[permaculture] Fwd: Re: [grazersedge] Re:Green manuring

Mark mpludwig at facstaff.wisc.edu
Mon Jul 22 11:18:24 EDT 2002


Folks,
forwarded from my grazing list.  Helps to answer some of out prairie vs 
forest questions.
Mark L



>Rick Williams wrote:
>
> > With the apparent large mass of trees in a forest above the ground, but 
> with
> > the minimal amount of roots below the ground in a forest, does the forest
> > above ground mass wind up back in the carbon cycle by decomposition and 
> most
> > go back into the air? I know that former President Reagan was severely
> > criticized for saying that trees "pollute" because they return so much
> > carbon back into the air. Is it correct that some areas (the Smoky 
> Mountains
> > for example) have a haze from this breakdown product that gets in the air?
> > Have you any approximate idea of what percentage organic matter is returned
> > to the soil by the above ground part of the forest? Then how does that
> > compare to prairie?  Are both able to build O.M. levels, but the forested
> > land is just slower at doing that?
> >
> > REPLY:
>
>The farm in Illinois lies on the break between prairie and forest in the 
>Driftless Area.  The prairie soil has organic matter
>content running about 6%.  The forested soils run about 2.5% on the soil 
>tests we get back.  This is a result of the long term
>vegetation growing there, because the parent material is the same, wind 
>blown silt.  The depth of the soil and the drainage class
>is the same.  I also did a special paper on this very subject while 
>attending UW-Stevens Point when the school was still Wisconsin
>State University.  Also, if you can find a copy of Jenny's "Factors of 
>Soil Formation", you can read about vegetative influences
>on soils.  Forested soils will never catch up to prairie soils in building 
>soil organic matter.  The chemistry of forested soils
>versus prairie soils works against organic matter accumulation except at 
>the very surface of a forested soil unless the soil is
>very wet to the point of being a swamp or bog.  In that instance, the soil 
>is low on oxygen and the organic matter accumulates
>since it is not oxidized into carbon dioxide very quickly if at all.
>
>
> > Isn't it normally done on large scale operations that you grow the organic
> > mass on the land and till it in for sheet composting?
> >
> > REPLY:  If you have a high residue crop, like grain corn, you do return 
> a lot of organic matter.  If it is tilled in, organic
> > matter content tends to be higher than if the corn had been taken off 
> for silage or a low residue crop had been planted
> > instead.  In the Upper Midwest and the Northeast, high residue crops, 
> such as corn, can maintain rather high levels of soil
> > organic matter.  Due to the cool climate (on a whole, not right now!) 
> less oxidation of organic matter takes place.  Since the
> > rate is slower, high residue crops can help maintain or even improve 
> soil organic matter content on tilled soils.  However, you
> > go further south, Mid-Atlantic states to Missouri and below, the 
> climate is warmer for a longer period of time and each year's
> > residue gets pretty much completely decomposed before the end of 
> summer, or sooner depending on moisture levels.  In that
> > climate, even high residue crops can do little to build organic matter 
> levels if tilled conventionally.  Well drained soils in
> > the South were naturally low in organic matter before cultivation 
> started so there was little to build on in the first place.
>
> > Perhaps this is a bit off the topic of grazing, but if you were going to do
> > moderate scale market gardening (one acre or larger), and you wanted to 
> stay
> > "organic," what would you recommend for a practical labor reducing approach
> > to weed control. This is our largest problem on our farm.
> >
> > We heavily mulch potatoes (Ruth Stout method mostly) but have not done this
> > with other plants to a great extent. Is it possible to use wood chips as
> > long term mulch? I am thinking that we need to mulch to retain moisture,
> > make it easier to walk on clay/loam type soils, and not add any weed seeds.
> > We have significant amounts of Ashleaf Maple on our property that could be
> > run through a chopper/chipper to provide this material. Or are other 
> methods
> > better?
>
>REPLY: I would still rely on a hay or straw mulch over wood chips.  The 
>wood chips have a very high carbon to nitrogen ratio and
>would make the plants nitrogen deficient unless you added some manure to 
>compensate before laying down the chips.  The box elder
>chips probably would not acidify the soil during breakdown as pine chips 
>would.  For potatoes, plant first and then roll out a
>large hay bales and let the potatoes come up through.  For set plants, it 
>depends on how those are set in the ground.  If doing it
>by hand with a trowel, roll out a large round bale first, use a sharp tool 
>to cut a hole in the hay, and then proceed with the
>trowel.  If using a machine like a tobacco planter, then it might be 
>better to use small square bales and use the slabs as formed
>by the baler to lay down between rows.  No matter what, you are looking at 
>a labor intensive operation compared to the non-organic
>way of clean till, plant, and spray.  However, if you feel you have a 
>cleaner, safer product that is worth the extra effort, go
>ahead.  For my two 50 foot rows of potatoes, I squash Colorado potato 
>beatles and their larva by hand rather than spray with an
>insecticide.  I have noticed wasps sting and take off with the larva 
>too.  However, I cannot rely on that as a very effective
>biocontrol.  A handful of larva killed by wasps when there are a couple of 
>hundred or so on 100 feet of potatoes is not my idea of
>economic control, no matter how in tune with nature it might be.
>
>Jim Cropper
>Forage Management Specialist
>
>
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Mark P. Ludwig
Poultry Research Lab
University of Wisconsin -Madison
608-262-1730 WK
608-846-7125 HM




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