permaculture

["Lawrence F. London, Jr." <lflj@intrex.net>]

http://lists.ifas.ufl.edu/cgi-bin/wa.exe?A2=ind0903&L=sanet-mg&T=0&O=D&P=39037
SANET-MG Archives -- March 2009 (#56)
For those interested in permanence, tilth, biological life, fertility and 
water and nutrient conservation in farm soils:

Subject:         Re: Soil Amendments - What do you thiink?
From:   STEVE GILMAN <[log in to unmask]>
Reply-To:       Sustainable Agriculture Network Discussion Group <[log in to 
unmask]>, STEVE GILMAN <[log in to unmask]>
Date:   Sat, 14 Mar 2009 09:32:06 -0400

Hi Dale,

        There's some other considerations for farmers here, beyond the old
simplistic in and out nutrient budget formulas. Over the decades many
conventional commodity crop varieties have been bred to have smaller
and smaller root systems. The thinking goes: why put crop yield
energy into building extensive root systems when the applied
synthetic fertilizers provide a soluble source of plant nutrients
right near the surface of the soil??

        Well, smaller root systems make the crop more vulnerable to droughty
conditions for one thing. And the chemical fertilizers and pesticides
that don't volatilize or run off into the waterways also negatively
impact beneficial mycorrhizae fungi -- whose miles of hyphae act as
pipelines to deeper down water and soil nutrient sources. And of
course, those fertilizers contain a lot of embedded petro-energy,
while increasing greenhouse gases.... looks like a losing proposition
to me.

        While researchers are in the process of developing organic crop
varieties with more extensive root systems that are not reliant on
soluble chemicals another option for farmers is to use deep rooted
cover crops whose extensive root systems harvest  deeper down and
migrated nutrients from lower soil horizons -- and which enhance
mycorrhizae and build soil organic matter to hold it all in topsoil
-- while also sequestering atmospheric CO2 in more intractable soil
glomalin carbonaceous forms. Ah, the synergy of holistic biological
systems!

Steve
Ruckytucks Farm
        

On Mar 14, 2009, at 12:00 AM, SANET-MG automatic digest system wrote:

> Date:    Fri, 13 Mar 2009 03:31:12 -0700
> From:    Dale Wilson <[log in to unmask]>
> Subject: Re: Soil Amendments - What do you thiink?
>
> Hi Sal and Eric,
>
> Eric wrote:
>>> Sal, trees may be closer to sustainable. To be certain
>>> one would need to measure the elements that are not recycled
>>> through the atmosphere. Carbon, oxygen, hydrogen, and
>>> nitrogen can be efficiently recycled by the atmosphere. The
>>> rest of the elements cannot. For your agroecosystem, Sal,
>>> you would need to calculate the phosphorus, potassium,
>>> calcium, sulfur, magnesium, etc. leaving your farm in the
>>> fruit, nuts, wood, etc. Then you would need some way to
>>> estimate the rate at which the bedrock and/or subsoil can
>>> resupply all these nutrients. If the export rate is greater
>>> than the breakdown of soil minerals, then you will need to
>>> fertilize.
>
> Sal wrote:
>> who puts the phosphorus, potassium, calcium,
>> sulfur, magnesium, in the forest or the bush.????????
>> some of those trees are easy over a 100 years old. and the
>> bush goes on and on without the help of man.      is that
>> sustainable .  yes tell man cuts them down and destroys all
>> that soil life that connects everything.
>
> Eric's point about "export rate" is the key here.  In a traditional
> forest, little material is taken out of the field.  It falls back
> as leaf litter and branches and the nutrients recycle.  But if you
> are farming and taking off 200 bu corn grain or 10,000 lbs potatoes
> per acre, you have to replace the nutrients carried off by that
> yield.  Of course if production is very low, nutrients can be
> replaced by slow processes like breakdown of soil minerals and rain
> deposition.  Many traditional systems involve farming land for a
> few years until the yields go down and weeds become insuperable,
> and then letting it lie fallow for many years as fertility is
> regained by slow processes.  But in the modern world with it's huge
> population, nutrient dynamics have to be carefully managed as Eric
> alluded to.  Ideally, those nutrients we flush down the toilet
> should be returned to the field to complete the cycle.  But it is
> hard to get there from here socially.
>
> Dale