permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

-------- Original Message --------
Subject: Re: [SANET-MG] soil organic matter in tropical vs. temperate soils
Date: Sat, 1 Jan 2011 09:59:15 -0500
From: Joel Gruver <jgruv@HOTMAIL.COM>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Hello folks,

the following Albrecht quote seems quite relevant to this discussion:

”Attempting to hoard as much organic matter as possible in the
soil, like a miser hoarding gold, is not the correct answer.Organic 
matter functions mainly as it is decayed and destroyed. Its
value lies in its dynamic nature. A soil is more productive as more
organic matter is regularly destroyed and its simpler constituents
made usable during the growing season. Its mere presence in the
soil is of value during certain stages of decay, when it influences
soil structure and water relations and when it functions in holding
plant food in readily available form much more effectively than
does any mineral fraction of the soil. The objective should be to
have a steady supply of organic matter undergoing these processes
for the benefit of the growing crop.

William Albrecht – Loss of Soil Organic Matter and Its Restoration - 
1938 Yearbook of Agriculture
http://www.soilandhealth.org/01aglibrary/010120albrecht.usdayrbk/lsom.html

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During Albrecht's career (and most of the history of SOM research), 
nearly all research on SOM focused on ways to isolate pure organic 
materials (i.e., separate organics from the dominant mineral matrix) and 
then analyze the organics using more and more sophisticated techniques.

the most widely used approach was alkali extraction and the artifacts of 
this classical method are "fulvic acids", "humic acids" and "humin".

I refer to FA, HA and humin as artifacts because they are the products 
of crude dissolving and then reprecipitating processes and are quite 
different than in-situ organic materials...

In the last several decades, organic matter research has greatly 
diversified and much progress has been made in understanding soil 
organic matter within its ecological context.

here are links to 2 of my favorite reviews that discuss the diversity of 
materials that constitute SOM and the varying effects these materials 
have on soil function.

Soil Organic matter fractions and their relevance to soil functions
ftp://ftp.cricyt.edu.ar/pub/jaranibar/isotopos/belowground/wander04.pdf

Functions of Soil Organic Matter and the Effect on Soil Properties
http://www.grdc.com.au/uploads/documents/cso00029.pdf

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in both tropical and temperate soils, biologically active fractions of 
SOM tell us far more about the effects of management on soil ecological 
function than total organic matter.

Joel

Joel Gruver
School of Agriculture
Western Illinois University
jgruv@hotmail.com