9071Re: [fukuoka_farming] Re: Wood chips as mulch: Re forest soils and more soil science
- Mar 1, 2009Linda, 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
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
> 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
> although it needed reapplication in year three. This treatment also
> 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
> 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
> Evidence: Actually, many studies have demonstrated that woody mulch
> materials increase nutrient levels in soils and/or associated plant
> My hypothesis is that a zone of nitrogen deficiency exists at the
> 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
> Cheers, Linda
> From: email@example.com
> <mailto:fukuoka_farming%40yahoogroups.com>] On Behalf Of Jeff
> Sent: Sunday, 1 March 2009 1:17 PM
> To: firstname.lastname@example.org
> 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
> 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
> 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.
> just say so you have any questions or need anything clarified..
> I'm fighting a cold and might have skipped over something important
> [Non-text portions of this message have been removed]
- << Previous post in topic Next post in topic >>