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permaculture - Re: [permaculture] [soilandhealth] Organic matter percentage

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  • From: Glenn Gall <glenngall@gmail.com>
  • To: permaculture@lists.ibiblio.org
  • Subject: Re: [permaculture] [soilandhealth] Organic matter percentage
  • Date: Mon, 26 Dec 2011 18:13:31 -0500

"How much compost or manure would one need to add to raise the Soil Organic
Matter SOM content of an acre of soil 6" deep by 1%?"
"To add 1% organic matter to the top 6" or 15cm of soil would require about
50,000 lbs/acre or 50,000 kg/ha of organic matter at 60% moisture content."


I'm not expert in soil science or soil biology, but I think there are a
number of things to consider here, especially in order to determine net
gains.

What is the source of the compost? Are soils being depleted by its
production, and what are the sources of energy to produce it? Is the
compost being incorporated into the soil, and how is this being done? Is
soil carbon being oxidized in the process, and are soil food web systems
being damaged? Is the compost being leached or eroded by this process? Is
the land producing pasture, hay, or market or commodity crops? Would less
compost stimulate enough biological activity to create a greater increase
in soil carbon? Are there more economical, practical, and sustainable
amendments or methods of increasing soil carbon, or combinations of
amendments or methods, besides adding 25 tons of compost per acre?
Soil carbon can be imported or induced. Photosynthesis produce sugars, a
large fraction of which are translocated to the rhizosphere to support
mineralization and humification in the soil food web. Additions of sea
minerals and humic substances have been known to stimulate soil carbon
increases. Grazing animals are commonly chosen as tools, often aided by
keyline plowing or aerated compost tea addition.

I know of a small vegetable farm that more than quadrupled its soil carbon
in its beds in ten years, but it took an enormous, and in my opinion
unsustainable, effort to generate the compost from outside sources of
leaves and food waste. I know of other farmers who have made similar
increases in their pastures, albeit at a slightly slower rate, but much
more sustainably. Compost is probably often best when not used as a
wholesale method to sink carbon, but as a method to increase plant health
and productivity, producing a sink in the process.

Glenn

Message: 3
> Date: Fri, 25 Nov 2011 20:47:24 -0500
> From: "Lawrence F. London, Jr." <venaurafarm@bellsouth.net>
> Subject: Re: [permaculture] [soilandhealth] Organic matter percentage
> To: soilandhealth@yahoogroups.com
> Message-ID: <4ED0452C.3060704@bellsouth.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 9/18/2011 2:03 AM, m_astera wrote:
> > How much compost or manure would one need to add to raise the Soil
> > Organic Matter SOM content of an acre of soil 6" deep by 1%?
> >
> > SOM percentage is calculated by weight, not volume. The convention
> > used is that 1 acre of soil 6-7" deep weighs 2,000,000 (two million)
> > pounds. Or a hectare of soil 15cm deep weighs 2,000,000 kg. One
> > percent of that is 20,000 lbs/acre or 20,000 kg/ha
> >
> > Compost and manure can be assumed to be around 60% moisture and 40%
> > dry organic matter. So
> >
> > 20,000 / 0.40 = 50,000
> >
> > To add 1% organic matter to the top 6" or 15cm of soil would require
> > about 50,000 lbs/acre or 50,000 kg/ha of organic matter at 60%
> > moisture content.
>
> Right on the money.
>
> > Probably makes more sense to grow it in place.
>
> Absolutely.
>
> The National Weather Service predicts more drought this winter.
>
> http://www.cpc.ncep.noaa.gov/products/expert_assessment/seasonal_drought.html
>
> If climate change is the cause then biological farmers could help stave
> this off by sequestering carbon in soil by growing nitrogen fixing
> crops, high biomass cover crops, weeds and, of course, application of
> manures to fertilize the land increase yield. Soil tests and balanced
> mineral application would be very important also.
>
> " If all landowners increased their soil organic matter by 1.6% then
> carbon dioxide levels would fall back to normal and our climate would
> stabilize, says farm expert Allan Yeomans in
> http://www.youtube.com/user/AllanYeomans1#p/a/u/0/-o2N6vJDLpE
> Free download of his book:
> http://www.yeomansplow.com.au/priority-one-contents.htm
> "...it could be done in a decade or two," says Yeomans.
> http://groups.google.com/group/soil-age "
>
>
>




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