Subject: Re: full throttle

From: Steve Diver <[email-masked]>
Date: Wed, 5 Nov 2003 15:03:37 -0500

Joel -

I know you have ideas on where that N is
coming from.  I'll be interested to hear
your thoughts.

Microbial biomass, humus complex, N pools,
OM pools... protozoan grazing... the whole basis
of organic agriculture is based on a holistic system
with mutliple components interacting to
support a cycle of nutrient availability,
growth promotion, and plant protection.

We have evidence that microorganisms communicate
with plant roots and make nutrients available
as the plant needs them, during certain periods
of the growing season. Later in the growing season,
these same nutrients are not produced by the
rhizosphere community.

Anyways, mineralization also came up on the
U.S. Compost Council list regarding compost
mineraliztaion rates. Greg Evanylo at Virginia
Tech completed recent SARE research on agronomic rates
of compost.  He shared ideas and figures on N
mineralization from composts, worth bookmarking
for future reference.

Yet, again, crop response in the field is greater
than what compost mineralization rates predict.

Interestingly, I'm on the road in Davis, California.
This is a very productive agricultural region.

The size of the trees and the diversity of plant
species to choose from for landscaping and
food production is amazing.

UC-SAREP at UC-Davis has published helpful papers
and publications on organic matter, worms, etc.

In my travels, observations on sustainability are
striking.  How will population growth, resource
consumption, fossil fuel reserves, transportation
methods and building structures, and global warming
effect our lives and our lifestyles in 5, 10,
20, and 50 years?

It occurs to me that we may have to look
at a lifestyle based on the bicycle and other
non-fossil fuel driven transporation, in the
next decade or two.  This will also be a time
when home food production becomes the norm, rather
than reliance on shipped-in food and commercial
agriculture.  I realize this is a bleak picture,
but it an impression that is real.  How do you support
these megatropolis populations with all those cars
zooming around, when fossil fuel reserves are predicted
to zero out in less than 100 years?

Steve Diver
NCAT / ATTRA

On Wed, 5 Nov 2003 14:07:27 -0500, Joel Gruver <[email-masked]> wrote:

>2 weeks ago I asked several soil scientists with long careers investigating
>nitrogen management to estimate how many lbs of the N taken up by a typical
>NC corn crop comes from the mineralization of organic matter.
>
>They all estimated 20-40 lbs and presented the following rationale (2%
>mineralization of 1% OM (~10 tons of OM in an acre plow layer) with a 5% N
>content  à 20 lbs N).
>
>They all agreed that :
>a 150 bushel/acre corn crop will take up 150-170 lbs/acre of N
>150 lbs/acre of fertilizer N is a normal rate
>fertilizer uptake efficiency is not likely to exceed 50%.
>
>I then showed them the following calculation:
>total N uptake – 50% of fertilizer N = 75 – 95 lbs of soil N/acre
>and asked them where all this soil N was coming from if organic matter was
>only providing 20-40 lbs.
>
>They all seemed genuinely perplexed… as if they had never contemplated this
>question.
>
>Joel Gruver
>Department of Soil Science
>NC State University
>919 515 4270
>[email-masked]

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From: Steve Diver <[email-masked]>
Date: Wed, 5 Nov 2003 15:03:37 -0500

Joel -

Steve Diver
NCAT / ATTRA