the wood chips... the bacteria being tiny and
      > > numerous are much better at getting the nitrogen then the plants are.
      > > so for 1-3 years you have low 'available' nitrogen until the bateria
      > > catch up with the wood chips...
      > >
      > > the nitrogen fertility of forest soils is usually built up during the
      > > early successional phase of the forest.. that is in the meadow and
      > > shrub stage.. there are many meadow and shrubs that fix nitrogen and
      > > very few trees that do so.. typically the nitrogen is maxed as a young
      > > forest and slowly declines as some is washed out...
      > > it is the bacteria and fungi's ability to hold onto the nitrogen so
      > > well that enables the forest to be so productive without fertilize..
      > > when you cut down a forest you do away with their food supply and the
      > > bateria and fungi die, and the nutrients get leached.
      > >
      > > > > Dear Jeremy,
      > > > >
      > > > > I think woody material contains high amount of cellulose. It
      > > > decomposes very> > slowly and after decomposition that releases
      > > toxic acids that can be problematic to the plants.. I dont know the
      > > specific names of these acids.
      > >
      > > this is only true of certain trees .. not all trees have these
      > > compounds..... trees that are noted for their resinous oils (Eucalpyt,
      > > leaurals) and conifers (pines, spruces etc) are likely to result in
      > > these acids..
      > > there are many many specific ones, and plant biologist and soil
      > > scientist have different terms for them.. the
      > > term I'm familiar with is phenolitic...
      > > pheno- refering to the benzene right structure of these acids...
      > > and litic refering to lysis.. or the breakdown of the orginal organic
      > > matter
      > > There may be other compounds that contribute to this but they are less
      > > known.. and don't occur in large families like the previously
      > > mentioned plants
      > >
      > > this is one of the reasons conifers are not highly recommended as
      > > mulch for gardening.....and braodleaved trees are prefered...
      > > I would think a moderate amount of conifers once or twice would have a
      > > minimal effect...
      > > generally when these things are measure and disscuessed it is in the
      > > terms of geologic time development of soils...
      > >
      > > I would think that after once or twice adding the conifers, and
      > > regular mulching of other organic matter, you would no longer need the
      > > conifer mulch to effectively garden and restore fertility
      > >
      > > > > > If I recall correctly, woody material has such a high carbon
      > > > content that it ties up nitrogen unless broken down by fungi. As
      > > already mentioned, you can bury the material to help it decompose. You
      > > could also spread the chips out and innoculate with fungi spores. You
      > > may want to try Stropharia rugoso-annulata or Pleurotus species.
      > > > > >
      > > >
      > >
      > > this is exactly correct...
      > > interestingly enough research pointed to by Stamets in Mycellium
      > > Running indicated increased yeild for certain vegetables when grown in
      > > combination with the above mentioned fungi...
      > > and even more interesting was that fact that the best yeild increases
      > > were for the brasicas ... which don't form VAM or AM mycorhizal
      > > assocaions like most other plants.
      > >
      > > ugh..
      > > just say so you have any questions or need anything clarified..
      > > I'm fighting a cold and might have skipped over something important
      > > jeff
      > >
      > > [Non-text portions of this message have been removed]
      > >
      > >
      >
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